Surface Plates: Granite vs Cast Iron
ฝัง
- เผยแพร่เมื่อ 27 พ.ค. 2024
- Surface Plates: Granite vs Cast Iron.
A bit of history on the development of surface plates over the years, why there was a change in preference between cast iron and granite plates during WWII and some of the pro's and con's of cast iron vs granite surface plates.
Support VintageMachinery.org on Patreon:
/ vintagemachinery
Make a one time donation to VintageMachinery via PayPal:
www.paypal.me/VintageMachinery
Please Visit: www.vintagemachinery.org
Sponsored by:
American Rotary Phase Converters
www.americanrotary.com/?sld=k...
Use checkout code "Vintage10" for a 10% discount on all AD, ADX and AI converters!
If you ever decide to give up your day job, you'd make a tremendous instructor. You take the time to research your subject matter before spouting off what you've found out. You also have a passion for the subject material. Let's face it, you've been part of several machine scraping classes and I'm sure that in those 5 days for each class, not everything is, or even can be, covered. I never tire of hearing you talk about these things. Keep it up! Hope your recovery continues to go well.
That's kind of what he did. He tried from teaching a&m and runs an educational website and TH-cam channel. He occasionally works at the Georgia museum of agriculture doing machine work and such. I would guess he considers this kind of thing his day job though.
Yes, mechanical accuracy, flatness etc and temperature dependence is a rabbit hole one may never emerge from. Very good background and history lesson, thank you!
One option I didn’t hear; portable propane shop griddle. You’d have the most precise pancakes around.
If you dont need extreme accuracy, a piece of 3cm granite from your local granite countertop shop is great, pick the closest tightest grain structure you can find in the scrap 'black absolute' is one of the best but other colors work great. Ive use it for lapping and scraping parts in with no issues, ex exhaust manifolds, headder flanges, filter housing mating surfaces, carb bases, water outlets and such.
For lapping components like carb mounting faces, oil pump faces, small heads, etc I just use a plate of glass.
A friend of mine went to a company that made tombstones. He got one where they misspelled the name of the deceased, it was really cheap. He then lapped it in.
Tempered glass works in a pinch too.
@@transmaster perfect scrap material for this purpose a mistake in a headstone cannot be fixed it must be replaced, theyd sell it to you for a song lol!
I'd be careful with glass plates, they are more flexible than you might think. Also the flatness isn't that great, I built a simple device for measuring flatness and tested a pane of glass, the indicator jumped all over the place even if it seemed to be flat.
Anyway, I built a simple surface plate out of a broken granite tile (actually two, both halves were usable). The surface was somewhat ground already, but just to be sure I got some abrasive powder (silicon carbide) and lapped both plates onto eachother. The result turned out pretty good. It's not perfect, but I'd definitely trust it way more than a piece of glass.
Keith a very useful ready reckoner for Fahrenheit to Centigrade is that 61ºF = 16ºC and 82ºF = 28ºC and then just interpolate between the two sets of equivalents.
C = (F-32)*5/8
F=8/5*C +32
Straightforward conversion every schoolboy knows
@David Martin actually it's 9/5 and 5/9, but you're right otherwise.
@@davidmam I think the conversion factor is actually 5/9 not 5/8. But therein lies the difficulty because it’s hard to remember! Otherwise I’d agree with you that the math isn’t too scary.
quick and dirty for C to F double the c and add 30 ,not completely accurate but near enough plus its a easy in the head one works the other way also - 30 / 2
Negative 40 is negative 40, in both.
steve
Nice find. I was recently in a shop of an older gentleman who builds and repairs some high-end race cars, and he had a cast-iron surface plate for inspecting for damage and alignment. He said it was 10 feet by 20 feet. The side rails under the perimeter of the top looked to be about three feet tall. I can only imagine how heavy this thing had to be.
Heavy enough to influence the orbit of the earth based on where it is sitting, I reckon. That's just plain huge.
My father was a Electrcal Engineer Inspector and his standard instruments were kept in the "Standards Room" never to leave at a constant temperature of 68F or 20C. Before he retired he took me on a visit to see all the amazing testing equipment they had. The most interesting for me was a 7KW lamp to imitate the sun and a Catapult Room with a sled on rails for acceleration measurements.
German brand Holex makes cast iron surface plates still, we have a large 1meter x 2 meter one brand new at work, thats the largest they make. its like 3x6 foot. the scraping job on it is just beautiful
I love the machining videos you produce, but I'm never disappointed with a talky one. Your enthusiasm is infectious, your teaching style engaging and your subject matter always of interest. Nice purchase.
Very well stated !!
The cast iron ones are also great because you can use them as a nice fixture plate for welding.
Now how many people just cringed at the above sentence? :)
Hmm, I still have the sink plug that came out of our granite counter top and I’ve been thinking about what to do with it. Now I at least have an idea. Great video.
absolutely!! use it for typical shop needs those are really good surface plates for us hobby shop machinists/mechanics. Ive used one for years and it works great!
Thank you Keith. This was great information and well presented. It also has an "Aboms, eat your heart out" bonus on this beautiful plate!!
Nice find! I was a scraper hand at a machine tool rebuilding shop in Cleveland Ohio in the 70's. My shop had a beautiful 4'x8' scraped cast iron plate, the master of the shop full of many smaller surface plates, straightedges, and squares. It was treated as such, not used for storage, and always clean. I have also used granite, but find a scraped surface a little better for spotting, the transfer of the blue marking medium for the piece being scraped, that's just my opinion.
Semi-related. We needed a 3x4 inspection surface for 120 pound ceramic objects to be sure the bottoms of the objects were flat within +/-0.06. Unglazed fired ceramic is extremely abrasive. I have purchased many surface plates both granite and, years ago, cast iron. Anything we used for a table would be highly abraded. So standard surface pates are not suitable. Granite surface plates would last only a few days. I searched for an old worn-out / damaged cast iron plate or machine base that could be repeatedly ground back to flat as it was worn from use. No such animal in the budget cost range. I resigned to building a cheap temporary table from steel. A local shop said they had a piece of WWII Sherman tank armor in their parking lot for years. They wanted it gone and at scrap steel prices. Could I use it for the inspection table if I altered some of the dimensions? Sure. I had the armor Blanchard ground both sides so it could be flipped over when one side wore out.
Wow! After thousands of heavy parts dragged around on the table, the surface was still flat within +/- 0.0001 after 3 years. Did not have to flip it over and use the other ground surface. Absolutely amazing. I have seen cast iron and steel worn -0.01 after a few hundred heavy ceramic parts.
Too bad the project is complete. Would like to keep that inspection table for the next future job.
Yeah no doubt. Armor plating is just that, armor. Hardened tool steel essentially. Ceramic will cut or abrade most anything. Even considering the plate was designed to stop ordnance, it's still impressive it stood up to 3 years of what amounts to the worst possible conditions outside of what it was made for. Pretty awesome.
We have a cast iron one at the shop I work at. Its 4’x6’. Hasnt been lapped in years and hasnt been used as as surface plate for a long time. Mostly used as a workbench now. We have a few smaller granite surface plates for inspection use.
You never really gave me the WHY but THANKS for the vid
Great information Keith, learned something new about the difference between those materials. Concerning the moving cart, use large wheeled castors that won't get hung up on small bits left on the floor. That thing has "top heavy" written all over it. Pretty sure you already thought of that but a reminder doesn't hurt.
A very sentimental old master, salute
Glad you're feeling better, sir.
Nice score! I use my cast plate for most of my work and only use my granite for the fine stuff.
Nice to see you coming along, Keith. The lesson on surface plates - Most informative and interesting.
I know of two HUGE Starrett granite surface plates that have been sitting at an abandoned machine shop site, outside in the Iowa weather, for 30 years. The small one is at least 4' x 8', and large one substantially bigger. Check out 41°58'34.24"N 91°35'10.93"W and zoom way in.
A great video Keith! So much information about the merits of cast iron versus granite surface plates. I've only room for a 12" x 12" granite in my tiny, tiny shop 7' X 5' yes that small in which I have a 12"x 19" lathe with a milling machine attachment. All the rest of my machinery is outside under cover lol. When I used to be a teacher we had a brand new 24"x 24" cast iron surface plate on a cast stand about 38" high and apart from myself on personal projects I only ever saw it used a couple of times by students. (My head of department taught the senior year examination students ) now it has probably been scrapped along with a 9" Viceroy Shaper, and a Tom Senior Horizontal mill that I was the only one to use. ( until I left of course) there were also 4 , 12"x and at least 24"lathes. One with a vertical milling attachment. Again I was the only one to use it in the 10 years I was there. All probably scrapped or just sold off. What a bloody waste!
The place that I work at has many of these. One was headed to the dumpster, so one of the guys grabbed it for a welding table. It's the size that you have.
I saw a 4x8 iron plate posted locally for scrap cost. I believe it was several tons and stood at bench height without legs.
If I had room for it, I would own it for the simple fact they look cool. Until i have more room, my little bench top iron plate will do.
I picked up a 16" x 16" cast iron plate with a wooden cover from an auction. I wasn't planning on buying it, but no one was interested and got it for next to nothing. As i'm a novice engineer, I have yet to used it in anger, however there's been several times when it's been useful for lapping on emery (had been using glass). I doubt it's accurate, but well within the tolerances I will be doing.
I'm really hoping Adam finds something similar and Keith would be willing to do a swap, to keep a tool that gramps might have used in the family.
Very interesting information.
I love Cast iron.
As an engine builder and working with Cast Iron for more than 45 to 50 years I have come to appreciate and understand the value of cast iron.
Remarkable how durable and resilient Cast Iron is.
That is a Beautiful piece of History your new Cast Iron Surface plate.
What a conversation piece.
Thanks for sharing.
Take care, Ed.
Great video Keith
my dad was a Fitter at the same iron works as I served my time as a sparks . away I digress the fitting shop had the old fashioned oak block floor end grain up set on pitch ( nice for the legs and does not ding your tools ) the surface plate was some 20 foot by 12 foot and was constructed on a raised concrete slab, said to be six foot deep, the interesting thing was the cast iron top was made up of separate CI cubes about 1 * 1 * 1 foot , it was used to sett up for machining large casting for the items they assembled , the overhead crane had two blocks one 5 ton and the other 20 ton ( that's 2240 pounds ton ) , I never knew how good it was
Thanks for the information. I have a small benchtop cast iron surface plate in my shop. I love it and use it all the time. Mine came from England, and is in great condition. I always kind of wondered how granite and cast stacked up against each other. Glad to see your recovery is going good. God bless you and your family!!!!
if I was doing a scrape job that had to really be close (say a P&W jig bore), I would always try to use a cast iron plate. I have always felt that cast iron rubs better than granite. Probably just me, but granite tends to smear the blue rather than simply hit the high spots. Still you can do quite well with granite if you know what you're after. Most people use way too much blue on the granite surface. Still for something really big there's usually no other way. I most always rubbed my strait edges off a granite plate that was cut to a certain contour (extremely important) but would be out of spec when measured.
Most folks start off on a bad footing when they start a scrape job (or lap a granite plate). Really big ones are never moved, so you have no real choice in the matter. Anything smaller than a 6' x 9' was brought to my shop, and I'd let it set for two or three days. Cast iron is easier and you can start on it in 24 hours. A machine must be leveled and then tweaked in till the bottom axis is as strait as you can get it. I might add here that I usually did this with a Federal Electronic level, or at least a laser (the electronic level is much easier). Sometimes it takes the better part of a week to get this done as the machine will change everyday. I once had a Devlieg jig mill that took a solid three weeks on the x-axis alone. Still the numbers were a bitch before you started (.000020" in 12 feet). After you level the base everyday, you can start on the next slide and rough it in. Once it quits moving you can go to work.
In the shop, I always had three or four strait edges to scrape, and several cast iron parallels. Angle plates can be nasty to do if done right. You need three angle plates to master off of, and this alone is rare. Yet they numbers are easy. Small ones (6"x 6") I had, but a big one I didn't. My master angle plates (a wooden box of five) were kept locked up and never used. My final check for squareness was with a 12" callibrated cylinder square.
"The Fundamentals Of Mechanical Accuracy", is simply one of the most fascinating technical books I have ever read. A must read for any machinist indeed just about anybody fullstop! Thanks for the great video
Looking good Keith! Thanks for the info. I wondered about the differences.
Thanks for sharing some very good information. I usually learn something with each episode you publish.
Friend's dad owns a "Machinery Rebuilding" place...OK, so they USED to rebuild A LOT. They now do more reselling and sourcing than anything. He has two MASSIVE surface plates, one is Cast Iron and it HAS to be at least 12 x 10. He said he got it out of the tank plant in the 80's when they no longer needed it. He also scored a MASSIVE (again, at least 12 x 10) Granite plate. I mean, i've NEVER seen something that big. He has had people look at the Cast Iron plate, but not the granite...at over 20 Tons the Granite plate is SUPER impractical for almost anybody anymore. He jokes that he's going to turn it into the family grave marker. I couldn't even imagine having that kind of hardware, even when I did small end machine building.
I do want the PM lathe he has there, but his son constantly says "No, that's mine". His dad continues to say "I'm going to sell it to him if you don't get it the h3ll out of here". BTW: He's closing the shop this year or next. :( Maybe I'll go over and see what kind of goodies I can get. :)
Great video Keith, keep'um coming..
Great content. Thanks for posting, I learned quite a bit
Great tutorial for me Keith.
Thanks for sharing.
Really interesting video cheers Keith
I really enjoyed the historical context in this video. I also liked the way that you worked in the macro shots of the surface plate details and the pages of the book. It must take lots of time to edit those details into the video, but I feel that it really adds to the quality of the video. Thanks again for the great content!
Thanks Keith. Great explanation!
3:43 - Good historical analysis.
5:03 - Problem: That level of accuracy is of value to those who are designing and producing very long-range optical instruments, and no one else outside of bragging rights. The trees got you again, Keith.
Always wondered about temperature change and stability.
Keith, very much enjoyed this ‘lecture’. Thank you …
You look really great Keith! Thanks for posting this, very informative. I have both types in my shop.
Very cool video thanks for sharing
Wonderful! Thank you Keith!
Good to see you still crankin out the videos!!!! Go man, go.
I watch Indians and Pakistanis do some ummm “interesting” repairs with welders and lathes….i would LOVE to see Keith comment objectively on those videos!!!
@@RASAllusion, Some of those videos are fun to watch, it’s almost unbelievable some of the stuff that they rebuild. They’re not afraid to work, that’s for sure.
Thank you for sharing. Enjoyed.👍
Excellent fine gorgeous piece of castle Love to find one of those thanks for the video
Well Thank You Keith for the demonstration of the different surface plate. Good topic and good video
I read "Machine Tool Reconditioning" by E.F. Connolly back in the eighties to check and correct all my machine tools. It's the best I ever read, probably similar to the one you show. When I got mine, I found a "carpet sample" at a flea market that was an exact fit for my 18 by 24 plate. I've had it for almost forty years, very handy to have for general machine work and for testing/try fit of precision fits. Before I found the granite, I had an apron from a large lathe, about three foot by one and a half, I scraped flat and true, used for ten or fifteen years.
Loved this video. It was a walk down memory lane for me. During the 1970s I worked for a UK company that made cast iron surface plates. 10"x 8" through to 48" X 24". Yes cast iron is a very messy material to work with.
I'm sorry to say the company has been gone for many years now.
That book is an incredible source of information and is a fascinating read. Nice to see it being mentioned here. I enjoyed this video, thanks for producing it.
Sadly, two or three of these went to the junk yard from the place where I used to work. Nobody wanted them. I did, but had no place to store them. These are good layout surfaces.
Enjoyed the video nice to know why there not a lot of cast iron surface plate
Around last place I worked at they put it in a storage build , had stuff piled on it
Thanks for the history lesson Mr Rucker 👍. By the way it reminded of Dan Gilbert, he built the ways of his lathe out of granite.
Until I started watching your videos I had never heard of surface plates.
Keith, when I was a youngster, car
enthusiasts used to LIKE engine
blocks from a car that had
experienced an engine fire, just
because the heat had removed
all the deformation. Yes, it needed
machining, especially the main
journal area, and the cam area.
Cast Iron is an interesting animal.
I'm quite a fan of the OLD ShopSmith
multi-tools. They used a LOT of Cast
Iron. (The sign in for the Model 10,
[10e and 10er] Forum, is Cast Iron.)
steve
My first job out of high school was for a machine tool rebuilder. They had a big granite surface plate, maybe 10ft long and a lot of cast iron plates of all sizes. They had precision lasers, precision levels all kinds of camel back straight edges... They also had a huge Favretto way grinder that they would use on big machines. When they needed to do precision measuring it was on the granite. When they needed to scrape in ways, tables or parts they used the cast iron. Every now and then they would do the 3 plate scrape in, to recalibrate them. I learned a lot there but I was a stupid kid and changed jobs.
Just ordered that book you referenced. Very expensive but right up my street. I remember my dad telling me that cast iron plates needed to be made in threes. My cast iron plate is only 12” by 12” and would have been purchased second hand in about 1950. When i get my precision ground stones i will certainly check for any high spots although the plate has a wooden cover which both my father and i have been careful to always used. Very interesting video!
As always a very informant video from Keith.. He is the man to look to and contact when you you need the facts from the way back in time and what we also what is acurate today when you are working with heavy machine's for your machineshop.
Great video! If one wants a welding table, two words... ACORN PLATE!!
Having a small home shop I cheat and use my cast iron table saw surface. I found this flatter than the granite "scrap". I have also used a wing of my 8" jointer for longer items. For the very few times, I have needed an accurate surface this has saved the day.
Thanks - I learned something today!
This was really interesting. I had the chance to install some signs at an aircraft parts manufacturer a few months ago, and they used a granite plate as a reference but had an old Air Force 6ftx12ft cast iron surface plate for absolute accuracy. It was scraped to an overall flatness of 1050 (grade AA). For reference the highest grade I've ever heard of is a 1100 overall flatness, I don't know if it's even possible to make one better. They said that using the cast iron plate is required by the FAA for absolute accuracy in turbine parts, since they are machined down to a +/- .0005 threshold. I honestly thought cast iron was inferior until they explained that in a climate controlled room, it needed less maintenance and was easier to clean. The only downside is that it should never be moved once installed and flattened. even a grain of sand under the leg can throw it off over time. mainly because it deform the feet and cause raised edges that will make it unscrapable until the feet are remachined flat.
That book is listed, used, for $500 to $1000! Craziness. Moore Tool sells it for $150. No idea why the used market is so inflated.
With all the new equipment Abomb 79 has in his new shop, for you to get something that has him envious is saying something. Lol
That looks just about perfect for building model aircraft on, I need one of those!
Thank you for the info. I never have or never will use a surface plate but I like knowing the differences.
I picked up a tablesaw wing from work, almost
2 feet by almost 3 feet. Cast Iron, and I don't
know what it came off of. If I can get it to
within 0.001, I'll be happy. I will not need much
more tolerance than that.
I work at a woodworking store that sells
machines, and hardwood lumber. I repair
(customer's stuff) and refurbish (consignment
stuff.) I ALWAYS hit the top of a tablesaw, with
a fine stone I have, just for that purpose. I see
the same exact thing you have shown, where a
burr was kicked up. I do NOT like sanding down
the whole table, especially if there is a shiny
patina there. That stone doesn't harm the patina.
steve
We have loads of medium size cast iron surface plates at my workplace, they're used for inspection near the machines (mostly with a height gauge and some jigs for the parts), and if you need more accuracy we have multiple CMMs for that.
No sir, you can cause a localized swelling on granite plate. Doall makes a small black granite gage block stone - used to remove positives. Iv'e use to stone down around such divots on black granite. They are known for being softer than the pink granite, for instance.
Thanks for your informative comparison of reference surfaces.
Thanks Keith you are looking good . Hi from the land down under
Good video, nice new toy!
and I see there that wonderful book... such a fantastic read about "how to start a machinery manufacturing company" without meaning to be so. It's worth noting also that another factor wher cast iron outperforms steel is vibration damping, which is another good reason to use it for building machine tools
How interesting that cast iron maintains flatness better than granite over temperature changes!
I always thought of granite as being immune to thermal variations, the fact that it isn’t is really interesting to me. (Not that I’ll ever do anything that even a grade B plate wouldn’t be massive overkill for, but I’m a measurement geek, so so this sort of thing is fascinating to me 😁)
Thanks for a great video as always!
Quite so. Even moving a granite to a different location on your shop floor, or jacks under the plate require calibration to assure plate is still to desired flatness after relaxing into new location. We're talking millionths here. Wouldn't matter for what I was doing in my shop; mattered to the aerospace shops I've worked in.
Hi Keith Very nice
I had a very talented friend who served his machnists apprenticeship at the old Frankford Arsenal in Philadelphia. He said they would place raw cast iron on the roof for at least a year to think he said to season it. I have done electrical work in machine and tool & die shops and amazed that they had a company to come in once a year to check surface plates and place a dated sticker on them if they passed. Never saw a cast iron surface plate. Great vidio.
Rough castings right out of the sand are FULL of stresses. Either you "season", as Frankford did, or you employ sophisticated thermal cycling, like Clarke Easterling does.
You got the trifecta. The brass pin made the difference. I'm kind of a shiny tool guy, but the bluing made it look original but didn't hide your surface finish. Great job!
Temperature is a constant that effects a lot of measurements,the set of gage blocks are most accurate at 68*f according to the information on the sheet on the box
Working at Kearney and Trecker I can attest to the fact steel weldments were a different animal. Cast iron was more stable, as machines would heat up tolerances would change with the steel til it leveled out.
Keith, I'm sure the past weeks have been hard physically, but I must say that you're looking really good. Recover on!
Well done Keith on beginning your weight-loss journey. I lost weight, 110lbs with KETO. A word of advice. You will get heaps of loose skin. I strongly advise you to start a weight lifting program as soon as you fully recover from the surgery. You are never too old to start at a gym. About 30-40 minutes, 3 times a week is plenty. I went back to the gym at age 50.Now as a 56 year old, in certain lifts (the squat) I not only keep up with the kids, but outlift them.
Nice !
I have a little 12x18 cast iron plate. I was told the smaller ones were used to drag across the larger ones, but I have no idea whether that's true. I like mine--similar patina to yours. It came with a nice wooden cover already built, which makes sense, since it came from an old boatyard.
The Abom connection is wonderful…
It would be interesting for you to demonstrate how to use a surface plate for inspections.
Many years ago the shops I worked in we used the surface plate to do layouts of one off or small numbers of parts.
Interesting!!
Saw a plate similar to that one in a navy small engine shop. was used to measure heads for warpage
60°F equals 15.8°C. In Germany, a temperature of 20°C (68.0°F) is considered the reference temperature (Maßbezugstemperatur).
I use mine as a welding table. I coat it with anti spatter gel. I don't weld to it, just weld on it. I cleaned my medium rust off (when I got it) using paper towels soaked in vinegar. For the metrology I use a granite plate. I think my cast iron plate is 18x18.. It weighs quite a bit.. I think about 80lbs maybe more. I would like to clean up the bottom and paint it because it's out in the garage.. but I've had it for so many years and have never gotten around to it, and probably won't.
You should restore it and give it to Adam booth, it would mean the world to him.
Very interesting that granite plates became popular in the USA decades before they did in the UK. I never saw a granite plate in any of the engineering works I worked in until the 1990's. Even then it was only really the beds on CCM machines andi think there were a couple in the metrology lab. Crown Windley still makes cast iron plates in reasonable numbers now but also supply granite as a lower cost option.
Very interesting. I wouldn’t have guessed that iron was better.
I have two cast iron surface plates and one granite surface plate. Your testimony to cast iron makes me reconsider the value of my cast iron. My last CI plate is small and was an auction purchase whim ($7). My years in the shop was entirely dismissive of CI. I suspect my "oldest" CI plate is low accuracy. It includes T slots. I don't know its original purpose. I thought it was a cheap investment into hobby shop capacity with machinery that couldn't boast high precision due to its inferior design, age or use/abuse. I own some of this level machinery in my hobby shop. I have often wished that a surface plate had mag base functionality. Maybe it is time see if my CI plates warrant more affection.
I was thinking Adams Grandfather could have used it also. And another advantage is Granit doesn't rust.
Never thought about cast iron as a surface plate but it makes sense. It is a very stable material.
On a side note what has happened to the large Dresser band saw restoration?
Thanks for sharing.
KEITH GREAT FIND, GLAD YOU ARE DOING FINE, TELL ALL HELLO...SEE YOU WHEN...
Book arrived safely in johannesburg on 27/1/2023. Most expensive book i have ever purchased!
Keith,
If an object is high in the middle and low at the ends, it's referred to as hog. If its low in the middle and high at ends, it is referred to as sag.
Bob
The book is available on order from Moore Tools for $150 USD.