- Joined
- May 3, 2017
- Messages
- 1,996
Congratulations!Pierre and Bob
SUCCESS!
After quite a few hours of perseverance I am pleased to report that I now have 1 thou in 5 1/2" (length of my unsupported alloy turning bar) taper.
So, I will be content with that. Trying to attain perfection would be an exercise in futility!
The printer rod was a huge help in that it gave me a reliable reference. Due to the spiral mark from the sponge coating, which was not going to come off without being aggressive, I chose 2 reference points and retracted the dial indicator probe when moving back and forth between the 2. It can be done accurately if you are gentle. The reduced diameter RHS end gave me a handy cross-check that the bar hadn't deflected with all the dial indicator probing that happened countless times today as I could gently revolve the chuck by hand and verify the runout had not altered.
It was a very frustrating experience due to the spring in the headstock. In the end I put a washer under the cap screw closest to the operator. This helped reduce the spring/unpredictable movement effect. Until I did that, I was on a hiding to nowhere!
Initially the other 3 cap screws were also having an effect on the spring back too, but after much moving of the headstock left to right whatever was causing the issue with them disappeared from the equation and it was just the front right cap screw that was the problem.
But I was still faced with 40 or so thou spring when backing the screw off to move the headstock. I discovered that if I left the other 3 loose and cinched down this one (front right) all the way I could then predict the end reading give or take a couple of thous, so had to keep at it until is landed at the the desired tolerance. Then a case of gently cinching up the other 3 in a regimented order every time. Bit like doing up the wheel nuts on your car in that set pattern.
Running between centres was not so successful as I have a 14 thou runout even after re-zeroing the tailstock using the razor blade method and a freshly turned centre point in the 3 jaw chuck.
The live centre point does not seem quite right - I think it is giving me a false zero - I need to take a very close look at it and even with 2 pairs of magnifying glasses on I can't focus on it - the joys of getting older!
So will need to find a magnifying glass.
I knew that bedding down a lathe was a precise affair but never imagined it could by this finicky. However, I do think there is a back story to the history of this lathe that I will probably never know.
I've been following this thread with curiosity. You've been getting great advice from obvious experts, and it's been a real education to me.
Hope you enjoy using your now-functional lathe.
Regards,
Terry