Which endmills?

[65535]

Well if plunging (the proper method) a hole saw is the best tool, as it only removes a thin cross section around the arc.

Really a Tube notcher is a better free standing unit, be it homemade or bought. I'm sure you could find a design or plans for a hand drill powered notcher, I know I've seen them around.

 

[precisionworks]

http://chopperhandbook.com/neatstuff/cbh-notcher.pdf

http://chopperhandbook.com/neatstuff/cbh-notcher.htm

 

[olephart]

is a broken endmill at low speeds really that much of a hazard?

I doubt that would hurt anything pink and tender. But, the failure mode I have been referring to is not breakage. I'm referring to the entire cutter departing from the chuck at high speed. It's sorta like starting up a lathe with the chuck key installed. It happens while cutting the work piece. Seems like that would hold it in the chuck, but it don't.

You can pay attention to speed, feed and depth of cut and probably get by with using a chuck for a lot of milling operations. Lots of people do. At least be aware of the problem. Put some fingernail polish where the mill meets the chuck so ya can see if it's moving. It's not an instant thing. Takes awhile to develop.

 

[precisionworks]

probably get by with using a chuck for a lot of milling operations

I sometimes use my keyless drill chuck (in the mill) to hold a small end mill when making one or two shallow cuts, .050" or so. Usually works.

Pipe & tube notching produces forces that are at least one order of magnitude greater, possibly more depending on your particular cutting data. All lathe chucks, whether 3/4/6 jaw, have the smalles of contact areas, with probably 10% of the work piece (or end mill shank) in contact with the jaws. End mill holders raise that number to about 75% contact, collets raise it to around 90% contact. Milling forces are primarily radial for side milling, axial for end milling, and collets do the best job retaining an end mill - short of heat shrink tool holders.

You can easily make a straight shank end mill holder for lathe use. Start with round stock just under the through hole size for your lathe chuck. Mill three flats on the OD that are 120 degrees apart. Ream a hole for the end mill that's .0002"-.0004" larger than the end mill shank, and drill & tap two set screw locations to bear on the Weldon flats. Not as good as a collet but many times better than the chuck.

 

[kd5ahl]

why not use hex stock? Then all you need to do is bore a hole for the endmill and drill and tap 2 setscrew holes.

 

[precisionworks]

why not use hex stock?

Great idea :D

If I were making one (having a welder) it would be even easier to bore the hole about .0005" too small, warm the sleeve, cool the end mill, & press fit the end mill into the sleeve. Weld the end of the shank to the end of the sleeve. You'd never have to worry about the grub screws coming loose.

 

[olephart]

Seems like any of those ideas would work. I made a collet holder for 5c collets to address the problem. About as easy as other options. My lathe has a threaded spindle, so it was simple.

I just threaded a piece of round bar to fit the spindle and made the rest of it in place. Can't get more accurate than that! It closes by tightening a "nut" against the face of the collet rather than pulling from the rear.

Once you attach the stock to the spindle, ya bore a hole for the collet body and cut the taper. Then thread the end to accept the "nut". Ya make the nut so it contacts the outer edge of the collet when tightened and drill holes in both parts to use a "Tommy bar" to tighten it.

It's a nice project to consider and results in a low cost, but very precise method of holding stuff.