Question on Atlas lathe endmill holder...

[56type]

No need to use tool steel , they are just bushings . If you do harden them , and they spin , it'll wipe out your original arbor . I would go with something soft . JMO .

Thanks. I just picked up a 3 ft. length of cold rolled 5/8" diameter steel from Tractor Supply while I was out earlier

 

[wa5cab]

@epanzella,​

reducing bushings in 1/16" increments down to 1/4". They were NOT intended for use with Weldon style cutter shanks. As I discovered the hard way.

First, I haven't actually looked for any MT equipped cutter holders threaded for draw bar as I already have two of the Atlas holders and bushing sets (had three sets until I ruined one set). I merely wanted to warn of the consequences of not using a draw bar to secure holders in spindles (applies to lathes and mills, both vertical and horizontal). I don't recall where I acquired the tanged holders but I must have nearly a dozen of them.

Second, you can use Weldon style cutters with the reducing bushings if they have 1/2" dia. shanks as you won't for this diameter use a reducing bushing. But you will probably need to use a longer set screw.

Third, you can also use them with smaller diameter shanks and factory style reducing bushings but you will have to rotate the cutter 180 degrees and pretend that they have plain shanks. I should have done that.

 

[mvagusta]

56type,

AFAIK, I am the one who posted the warning about NOT using the Atlas cutter holder and reducing bushings with the Weldon style shanks. Or if you do, turn the Weldon flat 180 degrees around so that the set screw does not try to go down into the Weldon flat,

The reason is because of how the flats are cut in the reducing bushings. If the shank diameter is 1/2", it will work fine because for that size you do not use a reducing bushing. But look at any of the reducing bushings. They each have a flat cut across the outside of the bushing that leaves a slot at the bottom, not a round clearance hole. The nose of the set screw doesn't actually ever touch the bottom of the slot because the cutter shank sticks up through the slot just a few thousands of an inch and that is what the set screw is tightened against, not the bottom of the slot.

However, if you stick a Weldon shank into the bushing and orient the Weldon flat with the set screw and start tightening the screw, you will begin to deform the bottom of the slot in the bushing into the Weldon slot cut across the cutter shank. And of course you make sure that the set screw is good and tight. Right??? Later, after using the milling cutter to do whatever it was that you needed to do, you will want to return the bushing and the cutter to wherever you store them so you loosen the set screw and go to pull the cutter and bushing out of the 2MT or 3MT adapter and discover that it won't come out. Because you have exceeded the elastic limit of the steel in the bushing and it now protrudes out into the space above the Weldon flat.

After several weeks or months of trying, I eventually got the cutter and bushing out of the 3MT holder but the bushing is still stuck on the cutter.

I know this is an old thread, but this is great information! I recently acquired one of these M6-945 milling tool holders and you probably saved me from bunging it up. Thanks, Robert.

Not sure if I understand exactly what you're doing but If you're making something why make a bushing to be used with a holder. Just make the holder to fit the end mill and put a set screw in it for the Weldon flat. I use a straight shank for the lathe and stick it in a 3 jaw. The reason you shouldn't stick an end mill into a 3 jaw is that they're both hardened. A mild steel adapter works just fine.

epanzella: This seems like a great idea and if I didn't already have one of the tool holders I think I would go the way you did.

But since I do already have a milling tool holder, I wonder ... wouldn't it be possible to swap out the standard cup point set screw with a dog point and avoid the problem when tightening up against the Weldon flats? As long as the window in the bushing was reasonably centered with respect to the dog point there should be no deformation of the bushing when tightened up, right?

 

[QwikKotaTx]

Why can you nut just secure an endmill in the chuck and use that to cut material that is being held in the milling attachment?

 

[epanzella]

Why can you nut just secure an endmill in the chuck and use that to cut material that is being held in the milling attachment?

The end mill and chuck jaws are both hard. The end mill will slip.

 

[QwikKotaTx]

The end mill and chuck jaws are both hard. The end mill will slip.

Thank you for the reply.

 

[SouthernChap]

Why can you nut just secure an endmill in the chuck and use that to cut material that is being held in the milling attachment?

You can, and most of the time, if you're disciplined enough to only ever take very light passes with shallow DOC, you'll probably be fine...most of the time.

But the mixture of hardened chuck jaws and hardened endmill shank is a very risky recipe for tool grip.

It's not just rotational slip that could happen. The forces will tend to pull the endmill axially towards your workpiece and outwards from the chuck. That would be bad for your work piece and potentially even dangerous.

Lathe collet chucks generally aren't expensive. There's no need to be putting on chaps and spurs and yee-hawing one's way into sub-par practice in this case.

 

[QwikKotaTx]

You can, and most of the time, if you're disciplined enough to only ever take very light passes with shallow DOC, you'll probably be fine...most of the time.

But the mixture of hardened chuck jaws and hardened endmill shank is a very risky recipe for tool grip.

It's not just rotational slip that could happen. The forces will tend to pull the endmill axially towards your workpiece and outwards from the chuck. That would be bad for your work piece and potentially even dangerous.

Lathe collet chucks generally aren't expensive. There's no need to be putting on chaps and spurs and yee-hawing one's way into sub-par practice in this case.

Ok. I am going to order some MT2 collets for my Atlas 6" and make a drawbar out of some 3/8"-16 all thread or a long bolt. Thanks.

 

[markba633csi]

You should forget all this Weldon jazz and just hold the endmill in the spindle with a Morse taper #2 collet and drawbar
Two collet sizes will cover most anything: 3/8" and 1/2"
Making a drawbar from mild steel is a great threading project for your MK2- much more classy than all-thread

 

[epanzella]

For end mills I use R8 or ER32 collets in my mill up to 1/2". Over that I go with R8 end mil holders setscrews and Weldon flat.