Myford ml7 not facing off square

[Chris LofthouseParticipant @chrislofthouse99011]

[Chris LofthouseParticipant @chrislofthouse99011]

Hi

My myford ml 7 has started to face parts off out of square producing a convex face. I’ve tried locking the carriage adjust the Gibs etc can anyone shed any light why it might be doing I?

Thanks

Chris

[Neil WyattModerator @neilwyatt]

Hi Chris,

Welcome to the forum.

Have you checked the spindle adjustment?

Does it turn parallel over, say, 4"/100mm?

Neil

[Chris LofthouseParticipant @chrislofthouse99011]

Hi Neil thanks for the promt reply. When you say the spindle do you mean the headstock spindle? Thanks chris

[blowlampParticipant @blowlamp]

The usual cause is wear to the fixed gib (on the saddle) that runs on the inner front shear of the bed.

It allows the whole carriage assemble to turn slightly and give the problem you're experiencing.

Martin.

[HopperParticipant @hopper]

+1 on what blowlamp said, providing headstock spindle is parallel to the bed and turning a cylinder without taper. The saddle guide, or fixed gib, ie the felt pen cross-hatched area in the pic below, is a high-wear area on well-used ML7s. On ours it was worn about .030" at one end and about .005" at the far end. This kicks the whole carriage around at an angle, thus facing concave. Usually, most wear is at the headstock end of the guide and is quite visible by eye.

The problem is most pronounced on high-mileage pre-1972 "narrow guide" models. The narrow guide is the one highlighted in the pic. As you can see, the load-bearing area is pathetically small. If yours is this model, the fix is not overly difficult. By adding a strip of gauge plate to the wide guide surface (at the rear in this pic) to bear on the unworn rear shear, the lathe can be bought back to as new. (In fact better than new!) Neil has a nice article on file on how to do this, so I would expect it to appear in MEW at some future point.

If you have a later wide guide model, you might be able to do the reverse and convert it to narrow guide to bring it back in line.

[EmgeeParticipant @emgee]

Chris, another cause can be too much angle on the cutting edge to achieve pipless parting, this will pull the blade in the direction of the point leaving a convex end in the chuck.

Emgee

Edited By Emgee on 29/09/2018 14:57:19

[KWILParticipant @kwil]

The adjustment of the front carriage gib screws is critcal (more so on the narrow guide versions). It is all too easy to over tighten the right hand one, thus pulling the carriage out of square, which adds to the wear rate as well.

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