Denham Junior toolpost -options

I've finally(nearly) completed restoring my Denham lathe, it runs fine but I have a little problem. The toolpost has been 'upgraded' with a 4 way, the issue is that the cutter, which is a 5/8", is set on the top slide and the 4 way locks down against it. This causes the plate to twist unless I compensate with a bar on the opposite side.

The dimension between the chuck centre and the top of the topslide is 0.6515.

What I would like some advice on is the best options for kitting out this lathe, its speed are 30rpm to 600rpm, it's superfast!!!

My main use will be for static and 5" gauge live steam so no real heavy engineering. Should I go for hss or indexed or both? Would it be worth looking at a different type of toolpost?

Another pic

Thanks

Roger

Might want to consider milling a bit off the top slide to allow for a floor on the 4 way. That was my method atleast.

How much did you mill off and what size tools did you use?

My first move would be to replace what looks like a bit of B&Q studding currently used for a toolpost stud, with a properly machined stud that is a snug fit in the bore of the 4 way toolpost.

That way, clamping down the tool holder on to the cutting tool should eliminate, or at least cut down considerably, the tilt to the tool holder that is currently occurring.

Alternately, depending what model of Denham you have, the centre height appears to be around 5". A 5/8" tool is pretty hefty for this size of lathe, so you may be able to fit a different 4 way tool holder with a floor on it, along with 3/8" or thereabouts cutters, thus eliminating the issue another way.

If you went for the latter, I would still get rid of the bit of studding and go for a plain snug fitting tool stud, regardless.

Can't see any point in that 4-way toolpost, as soon as you try to rotate it all 4 cutters will just fall out.

I'd just make up a triangular top clamp where two corners bear down on the tool and the third has a jack screw, pack individual tools as needed.

If you want a 4 way than make a new one with 1/4 of material at the bottom which would allos 1/4 or 5/16 tooling to be used.

Because there is effectively only half of a 4 way toolpost, i.e. the arrangement relies on the top surface of the top slide to lock the tool in place, consequently when you tighten the bolts to lock the tool in position then the top of the 4 way is tilting away because of the slack fit on the central stud. I would think that the only safe way to use this configuration is to have a corresponding block on the opposite side and clamp down equally on both, that should stabilise the setup and keep the the top of the 4 way level. Using this type of tool clamping you will always get movement and twisting because of the free play on the central mounting bolt, the only way to eliminate it would be for the mounting stud and hole to be a very close fit.

Dave

I have 0.689" thickness above the mortise, how much could I safely machine off without affecting the strength/stability of the topslide?

My thoughts are to put some type of qctp on probably using 3/8" tooling.

In fact I just checked the dimensions of the qctp on my mini lathe and it would fit using half inch tooling on the Denham.

Does anyone see any issues in doing that?

Edited By Roger Clark 1 on 12/10/2017 14:58:27

First question, have you measured how far above the face of the top slide the lathe centre is?

You may not need to mill anything off, if the QCTP holders take the tooling you want, and they can be set on centre.

EDIT - I was still typing my reply whilst you were editing in the second part of your post above

Edited By David Standing 1 on 12/10/2017 15:03:07

"The dimension between the chuck centre and the top of the topslide is 0.6515."

And following on from your edit, unless the bore of your mini lathe QCTP is a snug fit on your toolpost stud, this idea will be plagued with issues of the QCTP block moving around on the studding.

So, again, it will come back to getting rid of the studding, and having a plain shank tool post stud that is a snug fit in the QCTP block.

Yeah, okay, that was 3 hrs and 4 minutes ago Jason, I have done many laps of the goldfish bowl since then

Too quick for me Jason

I would need to machine a fresh centre closer to the chuck end David

Just remember David that other goldfish you're chasing is you.

I took mine from a 12.7mm distance to 20mm distance. That gives a 4mm toolpost base and room for a 16mm tool. Potentially overkill but I wanted to be able to have cheap second hand industrial insert tooling that could fit.

I have a different topslide to yours, mine was very thick and somewhat primitive. Not currently near the lathe to measure how much meat is left though.

Thanks I don't have the luxury of that thickness of meat to pare down but I'm happy with going for the honlable chinese qctp which will fit just by drilling a new centre closer to the chuck end of the topslide.

That will also let me share the cutters between the 2 lathes.

It is?