End mill holder for horizontal mill

[Bob Engelhardt]

I have a horizontal mill, with some collets for holding end mills. But the end mills don't extend very far and my work envelope is limited. So I want to make an extended holder:


With a great deal of trial and error on a practice piece I got the taper angle set "perfectly" on the lathe compound. The problem is that I set the angle as shown: increasing toward the head stock. But to keep the end mill socket and the taper perfectly coaxial, they should both be turned without removal from the chuck, which means having the stock held by the right end. And the taper decreasing towards the head stock. Sigh.

Now, my question is: if I hold the left end and turn the taper as I have it set (and turn the right end also), then turn it around and center in my 4 jaw, will I be able to get the end mill socket coaxial with the taper? As close as an end mill holder should be. Or do I really need to reset the compound angle the other way?

Thanks, Bob

[J Tiers]

Can you get the compound moved (via crosslide) to the far side of the work?

If you can, the taper will then be decreasing as you want it.

You will need to either turn the cutter over, or run in reverse. If you have a keyed (L) or camloc spindle, you would be fine in reverse, I do not think I would try it with a standard threaded nose, as it is sure to release on the last pass of the final operation, which is productive of "interesting" language and often foaming rage.

[Bob Engelhardt]

Can you get the compound moved (via crosslide) to the far side of the work?

If you can, the taper will then be decreasing as you want it.

You will need to either turn the cutter over, or run in reverse. If you have a keyed (L) or camloc spindle, you would be fine in reverse, I do not think I would try it with a standard threaded nose, as it is sure to release on the last pass of the final operation, which is productive of "interesting" language and often foaming rage.

What a clever idea. 'Never would have occurred to me. But ... yeah, threaded spindle.

[tom_d]

With time and a little patience when tightening the 4 jaw you should be able to get the part running true. That's the fun of a 4 jaw. They're adjustable.

What's been suggested in post #2 is also quite doable. I've never had a chuck run off a threaded spindle, but it wouldn't hurt to just take your time with light cuts just to be sure.

What are the diameters you're dealing with here, and what are the capacities of the 4 jaw? You may have other options depending on size constraints.

[Doozer]

I wish people would stop crying catastrophe when using thread spindle chucks.
Back in the day, I had a 10" Atlas. I ran the lathe in reverse plenty of times.
Maybe once I had it start to unscrew, but only because I (me) did not tighten it enough.
You figure out how much of an nudge that it takes to tighten it snug, and still be able
to get it loose again, without stripping your back gear teeth or whatever.
I had a very heavy chuck for my Atlas, an 8" Bison 3 jaw. It was not a light pattern chuck
so you had to go easy bumping it on, easier than a typical light pattern 6" chuck.
But you learn your lathe and what works. Don't be afraid of it.

-Doozer

[tom_d]

Another suggestion;
Looking at the part drawing I'm reminded of the shaft turning exercises done in basic machine shop classes. Start with a piece of stock slightly larger than the largest diameter and drill center holes in each end of the stock. Mount it between centers and turn the diameters to slightly oversize, then turn the taper. This method will allow removing the part from the lathe to do trial fits of the taper onto the mill while maintaining concentricity when returning the part to the lathe. Once all the outside diameters are finished, hold the od of the small end by a small amount in the 4 jaw and support the other end in a steady rest. This will allow for finishing the id that's used for the end mill.

[Doozer]

Leave the end mill socket undersize
and final bore it to dimension in context
mounted in the mill. Just mount the boring bar
in the mill vise, feed with the Z.

-D

[J Tiers]

I do not cry catastrophe on threaded spindles, but I have in fact had one come loose after putting it on tight, and, yes, it was on the next to last pass, which was very much not fun, as it messed up quite a lot of work.

I WILL run in reverse, but not on something like this, where it really needs to be right.

It's fine anyhow, he can turn over the cutter, and it will still be fine, with the cutter flipped, everything will work correctly, as long as he can get the cutter on center.

Leave the end mill socket undersize
and final bore it to dimension in context
mounted in the mill. Just mount the boring bar
in the mill vise, feed with the Z.

-D

Yes, that will be good. If you also have a mark to "clock it" to, then you can get a very low runout system by putting it back in that position every time.

[BCRider]

I'm a big believer in stub arbors to hold such work and ensure good centering.

So leave the compound alone since you don't need it for now. What I'd do is to chuck up the piece you're making the extended holder from and drill, bore then ream the hole for the end mills. Stop there for now.

I also would not reduce the size like you show other than right near the nose. The bigger you leave the majority of it the more rigid it will be. Plus this being a Weldon shank holder you want enough wall thickness to fully support a decent size set screw. So it needs to be left larger.

Now chuck up a piece of casual scrap and turn it to be a touch larger than the size needed for the end mill hole. Then relieve it in the middle and taper at the end. Then size down the remaining two slightly over size collars to be a "tap home" sort of press fit. Not big enough to stretch the metal and ruin the fit on the end mill shanks but enough interference that it takes a good hand push or some fairly gentle "love taps" to tap the holder onto the spud. And file a flat to take the locking set screw. And use the set screw to ensure it doesn't spin due to the load of any cuts. Don't tighten the snot out of it or it'll flex the bar and the final project will wobble badly. Just snug it up and stop.

With that done you'll want to center drill the end. Then you can use a live center to support the holder. Later on you can drill and thread for the drawbar.

Now with it supported from the stub which ensures a true center and the live center on the other end you can do all the shaping on the outside in one go. And because you started with it tapped onto the spud which is accurately centered from being turned in place and not removed your end mill shank receiver hole is dead on axial.

You might feel like you should use a steady rest during the center drilling, but don't. If the end is wobbly at all that's due to the chuck jaws not being axial. And who here trusts their three jaw, eh? So without using enough force to bend the stub arbor center drill the end of the holder blank. Ideally your tail stock is at the proper height.

Come to think of it you might be wiser to use a small sharp cutter to cut a center dimple. Something very pointy that just gently shaves off a whisker of metal. With a shallow conical dimple in place the center drill will seek the center without any fear of the work trying to climb around the center drill chisel point.

[Ian B]

I'd go with what Doozer said - use the horizontal mill to bore the socket, then you know it's spot on.

Ian

[dian]

With time and a little patience when tightening the 4 jaw you should be able to get the part running true. That's the fun of a 4 jaw. They're adjustable.

What's been suggested in post #2 is also quite doable. I've never had a chuck run off a threaded spindle, but it wouldn't hurt to just take your time with light cuts just to be sure.

What are the diameters you're dealing with here, and what are the capacities of the 4 jaw? You may have other options depending on size constraints.

you can take out the radial tir with a 4-jaw but not the tilt.

[J Tiers]

you can take out the radial tir with a 4-jaw but not the tilt.

That is done by shimming the jaws appropriately.

[Mcgyver]

you can take out the radial tir with a 4-jaw but not the tilt.

you're suppose to check run out in two planes. getting it spot on radially at chuck is one thing, but it can have an axial wobble if you don't check in twp planes. It takes a bit of futzing about to correct, but its very doable

[Bob Engelhardt]

I did some trials of various things and convinced myself that at my skill level I need to avoid opportunities for error. IOW, keeping it simple is essential. The simplest is turning the taper and boring the end mill socket in one hold in a chuck.

That does mean resetting the compound angle, but I'm almost there already. It helped a lot by being able to measure the first setting, in terms of thou's per inch.

I appreciate all the replies - there were good, creative suggestions. Thanks