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End mills in a drill chuck

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chris stephens24/09/2009 16:46:30
1049 forum posts
1 photos
Hi Guys,
Recently I mentioned that I had used an end mill in a drill chuck for a small job. I got the response that it beggared belief that I had done so. Well to that person and others may I point out a YouTube video, which is a trailer for a machining series by a "Master Machinist" of many years standing. About 4Mins 40secs in he seems to indicate that there are occasions when it is OK to put an end mill in a drill chuck in a Mill.
My question is, do the rest of you think it is OK sometimes, when needs must, to do it. May I point out that personally I mostly  use R8 collets in my mill, failling that an Autolock and sometimes an ER collet holder. The time I did use a drill chuck, I had no alternative. I do like to use the right ool for the job when possible.
I do use a drill chuck to hold an end mill, when using an end mill in the tail stock on the lathe to make a flat(ish) bottomed hole, does this count as a No-No.
 
 
chris stephens 
HasBean24/09/2009 17:17:32
141 forum posts
32 photos
Hi Chris,
I had written a long prose on this and then reread your thread and decided to delete it as I would only be copying what you have already written.
I use a posilock chuck for threaded cutters, 3MT collets,ER chuck etc but if you are not taking a 1/4" cut off some mild steel so be it.
My first attempt at milling was with a straight shank 3 flute cutter in a drill chuck at 300RPM on mild steel with a 5 thou facing cut! Wasn't a problem.
If you are taking cuts that amount to less force than using a drill bit I can't see a problem (referring to the endmill in the tailstock).
Now sideways pressure, that's a different subject.........
 
Paul
mgj24/09/2009 18:22:29
1017 forum posts
14 photos
I never used one for milling, but I have often used one for spotfacing with a slot drill.Never even budged a chuck on its taper.
 
I wouldn't do that now - nothing to do with a conversion of St Paul - just that I now have a mill with a dove-tailed column, so the repositioning problem has gone away . Its easy to lift the head whereas on the previous round column machine, you'd lose position.
Rob Manley24/09/2009 19:18:01
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71 forum posts
14 photos
I cannot see it as a problem for taking small or light cuts with a 1/4" endmill or smaller - so long as you don't require the cutter to run true.  Allot of effort goes into clarkson type collet chucks to ensure that they run parallel to the axis and true, there is no way you would get close in a drill chuck.  So, its OK in some situations (so long as no one is watching!).  Rob. 

Edited By Rob Manley on 24/09/2009 19:18:31

Geoff Theasby24/09/2009 20:25:57
615 forum posts
21 photos
I have an Emco Unimat 3 with milling attachment.
There is no provision for end mills, except in a chuck.   It works OK, but don't overload it.
My largest is 5 mm.
 
Regards
Geoff
The Harper24/09/2009 22:15:42
18 forum posts
12 photos
I'm sorry, if I had been caught using a drill chuck for milling during my apprenticeship, I would have been sacked! A drill chuck is for drilling there is a clue in the name.
If you use a drill chuck successfully for milling then you have been lucky. If the cutter picks up it will jump or kick and this can damage the jaws of the chuck (I have seen this happen), as it only has contact on 3 points. Whereas a milling collet has virtually total contact with the cutter shank giving less chance for jumping or kicking of the cutter. I don't mean to criticise, it is just how I have been taught, swapping toolholders over only takes a little while, so don't cut corners that may take a lot longer to put right.
Gordon W25/09/2009 09:55:25
2011 forum posts
I've used a drill chuck with end mill/slot drill for flat bottoming holes, also home made chuck, by drilling hole in soft end M/T arbour and holding with grub screw, I dont have any choice, like lots of others. Has nobody ever "opened up" a hole by using the side of the drill in a hand drill? Just use common sense
mgj26/09/2009 10:29:28
1017 forum posts
14 photos
Define milling.
 
Then define the directions and types of load.
 
Then look at what milling chucks will take, and what drilling chucks should take, and it becomes pretty obvious what you can and cannot do with a drill chuck.
 
But if someone is seriously attempting to suggest that the load with a slot drill/end mill cutting a flat bottom hole or  spotfacing is in any way different from the loads generated by an ordinary drill bit, then they need to do a little explaining of just how? (Except that an endmill may generate less vibration - in a pre drilled hole. If you are going straight in you'll need a slot drill of course. Nor are we discussing run out)
 
So perhaps we should be a little more specific and not attempt to apply generalities which in truth do not exist.
 
Plainly it is nothing to do with whether a cutter is short and fat, or long and thin - it is to do with the forces generated , and their vectors.

Edited By meyrick griffith-jones on 26/09/2009 10:32:05

John Stevenson26/09/2009 13:13:27
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5068 forum posts
3 photos
Lets look at this logically.
Milling puts sideways forces on the tool, to get technical these are called radial forces. Drilling puts downwards forces on the tool, again technically these are called axial forces so there is a difference.
 
What I have never seen explained is the fact that when milling the radial force is on a straight plane, say the X axis but a drill chuck is only a  3 jaw chuck so one side of the force is supported by a jaw but the opposite force is inbetween jaws.
 
Add to this the helix of a cutter wants to pull into the work as it's cutting and you get the situation where it want to wobble from side to side as it passes from supported to un-supported as it's being pulled out of the chuck.
 
Technically it's called "walking out" which in turn creates the technical term "buggered up "
 
John S.
Circlip26/09/2009 14:16:47
1723 forum posts
It's already been pointed out John
 
  "Just a bit of basic nomenclature Chris, DRILL chucks are for DRILLS, MILLING chucks are for MILLING cutters. Now consider the direction of cutting forces applied normally to the two types of machining. I'm not going to insult your intelligence by filling in the blanks."
 
  Regards  Ian, FW Extrodinaire.
mgj26/09/2009 15:31:35
1017 forum posts
14 photos
john - I believe you are talking of putting a radial load into a drill chuck, which agreed, is unwise in the general run of things.
 
That's rather different from putting an axial load from any form of cutter into a drill chuck which was designed to carry axial loads.
 
Are you sure that you don't have the signs in the axial loads the wrong way round, at least in steel. You need to apply a thrust to drive a drill bit or slot drill. (about 80lbs force to drive a sharp 1/4 bit).
 
As for supported unsupported - well not necessarily - depends on the strength of the chuck. Granted the forces in the jaws are not constant of course, but no one said they were - they are in fact cycling - reaching a maximum as the load is being taken on one jaw, and then being shared between two - in proprtion to the angular difference. (I have no doubt that we can can work out our sines and cosines as well as the next man). But that doesn't mean that the grip on the tool MUST be reduced below an unacceptable minimum.
 
As for walking out - you don't feel that might be more a phenomenon of worn chucks jaws of any sort which allow axial moment   - rather than a cycling of forces in the jaws of a chuck in good condition? Actually you can get walking out in chucks which wholly support the tool - such as ER32 collets - it they are not tight enough.
 
And no - milling cutters don't always generate radial forces. Not on plunging cuts.
 
And there are plenty of pretty flat tipped drills too - many gun drills for a start, and sheet metal drills - or drills ground for drilling into sheet.
 
So again - its not about milling or drilling - its about the direction of the forces being generated. And to some degree the magnitude of those forces vis a vis the strength and rigidity of the set up as a whole.

Edited By meyrick griffith-jones on 26/09/2009 15:32:51

John Stevenson26/09/2009 17:24:02
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5068 forum posts
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"And no - milling cutters don't always generate radial forces. Not on plunging cuts."
 
But if you are plunging technically you are not milling, as you say there are plenty of flat topped drills but there are no X Y tables on conventional drilling machines.
 
There should be no problems plunging as it's just drilling but move sideways and the whole ball game alters.
 
As you say cutters can walk out in ER collets if not tight enough but the problem with drill chucks is they can't be tightened up enough to hold a cutter against serious radial forces.
If it's a Jacob chuck then all bets are off, these people should have stuck to making cream crackers.
 
John S.
mgj26/09/2009 20:21:40
1017 forum posts
14 photos
John - I agree 100%
 
The point I was making was simply that just because one might be using a  milling cutter in a drill chuck, that doesn't  mean that one is doing something unsuitable - and htat perhaps one ought to specify what one is up to. You yourself have said "serious" radial loads, and the poster said "very light" milling. A thin skim in brass being one thing, and for sure, a drill chuck in good nick, properly secured, and you'll get away with that. Walk into NIMONIC and you certainly won't. 
 
I think also when it comes to radial and vibrating loads with drill chucks , very often there are 2 tapers involved, and not just one - unless your drill chuck is fitted for a drawbar and dedicated for use in a mill. (or more rarely it is one of the expensive monolithic ones0
 
Further, most drilling machines do not have the right bearings for milling - or may well not.
 
So all in all, I rather agree that milling in a drill or drill chuck is not a great idea, in general, but not always.
John Stevenson26/09/2009 20:47:47
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5068 forum posts
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Basically it boils down to :-
 
Would we recommend it ? and the answer is no but have we done it in emergencies and for odd jobs?, and the answer is yes
 
John S.
John Wood129/09/2009 16:06:55
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116 forum posts
Quite right John. We all know that it's technically not really the correct thing to do but, if needs must and it's just an odd job, AND IT WORKS then why not? We are mostly amateurs after all and are therefore permitted to bend the rules - isn't that what it's all about?
 
Have fun
 
John
Bill Pudney05/10/2009 03:20:03
622 forum posts
24 photos
I was once a draftsman for the UK Government.  Across the back wall of the office was about 70 feet of shelves full of Design Guideline books.  These covered almost every conceivable aspect of warship design.  As a newcomer the boss explained to me in my early days, that they were GUIDANCE.  If your particular situation matched those shown you had a proven solution.  However, if there was no match then the Wise Draftsman would use the guidelines as closely as possible.
Many of the rules in Engineering are based on precedent.  This applies equally to manufacturing.  The rules work because they are based on experience. 
However sometimes we must avoid being bound too tightly by The Rules.
cheers
Bill Pudney
John Haine05/10/2009 10:50:10
5563 forum posts
322 photos
My tuppence worth.
 
I use my VMB mill as my main drilling machine (not enough space for another machine).  Moving the head between a suitable position for milling up enough to fit a drill chuck and drill takes a lot of winding on the vertical feed. 
 
Now, a trick I learned from Lautard's Machinist's Bedside Reader is, when you want to cross-drill a bar (e.g. for a set screw), put it in the milling vice and take a very light skim on the circumference with an end-mill, which creates a tiny land on the circumference, little more than a line.  You can make this even simpler by mounting the end mill in the drill chuck, using the lever feed to bring it down so the teeth only just contact the workpiece, locking the feed, and then taking your skim with no additional downfeed.  Now replace the end-mill with a centre drill and position it over the centre of the land.  This will allow you to locate the hole quite accurately enough for 99% of cases with no need for wigglers, cross drilling jigs or whatever.  Putting the end-mill in the chuck saves winding time and is fine because the cut is absolutely minimal.
 
John.
Dunc12/10/2009 16:06:49
139 forum posts
From the Google library of old american Popular Mechanics & Popular Science issues
 
Popular Mechanics
Go to http://books.google.com/books?id=RdMDAAAAMBAJ and then locate the Jan 1969 issue for an article " How to Mill on a Drill Press". This article includes construction plans/notes to add lateral support to a drill chuck.
 
A similar, although more complex design is in the US magazine, Machinist's Workshop, Vol 22, #5, Oct/Nov 2009. ("A Spindle Support for your 8" Drill-to-Mill Conversion", by James Hornicek, pp28-32)

 Popular Science
Go to
http://books.google.com/books?id=iigDAAAAMBAJ&source=gbs_summary_r&cad=0_0# all_ issues_anchor and then find the Jan 1952 issue. There is no jig to provide lateral support. Some cutters are drill chuck mounted while others appear to be held in a single-size adapter.


Note that I have tried none of these setups. The usual waivers (not connected, etc) apply. 
calder percival 120/02/2010 23:21:11
19 forum posts
1 photos
when you have  destroyed the job after the endmill has pulled its way out of the chuck or the cutter shattered and hit you in the face you will know why at college you use an auto lock and not a Jacobs drill chuck. you maybe got away with it but luck will run out.
alan briggs 107/12/2010 15:29:04
1 forum posts
Nobody seems to mention that Drill bits and End Mills are hardened and tempered differently. The shank of a drill bit if fairly soft so that the jaws of the drill chuck can grip it reasonably tightly, this wont happen when an endmill is gripped in a drill chuck. Who here hasn't had a drill bit come loose in a chuck and for the chuck jaws to chew up the end of a dril bit or had to turn down the shank of a 13mm jobber drill to fit in a 10mm chuck to find out how soft they are.
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