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Cutting a keyway.

Hukshawn

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#1
I'm thinking about making some collet blocks for my R8 collet for the mill, mainly for tightening the nut in the vise before putting it in the mill.
I own a press, mini mill, and a 10" lathe and various hand tools. I need to cut a keyway to put a key in the block to slot in the R8 collet. Are my options limited to a needle file?
 

Hukshawn

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#3
That's a good idea...
That's why I asked!

The torque required to torque down the nut would likely damage a pin over time. But a set screw with the threads removed off the end with a jam screw above, that should work fine.
Don't think it would potentially wear a spot on the collet?
 

Tony Wells

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#5
I must be missing something. If your mill accepts R8 collets, does it not have a drawbar? What exactly are you wanting to tighten up before you put it in the spindle?
 

RJSakowski

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#6
I would opt for an actual key if you are using the keyway to resist having the R8 collet rturn while tightening/loosening a nut. The Pin will work well for locating but the contact area is really only a short line. A key will have contact on an entire surface. If you do decide to use a pin, locate it at a different position than the pin in the mill so any distortion that occurs won't affect the fit in the mill. Also avoid the ground cylindrical e4nd of the collet.

As to how to make a keyway in a block, I think that I would mill a slot from the outside into the interior of the block and insert a key flush with the outside and protruding appropriately on the interior. The key can be locked in with a pin or set screw.
Collet Block.JPG
 

Silverbullet

Active Member
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#8
Even the spindle in the mill uses a set screw style key to guide the collet till tightened. If making blocks it should work for them as well as the mill . Plus is it's easier to repair or replace it.
 

benmychree

John York
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#9
I can speak with experience regarding using a pin to lock the R8 in anything; I had an Induma (Italian) 1-S mill, much like a Bridgeport in design, and it used a pin to lock the R8 adaptors; the pin was sheared off when I bought it, and also a couple of teeth were missing from the spindle housing rack, so I had a customer who had business in Italy pick my up a new one and the sheared screw/pin. The spindle must be removed to replace the pin, and I think that I replaced the bearings at the same time; practically no sooner that the pin was replaced, a minor mishap sheared it again, that was near 30 years ago, it is still in use with no functional pin, as long as it is used in the normal CW rotation there is no problem. I'd have to think that Mr. Sakowski's suggestion above is an easy and elegant solution to the problem, even superior to cutting a keyway through and having to hold a key into the slot.
 

Bob Korves

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#10
My first Millrite mill had a broken pin in the R8 spindle. I used it and it worked. I did not want to take the spindle apart to put a new pin in. My second Millrite has the pin, and I use it and like it just about as well. R8 spindles seem to do just about as well with them as without them. I would hate to have the collet spin in the taper, though...
 

benmychree

John York
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#11
My first Millrite mill had a broken pin in the R8 spindle. I used it and it worked. I did not want to take the spindle apart to put a new pin in. My second Millrite has the pin, and I use it and like it just about as well. R8 spindles seem to do just about as well with them as without them. I would hate to have the collet spin in the taper, though...
As long as the rotation is CW, that is not going to happen, or at least not enough to cause any damage.
 

Hukshawn

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#13
I would opt for an actual key if you are using the keyway to resist having the R8 collet rturn while tightening/loosening a nut. The Pin will work well for locating but the contact area is really only a short line. A key will have contact on an entire surface. If you do decide to use a pin, locate it at a different position than the pin in the mill so any distortion that occurs won't affect the fit in the mill. Also avoid the ground cylindrical e4nd of the collet.

As to how to make a keyway in a block, I think that I would mill a slot from the outside into the interior of the block and insert a key flush with the outside and protruding appropriately on the interior. The key can be locked in with a pin or set screw.
View attachment 239291
I think this is the design I'm going to shoot for..
I really do not want to use the pin in the mill or my spindle lock in the aluminum pulley to crank down the er32 collet. If I mill the slot to reasonable tolerances, a set screw, amd some locktite, that key should never move no matter how hard I crank the collet nut.
 

Hukshawn

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#14
There's a good thread: http://www.hobby-machinist.com/threads/cutting-keyways-in-a-pulley.1050/ that might give you some ideas - the first few posts will probably be enough!

Dave H. (the other one)
I had tried that on my mini mill once, specifically, trying to make the mini Starrett tap holder mr Pete was making. The mini mill isn't rigid enough for that operation. Just didn't work. However, my lathe is. It had crossed my mind to try it, just haven't yet. And it would be reasonably easy to set up after boring out the r8 in the block still in the lathe.