Small drill chuck

[spillr]

Hello from an old newbe--I posted this question on another forum, but I don't know my way around here yet, so please forgive my mistakes. I am a retired machinist, just ordered a Go602 from Grizzly, planning to do some steam and internal combustion modeling. I have a Kennedy roll around full of stuff I used in the day, and among the odds and ends is a small Cushman drill chuck sans arbor. It has "C4OJT" stamped on the outside and will take a 5/32" bit max. I think it would come in handy in model building, but it has no arbor. Seems to be straight shank. I can make the arbor, but what I need to know is; if it is straight shank, should that end be turned slightly oversize and pressed into the chuck. Thanks for any help you can give me.
Regards--Spillr

[WayneHill]

From one old koot to another - welcome to the CNC Zone

JT = Jacob Taper

[gd.marsh]

Not an old machinist so I could be wrong ..

I would hazard a guess that it's a size-0 Jacobs Taper ..

Welcome!

[whateg01]

Here's a handy chart that lists the important dimensions, in case you need them.

Dave

[knudsen]

Welcome aboard, sir! You certainly out-experience me, but I've never seen a straight "taper" in a drill chuck. Got the straight "taper" in the head and tail of some Emco lathes and the HF 4 x 5 some of us recently picked up for peanuts. I have not figured out how that's supposed to work yet. Anyway, have you measured it to see if it is indeed straight? I agree probably JT0, maybe JT1, but you should be able to see that clearly. Good group here, we'll enjoy learning from each other. Well, be careful what you pick up from me, likely to lead you astray!

[spillr]

Thanks to all of you for the replies. I probably didn't make myself clear on my question. The machine I have ordered (Griz go602) has an mt3 taper in the tailstock--so I know the taper needed on that end, but the drill chuck I'm referring to (the thing's about the size of a walnut) is .246" at the top of the hole, is approximately 1/2" deep, and .223" at the bottom as near as I can tell. So it's not a straight shank. Hard to measure the little thing. So the question is what taper would fit it. I have a 5/64-1/2" Jacobs chuck that has 1/2-20 stamped on it, meaning it takes a 1/2-20 threaded arbor with whatever morse taper you want to use. But the Cushman only has C4OJT on it. I don't want to throw it away as it appears to be well made. Does anyone know what that small taper would be?
Thanks
Spillr

[hoss2006]

Looks like a JT0 taper,
http://www.tools-n-gizmos.com/specs/Tapers.html#JT
you'll probably have to get an MT2-JT0 arbor and use a MT2-MT3 sleeve.
http://www.msdiscount.com/columnar.a..._site=STARTOOL
Hoss

[spillr]

Thanks Hoss, I did what I should have done first and looked it up. Found what it was--too bad there's not a mt3 with a jt0 on the small end. Thanks for the links--plan to check them out. Thanks to the rest of you for your help.

[knudsen]

Cushmans are $$$, definitely a keeper. They don't seem to make those tiny chucks anymore

On the 1/2-20 threaded, I wouldn't buy an arbor for that one, because the runout will likely be huge. Best to make the threaded end, screw it into the chuck damned tight, center a 1/2" test bar in a 4 jaw, chuck up the protruding end of the test bar in the 1/2-20 threaded chuck, then cut the taper in the protruding end. Have to cut that taper gradually, so as not to flex the test bar. Setup should look something like attached photo (although I am just measuring runout in the photo). I am a hack, but IMHO, that is the only way to get a threaded arbor to be low runout, short of indexing it to a surface on the chuck that is true, which is difficult to do.

I was trying to do the same, but gave up as I acquired a small JT chuck, so making an arbor for that one.

[UUU]

Not being able to find an arbour of the right MT to JT size, I was fortunate that the spindle of my lathe is the same taper as the mill, so I was able to buy a blank-end MT arbour and turn the JT on the end to fit the drill chuck. Much nicer than using a sleeve - besides, I wanted a draw-bar thread on the MT end.

[knudsen]

I was s'prised to find out how easy a Phase II arbor machines. Ordered a cheapie, hoping it would be cheese, saw it was Phase II, worried a little, but skipped the file test. I did file test the American one a later destroyed Seemed harder, but only on the first pass.

[spillr]

Got the Griz 10 x 22 today--arrived unscathed, the crate was still intact. Got it on the shop floor planning to start cleaning it tomorrow. From the looks of the inspection sheet runout on average is less than .002"-so I may have to do some tweaking. Am impressed with the looks so far. Saw where someone in the "zone" mentioned a substitute for the Mobil DTE heavy-medium oil a few days ago. Anybody remember what it was?