Holding milling cutters in a drill chuck

But if you read the first post you would have known what Mag it was in

Re: End mill holder wear;

Googled and found the following link. Forrest Addy is well known in at least North America, and I believe, well regarded. He starts the following link:

**LINK**

I'm just the messenger; professional machinists I used to work with (scientific instrument/device makers) put me on to the end mill holder issue. The googled link above may explain holder/collet wear in a clear manner.

Anyway, just FYI, comments welcome.

John.

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Now I'm really confused, Martin

MichaelG.

There's a torrent of chaff going on here. But put simply, if your chip load (radial cut per tooth) is going to be in the region of 1-4 thous and your TIR is 4 thous, all the cutting will be done by one tooth. If you do that with a small diameter cutter in a typical hobby machine, it may work out expensive (breakages). With a bigger cutter it may simply cut oversize noisily before the cutter works its way out of the chuck. This isn't about safety or chucks falling off tapers.

How many posters here have actually measured the TIR at the cutting edge on their machines before commenting? <almost complete silence>. I suspect the 4 thou quoted earlier may be relatively good.

Don't see why you are confused.

1. I just cannot imagine breaking an end mill with 4thou runout.

2. I thought Jacobs chucks were better than that and I suspect most are.

3. If needs must hold milling cutters in a Jacobs rather than doing it properly, you already expect sub-optimum performance. So you must have had a sensible reason for doing it in the first place (Like producing a counter-bore or getting in somewhere to clean up a casting with a ball nose). It really is not normal practice but we all stretch a point now and again.

regards Martin

I do agree that to take very heavy cuts or use big (more than 1/2" ) cutters in a weldon shank endmill holder probably isn't a good idea, not even the makers of these things would condone that, hence why they don't generally go over that size. You wouldn't catch me dead holding a 7/8" cutter in an end mill holder, no way josé! I would always use a collet or drawbar taper type for that.

Like he said, it's a compromise, but then they are relatively easy to make and will sufficiently hold 1/4" cutters nicely for a good long while, provided you don't offend or abuse the above stated.

Michael W

Edited By Michael Walters on 06/10/2016 16:00:28

I don't know Michael, these Weldon holders seem to go upto 40mm dia and are good for 25,000rpm

I've got some 3/4" shank weldon type cutters which cut 1" dia ok

Yes and those cropped up earlier - no good due to balance?

My understand is that when power transfer is needed they are the best. Nice and simple too so less tolerance build up another plus at any size. The link isn't a blank end arbour with a hole reamed or bored in it though. Things do wear out too, even collets.

On the basis I would say BS to the link.

John

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John

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I stand corrected, i assumed they were only a remedial kind of workshop build for small cutters but clearly even some swish looking ones with big sizes are about!

Michael W

I thought you would have come across them Michael, as someone who teaches others to use CNC machines. These are often used on auto change tool holders on CNC machines

John Alexander Stewart . Ref end mill holder wear. I noticed the date on the link. 2001. It is worth mentioning that the design in cutting tools and tool-holding has progressed enormously in the last 15 years. Even the concept of taking big cuts with big cutters has been re-evaluated, spindle speeds of 20,000 Rev/min were in the infancy back then and now are common place in newly equipped machine shops. Cutting forces have been reduced by improved cutter geometry. Also no mention was made of shrink fit tool holding. ( just more 'stuff' to scramble the brain!). Hope this gives you a new line for research, Roy M.

I honestly haven't! i are in with a bunch of collet boys unfortunatelyCnc sliders. Floyd automatic* probably supplies em'.

Always get their name mixed up with automation, it's all the same surely! 

When i used mills it was generally bridgeport, large dc steppers, with hydraulic quick change shanks. 

Michael W

Edited By Michael Walters on 06/10/2016 19:26:03

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Confused because [so I believe] your original remark was about Drilling Chucks; but then you agreed with Andrew, about Milling Chucks ... and appeared to do so without breaking-step.

Just explaining my confusion ... I don't really want to continue the discussion.

MichaelG.

It's pretty clear to me that Google may not be people's best friend. Often more a source of confusion.

John

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Re the concern about drill chucks falling off their internal taper when used for millng with sideways load, I just noticed one well regarded supplier sells an ER collet chuck machined with an internal JT1 or 2 taper so it is fitted to a standard drill chuck arbor for use, eg MT2 one end, JT2 t'other. They do say that a small screw in the bottom end of the JT1or2 taper is used to retain the collet chuck for milling puropses.

So if an ER collet chuck can be retained and used sucessfully on a tapered arbor for milling, I wouldn't be too worried about a drill chuck coming adrift, providing it had that internal screw, as many do.

Hopper, when I first started with my mill, using a Jacobs chuck, the chuck was held to the MT3 arbor by a JT 6 taper, it was the MT 3 taper that let go. The JT taper is designed to be semi permanent, unlike the MT taper that is designed to be removed from it;s socket.

Ian S C

Hi there, John,

I have no dispute with any of your post - my comfortable operating zone is sort of defined in the first part of your first sentence (between the words 'OK' and 'but' ) .

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 07/10/2016 11:02:53

see WNT Tooling catalogue on line

So out of curiosity I measure the runout on my Jacobs chucks. Both very old 1/2" jobs and as far as I know have never been stripped and cleaned. The first one was around 2thou TIR and the other one considerably worse at 4thou. I have a tiny one which is 1Morse on a sleeve that came in at 1.5thou. This was at approx 1/2" from the jaws. So they are worse than I thought but still within Jacobs spec.

regards Martin

Did you measure it by holding say some silver steel in it and rotating that in a checked V block and measuring the run out at the end of the taper ?

The V block can be checked with the same bar assuming that the surface is flat and that can be checked by reversing it.

John

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