mini lathe dial accuracy

[s dParticipant @sd79178]

Posted by not done it yet on 09/06/2023 12:42:03:

My initial thoughts were the same as Tim and Andrew.

Next was when the OP said ‘sesitive but not necessarily that accurate made me wonder if a dti was being mistaken for a micrometer.

Other thoughts were whether the carriage and/or cross slides were locked down if/ when checking the compound travel. A decent thread gauge may well be good enough to prove/demonstrate if the threads are imperial or metric?

Don’t ‘sneak up” is my advice. The cut will be consistent only as long as the increments are the same. Get used to taking the last couple of cuts (at least) with the same depth of cut and feed rate. Better to take a deeper cut than trying to cut the last 0.02mm on the lathe – most especially if using un-polished carbide cutters/inserts.

Yes, I didn't understand that a dti was much more imprecise than a micrometer. I've been watching many videos on YouTube and ubiquity of their use especially for measuring machine set up made me trust mine perhaps more than I should have. All good learning experience.

I think I saw a clickspring video about 'sneaking up', and the way I understood what he meant was not taking ever smaller cuts, but dividing what you want removed into decent sized regular chunks, that way you can more easily keep track of errors and deflection as you go and then be able to make the final adjustment adding or subtracting a small amount from that final cut which is still of near optimal depth before spring and finishing passes. This makes a lot of sense to me as you're reducing variables as much as possible. It's still all theoretical as I've yet to make any super precise parts, but interesting. Good to hear the same thing from a 2nd source, thanks for the insight 👍🏻

[Howard LewisParticipant @howardlewis46836]

If you want to sneal up to take the final shallow finishing cut, use HSS or possibly ground carbide tips (Rathyer than moulded)

You may well find that spring cuts are your friend for the final cuts, based on the tool being as sharp as possible..

Howard

[Author]

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