Rotation, clamping tool post

[Kram]

Any time an object is only held down with one bolt, it can rotate?

Tried broaching some internal splines and couldnt to get the qctp to stay straight. This was only a 1mm tool in aluminium so should have been easy.
Im not sure if this is moving when turning/parting, will put an indicator to check..

Similar thing I dont understand why most accesorys/machine vices only have two fixing bolts, I would want 4.. My vertical slide has 5 bolts and a location pin - I added after as it could still move on a heavy cut.

 

[Seadog]

If the base of the QCTP or the surface of the compound slide are not perfectly flat you will get some movement. I don't have any problems with my single stud fixing, and I do like to take heavy cuts.

 

[Hood]

Definitely something wrong with your setup if it is moving under light conditions. As Seadog says check things are flat.

Regarding machine vices, quite often they are keyed to the table.

 

[grim_d]

Yep, my Create post is only 1 bolt and the only time it moved was when I had a crash. It moved out of the way thankfully.

My lathe will stall under heavy cut before the post moves.

 

[brightspark]

I've never had a tool post move no matter what the cut on any lathe. if the tool was just rubbing on the job in stead of cutting and it was on power feed I've had one move once

 

[dobbslc]

You could try flatting the two mating surfaces with some fine wet & dry on a bit of plate glass or a surface plate if you have one.

 

[brightspark]

You could try flatting the two mating surfaces with some fine wet & dry on a bit of plate glass or a surface plate if you have one.

then rub some micrometre blue on it to see how much surface contact there is

 

[8ob]

I've never had a tool post move no matter what the cut on any lathe. if the tool was just rubbing on the job in stead of cutting and it was on power feed I've had one move once

Yer not tryin ard enuff

Bob

 

[Pete.]

As above it's not flat. The top of the slide or the base of the post.

You could turn a very (very) slight concave in the base of the post to ensure it only bears on the outside edge. That way clamping forced won't pull a dish in the toolpost and make it bear on the centre.

 

[Kram]

Ive not noticed any movement in turning, only broaching. This might be light conditions on a bigger lathe but I was using about the maximum force I would want to though the handwheel.

I will dye the base and compound and check it next, then try again with an indicator on it.
Should be slightly concave as I used the boring head to turn the centre down.

The tool post has made the lathe more rigid, parting is a lot better. I expected the opppsite as the old 4 way is a solid lump, qctp has a lot of parts.. Only difference is bigger clamping screw.

 

[MrFluffy]

if we're talking rotary broaching. Is your broach geometry correct? its supposed to do a tiny cutting action every time it rotates but if the flank angles are wrong it takes too much force. When I made the broach for my lathe, I put a centre drill in the rear of the tool so I could apply the pushing force with a rolling centre in the tailstock for larger diameter stuff (25mm instead of 6mm allen bolt in-hex's for eg) instead of using the cross slide because it could *just* start to force the toolpost out of line with the forces, plus its kinder on the cross slide not subjecting it to this.

If you mean using the lathe to scrape out a slot or something like a shaper, ignore this.

 

[MrFluffy]

Oh, and my first harrison had problems with this in its past, because the indexing four post was pinned with four pin holes into the cross slide which each located on a pin in a hole with a spring underneath it when straight ahead. I took the pin out and it used to wander round under heavy load, but the rest of the lathe was such a dog I just put the pins back in and used it like that instead of trying to correct the underlying issue.