View Full Version : Mill/Drill collet question

12-19-2006, 12:54 PM
It seems that the more time I spend in the shop the behinder I get. Some type of an Amish saying. But it is true. I was viewing a rented dvd series for mills and I was shocked to hear I have been holding my mills wrong or am I? this video said I need to use a mill holder, I have collets but this video says not to use collets. I am not a mill operator very new to them but I was under the impression that is why I have collets.
So with all the know how on this board I hope to get this question answered. Am I doing this all wrong?
Thanks in advance for the help.

12-19-2006, 01:08 PM
Well, gee, I've been using collets on both the mill (Bridgeport, R8) and the lathe (South Bend 9, 5C) for years, and it works for me.

The advantage of dedicated mill holders on a mill is what's called tool height. When you have the mill in one holder, you can figure out where the tip of the tool is on the Z axis and it stays the same, even when you switch to another tool and back. This is especially handy when you have a DRO (digital readout).

I have a DRO and collets. Whenever I put a tool in a collet, if I need to know the exact depth of the tool's cut, I have to calibrate it. That means figuring out the exact height of the tool from the mill table. Otherwise, I could have an accident and mill into the table, and I hate when that happens.

Someday, I'll probaby upgrade.


12-19-2006, 01:14 PM
The reason you gave for not using collets was one they gave and they also said that the mill will walk out of the collet and cause you to mess up your work.

I have used the collets some and so far I have not had a problem but I am my own worst nightmare so anything I can do to make it right is a step up for me.

12-19-2006, 01:21 PM
I've had mills walk out of a collet only once. I got an oversized collet for the mill to allow me to use a roughing mill with a 1" shank. (The largest practical collet for my Bridgeport R8 is 7/8") With a 1" collet, the shank of the mill isn't actually drawn into the mill spindle - you're relying on lever action transmitted through the collet. (I hope this makes sense) Anyway, the mill walked all the way out of the collet and flew out onto the floor, scaring the hell out of me. You don't want a fast-spinning roughing mill flying around the room. After that, the 1" collet went back to the tool box, and I don't think I'll ever try to use it again.

I don't think I'll ever do work heavy enough to cause a mill to walk out of a (normal) collet. Those collets hang on pretty tightly, provided you don't do something crazy, like mentioned above. Things might be different if you're chucking a mill into a collet and taking heavy cuts with it 24-7, but most HSMs don't do that. :D


12-19-2006, 01:33 PM
What else would you use an R8 collet for, except to hold an end mill? I think the alleged problem of end mills walking out of collets is more theoretical than actual. Assuming one has decent collets that fit properly, I don't think it's an issue. Personally, I've never had it happen.

12-19-2006, 01:33 PM
You'll get differing opinions on this one. I will assume you are referencing R-8 collets. Some say mills will "pull themselves out", of collets while cutting.

IMO, B#lls*#@! As long as the taper, collet, and end mill are clean, tighten the drawbar, you should be fine.

After twenty years of doing this, I have had a collet slip only once. That was my own fault, when you forget to tighten the drawbar, what do you expect will happen.

Collets and endmill holders are among tool holding options you have. Endmill holders are IMO, not an "essential" for R-8 use. I have some, and have yet to ever use them.

If the spindle is MNTB, CAT-V, well, then endmill holders become an essential. At home, I have one mill that requires endmill holders as the spindle is NMTB 30. At work, a spindle which is NMTB 40.

Just do not use a drill chuck to hold an endmill.

Others will agree or disagree.

12-19-2006, 01:36 PM
Just do not use a drill chuck to hold an endmill.

That's worth repeating. Drill chucks are weaker and sloppier.

12-19-2006, 01:42 PM
Plus, the side load will take the drill chuck off its mounting taper!

12-19-2006, 01:43 PM
What I was told is that, particularly for large EMs, if you're really running it to max capacity, it can pull downward in the collet. But as long as you're not running larger mills and pushing them hard, no problem. I just use the R8s...

12-19-2006, 02:02 PM
There seem to be more than a few websites and videos that are being produced by people whose claim to expertise is owning a machine tool and a video camera. I find most of these guides a rather poor source of information and a waste of time and money.

To learn machining, stick to the texts and other books that are frequently listed here. Moltrecht, Burghardt, the Henry Ford manual, George Thomas and others. Several of the books by Village Press authored by Rudy Kouhoupt, Philip Duclos, Kozo Hirakoa, Frank McClean and othjers also have a wealth of information included in the projects and plans.

John Stevenson
12-19-2006, 02:05 PM
I was viewing a rented dvd series for mills and I was shocked to hear I have been holding my mills wrong or am I? this video said I need to use a mill holder, I have collets but this video says not to use collets.

Is this one the the Rodriguez DVD's ?


Forrest Addy
12-19-2006, 02:12 PM
BS. Blanket statements like "never use collets to hold end mills" might have a certain reasoning behind them but they deny perfectly acceptable resources from those whose circumstances may be driven by rules. Thus dicatorial absolutists narrow the opportunities available to the naif.

Whatever works works. By all means use collets to hold endmills. If the collet is in good shape it will hold against axial movement. If it is bell-mouthed, it cannot, in rough proportion to wear. Collets do wear. When they worn to degraded performance they should be replaced and the old ones demoted to meaner tasks.

Drill chucks do not have the rigidity or grip to adequately hold endmill for any but the lightest sort of cutting.

The choice of which among many will be suited for a particular application is first driven by what's available, then what's applicable, and finally what works. It's convenient to have a selection of spindle tooling but most people have to live within a budget. R8 collets, R8 endmill holders, DA collets, and EM collets with shank adaptors are all very well but expensive. The new mill drill owner may be limited by collets in the starter tooling set that came with the mill but it's cruel and unproductive to, in effect, sneer at him for lack of endmill adaptors.

You minimum tool guys know what you can afford. Groceries and shoes for the kids come before toys for the shop. Don't be afraid to snub the purists. Also learn not to persist in following a path that leads to difficulties. As in life, success in the machine shop comes from striking a careful balance. In the meantime you use what you have - which maybe collets - to hold endmills and you do so with my blessing drawn from 45 years in the trade.

12-19-2006, 06:59 PM
Good info,, No it was not a Roddy video although I have watched a few of his. I never quite understood someone trying to make parts on a mini lathe when you should be using at least a 36 -40 " one for the size stuff he tries to make. He even went as far as trying to help turn the chuck while it was under power saying the motor was too weak to turn it. Enough of that but getting back to the task at hand, I agree about the collets, the video I was watching was from PMS yep the wives new TV station:D but actually Precision Measurement Services. They supposedly make tools for the auto industry. Yes I am referring to R8 collets and so was the video. The video was old I think was on tape then turned into a dvd. I just cringe every time I hear this stuff. Being a newbie with a mill I never know if I am setting myself up for a meltdown by doing things backwards.
I am happy this board is here so you guys can straighten me out when I sway too far either way.

12-19-2006, 07:18 PM
cybor -
Also, you may have noticed by now that the members here are particularly quick to attack the "Popular Wisdom" when that wisdom is actually bullspit (sp?). For a laugh, search the archives for the term "billet". :D


Optics Curmudgeon
12-19-2006, 07:27 PM
Like many gems of wisdom the "never use an endmill in a collet" thing has taken on a viral characteristic. So far I've seen here many years of collective experience based opinion that there is no real problem doing it. Add my 38 years to that, this is something I had never heard of until this internet thing came to be. Part of the problem with the internet is that it has a really bad signal to noise ratio, newcomers to a field have a hard time telling the gems from the bs, and someone that has taken the time to produce a DVD can be seen as more believable. As has been said, keep everything clean and tight and if you can pull an endmill out of a collet you're trying harder than I ever have.


John Stevenson
12-19-2006, 07:47 PM
I have one 1/2" end mill holder, loads of 5C's, ER 11's, 16's 20's and 32's, shed loads of R8's.

All these various collets EXCEPT the end mill holder rely on gripping the correct sized shank on the whole of the shank inside the collet, which for a 1/2" collet, inside by 1" is just over 1-1/2 square inches.

The end mill holder relies on a simple allen screw with a surface area just shy of a gnat's left bollock and the contact area opposite the screw, not the whole of the inserted shank.

Any wear on the bore of the holder and you duplicate just what happens if you hold in a Jacobs type chuck with the exception that the allen screw on the flat prevents it moving down but won't prevent it coming loose.

If you are that worried about dragging a cutter out of a collet than swap onto the Clarkson system.
It's totally impossible to drag a cutter out of one of these, the more force is applied to the cutter the more it tightens up and winds itself IN

Save the end mill holders for wigglers, centre finders and lobbing at next doors cat.


12-20-2006, 12:28 PM
The masses have spoken and I agree, I will keep my collets and have remembered a saying I heard along time ago, don't believe everything you read in the newspaper! I guess that goes for video too.
Guys,, keep up the good work.

I know I rely on it. Some day when I grow up:D I can take what I learned here and apply it to things I do. I better hurry up because not many wig shacks (retirement homes) have machine shops!:confused:

Paul Alciatore
12-21-2006, 12:50 AM
Sounds like the video you were watching came from the commercial world where a lot of emphasis is placed on getting the most out of every cut. This is necessary in a commercial setting where time is money. The holders make a lot of sense there as the forces on the tool are a lot greater than in a home shop where you may only be using the cutter to 10 or 20 percent of it's capability on most cuts.

If I were in a commercial shop I would probably use the holders or an even better system. At home, the collets are fine for most jobs.

Spin Doctor
12-21-2006, 10:13 AM
Properly used R-8s should not slip. But it can happen. The one thing I do not like with End Mill Holders is the fact they move the tool that much farther from the admittedly weak bearing set-up in a Bridgeport much lise a Mill/Drill. Especially in the larger sizes such as 3/4