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Making a Special Beaver Partsmaster CAT 40 Pull Stud

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awemawson:
Ever since I first got my Beaver Partsmaster CNC Milling Machine I've been short of the special pull studs that retain the CAT 40 tools in the spindle. They are similar, but not interchangeable, with other manufacturers studs.

Some time ago I decided to have a go at making some but two things held me back. Firstly these are a highly stressed item - the originals are made from an unknown steel type that has obviously been heat treated. Secondly I wanted to avoid an extra machining operation milling the spanner flat with which they are tightened, and wanted to find a way of doing it on the Beaver TC-20 CNC lathe that I've been rebuilding recently.

The second of these conundrums was solved by much help from other forum members, with Archie (a new member) being very generous with his time helping me, so I have now a method of cutting flats using an axially mounted endmill in a powered tool holder as featured in my recent plea for help with the mathematics of the motion.

So I have decided to go ahead and try and make some initially from mild steel as a 'proof of concept' but no way will these serve as the final items as they will not be resilient enough for tool changing service.

Some time ago I measured up a pull stud and drew it in Autocad, but for this exercise I have re-drawn it, hopefully somewhat more accurately - it's not the easiest thing to measure, but careful cogitation hopefully got me inside the head of the original designer deducing that his angles were standard at 90 and 60 degrees (included angle) thus forcing some of the dimensions to work out as exact millimetres allowing me to predict other dimensions such as fillet radii.

So here is a picture of what I am aiming for, and my drawing of it in AutoCAD

awemawson:
Now the intention is to make several blank threaded ends with the flats milled on - so standard M16 by 2 mm pitch with flats of 19 mm AF (yes I know in my maths plea thread I was doing them at 18 mm - some are and some are not!)

Once these threaded blanks have been made, I'll screw them into a female M16 thread in stock in the chuck as a 'receiver' then make the 'pointed end'

So next job, draw up both sequences in FeatureCAM and model the cutting and choose the tooling

awemawson:
Now FeatureCAM lets you run a simulation, which is very handy to check tool clearances and make sure that tools can get at the faces that you want to turn.

So I ran the two operations and took videos of them. On the threading video you will see that there is a threading tool interference issue with the adjacent shoulder - it may not happen in reality as my threading insert has a different approach, but if it does then I'll have to tweak things a bit more

awemawson:
So that's where I'm up to at the moment. All tools are in the FeatureCAM crib, but I need to mount the SE facing 55 degree diamond tool in a holder on the actual lathe and check the tool setting is spot on before cutting metal.

Workshop time limited today due to external influences (dentist, worming pigs, wife flying to Houston and preparing for one set of guests leaving and two sets of holiday cottage guests coming tomorrow) So probably no more will happen until the week end  :bang:

Here is the code generated by FeatureCAM for both operations and also the flat cutting program (yet to be modified for 19 mm flats) just to whet your appetite

Muzzerboy:
Hi Andrew

A couple of years ago I bought a dozen or so BT40 toolholders from John Stevenson. As you may or may not know, he had a Beaver turret-type vertical milling machine with CNC control. Although it wasn't a Partmaster, the pullstuds look very similar. I have 7 of them that I removed from the toolholders, which you are welcome to.

The critical dimensions agree with your drawing, give or take, and although your example looks a little different (pointy nose, no register next to the thread etc), they would certainly work the same. Mine look somewhat better made, with ground surfaces etc, so if anything I'd guess they are possibly "more original"? Just guessing.

PM me if you are interested. They are yours if you have a use for them and there is little to lose....

Murray

Edit - make that 8.

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