QCTP Baseplate

Hi All,

I am new to model engineering and read this forum frequently.

I have a Boxford AUD lathe and have been given a QCTP similar to the Phase II.

Not yet having a mill or vertical slide I have no way of machining the supplied baseplate to a T-section to fit the Boxford cross slide.

Is there anyone near to south London with a milling machine that would be willing to machine the T-section for me?

Thanks
Peter

My current lathe has the QCTP affixed via a T slot, but my previous model used the (same) QCTP fixed to the compound slide with a simple stud which, incidentally, I made.

While the QCTP could not be adjusted quite as much as the current lathe, it made not so much difference for most jobs.

Alternatively, if you are simply looking for a T-nut, there are numerous sizes available from suppliers.

If special dimensions are required, posting them up might be a good move on your part.

Peter

The slot in the Boxford top slide is essentially the same size as that in the Southbend 9" so its practical to make your own T nut from two pieces of standard flat stock screwed and glued together. I did this several times many years ago when assembling my "poor boys Quick Change system" based on interchangeable 4 and 2 way toolposts for my two SouthBend 9" lathes and similar ones for my Heavy 10 lathe. Each toolpost unit was complete with T nut, stud and locking lever so they could be easily slid out and changed. I made mine T nuts about 2 1/2 inches long, pretty much the whole width of the slide, so plenty of room for screws to hold the two parts together.

According to the SouthBend book both slots are 9/32" deep, and the narrow, upper part 7/8" nominal wide. Book doesn't give the width of the bottom one From memory something between 1 1/8 " and 1 3/8" sounds right. Had aBoxford top slide on one lathe and SouthBend original on the other. My nuts fiited both.

I sawed the two parts out of 1/4" or 6 mm steel bar, whatever I had about the place. Probably held them together with a brace of 5 mm countersunk screws (maybe 4 or 6 mm, whatever was to hand). Used a 12 mm thread in the middle for the stud. High strength loctite on the screws. Something strong for the glue to ensure the two parts stayed together. Probably a loctite structural adhesive for me in those days but anything that will accept a thin glue line will do. Plenty of area for a strong grip. Not sure how well epoxy glues do with such a thin glue line tho'. I imagine I stuck my bits together first then drilled the holes. Probably made about 12 or 16 all told, none broke.

Do verify that the top of the slide is flat as they tend to bow over the years under localised loading.

Clive

PS Having written all that I've just remembered I have a couple of made from solid Tee nuts with a 12 mm thread for the stud made to fit a Heavy 10 lying around. I could easily modify one for you. They are little wider and thicker than the Boxford slot so I'll need the dimensions, primarily the width of the bottom part. PM me if you want one done and I'll send it up.

Edited By Clive Foster on 26/12/2019 14:12:49

Thanks Guys,

The t section from my old tool post is 31.64mm x 11.05mm overall with two rebates creating the narrow section 21.6mm x 4.84mm

The slot on the lathe is 32.84mm x 7.3mm and the narrow section is 22mm x 6.8mm

Just to start an argument, it should be possible to make a Tee nut in the lathe.

Put an end mill in the chuck, fix the workpiece in the current toolpost, and with a bit of thought and some ingenuity, away you go!

I have seen hexagon nuts produced in a lathe, and my turning instructor made his rectangular cigarette lighter on a capstan lathe.

Howard

The Boxford is designed for a US Lantern style tool holder all it needs is a square shaped 1/4 " thick plate with a threaded hole, that will also stop you overtightening and breaking out the 'tee slot'.

Dave

The Boxford is a copy of a not particularly well designed system for using a lantern toolholder (probably the most ill-conceived and functionally obnoxious lathe tool mounting system ever).

If you use a simple square plate it will distort the top of the slide. Most especially so with a QCTP system as these invariably have a centre recess of greater or lesser size to ensure that any rising of the top-slide upper surface around the stud will not result in the post only being held close to the centre. With a QC post the Tee nut should be approximately at least as long as the (square) post sides. Ideally it should be as long as the diagonal. In practice, for our sizes of machine, you usually need to accept a nut as long as the slide is wide. On our small lathes the top of the slide is invariably thinner and weaker than you'd ideally wish.

I've flattened enough slide upper surfaces after such abuse to know this for sure. My P&W model B 12 x 30 being a particularly egregious example. As the Tee nut was slightly smaller than the recess in the Dickson T2 toolpost base many years of abusive tightening by previous owners left a surface something like a (shallowly) ploughed field. As purchased finding a position where the post stayed put would have been an exercise in patience and long spanner brutality. Mostly fixed now after building up with weld and re-flatting using a nut I had, albeit a little shorter than the diagonal.

Someday I will re-do things properly with a both a longer nut and a screw down collar made a running fit in the toolpost base so I can turn the toolpost without it sliding sideways. Not an urgent issue as I generally dont rotate the toolpost. Angles belong on the tools not the holder.

Clive

Surely a few minutes with a hacksaw and file will produce a usable part?

Clive,

I'm sorry but I don't see how a 32mm square plate is going to distort the top slide. Admittedly I'm using a T0 post and only a 6" spanner to tighten it on my old Rockwell 10". I would expect the threads to tear out of the plate before the slot took damage.

All I'm really trying to suggest to the OP is a tee nut is unnecessary overkill as you don't actually need that much depth of thread. As Nick says above a few minutes with a hacksaw and file will produce a usable part.

Dave

I don't think I've ever seen a lathe with "some history" behind it that hasn't had the upper surface of the topslide distorted or dinged in some way.

Certainly flatting off the surface and using a nicely fitted Tee nut or stud as appropriate was always a good start when sorting self rotation during a cut by QC and 4 way posts. QC posts in particular put the tool a considerable distance to the side of the stud so it seems logical that a long stiff Tee nut reaching right to the edge of the post will do a better holding job than a square, not exceptionally stiff plate in the middle. Even after flatting a short nut on the P&W needed more tightening if the toolpost were to sit stiil than a long one.

I guess theoretical perfection would require the slot overhang to be evenly squeezed between nut and toolpost over the whole possible contact area with no uneven force or bending effects. Perfection being at least impractical and, probably impossible, the $64,000 question is how much imperfection is acceptable before you hit trouble. Not a question I'd care to try and answer, even if its realistically possible to get a sensible one. What I do know is that a long, stiff, Tee nut is the best simple way of providing pretty even clamping over a reasonable area with minimal bending forces on the slot. Given that its not much more trouble to make a long one it seems false to make something that may prove not to be good enough. How much performance margin there is between a long nut and the minimum "just manages to work" fitting is another impossible question. Especially when you factor in years of use and how careful or not carful the users are.

Clive

A simple nut like Dave suggests would allow the toolpost to be fitted (assuming you don't have another one) so you can hold the supplied nut in it to modify or even a bit of barstock to make a new one, I'm sure one careful use would be OK.

Just check the supplied one has not had any form of hardening before you go and muck up a milling cutter on it.