Holding milling cutters in a drill chuck

[Martin KyteParticipant @martinkyte99762]

re uneven loading Jacobs specify 4thou tir at 38mm so is that really a problem?

Martin

[AjohnwParticipant @ajohnw51620]

Posted by Michael Gilligan on 06/10/2016 08:52:17:

Posted by Neil Wyatt on 06/10/2016 07:53:26:

P.S. holding cutters in three-jaw lathe chucks is a special issue – hardened cutters are not held as securely by hardened jaws.

.

^^^

An obvious, and very appropriate, use for custom-machined Soft Jaws.

MichaelG.

They will hold them well enough to cut. The advantage of the soft jaws is that they will run as true as the machine does. The catch really is that many lathes turn a taper but that wont matter either providing it's marginal. How much taper would be ok is debatable but it obviously needs to be very small.

John

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[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 06/10/2016 08:58:15:

re uneven loading Jacobs specify 4thou tir at 38mm so is that really a problem?

.

That would depend on several things, Martin … Not least which product [?] and how long does it hold that tolerance before it wears ?

Whether 2thou of offset is really a problem might depend on the size of the cutter, the depth of cut, and whether [say] 4thou over-size hole or slot is 'really a problem'.

Therefore: Short answer to your rhetorical question = I don't know

MichaelG.

[Martin KyteParticipant @martinkyte99762]

The question was regarding uneven loading ? The figure quoted was for 1 1/2 inches from the chuck so at that runout the cutter is not going to be tiny and its also max expected TIR too. So I suggest runout as far as the cutter is concerned is tilting at windows.

Martin

[AjohnwParticipant @ajohnw51620]

Seems to have turned into a great debate.

Really the answer is that if some one needs to do it try it bearing in mind that it might go wrong but is unlikely to harm any one – it might "harm" the work.

It probably helps going on the various posts to use a good quality Jacobs chuck that isn't made of Chinese toffee. Lathe chucks used to be a separate part of Jacob's repertoire. Probably still is.

In the past it wasn't all that unusual to see drill chucks being used to hold small work in a lathe instead of a collet. Drill chucks really do have a min grip length that is very close to the length of the jaws or longer. This includes those rather strange looking very old ones that have a very steep taper on the outer nose of the body.

John

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[MWParticipant @mw27036]

Posted by Ajohnw on 06/10/2016 10:02:19:

Seems to have turned into a great debate.

Or rather a great "bait".

[MuzzerParticipant @muzzer]

..

Edited By Muzzer on 06/10/2016 10:20:40

[Ian S CParticipant @iansc]

The main problem with milling with a drill chuck is the method of holding the chuck in the machine. The chuck is held in the spindle by friction alone, were as a collet chuck has a draw bar, also the drill chuck is attached to the MT arbor with a (in many cases) Jacobs taper, sometimes held in by a screw from the inside. Also, compared to the collet chuck, the jaws are fairly weak, particularly if they are used side ways as in milling.

Ian S C

[Tim StevensParticipant @timstevens64731]

It was not my intention to bait anyone – just to establish what is, and what is not 'good practice'.

I draw two major conclusions from the debate:

1. that there is a clear distinction between cutting endways (ie drilling) with a slot drill or end mill in a drill chuck, which is OK, and cutting sideways as this is what tends to cause the tool to walk out of its location.

2. the examples shown to us all, beginners and experts, need to be in line with 'good practice' and should not assume that all readers will know what they are about. Knowing that you can get away with something in some circumstances relies on us having the skill, & experience, to know where the limits are.

So, I would have expected some sort of editorial comment on the lines of 'don't try this at home' – or, better, a little panel explaining that this might be OK for narrow slots in the hands of an expert, or when deepening a hole, etc, but not otherwise.

And I see no distinction between a column drill and a column mill, in relation to this problem. It is the chuck that is the concern, not what drives it.

Cheers, Tim

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Michael Gilligan on 06/10/2016 08:52:17:

Posted by Neil Wyatt on 06/10/2016 07:53:26:

P.S. holding cutters in three-jaw lathe chucks is a special issue – hardened cutters are not held as securely by hardened jaws.

.

^^^

An obvious, and very appropriate, use for custom-machined Soft Jaws.

MichaelG.

Or just wrap the cutter with some brass shim. That's what I used to do when using a vertical slide on the lathe.

Russell.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 06/10/2016 09:59:16:

The question was regarding uneven loading ? The figure quoted was for 1 1/2 inches from the chuck so at that runout the cutter is not going to be tiny and its also max expected TIR too. So I suggest runout as far as the cutter is concerned is tilting at windows.

Martin

.

But you still haven't identified the Jacobs product, Martin

& personally [despite being a Mac user] I would tilt at Windmills

MichaelG.

[Russell EberhardtParticipant @russelleberhardt48058]

A little off topic but Jacobs used to supply a "headstock chuck". It was of the standard drill chuck pattern but designed to screw onto the headstock to hold small diameter (up to 3/4 inch) work accurately as a convenient alternative to collets.

Russell.

[Martin KyteParticipant @martinkyte99762]

The 4thou tir applies to virtually all Jacobs list. Extracted from rotagrip's link.

Martin

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 06/10/2016 10:49:44:

The 4thou tir applies to virtually all Jacobs list. Extracted from rotagrip's link.

.

Thanks for that, Martin

I have no further comment

[simply because I have already said what I have to say]

MichaelG.

[Swarf, Mostly!Participant @swarfmostly]

Hi there, all,

I'd like to put in a word for the 'holder for throw-away end mills' described by Tubal Cain on pages 106 & following of his book 'Simple Workshop Devices'.

I was recently given some small 'throw away' end-mills which have 6 mm shanks and a grub-screw flat. Tubal Cain's account is based on a Jacobs chuck arbor and describes a method for removing the tang and drilling & tapping for a draw-bar but I made mine from a 2 MT blank end arbor with a 1" diameter by 1" long blank end and its rear end tapped 3/8" BSW. I reduced the blank end to ¾" OD and still had plenty of wall thickness for the 2 BA by ¼" socket grub-screw. The 1" OD would have left plenty of meat for a bigger end-mill if that had been my requirement.  3/8" or maybe even ½". 

NB, we are talking about end-mills with a grub-screw flat here.

If I still had access to 'the Company skip' as I had before retirement, I might well have looked for a broken 2MT shank drill but the blank end arbor was quite affordable. I also had to buy a 6 mm reamer but making one end-mill holder in no way uses up all the life of the reamer!!

Once I had material and tooling to hand, it didn't take long, even for me, to make the holder. I am now able to use my 'throw away' end-mills safely and without any of the fear or uncertainty associated with holding them in a drill-chuck.

Try it – you'll like it!

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 06/10/2016 11:11:48

Edited By Swarf, Mostly! on 06/10/2016 11:12:08

Edited By Swarf, Mostly! on 06/10/2016 11:12:40

[MWParticipant @mw27036]

Alot of people might not know that jacobs make alot of small chucks as well, if you're intending to use small drills but can't grip them in a lathe sized chuck. I have 3 small ones, normally covering an imperial range, they weren't cheap but are very useful for the small drills department.(all have 1/4" threaded J0-J1 taper shanks)

So, for mill shanks that have ground flats on them,(my question kinda got lost in all the hubub!) surely the same rule no longer applies with regards to grip, as this is far superior to a round shanks grip with a jacobs?

As with regards to S.M's post, I have a cigarette tin full of the described HSS throw away cutters, mostly 1/4" shank with the said grub holder, very very useful! some 3/16" too.

The name is a bit of a misnomer,probably described original purpose,  because the edges are still quite sharp after along time in a dusty cavernous workshop. 

Sherline actually sell a grubscrew endmill holder but they are so simple to make, it would be no trouble with the usual workshop equipment. 

Michael W

Edited By Michael Walters on 06/10/2016 11:35:20

[Swarf, Mostly!Participant @swarfmostly]

Thank you, Michael, for your post, especially for your endorsement that the holders are easy to make. I would have posted earlier in the thread but held off until I had the opportunity to take a photo of my holder – then I decided that a photo wouldn't really contribute to the subject.

I agree with what you say about 'throw away' being a misnomer.

You say that your end-mills have  ¼" shanks – so did Tubal Cain's.  I actually bought two blank end arbors, a 6 mm reamer and a ¼" reamer to play safe but, so far, my gift seems to include only 6 mm shanks.

And I make no apology for my plug for Tubal Cain's book.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 06/10/2016 11:48:26

[Another JohnSParticipant @anotherjohns]

Posted by Russell Eberhardt on 05/10/2016 20:34:52:

They usually come on an arbour with a drawbar thread but that won't help much as the chuck is usually fitted to the arbour using a Jacobs taper fitting. A sideways force, particularly when combined with a vibration, can detach the chuck from the arbour. Don't ask how I know!

Bingo! It's the tapers holding that is the issue. a threaded drill chuck (like Jason's EMCO work) would be fine in this regard.

John.

[CirclipParticipant @circlip]

Made two "Adaptors" to allow use of "Weldon" throwaway cutters (plain shank grubscrew flatted notch) in a Modeloy Clarkson type cutter holder. One for 1/4" dia body and one for 6mm dia. Adaptors fitted 12mm bore threaded collet.

Using a drill chuck to hold cutters? Only needed one clip behind lughole from toolroom foreman.

Regards Ian.

[MWParticipant @mw27036]

Posted by Swarf, Mostly! on 06/10/2016 11:43:11:

Thank you, Michael, for your post, especially for your endorsement that the holders are easy to make. I would have posted earlier in the thread but held off until I had the opportunity to take a photo of my holder – then I decided that a photo wouldn't really contribute to the subject.

Swarf, Mostly!

No problem, you just reminded me of them really! i actually think it is a point worth bringing up here. I think the whole problem around using jacobs for mills is kind of a backlash if that makes sense? Like "no, i wont follow convention!". It's also very fiddly to change collets and arbors all the time and they are also expensive. So maybe this is where the idea comes from people who know better essentially.

This would be a great post, or "mini article" if you could do it because it would provide a neat solution to hold cutters in an affordable chuck, you would only need 1 collet with straight/plain shank or taper to hold the arbor and can hold a variety of end mills of the same shank size. I'd certainly read it and it would only encourage other people. This way is condoned by a whole host of writers and manufacturers as a safe way to hold them.

Kind regards,

Michael Walters

[Anonymous]

Posted by Martin Kyte on 06/10/2016 08:58:15:

re uneven loading Jacobs specify 4thou tir at 38mm so is that really a problem?

That's awful, I'd expect any decent milling chuck to be less than a thou TIR, and preferably only a few tenths.

Andrew

[Mark P.Participant @markp]

I think people are making a mountain out of a molehill. I agree that holding milling cutters in a drill chuck is not good practice I have done it in the past with no problems, not a regular occurance. I remember that some years ago I needed to cut an 8mm x 50mm rebate in a bit of ally plate, I had only a cheap pillar drill and no cross vise. I made fence with a bit of steel angle and hand fed the plate in with the cutter held in the drill chuck!! It worked but definaly not good practice at all.
mark P.

[VicParticipant @vic]

Posted by John Alexander Stewart on 06/10/2016 11:57:02:

Bingo! It's the tapers holding that is the issue. a threaded drill chuck (like Jason's EMCO work) would be fine in this regard.

John.

Exactly. Some otherwise inteligent folks on here though just don't seem to get it. A threaded drill chuck may still not be ideal but it would at least be safe.

[JasonBModerator @jasonb]

Infact if you already have a finger or ER collet you can make very simple holders for teh FC-3 type cutters and other things as well. Handy when you need all your mills head room and don't have a suitable size finger collet. Run out is only as good as the fit of the cutter in the holder and the "nominal" 6mm or 1/4" shanks can vary slightly from one maker to another

For those that don't want to make a holder for the Wealden shank cutters Uncle Ketan has them in his ARC

[AjohnwParticipant @ajohnw51620]

JT tapers coming loose ? They are supposed to be very accurately made and joined with some force.

The more taper is far more likely to loosen hence draw bars.

The threaded chucks are generally aimed at hand drills.

It's possible to make a "disposable" cutter out of threaded end milling cutters and other type via an off hand grinder. Just add the flat. Reams could be written about doing that as there could be some obvious problems.

Sounds to me like Neil should recall all issues of this particular magazine issue on the grounds of health and safety and as people have paid for them, get the who lot reprinted and sent back to the people who bought them. Or maybe full kevlar body armour is in order not forgetting the head or a very impact resistant transparent face mask. People who are concerned about this area should clearly take out a class action against the publishers.

Maybe another thread should be started on people who dangle things that are way to big on the end of 2 and 3 morse tapers.

John

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