At the tolerances being discussed I would expect an on-size part to measure exactly the way this OD measured. It was being handled extensively from its ends during the video and the heat from doing so will cause the ends to expand. If it were left to properly stabilise on the comparator for a while it would most likely measure far closer across its length. I think this point should have been made in the video, as how much metal expands and moves is probably quite a surprise to viewers not used to working at this order of precision and will easily catch people out of they don't consider it properly.
There's really something cool about how 2 perfectly lapped parts will fit together.But what I dont get is why people are afraid to do it or think they cant.It takes a bit of feel but once you get it you can make things incredibly precise.Last but not least is you dont have to go and buy the laps,they are super easy to make from scrap stock although for a commercial shop where they make a lot of one thing I see why he uses that one.But for myself I use a jig i have that can do rifling to cut the grooves inside to hold the compound and then I'll cut a slit like normal.
don, i love watching your instructional videos because you look so much like my grandpa harold. it us uncanny. i didnt get to know him well because he was a quiet stoic son of a finlander and he died when i was young. he would have been a terrible machinist. he only had one eye and he had parkinsons haha.
Hi my name is Joe Navarro. I watched your video on squaring the head on a vertical mill like a Bridgeport. It was especially interesting to me because I have a product called "Spindle Square". Some say they can square the head within a Tenth so I appreciate your comments about the accuracy involved in tramming a manual mill.
Don, thanks for your videos. Your demonstrations and explanations are great! I am a new subscriber and will be watching many of your previous videos. Best Regards, Harvey from Nebraska
nice vids. I also do internal and external lapping using diamond compounds, silicon carbide, aluminum oxide and some mixtures. with finish of 5Ra and .000050 roundness or better. I lap match assemblies of bushing and spool with clearance of .0001-.000130. It's a challenging job but I honed my skill to do it.
Great video! It's always great to experience Don's tutelage and positive nature. So methodical, showing us a craft and taking care in our work. Lapped parts fit so nice. Fine actuators for machines that operate in cleanrooms manufacturing computer CPU's. A lot of those things fit essentially perfectly and they have control systems to monitor their precision further, to make parts 30 atoms across. Meanwhile, we take apart a hydraulic pump and marvel at how slick the fit is. It's humbling.
Id like to know this too. Watching Dan Gelbart's vid on his air bearing lathe, it sounds like his is 1micron. Hell knows how you achieve that with manual lapping.
What is the clearance between the lap and the part? I'm assuming there has to be little room for the abrasive? And then, when the parts are done, how much bigger is the OD than the ID of the mating parts- one tenth? two tenths? I'm teaching myself to machine to this precision but not sure my digital micrometers are accurate enough to know what I'm actually accomplishing to a tenth. Thanks!
+Josh Kopel While we do use diamond compound on our automatic lapping machine , for this demonstration we are using white aluminum oxide lapping compound.
What is the surface roughness you get after such a process? I am looking to lap a 1.5mm diameter spindel to an Ra of 0.015um. Is this possible? Thanks for your instructional video.
thank you for your video! can I ask - how common is it to lap a hard anodized aluminum part to size? I have a part with a -0.0004" od tolerance and +0.0004" id tolerance spec. (after hard anodize)
+Bertrand Labelle I'd love to answer your question but I'm not quite sure what you're asking. Are you referring to the ID lap we are using to lap the OD of the part?
Hi Don, as usual a good and informative video. On the subject of lapping, have you seen Dan Gelbart's take on the subject? ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-sFrVdoOhu1Q.html I can't say anything about comparing methods but his machine is fascinating.
Another fine video Don, I sure would like it if you made a video tour of your shop. You did that nice one of your parts suppliers. I think something like that would be great. Well thanks for sharing your time and your knowledge. Thank you.
Sorry if i did't check all your videos. But do you have something like that explaining how to make fluted reamers in conditions more close to home shop, if small tool grinder availible? Heat treating is not a problem, but fluts grinding setup is interesting and also some old school tricks. ) Thanks a lot for your chanel and videos. I am still young but it's clear to me that an old art to be a machinist and toolmaker is dying in Europe and US. And i want to learn more from an old school until some last of mohicans still alive. )))
I had a little problem job to do, I needed to size about a 100 .250" shafts to fit a bearing bore. The shafts were a 10th or two over, and I needed them to be a couple 10ths under and so I found this video. I am not unfamiliar with the concept of lapping but didn't know what equipent was out there. Watching this vid I learned about Americal Lap so I got in touch with them and bought the holder and some laps. Nice guy there, had a chat, and the laps came yesterday and they work perfect. This little rig works way better than I thought it would! Thanks Suburban Tool and American Lap.
+Bob Cartwright We have only been doing this for around a year. It takes time for people to find you on RU-vid. Please share with your friends. That always helps. Thanks for watching.
Bob,I just said the same thing.I really hope they keep it up because the knowledge they share is very helpful and the Investment casting tour was awesome and one of the best on RU-vid.
Don, Thanks for sharing. A hobbyst question: Is there a limit to how precise things can be manufactured? I mean, could you manufacture a steel cube where each side is, say, 3 inches, with under a millionth tolerance? That is, each side is 3.000000 inch exactly. What about 9 decimal points? Is 12 decimal points possible? What are the limits of our manufacturing capabilities, precision-wise? Thanks, hope my question was clear :)
The thermal expansion of steel is anywhere from 0.0000061 to 0.00000683 inches per inch per degree Fahrenheit. So lets take the median and call it 0.00000652. So if you had a block that had been machined to 3.000000 +/- 0.0000005 in a room at exactly 65 degrees Fahrenheit. When you picked it up to measure it you may increase the temperature by 1 degree, which would make that block 3.000019. The practical limits of dimensional accuracy are the ability to control variables like temperature. In addition to that there is flatness. A lab grade AA surface plate has a local area flatness (known as repeat reading) of +/-0.0000175. You would need something flatter than that to lap it on (not that you would lap on a surface plate) to have a surface flat enough to measure such dimensions.
Thanks everyone who replied. Yup, variable control at such levels seem to be the most important/hard thing to achieve. Just reading Moore's book on mechanical accuracy, he speaks about these topics at length. Very interesting. :)
