Mill spindle mt#3 - what’s my options ?

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Bill Shields
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Re: Mill spindle mt#3 - what’s my options ?

Post by Bill Shields »

Tough on bearings for MT engagements.

Suggest you use a dead blow hammer
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John Hasler
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Re: Mill spindle mt#3 - what’s my options ?

Post by John Hasler »

Torch wrote: Mon Jan 24, 2022 10:34 am Most MT spindles have a slot in the side. A provided steel wedge is inserted in the slot, resting above the collet and then lightly tapped to dislodge the collet, eliminating the need to hammer on the top of the drawbar.
MT collets don't have tangs.
pete
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Re: Mill spindle mt#3 - what’s my options ?

Post by pete »

Correct, those collets don't have a tang at all. I'm not all that sure the collets themselves are long enough for those wedges to work, they might? But some MT mills including the one I had don't even come with that wedge slot. While those MT collets obviously can and do work, they also almost work against themselves when using them. You have to use the draw bar and tighten it enough so the collet then provides enough grip on the tooling so it can't move vertically or spin inside the collet. When that's done, the spindle taper is doing what it's supposed to and the collets O.D. taper has wedged itself inside the spindle. That would be ideal if you never had to remove or change tools and collets. Having that built in extractor where the loosened draw bar then helps force the collet out and release would be something I'd sure want. It's also why every lathe I know about pops the MT loose just by retracting it enough. Yes it's a trade off with a bit less Z clearance and the same for over all rigidity, but those ER collets will save a whole lot of pounding on the draw bar and making your bearings unhappy. They won't totally eliminate changing to other MT shank tools, but will sure reduce those changes. I've had a MT 3 mill and I then bought larger and better with an R8 taper, there's no comparison between the two. I think MT's are great when the cutting loads are axial like on drill presses or lathe tail stocks, for mill spindles maybe not so much unless you have or can figure out how to add some type of built in extractor.
John Hasler
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Re: Mill spindle mt#3 - what’s my options ?

Post by John Hasler »

pete writes:
Correct, those collets don't have a tang at all. I'm not all that sure the collets themselves are long enough for those wedges to work,

They are not. I use them on my Frankenmill, which has slots. Adding a hole for a drawbar would have required a gun drill and a larger lathe than I have so I designed a collet chuck mechanism that operates through the slots. It takes care of the extraction problem.
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Bill Shields
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Re: Mill spindle mt#3 - what’s my options ?

Post by Bill Shields »

THE LATHE TAILSTOCKS basically use the 'handwheel screw' that retracts the quill to push out the tool in the tailstock..
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pete
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Re: Mill spindle mt#3 - what’s my options ?

Post by pete »

Yes it does, You'd already know it, but others might not have thought about this. The MT's shank does have to be the correct length to do so. Just any MT that does fit the tail stock doesn't automatically mean it can be used as is. I have some MT 3 mill tooling from my older smaller mill that I'll sometimes use in my lathes MT 3 tail stock. All that tooling has the usual draw bar threads so I have to use those and screw in a plug of the correct length to allow the tail stock to eject the shanks as normal. Forgetting about that little detail, your going to end up with no way to easily remove those tool shanks. Then it's pull the tail stock apart and tap the shank out through the back end of the tail stock quill. Don't ask how I know that. :-)
Torch
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Re: Mill spindle mt#3 - what’s my options ?

Post by Torch »

SteveM wrote: Tue Jan 25, 2022 5:15 pm
This one has a drawbar (actually just a long bolt) and the manual says to tap it.
I downloaded the manual, and found the part where the manual says to tap the drawbar to remove the Jacob's chuck, however this image from the manual clearly shows the slot in the front of the mill quill and the accompanying parts list lists a drift as one of the included accessories:
Pages from g9729_m.jpg
I don't know if the slot is appropriately located for a collet. I have an R8 quill which does require a tap on the drawbar -- but R8 is a steep pitch and doesn't require much of a tap to loosen.
pete
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Re: Mill spindle mt#3 - what’s my options ?

Post by pete »

At a guess, that slot is probably intended for when MT drill shanks are being used that don't have drawbar threads. So the same idea and method is used with an extraction wedge and what gets done on drill press spindles to force the shank loose.
Farmer Dan
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Re: Mill spindle mt#3 - what’s my options ?

Post by Farmer Dan »

I’ll let you guys know how much banging it takes to release the MT but it might take awhile. I’m still waiting for the Grizzly to arrive . I have purchased grizzlies SB1350 collet set and 2 MT tool holders . I’m welding on the bench this evening and I think I went overboard . Came across ( in the old junk yard , every farm has one ) 3” channel doubled together making it 3 by 3 . Using this as my framework .
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