Strange effect when turning

[Howard LewisParticipant @howardlewis46836]

My lathe (A BL 12-24 ) is a very similar machine (Typical Taiwanese clone ) to the Craftsman and despite its 300 Kg weight, the bed will twist. Mine sits on six 1/2 UNF setscrews, between the lathe and the bench, which provides a convenient means of fine adjustment to remove any twist.

Previously, I have mounted lathes on box section, as riser blocks, with M8 studs for adjustment.

Howard

[John ReeseParticipant @johnreese12848]

I strongly suggest that you use HSS tools instead of carbide insert tooling. If you don't want to learn to grind HSS I recommend a tangential tool holder similar to what Eccentric Engineering sells. If you insist on using carbide get inserts made specifically made for aluminum. The object is to minimize the pressure the tool exerts on the work in order to minimize deflection of the work.

It becomes more difficult to track down alignment issues when your test pieces are deflected due to tool pressure.

[Howard LewisParticipant @howardlewis46836]

Well Larry, Put us out of our suspense!

How have you got on?

Hope that you have not fiddled with the Headstock alignment!

Did you find any twist in the bed?

Have you corrected it? (By shims or adjustment of the mounting bolts at the Tailstock end.)

If YES, has the taper situation improved?

Once you have the twist out, you can start checking that the Tailstock is correctly aligned.

For this, you use the two grubscrews low down on front and back sides of the Tailstock, so that a DTI gives the same reading at Headstock and Tailstock end of an Alignment Bar held between centres.

If you are unsure, PM me and I'll take a picture of mine. I can also tell you how to make up your own Alignment Bar from a piece of precision ground stock, or silver steel, if you want.

Howard

[Michael GilliganParticipant @michaelgilligan61133]

Posted by larry phelan 1 on 26/05/2021 13:15:09:

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I am happy to be able to report that due to careful shimming, I have reduced the error to almost nothing, something like 0,002mm as far as I can see, over 150mm. […]

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Howard … for info. ^^^

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Thank You.

Good to know a successful conclusion has been reached

Onwards and upwards!.

Howard

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