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End mills in lathe chuck

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Derrick Watson18/10/2010 16:21:10
18 forum posts
Hi,
 
I've read a previous post on here in which most people thought that you should not use an end mill in a drill chuck. But, it is OK to use an end mill in a lathe, using a 3 jaw lathe chuck ?
 
cheers, d.
Andrew Johnston18/10/2010 16:56:12
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It has been done, but personally I wouldn't do so, for the following reasons:
 
1) The TIR of a 3 jaw chuck probably isn't that good, and if it is, you shouldn't be using it for milling!
 
2) The milling cutter will be much harder than the chuck jaws, so the grip will not be particularly good
 
3) The jaws will only grip over a small area, compared to a proper milling chuck - see above
 
4) A largish chuck holding a small endmill increases your chances of getting a bonk on the nose or hand when getting close to see what is going on
 
No doubt there are many other reasons too. Use an ER style collet chuck, preferably mounted directly on the lathe spindle nose.
 
Regards,
 
Andrew
 
Edit: Of course there's no reason not to use an end mill in a lathe, just not in a 3 jaw chuck

Edited By Andrew Johnston on 18/10/2010 16:57:34

mick18/10/2010 17:14:03
421 forum posts
49 photos
Just use the auto lock chuck held in the spindle taper, for light work there shouldn't be any need for a draw bar. 
Tony Pratt 118/10/2010 17:38:34
2319 forum posts
13 photos
I agree with using a milling chuck in the internal taper but please use a draw bar
Tony
JasonB18/10/2010 17:48:37
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Or if you don't want the cost of an ER or Milling chuck then a MT collet with drawbar will do nicely. Just make sure you can get the cross slide close enough to the spindle.
 
Jason
Derrick Watson18/10/2010 18:32:08
18 forum posts
thanks all, looks like I should probably think about getting a collet. A couple of follow up questions tho:
 
1) what is TIR (showing my newness to the hobby here).
 
2) a drawbar is? - from a quick google search I'm guessing it's something that holds the taper into the head stock (from the gear side).
 
3) how would you get a taper out of the headstock spindle - it wouldn't be like a tailstock mechanism
 
4) what's the difference between an ER and a milling chuck?
 
5) I've got a Sieg C2, it looks like the following ER32 attaches to the backplate having removed the chuck rather than being spindle mounted
 
 
would this be better than a spindle taper type of setup?
 
Sorry for all the questions, cheers, d.
Andrew Johnston18/10/2010 18:43:28
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Hi Derrick,
 
TIR = total indicated runout
 
In simple terms, how wobbly the tool is compared to the spindle axis with which it should be concentric.
 
Regards,
 
Andrew
James fortin18/10/2010 18:52:56
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ive used a 3 jaw for light milling using no bigger than 1/4 inch endmills and this is 'ok.'
 
i think i saw a article by harold hall telling you that if you didnt have a collet chuck then bore out a hole in some bar stock the size of your endmill ,and put a grub screw in the side to hold the endmill in.
JasonB18/10/2010 18:53:15
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1. Total Indicated Runout. if you hold a bar in te chuck and then measure the runout with a dial gauge this will show the TIR, 3 jaw chucks are not the most accurate and usually have a few thou TIR particularly the cheaper end of the market. This runout will cause a milling cutter to cut oversize
 
2. Its basically a bolt that screws into a thread in the end of teh tapered tooling and draws it into the socket and prevents it from comming out.
 
3. Loosen the drawbar slightly and give the end a tap with a lead or copper hammer, this will break the tapers grip.
 
4. A milling chuck is made to hold screwed shank milling cutters and prevents them being pulled out by heavy loads, often called a Posi-loc or auto-loc chuck. Er collets can hold a larger range of sizes than milling chucks which just cover the common shank sizes, Metric ER collets can also be used on imperial stock but its best to have the correct sizes.
 
5 Provided the backplate is perfectly concentric with the lateh spindle nose then it will be fine but bear in mind that if you later get a milling machine you will need a taper mounted one although the actual collets can be used in both.
 
A MT collet like these will be a cheaper option if you just want to hold a couple of milling cutters.
 
 
 
Jason
KWIL18/10/2010 18:57:46
3681 forum posts
70 photos
OK to use a collet in the headstock spindle with A FULL length shear, but do not try it with a gap bed machine because the carriage will not get close enough because of it.
Dinosaur Engineer18/10/2010 19:23:51
147 forum posts
4 photos
Derrick,
TIR or the more correct abbreviation T.I.R. is the total swing of an indicator . If for example a dial test indicator (D.T.I.)  is adjusted to read Zero on a perfect spindle which has no run-out then the T.I.R. will be zero.   If say the D.T.I. is set to read zero at one particular point on a piece of silver steel ( smooth round piece of steel) in the 3 jaw chuck , then the indcator may for example go to minus 0.003" at it's lowest point to say plus 0.002" at it's highest point for one full revolution . Thus the T.I.R. would be 0.005" which is the total indicator "swing". You may hear of eccentrics or eccentricity. Eccentricity is the amount the actual centre of say the piece of silver steel in the chuck, is from the true centre of  the spindle revolution. Thus the chuck at the gripping point of the silver steel diameter is said to be eccentric by an amount of 0.0025" . This is half the T.I.R.
Hope this helps

Edited By Dinosaur Engineer on 18/10/2010 19:40:36

The Merry Miller18/10/2010 21:16:25
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484 forum posts
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What are the chances of  an endmill walking out of a Myford ER25 collet without additional restraining devices?
I am asking  the question before I try it out.
At present I use the three jaw chuck and wrap a piece of paper around the endmill before I clamp up. (not for precision milling I might add)
 
Len P.
Andrew Johnston18/10/2010 21:54:33
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7061 forum posts
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Unlikely, if it is done up properly. ER collets need to be done up 'pretty damn tight', to at least two grunts worth.
 
For ER25 collets above about 8mm, a quick search on the internet shows tightening torques between 70 and 90 foot-pounds. Unless you're the proverbial gorilla you're not likely to achieve that with normal spanners!
 
Regards,
 
Andrew
Tony Pratt 118/10/2010 21:56:41
2319 forum posts
13 photos
Very little chance of it moving if you are sensible ie don't take massive cuts and extremely fast feeds, you have got nearly total clamping area with the ER series collets so don't worry too much. I used them on industrial CNC machines and had no problem that I can recall, you will find them a lot more secure than a 3 jaw chuck.
Tony
John Olsen19/10/2010 00:26:48
1294 forum posts
108 photos
1 articles
The cheapest way of holding endmills securely that I can think off  is a taper fitting for the lathe mandrel with a hole bored in the end to fit the milling cutter. The cutter is then secured by a set screw, or preferably two at right angles. The hole does need to be a good close fit on the shank of the cutter. These are made commercially, but would be not too hard to make at home, assumming you are able to turn a taper. The far end should be tapped for a drawbar. You do of course need one for each shank size. There is the objection that if the hole is slightly oversize, the cutter will be eccentric, while if the hole is exact it will be hard to get the cutter out.
 
I have a commercal one acquired somewhere along the way with a no 4 Morse taper that fits my mill drill, however it has hardly been used since I have two Posilock chucks and one Clarkson, as well as a set of ER16 colletts which is handy for  the smaller plain shank cutters.
 
I would note that although the lobing seen on the silver steel may be similar, it actually has a different cause, it is a problem with the centreless grinder that they have used.
 
The action of the forces on a milling cutter, or on a job in the lathe for that matter, is very like what you do to get a post out of the ground, grab it at the top and wiggle it in a circular motion.
 
regards
John
Gordon W19/10/2010 10:44:51
2011 forum posts
Blank, soft ended Morse tapers are easily bought, with draw bar hole. Just put one in the mandrel and drill the needed hole. Tap for grub screw. Ample for the very light milling you will do on a lathe.
Peter G. Shaw19/10/2010 12:01:03
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1531 forum posts
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I'd just like to add my two pennorth, not that I'm any sort of expert, but through experience on my lathe.
 
I have tried to use the 3 jaw chuck to hold a milling cutter. It wasn't particularly good with much vibration. It did do it though - eventually. I think I also experienced the dreaded walk out of the cutter, ie where due to the vibration, the cutter slowly works it's way out of the chuck.
 
Using a direct MT3 collet and drawbar, cutting was much better and smoother.
 
The drawbar is inserted into the lathe mandrel from the opposite end to the collet, and is used to force (by pulling) the collet further into the taper in the mandrel. This in turn causes the slightly flexible parts of the collet to clamp down even tighter onto the cutter thus hopefully preventing any further movement. I think as well, by using the collet, I reduced the overhang away from the mandrel bearings thus stiffening up everything. Finally, the collet is likely to be more accurate than the 3 jaw chuck, thus reducing out of balance forces.
 
Now, I use a milling machine!
 
Regards,
 
Peter G. Shaw
John Wood119/10/2010 15:26:36
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116 forum posts
Thanks Derrick for starting this thread, it's been a real eye opener for me who naively thought that 3-jaw chucks were pretty good and that milling in the lathe was easy and accurate.  In the light of all the valuable gen which has come to light from those learned scribes above, I am now going off to review my turning and milling techniques with the view to improving accuracy across the board.  Thanks guys.
 
All the best
John  
Derrick Watson19/10/2010 17:58:37
18 forum posts
Thanks, I'm glad it's been of use to others.
 
On a related note, I'm now wondering whether a collet could also be used to hold a work piece. I'm thinking about small (e.g., 3 to 8 diameter mm) rods - obviously the collet would need to be an appropriate size. Would the stability etc advantages of the collet over the 3-jaw chuck also transfer to this use?, or is there a reason not to do this?
 
Again thanks for all the help, d.
JasonB19/10/2010 18:38:45
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Provided the collet chuck is accurate then its an ideal way to hold small items, often the main method of workholding on watchmakers lathes etc.
 
Jason

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