Lathe facing convex or concave

[Neil WyattModerator @neilwyatt]

Michael,

That was part of my plan, although it doesn't give me a flat top, but I've been offered a chance to get it surface ground

Neil

[Steve WithnellParticipant @stevewithnell34426]

OK so after all that, a friend of mine has a big english lathe a proper one (DSG from memory) with a clutch and gearbox an everything (like power cross feed). This machine is facing off concave to the extent that it is buggering up some two inch washers he is trying to make.

He is not a machinist – where does he start pulling this into some sort of reasonable alignment?

Regards

Steve

[BazyleParticipant @bazyle]

First thing for him to check is that the saddle is not moving during the cut, and of course that the gibs are set for low play.

If it is just a few items to get done rather than a longer term solution then it should be possible to swing the topslide round to do the facing cut, though will take a bit of fine adjustment to get dead true.

Correcting wear is much more difficult.

[egaParticipant @ega]

Is that quote from ETW?

[larry PhelanParticipant @larryphelan54019]

Very interested in this Badgers Arse spec,this might go some way towards explaining my table problems.!

I do have a badger come to visit from time to time,I,ve never seen him,but he leaves his mark. N o need to dig holes when they are around,nothing stops them. I dont fancy trying to measure his arse since I suspect he might object to it,and when they get annoyed,it,s time to hit the trail,fast.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Steve Withnell on 18/03/2017 12:15:28:

OK so after all that, a friend of mine has a big english lathe a proper one (DSG from memory) with a clutch and gearbox an everything (like power cross feed). This machine is facing off concave to the extent that it is buggering up some two inch washers he is trying to make.

He is not a machinist – where does he start pulling this into some sort of reasonable alignment?

Regards

Steve

Well as no real experts have suggested anything yet, I'd try to find out what gives under pressure by pushing and rocking the various bits and pieces. Nothing should move! In no particular order:

• Tool bending or not clamped firmly
• Loose cross-slide gibs
• Worn cross-slide
• worn headstock bearings
• headstock bearings need adjustment

Dave

[Phil WhitleyParticipant @philwhitley94135]

Or possibly, given that he is not a machinist, he is facing a washer with a topslie/compound slide which is not quite zeroed, and thus not cutting perpendicular to the axis of the lathe?

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