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- เผยแพร่เมื่อ 3 มี.ค. 2018
- Part 1 of a series of lapping my 3' x 4' master pink surface plate.
You will be following along as I learn as I go on this project. This covers using a precision level to determine flatness and lapping techniques.
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A lot of people here are watching your videos 2-3 times over again, don't be worry about video speeding up :) . Thank you for your time to make this masterpiece videos.
I uploaded a new version with fixed audio. thanks for watching and commenting.
Your thought processes are the most valuable parts of your videos! Please continue to over share them! :)
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Robin,
Having just done my plate and gone down the same learning curve you are now showing us I want to say you are precisely right on track. There are faster methods but they require experience. The most important part of this process is to have the tools to measure the surface know what the lap is doing and working out what you need to do to head it in the right direction.
I was using a 10 X14" cast iron slotted lap and did my roughing wet. I tried a number of methods but found simple water was best with the slotted lap. I used 40um diamond grease suspension that comes in 10cc syringes (5 for $8 on ebay) and as you say a combination of charging the lap as you are doing and just letting the particles roll works best. Various stroke directions as you are doing but a figure 8 stroke rotating the lap about 45° degrees each way gave the best results for me. Finish lapping was done dry with finer diamond. The grease is not a problem for the wet lap but complicates dry lapping, a bit of acetone took care of the grease leaving just the diamonds. I was happy and quit when I got it to a 24"X36" grade A plate verified by a 0.0002"/10" level and the repeatometer with a 50 micro inch indicator I made for this project. A good 36" strait edge was a big help in the roughing stage.
You comment on and I was amazed to see how much my concrete floor flexed from my weight as I walked around the plate checking with the level!
Normal video speed please I am willing to watch what you produce.
Your lapping and measurement process is correct and I am sure you will get the results you are looking for.
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You could slow this down to 1/4 speed and I'd watch every second...four times. Thanks for sharing!
I uploaded a new version with fixed audio. thanks for watching and commenting.
High precision work is all in the finer details, appreciated...
Best, Pierre
Thanks Pierre, and thanks for watching and commenting.
ATB, Robin
TIL a shit ton of stuff about lapping. Thank you for this real quality content. Many people can learn from you in this format. I'll follow this, definetely!
Super stoked for this, precision toolmaking (or tool reconditioning) is really cool
I uploaded a new version with fixed audio. thanks for watching and commenting.
Awesome help. I have had a set of lapping plates for years, and did not know what they were truly for, (thought they were for lapping diesel injector parts)! Now I know they are for lapping surface plates. Now, all I need is to get a granite surface plate!
Thanks Robin; fascinating as always. In this 'hi-tech' era of lasers and CNC, it never ceases to amaze me that a guy in his garage manually sliding two surfaces against one another can deliver a degree of precision eclipsing anything the 'hi-tech' stuff can.
the guys in the large companies do it the same way.. and no .. certain machines can reach few nanometers level precision which is impossible by hand especially on more complex surfaces (*curved surfaces).. lapping is lapping.. nothing to do with "hi-tech" stuff
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Thanks for the excellent videos Rob!
A few years ago I lapped my old 1960's or so English made, factory hand scraped 16 inch O.M.T. optical rotary table with a Chinese 9x12x3 inch grade AA black granite surface plate off eBay and the rotary table platten showed up significant flaws in the surface plate!
The dry bare granite was doing the lapping and I just rubbed in circular motions whilst the table rotated slowly and it showed that the surface plate or lap had four low spots or grooves in a kind of swastika formation about three inches in from the corners where the plate lappers had somehow ground or abraded it in four 90 degree directions. After lapping the rotary table, my new surface plate was visibly polished and smooth with no significant surface defects or low areas and the steel rotary table was also polished to a bright finish on the high spots left by the original hand scraping.
Due to other priorities, I never did run an indicator on the table as it rotated but I wouldn't be surprised if it showed zero tenths of vertical runout apart from the scraped low spots. Even the base of the body was hand scraped flat. The overall quality is mindblowing compared to anything more modern that I've seen. I have another old O.M.T. 12 inch optical rotary table that reads to 30 seconds of arc on the scale that can be imagined down to 5 seconds and the 16 inch scale reads to 1 second or even less if you mentally split it. The only problem is with how they are used as they were designed for inspection and you need to zero the optical readouts once you're in range and deduct degrees of rotation from a known datum or reference point, presumably to measure deviation from standard at varying locations on a part like a ring gear tooth. The scales look like they are chemically or lazer etched into glass like D.R.O. scales but obviously circular and illuminated by a 12v bulb, viewed through a lensed eyepiece with focus adjustment. They're built like lab microscopes. God only knows what they would cost nowadays but I paid about USD$150 each or GBP£120 for the 12" and £100 for the 16" in English money. One day I'll make some videos but don't hold your breath.
Robin, I appreciate you videoing your work here even though as you stated, you've not done this before. Still very appreciated! :-) If I ever own a surface plate this large, I'll die happy :-D
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Thank you Robin !!! The way you teach is "OUTSTANDING" !!! and having the vernacular to express your point without putting everyone to sleep.
The BIGGEST problem with shop people is "TRYING TO FOLLOW THE BOUNCING BALL" ..when they are trying to convey a point, thought or action. They lose ya with all the grandstanding and 90deg tangents ...or simply lose you from A-B .
Good Job !!! (im ur biggest fan, yo)
Thanks for the kind words.
With no attempt at flattery your uploads impress me the most within the scope that precision in mechanical systems are paramount. Thank you for your persistence both in actual work content and clarity of video presentation. I eagerly await the continuation of your efforts. My humble kudos for raising the bar on TH-cam offerings.
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Just got my surface plate re lapped at work today and came back to this video 2 years latter, officaly a journyman now. Goahdarn robin, I finnally know enough to watch your videos, and am happy. thanks for all of the great info!
Congratulations!
At this rate you should be a expert by the time I am ready to do my little surface plate. My primary interest in this is how you are checking the plate. I am hoping that I can apply some of these principals to check my own with the metrology that I have on hand. Great video.
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Thanks for being aware of the time. Your information is priceless and I always watch your posts more than once. All the explanation of thought process is appreciated. Starrett will be able to use that thing as a master when you're done.
Not a single nit in your wit Robin!
Quite the contrary, you're one of the biggest brains in TH-cam machining!
Thanks for another wonderful series!
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Ah I love this stuff! It is going well with having begun to read Foundations of Mechanical Accuracy. Thank you for sharing.
Thanks so much for the great videos!
Thanks for your keen incites. The way you deliver your thoughts is very well organized and comprehensive. Your passion for accuracy is a joy to watch. Thanks!
Love your channel, love the fact that you share with the world and " us " all that know how that you have. Keep it up Brother. GOOD LUCK and have a Great year...:)
Absolutely can't wait until the next video. Thank's Robin!
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Always enjoy your videos. Thanx for sharing
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Thanks Robin, great vídeo.
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I'm very much looking forward to this series ! Thank you for your time and energy to make these videos.
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Very educational - of course thanks for posting!
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Thank you for sharing! I can't wait for part 2.
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Thank so much for sharing and showing your thought process.
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Great video thank you for sharing your thoughts and experience throughout this. Keep them coming. 👍👍
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I really appreciate your motivation to restore and re-purpose things. I have acquired lots of good stuff just because it wasn't worth someone else's time to repair. Bravo! It's very motivational.
You needn't apologize for your unfamiliarity with "Approved technique". You know exactly what you're doing. "pros" often cut corners to get the job done. Hence "professional" only means you do it for a living, it dosen't make one an expert.
Lastly, I STILL want to know how you do your little half moon stroke when scraping!!!
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Excellent video Robin! A great approach to presenting the information and your commentary was spot on.
Paul
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Robin, fascinating video. Good idea for a multi-part series. I am looking forward to the part 2! Having watched Tom Lipton, and others discuss surface plates, yours is a DIY take, with good explanations that I can understand! Thanks!!
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Hi Robin, as always lots of golden tips and tricks, a good old lapped thumbs up to you.
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Good work, looking forward to the next segment.
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Great stuff as usual. I am amazed at how quickly the fine diamond abrades the stone, especially at such low contact pressure.
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“Fast” “ quick” are really relative terms but I thought the same. I was surprised when I saw all the dust being wiped away.
Robin thanks for the lesson keep up the good work.
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Oh man what a beautiful surface plate. Thanks for putting all the time into editing to save your viewers
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Stellar way to start the week, thanks for your work Robin. It's great to get a glimpse into the art.
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watching you is always a learning experience
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Thank you for letting us go along with you on this adventure. The chance to experience your real time thinking about what it is you are trying to do, what is actually happening as you try to do it and as always the wealth of knowledge you bring to your work is very unique and much appreciated.
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Excellent start. I see complaints about the sound but personally I don't see an issue. Looking forward to the next stage.
I uploaded a new version with fixed audio. thanks for watching and commenting.
This is great Robin ! I am going to watch these videos again. I have done diamond charged lapping of small parts many times over the years, but I have not done big surfaces like this, and I am learning from your journey. Thanks Cliff
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ATB, Robin
Very helpful great explanation. Thank you for sharing.
Thanks Randy, and thanks for watching and commenting.
ATB, Robin
I can watch your videos a 1000 times over and pick up on a new something every time. I've seriously watched several videos 5-6 times thru; so I completely caought every detail and center my mind in to the train of thought. Looking 20 steps ahead rather than 1 step ahead.
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Very informative Robyn. Keep it up. Can't wait to see the renzomeater in action.
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Absolutely brilliant, Robin! Your approach of letting us hear your thoughts as you are going along are phantastic. This is REAL teaching.
While I think you are courageous going beyond what the "experts" think is unfixable - it is right up my alley. How else can you learn?
Sometimes it is not sensible to fix things experts don't want to fix, but everything can be.
Thank you for making your experience, knowledge and logic accessible to mere mortals!
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Thank you for the video.
Robin, yet again, as mentioned below, the bar has been raised. Also the pace of this video was just right for me and i know it must have taken extensive editing to get it where it is. Really looking forward to the next parts. Thanks for sharing. Kindest regards. Joe.
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Looking forward to the next installment :)
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Thanks for the video Rob, following with interest..
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It may be more educational and is more interesting to see you work something out like you are doing. I'm looking forward to the next video! Thank You for taking us along!
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This is very interesting indeed. I am planning to build an epoxy granite CNC with as much precision as possible, so understanding the various techniques for machine tool surface flatness is crucial. Many years ago I hand ground a telescope mirror. At the final point of correction I got frustrated and paid my friend who was a master telescope optician to finish and figure it. In the ATM community it is well known that getting something absolutely flat, near optically flat, at 1/4 wave for example is very difficult. For this reason, the majority of builders buy their secondary mirrors. From what I have seen of other videos demonstrating surface plate lapping, it seems making a telescope mirror is much easier.
Information density is appreciated! That granite plate is going to be fantastic!
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really good video robin, all you said about the concavity the convexity and the overhang. a lot of good stuff in there and cant wait for the comments list to grow. there'll be some good stuff in there for sure. and for the Renzomiter to come into play. never seen that done before real suspense that's gonna be a niiiice plate
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Looking great, Robin!
I quite enjoyed the sped up video/audio aswell, eventhough it's easy enough to do with youtube already. Anyways, looking forward to the next video, this is great learning and I might just have to try out and lap my own plate - eventhough it's just a small chinese one.
I uploaded a new version with fixed audio. thanks for watching and commenting.
i see whats going on, i might do mine some time.
i learn a lot, thank you.
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I have been waiting with bated breath for this video.
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fun to watch. not sure ill be doing this. (unless i score a free starrett master pink plate) interesting to learn about too.thanks for taking the time to include us.
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very interesting as always, anxious to the Rensometer
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I’ve got a granite surface plate that size that needs 2 tenths worth of lapping, this could be the video to get me onto it. Thanks Robin I like the speed up thing too.
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Excellent video! I learned a lot of small details.
one thing that also surprised med when I lapped the one granite plate I have done was the speed of material removal. I applied the coarser diamond and it didn't take long before most of the surface was even within the tolrance I wanted
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Very interesting! Almost so I want to buy myself a worn out plate (again)..
Sir you're attention to detail is unsurpassed. Absolutely critical. I really enjoy your videos. You never overlook anything.. question, could a sine bar have been used as part of the level apparatice?
It would not help with flatness measurements but there are levels like that that are useful for other purposes
Thank you Rob. Great presentation. and head up for video speed.
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Good stuff. Not boring at all. I prefer dense videos.
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I use add-ons to speed up everything i watch. appreciate the effort
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Great training video, Yes I will be following along but it seems like it will be hard to keep up with you, there is a lot to take in. Thank you.
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Man you just made my morning coffee taste that much better. Kids are at play group and I can actually think about something technical thank you. Nothing is a secret black box and that's why I love your teaching style. I only noticed the speed up sound maybe 1/3 esp the charging scene of the video the rest sounded normal. Question about the differential level. Does having the big heavy lap on there effect your readings? Does the counter weight have less effect the closer it gets to a support foot and the level further away. Great video keep them coming!
I will cover this in a follow up video. Thanks for watching and commenting.
I can appreciate wanting to cut out time, but it seems like there might be some kind of aliasing or other artifacts from the speeding up process, which were a bit distracting
I uploaded a new version with fixed audio. thanks for watching and commenting.
2:50 ("blink density") ...that's awesome and what I'd aspire to if I ever get into making more instructional videos. That's probably why I had a slightly hard time at 2x speed and had to slow down to 1.5x to catch more of the words. :)
Nice video -- if nothing else you don't need to go the the gym tomorrow.
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This, as all your YTs is incredibly informative. I don’t imagine I will ever need to do such a project, but it is very informative. I found myself wondering, if it takes this sort of effort to bring that surface back to true and flat, how is it used as in a shop that makes it go unflat and not true? Hard to imagine it is roughed up in normal practice. I suppose abuse can happen, but I would think that piece of rock isn’t cheap and abusing it by, I suppose, a crew using it as a perch during lunch time, might be grounds for mass dismissal.
If you had asked me before you moved that weight, I would have said, “Yes, of course the bubble will move,” but in the back of my mind I would have thought, “And pigs can fly.” But danged if that bubble didn’t actually move a tiny little bit.
Following your journey.
Hi Forrest,
Somebody posed a question on the other video (the fixed audio version) about whether the CI lap sitting on the plate will mess with the level readings when used to gauge the shape (not level) of the plate.
My answer to him was this: ''I guess you're asking whether the elastic deformation form the weight force of the CI lap sitting on the plate and the subsequent spring-back when it's removed affects the measurements taken with the level regarding the shape (not level) of the plate? I think the answer is it's there, but it's literally negligible.''
Would you agree with this?
Lite Roadie Yup. Work the big details first but plan ahead for the little ones when the time comes.
Watch Robin. His self deprication doesn't fool me for a minute. He will work out every last detail and flatten that plate within an inch of its life and tell you how he did it.
You all realize the cast iron plates he started with were hand scraped to full bearing to small tenths. They'll have to be re-ground and scraped again before they're usable for their original function. Robin sacrificed his painfully developed precision surfaces to work down that 3 X 4 granite plate. In the end he will have a $2000 Grade AA granite plate for free not counting ten hours of damn hard work plus the tools he had to make plus the re-condition time for the CI plates he used as lapping tools.
Which poses the question: what's your time REALLY worth?
Thanks. I'm a big fan of your posts on PM. I especially liked the one about drill sharpening (lifting the whole drill on the wheel to get the relief as opposed to ''dropping'' the shank) and the ones about the two collar method, making two matching diameters concentric with the spindle axis and running an indicator to read the angle as opposed to taking a cut on the same setting and measuring taper).
Hi Forrest,I have not used those plates yet and may not. That plate is an auction piece and I am using it as is.
I can't wait to see the Renz-o-meter. How are you accounting for the movement of your body weight? If you put the level in the middle of the plate and walk around it, you should see the bubble move all over. Even in my shop with a 1600lb plate and 8" floors, you can see it move just from my weight on the floor. A true differential level or autocollimator would account for that.
I will cover this in a follow up video. Thanks for watching and commenting.
I know everybody seems to dislike the audio artifacts from the speed. While maybe I'm alone in appreciating that effort, perhaps there are other ways to compress your content if that's what you want.
If you want to make the recording more dense, instead of limiting your editing to the comprehensibility limits of fast audio, you could just do some of your narration as a voiceover or as occasional text annotation. Doing these things in post would both allow you to work freely without needing to keep chunks of video unedited because they were full of narration, and it would give you time to make your statements as concise and pointed as you want them to be.
They say hindsight is 20/20; narrating/annotating after the performance takes advantage of this.
I uploaded a new version with fixed audio. thanks for watching and commenting.
Wonderful. Two questions: 1- weight of the cast lap not throwing off your precision level? 2- How do you uncharge your lap (for changing to a lower grit and/or not ruing your cast plat for printing)?
Superbly done Robin, well done. I'm looking forward to seeing the next video.
A minor point, but one worth mentioning as I see this confusion coming up constantly in forums. At 08:00 that measurement doesn't indicate the plate is "straight", flat, or much else really. It merely indicates that there are no local deviations along the path that indicator ball travelled. The very same test could be done on a precise sphere and it would provide the same results. That test is similar to the so called "repeat" test, something that I see confuses many people who feel a plate can be tested for overall flatness with merely that test. Robin explained later in the video why that is not so.
Bravo for showing the effects of a level's own weight Robin. I have had many "spirited" conversations with people over the years, many very experienced in the field, where I have insisted that a surface plate cannot be calibrated with a single level. That was a large plate on a solid stand, yet the effect of the weight of the level was quite significant and if the level's reading was taken alone as gospel would provide a completely inaccurate picture of the plate. Even Taylor Hobson produced a video showing a surface plate being "calibrated" with a single level, a point I took up with them where they confessed it wasn't a valid test. Why the heck they would therefore produce that video is anyone's guess. A counter weight would certainly help at a pinch when roughing and was an excellent idea.
The "proof" you seek is provided by Robin in his video and correlates with both my own experience, principles of metrology, and just plain basic laws of physics and logic. The level has a certain weight and that will cause the plate to tilt as the level is moved around it, as you stand in a different part of the floor, etc. Everything is compliant, it is only the extent it's compliant that will vary. How much will the plate tilt? Pick a number. You won't know without a reference. That is why differential levels are generally used to calibrate surface plates these days as they measure the difference between one level that remains stationary and the level that is actually doing the measuring. As the plate tilts the stationary levels provides the compensation. This effect is not, as some might suppose, insignificant, and a good level will resolve the flexing of a thick concrete slab as a person moves around it.
The grade of plate is irrelevant, as the measuring technique is invalid. A surface plate cannot be "calibrated" or properly measured with a single level, end of story. Robin knows this, and as he explains he helped to compensate for this effect by providing a counterweight. That is also not a valid technique for actual calibration, as he clearly stated, but for roughing in would be good enough and at least acknowledges the effect.
Electronic differential levels are horrendously expensive, although it strikes me as entirely plausible for a smart guy like Robin to fabricate some form of optical comparison setup to look at a conventional bubble in standard bubble levels. An alternative that's not too expensive is to autocollimate the surface, which is what I have. It is independent of gravity therefore won't be affected by the plate tilting. It does take a long time however. The modern differential levels are interfaced directly to measuring software and will calculate the Union Jack errors with a simple keystroke at each measuring point.
Do what you like mate, I couldn't give a shit quite frankly. This is not a court of law and I don't have to "prove" squat. I had you figured immediately as a nothing more than a troll, thank you for proving that. I very clearly answered your "question" with my initial answer.
I explained why a single level can't be used to calibrate a surface plate and if that's not good enough for you then stiff shit, I couldn't care any less how "comfortable" you are or aren't. It should be obvious why that's so, and if you can't understand that it's no skin off my nose. As I said it's due to the compliance of the surfaces that interface the surface of the plate to the reference ie gravity. As one example, it should be obvious that if the stand is compliant (which it will be to a greater of lesser extent) the plate will tilt as a weight (ie the level) moves across it. Robin demonstrated that in the video, maybe you missed that bit. How do you suppose you're going to "calibrate" the surface plate when the entire plate itself is tilting each time the level is moved? How much is due to the inaccuracy of the plate and how much is due to compliance? Do you think the compliance is linear? You've apparently got yourself figured as a smart guy, you tell me. On second thoughts, don't bother. Walk around the plate and the level will move. Maybe you could spend a little less time trolling and a little more time actually trying some of this stuff and then you would be "comfortable". I have seen a situation where a level would go to its extremes just from the compliance of the stand and the mounts simply from the weight of the level moving.
Taylor Hobson isn't a "he" it's a company brainiac, and yes when I contacted them they agreed. It was a private email, and again, if that's not good enough for you, then stiff shit.
I have zero intention of feeding a troll, so when (not if but when) you come back with your predictable answer don't expect another from myself. You reckon you can calibrate a surface plate with a single level then knock yourself out. I tell you what, seeing as you have put up precisely zero on TH-cam why don't you upload a video of yourself lapping and calibrating a surface plate with a single level? .... no I didn't think so. People like you never do.
Ok, against my better judgement I will respond in the interests that you are sincere in not understanding.
Imagine the world is made of rubber. It is, it's just that we don't see it that way because it's normally too small to bother us or even notice. Everything you look at around you is bending and swaying. Everything! Your surface plate is perched on top of this rubbery stand. You put your single level in the centre of the plate and it reads zero. The plate is "perfectly flat" for this argument. Happy days. You then move it to the edge of the plate. Since your stand is made of rubber the stand bends because of the extra weight on that side. The level now reads one line out. However we already know the plate is perfectly flat right. So that reading is obviously not the plate error, it's our rubber stand. More happy days. We have proved the compliance of the stand.
Ok now let's say we don't know if the surface plate is "perfectly flat". We're calibrating it so that's what we're testing. We also don't know how compliant (rubbery) is our stand. How could we! You put the level to the edge of the plate and it's one line out. Ok now what? How much of that error is the rubbery stand and how much is the plate not flat? There is no answer to this, hence why this is not a test. It doesn't matter what grade of plate you like to consider, there is no "good enough" for this situation. The stand may genuinely be made of rubber. Or it may be made of solid concrete. You may be standing on a floor of wood, or of granite on a 10' slab. You are measuring the total error with respect to the earth's gravity. That includes everything between the surface of the plate and the centre of the earth. For this reason if we are to use earth's gravity for the reference, we need to check the overall surface we're measuring hasn't changed with respect to that reference. That's why we need a second level to remain stationary while we're moving weights around our plate. That is the referee to check everything is still in the same plane it all began in, and if/when it changes, tell the measuring level how much it's changed.
That's about as basic as I can make it, and as I've run out of single malt, and aren't normally a drinker, where I'll leave it. I'll leave you to fill in any vacant blanks.
The bottom line is you can't calibrate a surface plate with a single level. That's just how it works on planet earth. Anyone orbiting another planet can choose any other interpretation they like. You can compensate and fudge and dodge, and you may finish up with a flat piece of granite, but it won't be a "surface plate" by the definition of the term.
Complete with a fancy shop apron.
Excellent video!! Don't worry about speeding up the video, I'm watching because I want to. Also I may be wrong, but I think your counterbalance was in slightly the wrong position at timestamp 28:07. I think it needed to be one mark over. This was I think confirmed when you "swapped" positions, but they moved different amounts
Good eyes, correct. Thanks, and thanks for watching and commenting.
Enjoyed the video, I had no issue with audio or speed....just amazing when you shifted the weight to see the level move....when your done you will be able to arm wrestle Samson...lol
Thanks Chuck, and thanks for watching and commenting.
ATB, Robin
I'm pretty sure granite contains crystalline silica. Wouldn't this warrant a respirator or similar PPE Robin? Silicosis is a nasty beast. Looking forward to the next in the series.
I am wearing one off camera. I had it off so I could narrate. I will mention it in the next video. Thanks for bringing that up and thanks for watching and commenting.
I'll bet 99.99999% of your crowd learned something from this video, if you learned something we have learned something!
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Great video. I ironically wasted time checking my playback speed multiple times until you told us you had sped yourself up to save time.
I uploaded a new version with fixed audio. thanks for watching and commenting.
Great content as always. Very educational! I don't think I'll be trying this with my el-cheapo surface plate (well, maybe) anytime soon, but it's good to see the process. It would also be good to know what 'minimum' tool set is needed to improve a small plate... Thanks for taking the time to share!
sorry...that should have read "...'minimum' measurement tool set..."
You Refer to your plate as an ''el-cheapo'', is there a big difference in the actual granite used in cheap plates as opposed to something like a Starrett? What about between the different flatness grades? I thought the cost difference was more in the work that had gone into them rather than the actual granite. Btw, you can edit your comment by hovering over it and then clicking on the three vertical dots that appear on the top right of the text.
I refer to mine as an el-cheapo, primarily because (at the time I purchased it) Enco was offering a large percentage discount (around 30% if memory serves) as well as free shipping for orders over a certain amount. It's a small Grade B plate (12 x 18 x 3 inches), but if the included certs are to be believed (i.e., accuracy is stated as "0001" by inspector "O1"), then it may be as flat as a Grade A lab plate of the same size. As for the quality of the granite, my understanding is that those with higher amounts of quartz (by volume) tend to be more durable, and wear more slowly. My plate is a darker one, sort of bluish in color. However, there are areas or 'blotches' where the granite appears to be of different density (?). I have no idea of the quartz content of my plate. I'm still new to this subject, so it's best to research your question(s) online, or at the local university; as that is what I've been doing. Starrett has what appears to be some good info: www.starrett.com/metrology/metrology-products/precision-granite/precision-granite-faq. While I personally have no way to know exactly where my plate originates, I think it's a pretty good bet it's from Asia somewhere (India or China perhaps). Looking at the Certificate of Inspection document that was packed with my plate, has "MHC Industrial Supply CO., INC". Hope this helps...
Thanks for the info, I will look into it further.
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I liked the video. Once the gross surface irregularities are removed would a mapping of the surface plate with a autocollimator make the next stage of finishing more efficient?
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Thank you for sharing your knowledge and taking your time to document this. I would love to know where you get your abrasives, quantity, and particle size. We know about the three-phase method, but what about this gets around the aspect of needing the 3rd surface? Is it that you start with a relatively flat lapping plate, or that you will tune the surface based on measurements, etc? I'm planning to lap a granite slab mounted on rebar reinforced concrete with come ivanko 45lb cast iron plates that I've lapped with the three plate method. They don't have ribbing like your lapping plate, but if the bottom of the plate is supported at three points, I'm getting 3 tenths. Thanks, Robin!
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I think there was supposed to be a handle that sat in those machined holes at the ends of the plate. I seem to recall seeing a plate like that (different size) where two plastic handles with balls on the ends came out, curved and reached somewhere over the plate.
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found this very interesting to be honest
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@robrenz do you have to grind or rescrape the cast iron plate to get the diamond off or change grits? What did you find? How flat was your cast iron before you started?
Your demo with the precision level was interesting.
Won't the cast surface plate weight grossly affect the contour of the granite plate?
Thanks for the vid
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1x speed please Robin. This is not the Pewdiepie channel. Watched this in 360p with 0 views. Yes I know, I need to get a life :)
I uploaded a new version with fixed audio. thanks for watching and commenting.
I don't know very much about lapping, but I wonder how this process works in comparison to three plate lapping where the principle of adding in a third plate is supposed to correct for convexity/concavity that can occur when just lapping two "flat" plates together (as one does to get curved surfaces when grinding lenses)?
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Agreed. I don’t often watch a YT without hitting the 10 sec advance but every now and then I find one. Good content doesn’t necessarily need flash and explosions. Although, I will still watch Tech Ingredients explode his hydrogen snd oxygen ballon front to back without the advance button and still cackle like it is the first time.
I know I’m late to this party but is the reason you don’t use a figure-8 pattern because the lapping plate is just too heavy? Or in a surface appreciably bigger than the lapping plate, is the figure-8 pattern not the correct method?
Is it possible to clean and recycle your abrasive? You mention that the plate needs to be cleaned when you can feel there is too much abraded material on the surface, but it seems like you'd also be throwing away some of your abrasive when you do that. I know that Cody Reeder was able to use gold panning to extract just 2 or 3 diamonds from a bag of the cuttings from a concrete saw, so there are some pretty powerful separation techniques available, but I have no idea if it would be economical
I did have a bit of a look a while ago, looking for diamonds to use for playing around with lapping, and I recall thinking they were more expensive than I'd really want a pay. I'm having another look on ebay now, and i'm seeing around 0.50c to $1 per gram, which I suppose is pretty reasonable.
I will cover this in a follow up video. Thanks for watching and commenting.
Почему уровень и потивовес размещаются не на одной линии (оси)?
Thank you. That was one expensive plate when new. The audio doesn't bother me, more interested in the facts. I didn't see you mount the plate on the cart. Even with 3 point contact it seems like there would be give from the cast Iron. I've watched the pros do a couple of laps. Their ability to measure would be great for you to have. I'm sure the cast iron wears a lot faster than the granite does having a lot more wear in some areas of the plate affect the outcome? Guys buying diamond grit on fleaBay, do they get misc. odd chunks mixed in?
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I would be interested to see how much the precision level changes as you walk around the surface plate.
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I'm about halfway in so maybe you'll explain later but is there a reason you do this dry?
Wouldn't you get better glide and swarf removal if you had a layer of water in between?
Edit: I just presses play after this comment and you started to talk about why.
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Please leave video speed for viewers to decide, especially since some of your viewers only speak English as our second or third language. It is more difficult to understand you and reduction of a faster video introduces sound problems making much more work for the viewer (I think the opposite of what you intended). Thank you sincerely for sharing your knowledge and experience Mr Renzetti.
-Rov
I uploaded a new version with fixed audio. thanks for watching and commenting.
Will you need a different charge roller for each grit?
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Very cool... I hope this isn’t a stupid question, but shouldn’t the cast iron lapping plate be removed from the surface plate before rough checking the flatness of the plate with the level?
I would think so! After seeing the difference the counter weight makes to that massive thing I'm certain the weight of the lapping plate would influence any comparative readings. Robin, could you do that sequence again but without the lapping plate, so we can see if there's a significant difference? Cheers! ;)
I am guessing it is not an issue if the lap is not moved during the process. The counterweight seems to be to compensate for the changes caused by the movement of the level itself.
I would expect the deformation under the weight of the lap would be in the millionths. Well below the measurements used for rough checking.
I agree with the commenter who said it's okay of you don't move it, especially at the roughing stage. It's going to distort the surface by a very small amount, but not enough to matter. The problem would come in if I start moving the iron plate, because that's going to mess with the levelness of the whole surface
chris0tube changing the weight distribution on the plate moves the whole surface with respect to level, that's what was being shown with the small weight, but if the larger weight isn't being moved it won't influence the measurement reading to reading. It will slightly alter the geometry of the surface, but by such a small amount that it doesn't matter at this stage.