Collets for SHOPTASK 1720XMTC

[stanger53]

I have a SHOPTASK 1720XMTC that I bought back in the mid 1990's, mounted onto a bench and have barely turned it on in all these years. I am just now starting to use it for some things and am basically familiar with some machining methods, but am no machinist, so I have a basic question.

One of the products I work on is a spool valve that is often rust pitted and needs to be ground down to smoothly slide in a rubber seal. The area in question is .50" diameter and can only be turned down .020" max and still seal, so I turn it as little as I can to get a smooth finish, usually les than .010".

Actually, it is hard to turn this hardened steel item with a bit, so I grind it down with a tool post grinder - leaves the surface much smoother and cleaner than I can get with a bit. I currently do this on a little 9x10 mini-lathe and clamp the outer area of the spool (.875" diameter) in a self-centering 3-jaw chuck. Of course, this is not well centered for grinding, but works out well for the accuracy needed for my work.

I would like to grind these down on my Shoptask and do a more accurate job. Am I correct that the part would be better centered if it was secured in a collet as opposed to a self-centering 3-jaw chuck? What style of collets will work in my Shoptask and what is needed to adapt them to my lathe spindle?

[ajbarrell]

I'm not sure if Shopmaster has changed the tapers over the years, but my Tri-Power uses MT-4 collets in the lathe spindle and R-8 in the mill. In addition to the collet, you'll need a draw bar to secure the collet in the spindle.

Tony

[dahui]

Do you have a 4 jaw chuck? That might do the trick if you have a good indicator to dial it in. Should be able to get in on center by less than a thou without too much trouble...unless you are doing a lot of them.

I've heard of people with an MT4 to R8 adaptor but I haven't been able to find one. Let me know if you do.

cheers

[sch]

1990's era 17-20 typically had the 4J thrown in with the machine,
so that would be the simplest method. OTOH rusty pitted shaft
clamped in 4J might be damaged by the 4J jaws or be clamped
'off center'. Smithy sells a 5c collet holder that is a bolt on on
the 3n1 flange mount for about $120. They also sell a D1-4
mount version, which you don't want. Chuck McGee (Ghee?)
whose website seems to have disappeared from Brinkster, sold
an R8 collet adapter for the lathe spindle, mounted about the
same as the Smithy 5c collet holder did allowing R8 collets to
be used for work holding in the lathe spindle. (He also would
take your MT3 MILL spindle and bore/ream it to R8 and send
it back to you for about $100.) I tried his website last week
and googled his name with out any luck though, so that route
may be caput.