Whoever made that surface plate supported it from the three points that they calculated when they lapped it flat. Unless you support it from the same three points that they used, the granite will sag differently than it was when they lapped the plate and it won't be flat. My Starrett surface plate actually has three little recesses on the bottom of the surface plate that clearly shows where the mounting points should be located. I believe the mounting points on your surface plate should be identified as well. If so, you should design your stand to support the granite from those three marked points. Chris
Got a 36 x 36 x 6 and the same applies with the 3 recess points under where to land it on... Wonder if Dale checked if there were those 3 points under his table... ???
Mark Abraham “And the Lord spake, saying Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, nor either count thou two, excepting that thou then proceed to three. Five is right out! “. Sorry, I couldn’t resist throwing in a Monty Python search for the holy grail quote! Surface plates have 3 support points because three points always provide a stable support with no rocking. Anyone who ever had to put a packet of sugar under a table leg at a Resturant will tell you that four or more legs don’t Always provide stable support. Even if you did adjust the 4 contact points so they all had contact, you still wouldn’t know if the support given by each leg is the same every time you set it up. Section 12 of this Starrett link points this out. www.starrett.com/precision-granite/precision-granite-faq
Dale. I just bought a Starrett 24" by 36" by 4" surface plate for my basement shop. I'm not an engineer, rather I fly for an airline, and as such I'm looking to guys like yourself to teach me. Please continue this series. I had no idea about the intricacies and am a proverbial sponge..... Looking forward to building a similar cabinet/table. Cheers.
Dale, this will be an interesting series and will be following and learning. I hope you will be going into more detail on your engineering design so we can apply the technique to any size surface plate. I just saw your shop on Keth Rucker's channel and enjoyed seeing parts of your shop we normally do not see. Thank you, Paul
Can't wait to see this project going! I'm in no situation where I can buy a surface plate and do this myself, but this is really interesting stuff. Thanks for sharing the video - and please, keep'em coming!
( Side note you're missing "92" from your PI ) Love your approach to leveling and supporting surface plate. Whole heartedly agree that while you only need 3 points to define a level plane, that's not to say that you can't actually support it from more points if you approach it methodically, correctly & accurately. I enjoy your videos almost as much as Stefan Gotteswinters; and I rate his videos up there with "This Old Tony" and "Post Apocalyptic Inventor"
Just unboxed two small, 12 x 18 x 3" surface plates last night. Running across your vid this morning, was perfect. It looks as though three points will work for me, and now I don't have to research the multiplier for location, either. Thanks, as always. GeoD
Interesting. I was under the impression that three points were the standard. My Starrett plate and stand came with no points so I have been pondering how to go about adding them. Looking forward to more episodes in this series.
Hi Dale Never heard or read of these terms before when setting up a Surface Plate. One never stops learning, thanks to U Guys for showing and sharing. Great stuff. Keep 'em rolling ATB aRM
Yup, shadowdog500 has it correct, use the pads that the plate supplier used to grind and lap. The other thing is to have 3 bolts or feet fastened to the table between the table and the plate so you can level the plate. The other thing is not to get carried away making the stand excessively stiff else it will rock unless you have only 3 feet or legs. Of course the problem with a 3 leg table is that they can have more tendency to tip over if you have an earthquake. Lots of fun.
This is awesome. I wouldn't mind if you did more videos like this one. I too like to know as much about what I am doing as possible. This was a great help.
I thought it was a great Idea too, and thought I had thought of it. Then a few weeks ago I was looking at a surface plate and stand made by Starret and found out they did it first. LOL
All good stuff Dale. The language of engineering is mathematics and with a wibbly-wobbly surface-table one will be forever chasing ones' tail, won't one.
Ditch the hook scale for flat layouts, I can see the cosine error. Which is to say you'll get more accurate markings by holding your scale flat against the paper. ALSO this was a very helpful video, you've given me plenty to think about 😁
This is going to be a fun series. My friend and machining mentor just bought a surface plate at auction about a month ago. I'm going to drive him crazy with technical terms from this video as he sets his up. Damn it Barry, it's sagging in the middle. You need to get you some aerial and bustle points or a set of collets.
Very interesting video. It would be fantastic if you could show a before/after of measuring the suface plate, to fully analyze the results of your build & design.
I did know about the airy points and how to calculate there location. That information is pretty easy to find. Bessel points was a new one to me. Not sure I'd agree about putting a surface plate and it's stand on castors though. Every single one I've seen being used for commercial use is fixed. Must be a good reason for that? Should still be pretty interesting to see what you come up with. To be accurate with the information an email to Starrett, Mitutoyo,, Precision Granite, Standridge etc to see what there views are about castors might be worth while. Maybe for the smaller 3'-4' sized plates it doesn't or wouldn't degrade the accuracy enough to be measurable in the usual shop, but maybe it does. I just don't know enough to say my thoughts about those castors are right or wrong. For smaller parts and doing lay outs then even thick plate glass might be good enough for most of what we'd need. I want a surface plate for scraping parts in, so using the full length or width of a plate isn't out of the question. That might be where castors could create possible issues maybe. But proving it's a good / bad idea either way might be real tough without doing checks over a period of time with at least an autocollimator. But in a non temperature controlled to metrology levels shop my thoughts may still be worthless.
A. What grade is your plate? B. Does granite undergo continuously increasing droop over time? C. I do like the idea of supporting it with liquid, perfectly even support, but that was not how it was supported when made. D. How are you going to measure your results?
While I have a modest surface plate, I am excited by this project. Please include some design elements that are applicable to smaller, modest surface plates. Paul
Thanks for the video I just got done building my stand for my Surface plate and I didn't believe that you didn't know the thickness of that surface plate without measuring nice try though LOL great video thanks again
Hey Dale, my troll friends have some drooling feedback for you : - troll 1 says "how dare you steal from Keith "I'm a rucker, baby I'm a rucker" ?! - troll 2 says "omfg this is gonna be so much cooler and in-depth than that other guy's fuzzy three-point stool stand thing, yeah !" Anyway, don't pay attention, they're already gone to other slimy troll pastures, and as for me I'll be watching in rapture, all the more since this will feature some hard-core surface plate info that has zero relevance to my world, and is therefore absolutely indispensable ! Cheers and keep on trucking (from France) !
Dale. I suggest that you look up how large primary glass mirrors in telescopes are supported to keep them from distorting with gravity load. (i.e. mirrors that are 16 or 18 inches diameter up to 36 and 40+ inches in diameter - 2" to 4" thick) Typically they are supported on a series of triangular plates over other triangular plates/beams, with the ultimate main support being three points, two on one beam and the third on another beam to the telescope frame. Good luck, Warren
Your value of Pi is off. :-) If you move your plate you are likely to have to readjust your plate every time if you want ultimate accuracy. It is unrealistic that your stand could be stiff enough to apply the same loading all the time to your supports, thanks to gravity unless your floor is perfectly level anytime your plate is not leveled the same way as it was when it was calibrated then it will no longer be accurate. The reality is that unless you are going for a very high grade of plate then it is all not a big deal for most use. The only big deal is that the plate be supported and leveled at the same points that it was when it was made. For most quality manufacturers this means 3 points for some really big plates they may use more supports and in those cases they use jack screws and a torque wrench to obtain level and even loads identical to when it was made. There are import plates with no locating marks for the setup when the plate was made and these plates are merely rocks as they can not be repeat calibrated.
bcbloc02 I think because he is using three points that the loads will be the same. After all the load supplied to the plate is equal to the load supplied by the plate, which can't change. The loads on the four castor wheels may change but the three points won't in my opinion.
Have you considered using a high to medium pressure hydraulic hose around the periphery, connecting the Bessel points, then pressurize it with fluid?? This would allow the cart to flex and still be flat.
I was looking for tips on how to get the perfect level for my telescope mount and this came up. I can't get my head around a 6-inch thick slab of granite bending anyway or anyhow.
In watching your episode on setting up a surface plate, here is what I notice: 1 I have a cast Iron surface plate which has 2 protrusions on one side (bottom) and one protrusion on the opposite bottom end and it is supported only at those points. 2 In setting up a small lathe (Bench top model). How should one best proceed 2 steel balls under the head stock end and one steel ball under the. tail stock end or just bolting down the four corners at the provided holes.
The same suspension concept is used in a variety of applications, and was standard in the days of steam locomotives, under the term equalization. I don't know if I would go for more points with a large whiffletree (as suggested in one comment), as friction and small errors in centering add up and won't likely improve support, but with a lot of complexity. Foam or floating are options, but, again come with other problems, like rigidity to maintain level and indeterminacy of support. A lot of things have been tried, and simple mechanical support is used because the advantages outweigh the disadvantages of other methods. The concern I would have matches shadowdog: What were the supports when the plate was flattened. It doesn't matter if you are going to have it resurfaced after mounting, but, if not, then you may find some unwanted deflection from best condition.
There is actually a federal white paper on surface plates. It does discuss how to support a plate if the 3 points are unsatisfactory. Look up "GGG-P-463C"
who says that we can support a plate on only 2 points (in one section) or 3 or 5 points on its surface? why not 10 or 20 points supported by a whiffle tree so that all points carry equal loads? Or an infinite number of points by a full area support e.g. by a fluid cushion. or a piece of foam . Or you could support the plate on 3 arbitrary points only but then hone the plate surface flat when sitting on those points. If you dont shift the plate afterwards it stays dead flat also.
Hi Dale, have you checked if the manufacturer of the plate made provision on how to lay the plate, normally they stand on 3 points cause they were manufactured that way... Just curious, even if the cantilever idea is interesting for auto leveling.
Yes I did and they had none. I came up with this idea a few months ago. Then found out my idea was correct when I discover that Starrett has done the same think with some of there surface plate stands
Hi Dale, looking up the Bessel point , it appears the Bessel point (0.5594 of length) is the point of support that results in the minimum amount of centreline divergence (shortening of beam), not the point where there is minimum deflection. the support points for minimum overall sag is different at 0.5536 of the length. I agree that this is minor but speaking theoretically , as the discussion was, the terms are different. For a one metre beam it is only 5.8mm (228 thou) closer together. again good work and thanks for introducing the subject. see Wiki at en.wikipedia.org/wiki/Airy_points
That was a very clear explantation of Airy and Bessel points. Both these guys were geniuses of their day. The explanation with a piece of paper should be recorded on stone tablets. But there is one thing you did not mention. and it is important. When that granite plate was lapped in at the factory they suspended it on 3 Airy/.Bessel points just as you did. So the plate is flat -- as long as it is suspended same place the manufacturer did. There is usually a small indication of this on the bottom of the plate, and you would be wise to heed it. Else it will be slightly off kilter. Then there is the whole business of leveling, but I refer anyone to Tom Lipton for this. In metrology (quote Tom Lipton) *everything* matters, even if it means turning that giant plate upside down to find the suspension marks. Ugh.
Dale, a question. In the Keith Rucker video tour I think there is a lathe in the back opposite the milling machine. I dont think you mentioned it or am I wrong?
The general rule is to use one more decimal place than the least significant number in the calculation. You are using 4 places and 0 places so use 1 decimal place for your answer. The theory is the last decimal place is +/- 0.5 of the last place. In actuality you should be able to easily measure 11 inches plus or minus 0.1 inches so the answer could realistically be to 2 places. Since I am an engineer and a stickler for detail, PIE is actually PI but I will take the first in chocolate is you please. I do think you can easily measure and mark to 2 decimal places with a pen or marker on paper.
Do you do inspection, use the plate for shop layout, or simple metrology or complex metrology or even laboratory like metrology or a mix of that? That would define how accurate you need to be in your surface plates plane.
I'll bite on your troll food Dale. I seen how you wrote a 2 for a 3 at 5:25. Also it should be 1.8526 Not 1.8525. The number was 1.85255 and the 5 rounds up to 6. Just funning with you. Looks like a great series and looking forward to it. You do produce very good problem solving videos. Also your shop tour with Keith was a nice touch.
5:10 The formula work with metric? and another question: how many 1/1000 inch or micrometer can flex a plane surface (in the horizontal plane) (such as your 6-inch) to its extreme edges in the worst case (like a single central point of support)?
just last week saw Airy and Bessel points in a 1950's mechanical drawing workbook that I picked up at a garage sale... Coincidence....? ?? LOL. Great idea to put some serious effort into the design and build of this piece.
Dale I have a laser table 8'x4' that sits on six rubber inflated pads that absorb natural earth vidrations and keep it level at all times, could this concept be used with your granite plate? This table weighs 3 tons! Ian. Digitron Technology
You're going to think I'm crazy for saying this, but did you type in pi ("PIE" in your video) and skip a couple of digits? 3.14159265358979 is what I had memorized, and it looks like you skipped the .000092! Obviously it's not important, but I am curious how you ended up with a couple of digits missing!
I can't wait to see the finished project and how you solve the problems on the way. there is a FREE program that I use to help me with my own designs call Google SketchUp it is a 3D program it OK but it only works with straight lines even for circles (it default setting is 24 sides to a circle or an arc). It's better for building than engineering but with a little thought you can get away with it and it is easy to use. NO I don't work for Google and I don't get commission for this LoL
I'm 6 years late. Oh well.. AIRY POINTS, BESSEL POINTS, MINIMUM GRAVITY SAG, AND VIBRATION NODAL POINTS OF UNIFORM BEAMS 1. Airy points - zero slope at ends - supports located 0.21132 L from each end 2. Bessel points - minimum change in length - supports located 0.2203 L from each end 3. Minimum deflection due to gravity - supports located 0.2232 L from each end 4. Nodal points of first vibration mode - zero deflection at these points during free vibration - supports located 0.2242 L from each end I think #3, 0.2232 L is what you want. The pivot beam on one end is a good idea. Just don't put a lot of weight on either corner on that end. It will stress the plate diagonally from one corner to the opposite corner..
If your metrology will include vibration evaluation, then you'll need to set your granite slab on a bed of sand to eliminate the high frequencies which would otherwise be transmitted through th granite. At that point you could start doing your own holograms!
Dale, I think you've been misled about Bessel points. Bessel points are for supporting a rod with minimal change in horizontal length. Bessel points do not provide the minimum amount of sag. The minium sag points are located slightly inward of the Bessel points at 0.2232 x length (as opposed to 0.2203). Now while this makes little practical difference, you are introducing a concept and terminology not relevant to your goal (length change in your surface plate is not important). www.mechanicsandmachines.com/?p=330
Why not just set the plate on a clay base within a steel container, and let the plate seek its most naturally stress relieved shape, then surface it like that?
That is an interesting idea. I don't think it will work with my project because the table gets moved around from time to time. so I don't think the clay would hold for me over the long run. if you do it let me know how it worked for you.
My company has a granite table that is 9' x 15' and it is still supported on three points so whoever told you you cannot do that or a larger table is a liar
there is a mil spec that tells you how to mount a suface plate it is alwas 3 piont google ggg-p-463c this is the holy grail for surface plates this is what all plate are manifactued two
Whoever made that surface plate supported it from the three points that they calculated when they lapped it flat. Unless you support it from the same three points that they used, the granite will sag differently than it was when they lapped the plate and it won't be flat. My Starrett surface plate actually has three little recesses on the bottom of the surface plate that clearly shows where the mounting points should be located. I believe the mounting points on your surface plate should be identified as well. If so, you should design your stand to support the granite from those three marked points. Chris
Got a 36 x 36 x 6 and the same applies with the 3 recess points under where to land it on... Wonder if Dale checked if there were those 3 points under his table... ???
why doesnt he use 5??
Mark Abraham “And the Lord spake, saying Three shall be the number thou shalt count, and the number of the counting shall be three. Four shalt thou not count, nor either count thou two, excepting that thou then proceed to three. Five is right out! “. Sorry, I couldn’t resist throwing in a Monty Python search for the holy grail quote! Surface plates have 3 support points because three points always provide a stable support with no rocking. Anyone who ever had to put a packet of sugar under a table leg at a Resturant will tell you that four or more legs don’t Always provide stable support. Even if you did adjust the 4 contact points so they all had contact, you still wouldn’t know if the support given by each leg is the same every time you set it up. Section 12 of this Starrett link points this out. www.starrett.com/precision-granite/precision-granite-faq
@@shadowdog500 right on bro thanks for the quick answer *and* monty python quote - you rock
Thanks for that info.
Dale. I just bought a Starrett 24" by 36" by 4" surface plate for my basement shop. I'm not an engineer, rather I fly for an airline, and as such I'm looking to guys like yourself to teach me. Please continue this series. I had no idea about the intricacies and am a proverbial sponge..... Looking forward to building a similar cabinet/table. Cheers.
Thanks for your comment and congratulations on your new surface plate. :-)
nice! looking forward to the build!
Me too, Its been on my list for the last 6 months.
I love the beam pivoting over a single point!
Genius!
:)
Dale, this will be an interesting series and will be following and learning. I hope you will be going into more detail on your engineering design so we can apply the technique to any size surface plate. I just saw your shop on Keth Rucker's channel and enjoyed seeing parts of your shop we normally do not see. Thank you, Paul
your wish is my command
Good presentation, Dale. Clear and to the point, easily understood and practical.
thank you very much of your comment. :-)
Can't wait to see this project going! I'm in no situation where I can buy a surface plate and do this myself, but this is really interesting stuff. Thanks for sharing the video - and please, keep'em coming!
Thanks for your comment
( Side note you're missing "92" from your PI )
Love your approach to leveling and supporting surface plate. Whole heartedly agree that while you only need 3 points to define a level plane, that's not to say that you can't actually support it from more points if you approach it methodically, correctly & accurately.
I enjoy your videos almost as much as Stefan Gotteswinters; and I rate his videos up there with "This Old Tony" and "Post Apocalyptic Inventor"
Just unboxed two small, 12 x 18 x 3" surface plates last night. Running across your vid this morning, was perfect. It looks as though three points will work for me, and now I don't have to research the multiplier for location, either.
Thanks, as always.
GeoD
Interesting. I was under the impression that three points were the standard. My Starrett plate and stand came with no points so I have been pondering how to go about adding them. Looking forward to more episodes in this series.
thanks for your comment
Hi Dale
Never heard or read of these terms before when setting up a Surface Plate. One never stops learning, thanks to U Guys for showing and sharing. Great stuff.
Keep 'em rolling
ATB
aRM
Yup, shadowdog500 has it correct, use the pads that the plate supplier used to grind and lap. The other thing is to have 3 bolts or feet fastened to the table between the table and the plate so you can level the plate. The other thing is not to get carried away making the stand excessively stiff else it will rock unless you have only 3 feet or legs. Of course the problem with a 3 leg table is that they can have more tendency to tip over if you have an earthquake. Lots of fun.
Thanks for your comment
This is awesome. I wouldn't mind if you did more videos like this one. I too like to know as much about what I am doing as possible. This was a great help.
Thanks
Really interesting Dale, I'm looking forward to seeing the rest of this. The pivoting beam idea is really clever! :)
I thought it was a great Idea too, and thought I had thought of it. Then a few weeks ago I was looking at a surface plate and stand made by Starret and found out they did it first. LOL
Lol story of my life, Dale! Keep up the great videos, I really enjoy them.
All good stuff Dale. The language of engineering is mathematics and with a wibbly-wobbly surface-table one will be forever chasing ones' tail, won't one.
LOL
Good job, looking forward to the series. I enjoy the why as well as the how, keep it up!
Thanks Roger :-)
Ditch the hook scale for flat layouts, I can see the cosine error.
Which is to say you'll get more accurate markings by holding your scale flat against the paper.
ALSO this was a very helpful video, you've given me plenty to think about 😁
Dale,
Great subject matter. I look forward to this series, especially the bead roller work.
thanks for your commnet. the bead rolling stud is cool. :-)
as a hobby machinist and a electrician by trade, good video friend. can't wait to see the series
Thanks :-)
This is going to be a fun series. My friend and machining mentor just bought a surface plate at auction about a month ago. I'm going to drive him crazy with technical terms from this video as he sets his up. Damn it Barry, it's sagging in the middle. You need to get you some aerial and bustle points or a set of collets.
LAUGHT OUT LOUD :-)
Good job, Dale. Look forward to following along. Always wondered about this stuff, so very on-target for me.
I hope I don't disappoint you:-)
Excellent video Dale, looking forward to seeing the rest of the series. Greg
Thanks
another great video dale, I'm looking forward to this series.
Thanks
God I miss your videos have seen you on Randy Richards and ARW discussion.
Hope your okay.
Your always welcome in Adelaide Australia
CHEERS TROY
Very interesting video. It would be fantastic if you could show a before/after of measuring the suface plate, to fully analyze the results of your build & design.
Interesting Idea. I wish I had the tools to do that.
I did know about the airy points and how to calculate there location. That information is pretty easy to find. Bessel points was a new one to me. Not sure I'd agree about putting a surface plate and it's stand on castors though. Every single one I've seen being used for commercial use is fixed. Must be a good reason for that? Should still be pretty interesting to see what you come up with. To be accurate with the information an email to Starrett, Mitutoyo,, Precision Granite, Standridge etc to see what there views are about castors might be worth while. Maybe for the smaller 3'-4' sized plates it doesn't or wouldn't degrade the accuracy enough to be measurable in the usual shop, but maybe it does. I just don't know enough to say my thoughts about those castors are right or wrong.
For smaller parts and doing lay outs then even thick plate glass might be good enough for most of what we'd need. I want a surface plate for scraping parts in, so using the full length or width of a plate isn't out of the question. That might be where castors could create possible issues maybe. But proving it's a good / bad idea either way might be real tough without doing checks over a period of time with at least an autocollimator. But in a non temperature controlled to metrology levels shop my thoughts may still be worthless.
You make people think. That's a gift.
A. What grade is your plate? B. Does granite undergo continuously increasing droop over time? C. I do like the idea of supporting it with liquid, perfectly even support, but that was not how it was supported when made. D. How are you going to measure your results?
While I have a modest surface plate, I am excited by this project. Please include some design elements that are applicable to smaller, modest surface plates.
Paul
I will do my best
Good information for every machinist, but especially for the 'learn as you go' home machinist!
Im glad you liked it
Thanks for the video I just got done building my stand for my Surface plate and I didn't believe that you didn't know the thickness of that surface plate without measuring nice try though LOL great video thanks again
I fully expect to see a set of drawers that, when completed, resemble a game of Tetris.
I hope its not that complicated laugh out loud
Hey Dale, my troll friends have some drooling feedback for you :
- troll 1 says "how dare you steal from Keith "I'm a rucker, baby I'm a rucker" ?!
- troll 2 says "omfg this is gonna be so much cooler and in-depth than that other guy's fuzzy three-point stool stand thing, yeah !"
Anyway, don't pay attention, they're already gone to other slimy troll pastures, and as for me I'll be watching in rapture, all the more since this will feature some hard-core surface plate info that has zero relevance to my world, and is therefore absolutely indispensable !
Cheers and keep on trucking (from France) !
LOL
Dale. I suggest that you look up how large primary glass mirrors in telescopes are supported to keep them from distorting with gravity load. (i.e. mirrors that are 16 or 18 inches diameter up to 36 and 40+ inches in diameter - 2" to 4" thick) Typically they are supported on a series of triangular plates over other triangular plates/beams, with the ultimate main support being three points, two on one beam and the third on another beam to the telescope frame.
Good luck, Warren
Oh, and their spacing, I believe, is based on some rule related to the thickness. Warren
genius pivoting support!
I like it! :)
Looking forward to the rest of this series. That's gonna have to be one stiff beam.
Im looking forward to doing it. This project has been on my list for the past 6 months
OMG....anyone would think you're making parts for NASA!!!
Hello Dale, when will you be continuing this project?
Your value of Pi is off. :-) If you move your plate you are likely to have to readjust your plate every time if you want ultimate accuracy. It is unrealistic that your stand could be stiff enough to apply the same loading all the time to your supports, thanks to gravity unless your floor is perfectly level anytime your plate is not leveled the same way as it was when it was calibrated then it will no longer be accurate. The reality is that unless you are going for a very high grade of plate then it is all not a big deal for most use. The only big deal is that the plate be supported and leveled at the same points that it was when it was made. For most quality manufacturers this means 3 points for some really big plates they may use more supports and in those cases they use jack screws and a torque wrench to obtain level and even loads identical to when it was made. There are import plates with no locating marks for the setup when the plate was made and these plates are merely rocks as they can not be repeat calibrated.
bcbloc02 aa
bcbloc02
I think because he is using three points that the loads will be the same. After all the load supplied to the plate is equal to the load supplied by the plate, which can't change. The loads on the four castor wheels may change but the three points won't in my opinion.
Ian9toes I suggest you look into Brian's credentials. ;)
Dale I to have a plate but it is much smaller. Will be very interested in what a small plate would n ee 2 feet x 2 feet x6 inches. Thanks !
excited to see this! I just bought a same size surface plate!
Hi Shelly, I going to start shooting the rest of that video today. I hope to have it out by xmas.
I think your audio is having some issues, Dale. Kinda "digital" breaking up. Good stuff tho.
Im trying a new mic. it sucks. :-(
interesting.. a lofty aim to have a clean area of your shop for measuring.. good luck with that!
LAUGHT OUT LOUD
im actually pretty interested to see what you come up with. everyone needs more tool storage.
Have you considered using a high to medium pressure hydraulic hose around the periphery, connecting the Bessel points, then pressurize it with fluid?? This would allow the cart to flex and still be flat.
No, I have not. it is an interesting Idea.
Good stuff. Thanks, Dale.
Thanks
I was looking for tips on how to get the perfect level for my telescope mount and this came up. I can't get my head around a 6-inch thick slab of granite bending anyway or anyhow.
In watching your episode on setting up a surface plate, here is what I notice:
1 I have a cast Iron surface plate which has 2 protrusions on one side (bottom) and one protrusion on the opposite bottom end and it is supported only at those points.
2 In setting up a small lathe (Bench top model). How should one best proceed 2 steel balls under the head stock end and one steel ball under the. tail stock end or just bolting down the four corners at the provided holes.
Great topic and project to follow👍👍👍
Thanks
Very interesting
I learned something new
Can we estimate the expected distortion error ?
Im sure someone can, but that not me. :-)
The same suspension concept is used in a variety of applications, and was standard in the days of steam locomotives, under the term equalization. I don't know if I would go for more points with a large whiffletree (as suggested in one comment), as friction and small errors in centering add up and won't likely improve support, but with a lot of complexity. Foam or floating are options, but, again come with other problems, like rigidity to maintain level and indeterminacy of support. A lot of things have been tried, and simple mechanical support is used because the advantages outweigh the disadvantages of other methods.
The concern I would have matches shadowdog: What were the supports when the plate was flattened. It doesn't matter if you are going to have it resurfaced after mounting, but, if not, then you may find some unwanted deflection from best condition.
Great comment, Thanks
There is actually a federal white paper on surface plates. It does discuss how to support a plate if the 3 points are unsatisfactory. Look up "GGG-P-463C"
Looking forward next series
It should be a fun one
For me to obtain a clean place to do measuring I would have to leave my shop, but its still my favorite place :)
LOL
GREAT VIDEO !!!
CASTERS = MISTAKE , PALLET JACK READY .
I will be addressing that in my up coming video. Thank for the comment. :-)
who says that we can support a plate on only 2 points (in one section) or 3 or 5 points on its surface? why not 10 or 20 points supported by a whiffle tree so that all points carry equal loads? Or an infinite number of points by a full area support e.g. by a fluid cushion. or a piece of foam .
Or you could support the plate on 3 arbitrary points only but then hone the plate surface flat when sitting on those points. If you dont shift the plate afterwards it stays dead flat also.
Hi Dale, have you checked if the manufacturer of the plate made provision on how to lay the plate, normally they stand on 3 points cause they were manufactured that way...
Just curious, even if the cantilever idea is interesting for auto leveling.
Yes I did and they had none. I came up with this idea a few months ago. Then found out my idea was correct when I discover that Starrett has done the same think with some of there surface plate stands
Hi Dale,
looking up the Bessel point , it appears the Bessel point (0.5594 of length) is the point of support that results in the minimum amount of centreline divergence (shortening of beam), not the point where there is minimum deflection.
the support points for minimum overall sag is different at 0.5536 of the length.
I agree that this is minor but speaking theoretically , as the discussion was, the terms are different. For a one metre beam it is only 5.8mm (228 thou) closer together.
again good work and thanks for introducing the subject.
see Wiki at en.wikipedia.org/wiki/Airy_points
Yes points of minimum deflection
I had a premonition that you would do a video on this!!! LOL Chris
:-)
What material is your beam? Is it less "saggy" than 6" of granite?
Interesting topic--keep it up!
Thanks, I will. :-)
That was a very clear explantation of Airy and Bessel points. Both these guys were geniuses of their day. The explanation with a piece of paper should be recorded on stone tablets. But there is one thing you did not mention. and it is important. When that granite plate was lapped in at the factory they suspended it on 3 Airy/.Bessel points just as you did. So the plate is flat -- as long as it is suspended same place the manufacturer did. There is usually a small indication of this on the bottom of the plate, and you would be wise to heed it. Else it will be slightly off kilter. Then there is the whole business of leveling, but I refer anyone to Tom Lipton for this. In metrology (quote Tom Lipton) *everything* matters, even if it means turning that giant plate upside down to find the suspension marks. Ugh.
Thanks for your comment:-)
Excellent video, Dale. I think your calculations would have been limited to two significant digits.
I agree LOL
Dale, a question. In the Keith Rucker video tour I think there is a lathe in the back opposite the milling machine. I dont think you mentioned it or am I wrong?
The general rule is to use one more decimal place than the least significant number in the calculation. You are using 4 places and 0 places so use 1 decimal place for your answer. The theory is the last decimal place is +/- 0.5 of the last place. In actuality you should be able to easily measure 11 inches plus or minus 0.1 inches so the answer could realistically be to 2 places.
Since I am an engineer and a stickler for detail, PIE is actually PI but I will take the first in chocolate is you please. I do think you can easily measure and mark to 2 decimal places with a pen or marker on paper.
Do you do inspection, use the plate for shop layout, or simple metrology or complex metrology or even laboratory like metrology or a mix of that? That would define how accurate you need to be in your surface plates plane.
I use it for everything. except a table to put garbage on. LOL
I'll bite on your troll food Dale. I seen how you wrote a 2 for a 3 at 5:25. Also it should be 1.8526 Not 1.8525. The number was 1.85255 and the 5 rounds up to 6. Just funning with you. Looks like a great series and looking forward to it. You do produce very good problem solving videos. Also your shop tour with Keith was a nice touch.
Hows was the troll PI LOL
5:10 The formula work with metric? and another question: how many 1/1000 inch or micrometer can flex a plane surface (in the horizontal plane) (such as your 6-inch) to its extreme edges in the worst case (like a single central point of support)?
Cool, thanks for the info.
Thank for your commnet
Now would you prices used tooling.this would be a great video.thank you for the great videos
Its a difficult subject. Because every part of the country has different prices for tooling.
just last week saw Airy and Bessel points in a 1950's mechanical drawing workbook that I picked up at a garage sale... Coincidence....? ?? LOL. Great idea to put some serious effort into the design and build of this piece.
Thanks for the comment . Im looking for ward to this build
I have a plate identical. I always wanted to put my equipment underneath 👍 I will be copying your idea🤓as your on the money (usually) 😀
Dale
I have a laser table 8'x4' that sits on six rubber inflated pads that absorb natural earth vidrations and keep it level at all times, could this concept be used with your granite plate? This table weighs 3 tons! Ian. Digitron Technology
I think it would work
What happened to Dale? its been a good while since he posted something - hope all is well
I'm surprised there isn't a 3 point hydraulic auto-leveling support. Or maybe there is and I just don't know about it.
how critical is Bessel points for a smaller surface plate like 24x18. also mine is on a table top. does this matter?
From what I herd you should be fine on the 3 points that it was originally lap on.
You're going to think I'm crazy for saying this, but did you type in pi ("PIE" in your video) and skip a couple of digits? 3.14159265358979 is what I had memorized, and it looks like you skipped the .000092! Obviously it's not important, but I am curious how you ended up with a couple of digits missing!
I call it troll food, or troll PI. LOL Good job finding the mistake. :-)
The rocker device you suggest is called a Wiffletree.
Thanks :-)
I can't wait to see the finished project and how you solve the problems on the way.
there is a FREE program that I use to help me with my own designs call Google SketchUp it is a 3D program it OK but it only works with straight lines even for circles (it default setting is 24 sides to a circle or an arc).
It's better for building than engineering but with a little thought you can get away with it and it is easy to use.
NO I don't work for Google and I don't get commission for this LoL
good insight. thanks
Thanks
I would like to see more
More to come very soon
I'm 6 years late. Oh well..
AIRY POINTS, BESSEL POINTS, MINIMUM GRAVITY SAG, AND VIBRATION NODAL POINTS OF UNIFORM BEAMS
1. Airy points - zero slope at ends - supports located 0.21132 L from each end
2. Bessel points - minimum change in length - supports located 0.2203 L from each end
3. Minimum deflection due to gravity - supports located 0.2232 L from each end
4. Nodal points of first vibration mode - zero deflection at these points during free vibration - supports located 0.2242 L from each end
I think #3, 0.2232 L is what you want. The pivot beam on one end is a good idea. Just don't put a lot of weight on either corner on that end. It will stress the plate diagonally from one corner to the opposite corner..
It's a nice idea, but as long as it was not ground and lapped with that sort of support it will not be accurate.
it will be more than accurate for what I do
Let's break out the lasers also. Yep, like where you are going. The floating beam is the best idea.
thanks
SO that's what he does when he is not staring in the flash.
Why does every video seem to talk about granite? I have a cast iron surface table and can't find much of use on TH-cam!
If your metrology will include vibration evaluation, then you'll need to set your granite slab on a bed of sand to eliminate the high frequencies which would otherwise be transmitted through th granite. At that point you could start doing your own holograms!
I did study Holograms in College. We floated the surface plate on rubber bladders
*****
YES! Highly recommended.
kind o air-bearing system, like a air-hockey table, you know ideer work,
why not just epoxy level a socket underneeth the plate, and sit it on top?
Dale, I think you've been misled about Bessel points. Bessel points are for supporting a rod with minimal change in horizontal length. Bessel points do not provide the minimum amount of sag.
The minium sag points are located slightly inward of the Bessel points at 0.2232 x length (as opposed to 0.2203).
Now while this makes little practical difference, you are introducing a concept and terminology not relevant to your goal (length change in your surface plate is not important).
www.mechanicsandmachines.com/?p=330
American PI is different to English !
I never knew that !
I can't make any comments about the engineering, but we need to have a frank discussion about what an Internet "troll" is.
interesting video.
thanks
Hej, you missed the opportunity to beat up on import surface tables not being as good as good old made in america stuff costing 5 times the price.
Why not just set the plate on a clay base within a steel container, and let the plate seek its most naturally stress relieved shape, then surface it like that?
That is an interesting idea. I don't think it will work with my project because the table gets moved around from time to time. so I don't think the clay would hold for me over the long run. if you do it let me know how it worked for you.
Pie, is a dessert, Pi is the ratio of a circles circumference to it's diameter.
Blimey Robert - that is nonsense!
Pie is a main course. It should be filled with steak and mushrooms! :)
A valid point. My mistake.
NO Pie should be Filled with Apples!
There's just no accounting for taste... :)
"Pi" in this situation was dessert for the trolls :-) LOL
My company has a granite table that is 9' x 15' and it is still supported on three points so whoever told you you cannot do that or a larger table is a liar
Misrepresenting Pi is a criminal offense in some places.
I call it a troll food or PI LOL
*****
Hahaha Good one.
Maybe troll BAIT?
there is a mil spec that tells you how to mount a suface plate it is alwas 3 piont
google ggg-p-463c this is the holy grail for surface plates this is what all plate are manifactued two
Thanks for the info
Your bad value for "pie" is good comedy, but why not "float" it on a cushioned pad to minimize stresses?
Sorry vibrations!
pie=Pi ? :-)
Troll food :-)
copy cat (just poking fun)
LOL