Taking a milling cutter for "walkies"

[arnoldb]

Newbie Boo Boo:

I needed to cut some longitudinal slots in silver steel rounds today. This had to be done on the lathe and vertical slide, as I don't have a milling machine.

I know that if I shove my tailstock Jacob's chuck in the headstock, and try to use that to mill, that chuck is coming right out ( pretty please - don't ask how I know that :-[ )

At the risk of getting told I should use a collet chuck for milling in the lathe: I know - I don't have any!

My normal 3-jaw is out of center by a good amount, so no go...

Only the 4-jaw is left, so loaded that on the spindle, and centered the 4mm cutter in it.

Now, my 4-jaw is the best chuck I have, so no over-tightening of the jaws, and it is "horrible" to have a HSS tool bit clamped in there - I might hurt it's jaws, but I have no choice...

Started cutting, and the cutter bit went walkies, so serenely I didn't even notice, until too late - result in the picture - lower part.

So re-setup everything, and tightened slightly more, and thing worked out OK, though not beautifully - top part of picture.

Regards, Arnold.

 

[mklotz]

Unlike drills, milling cutters have hardened shanks so chucks can't get a grip on them - hence the "walkies" (Wallace and Gromit?) problem.

On mills one can use a collet or an endmill holder

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=210-1234&PMPXNO=24048519

which retains the endmill in a closely fitted hole with a setscrew that seats on the flat ground into the endmill shaft.

I'm wondering if folks in your position (i.e., needing to hold an endmill in a chuck) could fabricate something similar. Round stock drilled, bored and reamed to the right size for the endmill (typically 3/8" or 1/2" here in the Imperial erstwhile colony), then fitted with a setscrew a la the commercial model above.

The chuck could get a good bite on the holder and the setscrew would keep it from pulling out. [Aside: With the setscrew nearly seated on the flat, pull the endmill out as far as possible and then tighten the setscrew. DAMHIKT.]

It might require centering each time it was used but, since the number of endmill shank sizes is rather limited, that might not be an overpowering limitation - recentering would not be necessary if the next endmill used had the same size shank.

 

[bentprop]

I have a feeling this was more the work moving,rather than the cutter.If the cutter was moving,surely it would have broken?On the other hand,milling in the lathe is always going to be a compromise.
Lack of rigidity could be another culprit in this case.How solid is your vertical slide?Did you use a 4 flute,or 2 flute?2 flute would be the best in this application.

 

[Stan]

MT2 or MT3 collets are very inexpensive and using a piece of all thread rod, as a drawbar, to pull the collet tight into the spindle is probably your cheapest and best solution. This gets about the best centering and least runout at the cutting end possible. Morse Taper collets come in sets or individually, so you only need a couple if you buy endmills with standard size shank.

 

[arnoldb]

Thanks Marv, bentprop & Stan.

Most of my endmills do not have a flat on them - nothing a trip to the bench grinder cannot cure. What they do have is thread at the back, so I'm thinking for now to get/make a nut that will fit that thread, and a simple split collar I can grip in the 4 jaw. Centering in the 4 jaw is not a problem anymore; I've got that down to a quick job by now.

Rigidity _is_ a problem - my machine is nowhere near as rigid as I'd like for milling - even with all unused surfaces clamped, and it has some play in the headstock bearings. I have thought a bit, and I'd be better off cutting slots vertically as close as possible to the vertical slide's center line - instead of horizontally; that should help as well.

I'll also go around the engineering tool suppliers here in Windhoek and see who can source MT2 collets; that will be the best solution for me

Regards, Arnold

 

[Maryak]

What they do have is thread at the back, so I'm thinking for now to get/make a nut that will fit that thread, and a simple split collar I can grip in the 4 jaw.

Arnold,

I'm not sure that's such a good idea ??? The cutting forces will tend to drive the cutter hard up into the nut and jam it in good and solid. Milling cutter chucks have a flat face behind the holding collet which prevents this and the collets are also tapered to match the inside of the chuck which, if the cutters are pushed down against the chuck tightens the collet around the cutters.

There are plans available from my hobby store to make a cutter chuck otherwise IMHO, the best option is the morse tapers.

Best Regards
Bob

 

[arnoldb]

Thanks Bob.

There are plans available from my hobby store to make a cutter chuck otherwise IMHO, the best option is the morse tapers.

I was about to ask: Is that _your_ hobby store, or an online hobby store... Then I decided not to appear too stupid ;D and googled for "my hobby store" - Thanks! - there's a lot to drool about there :big:

For now, it looks like I'll have to get the morse tapers - at least that will also save me some time centering pieces. If I can't get them, I guess I'll just have to make them - Maybe it is high time I started to practice taper-turning ;D

Kind regards, Arnold

 

[Maryak]

Arnold,

Apologies. :-[

Marvellous what a difference a set of "" can make. Glad you sorted it out.

Best Regards
Bob

 

[Philjoe5]

I often use end mills in drill chucks on the lathe or mill/drill machine to make flat bottom holes. I use a standard drill to make the hole, then right away chuck up the end mill to make the bottom flat. I haven't had one slip yet. Am I just lucky or is it the application of side forces in the milling operation that causes the end mill to "walk"? Any advice appreciated.

Cheers,
Phil

 

[Thad Swarfburn III]

MT2 or MT3 collets are very inexpensive ...

I don't see these either with Enco or McMaster. Can you quote a source? Or do you mean with an adaptor?

Thanks,
Matt

 

[ozzie46]

"Little Machine Shop " has them.

Do a google for Little Machine Shop. Hope this helps.


ROn

 

[arnoldb]

Bob, no apologies required - It's good to keep the grey matter working

I often use end mills in drill chucks on the lathe or mill/drill machine to make flat bottom holes. I use a standard drill to make the hole, then right away chuck up the end mill to make the bottom flat. I haven't had one slip yet. Am I just lucky or is it the application of side forces in the milling operation that causes the end mill to "walk"? Any advice appreciated.

Phil, I'd advise against that, especially if you are working brass. If the end mill digs in, and does not pull the mill out of the chuck, the entire chuck is liable to be pulled out of it's taper if it is not fitted with a draw-bar. I've had this happen with my drill press and just a normal drill :-[ ...

Regards, Arnold