Measuring accuracy of a metal lathe & Leveling, test bar, & other techniques to identify wear points
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- čas přidán 28. 12. 2023
- Long video with lots of content, see timeline below description.
We ask ourselves (at least I ask myself) “Is it me making these inaccurate parts or is it the machine?” As a hobby machinist it’s likely me. However understanding what your machine is capable of or just knowing its weaknesses is a key to success in any shop.
I invested a lot of time to determine where my machine was accurate and where it had some weakness. Knowing that gives me the confidence to move forward knowing what I (and the machine) is capable of.
For my lathe it was a combination of inherent tolerance limitations and wear in the carriage ways.
Timeline:
4:00 checking lathe level across ways
10:40 what? My flat ways aren’t level?
15:14 checking longitudinal level
18:36 measuring wear along the ways off the carriage
22:00 first indications of wear identified
23:45 second indication of wear
26:30 using tailstock ways as reference to test for wear
31:08 spindle test - center
32:00 spindle test - nose
32:55 spindle test - end play
34:20 spindle base plate
35:25 Tailstock spindle horizontal
37:15 Tailstock spindle vertical
38:45 tailstock alignment check
39:54 chuck face
41:10 chuck jaws
41:50 chuck perimeter
42:18 setting up test bar
44:45 tailstock alignment with test bar
48:25 set up for test cuts
51:00 1” test cut
52:25 3” test cut
54:20 12” test cut
101:57 wrap up and conclusion
Nice ,I have been doing this exact same thing the last day or so , that’s a fine lathe you got
Thank you, and good luck with yours!
I'd make up some adjustable steel leg extensions for the stand, so that they lift the table to the height you want. I think the timber blocks will swell and shrink over time constantly moving the lathe out of spec, basically as the weather changes.
Yes, you are right. The original table was so short, I had to jack it up a bit to a more usable height. The wood blocks were quick and easy, but replacing them with metal is the right move. Another project on the list!
Jamie, thanks for doing this video, I finally got through the whole thing (while on my stationary bike.....). I really need to do this on my lathe. As expected, the ways are worn where the carriage rides the most. I was once told that ways that are worn on the top surface has less impact on the diameter than wear on the side of the ways (front / back). The tip of the tool does not change as much relative to the diameter. Perhaps you could measure the deflection of the carriage as you rock it front to back. Do this near the chuck and near the tail stock. You may want to check the gibs, if you could tighten them up just a little but still allow good movement of the carriage at tail stock end you may be able to gain a .001. I'm very much a hobbyist but I'm at the point where I'm chasing tenths now, not just .001's. I'm not sure I'll ever determine if it's me of the machine.😒
Yeah, it’s a long video! And that’s with a lot of editing…! Thanks for the advice and suggestions. I’ll check out the gibs on my lathe and see what I come up with.
Thank you for doing this video its on my list of jobs to do, I have nearly the same lathe as you so everything you have done compares to mine. Keep up the good and entertaining work its appreciated.
Thank you David! I learned a lot about my lathe during this project. And I’ll now be more confident in my results.
have you not noticed your drop off occur as the carriage come off the 4 ways and goes to 2? watch your video and it becomes obvious lol keep at it be safe Dave
That is a great point and I’ll check that out. I appreciate the feedback!
I guess the question is how accurate do you need the lathe to be for what you are making. People buy these 50 year old lathes because they are "better than modern rubbish" but forgot about all the wear they will have.
Crazy to think this lathe is 40 years old. 1987 doesn’t feel that long ago…! You are spot on though, and why I made the video so I could understand just how accurate it is. That will go a long way in letting me know its limits. Thanks for the comment!