Ok, so I want to fit a 100mm 4-jaw (as used on minilathes, 20mm central bore) with mounting holes in the back, to a SOBA 4" rotary table with 3 x 120degree t-slots and an MT2 central taper.
One option would be a backplate screwed to a MT2 arbor. I suppose with the table horizontal this wouldnt need a retaining bolt on the rear of the table (otherwise that would prevent the table being bolted down to the milling table without some spacers in between), but might need one when the table was vertical?
I looked at the way RDGTools/Chronos do it but they fit a 80mm chuck to a 100mm plate and therefore there is room to have bolts round the outside, or they use a front-mounting chuck and I want to use what I already have..
To use 4 inch onto 100mm you could use a back plate that has a fixed 2mt spigot and 3 equal spaced spigots that fit the T-slots it should fit tight enough to resist lifting.
I have thought of another option. Since this is an independent 4-jaw theres no scroll.... so no reason (at least I can't see one) why I cant drill right through from front and counterbore for some allen cap screws and use t-nuts in the slots...
Of course getting the holes in the right place needs a rotary table...lol
John Stevenson came up with an idea to fix the chuck using tappered screws screwed into t-nuts fitted to the back.
Not sure if anyone tried it but it should be worth a try!
Not sure where I saw this idea perhaps sit John will be along soon.
They say talking to oneself is the first sign of madness
anyway, that last thought nearly works... for accuracy I could drill through the three 120deg mounting holes on the back, but then it occured to me that I wont be able to use the chuck on the minilathe afterwards as there wont be any threads left, although there's no reason why I can't front mount on the lathe - is there?
I'd drill through but a smaller size and preserve lathe mount threads (stick some centre marked studs in the thread first and drill through them)? Not sure what size the mounting bolts would be then? If too small for the job...... drill out any way to fit rotary table, then carefully make a back plate with six holes, three to take the new bolts to hold the chuck and three to mount the chuck on the lathe? Or, drill and tap three new mount lathe mount holes in the chuck.
Or, can you get long (1 1/2 inch) bits of t nut profile to fit? Drill and tap the ends. Take the chuck apart and turn a groove 1/8 to 1/4 from the mount end, only needs to be shallow. Make 3 L shaped clamps with a hole in the midle of one side, the other the same length as the groove from the back of the chuck. That end goes in the groove and clamp it down using the t nut overhang?
I'm trying to visualise your suggestion and failing badly, can you expand on it...
Art is not my strong point! I hope this comes out! I have looked at the pic of the table at Chronos and this will foul the locking nut preventing full rotation? Another thought. Why not make a round plate that fits the top of the table but bigger diameter, counter sunk short bolts for the t nuts so the front is flush and it doesnt foul that nut (you could turn a recess so it doesnt). Now you will have a table with a surface that is a bigger diameter than the chuck? Make (or buy) another plate like the chrnos mount plate and bolt straight to it?
Wow, I can see my rubbish drawing!
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