drive pin on R8 collets

Mixed reviews on that subject. Personally, I'd fix it, but there are some that go out of their way to remove it. It's nice to know that the collet isn't going to spin on you when you tighten the draw bar, which is it's real intended purpose, not to drive the cutting tool, although I have no doubt that it also helps in that department. In all my years on the machines I've never run a mill without one, nor have I ever busted one, although the shank of one of my boring heads is a little buggered up from one from a crash many years ago. I guess you might say it's a personal judgment call.

Harold

Lots of guys don't use 'em. My BP didn't have one when I got it, but I replaced it.

Grant

Charles A. Sherwood wrote:

All the indexing pins, thats what it actually is and serves onbly that purpose and thats to index the tooling........were removed from all the machines in the USArmy machinist tech school, for no other reason other than to eliminate a screwed up spindle or collet if a student crashed the mill. An R-8 collet / spindle setup is self locking by design, and the pin serves no part in driving it or keeping the collet from rotating.

Its a mixed bag if you need to ndex your tooling replace it, other than that its not needed. Visit my website:

expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.

I noticed that a mill I was using in one "high end shop" had had the indexing pin removed and asked the shop foreman about it. He told me that it was really there for indexing of the collet to keep it from turning when tighting or loosening the drawbar, but they'd pulled them from all of the mills after someone engaged the drawbar and started tightening it before the collet was indexed into the pin slot. The pin was soft enough to shear off, but they had the devil of a time getting the collet out without causing more damage.

Gretings Chuck, A friend of mine who is probably the best machinist I know removes his because the speed up tool changes. You don't need the key to hold the collet still when tightening the drawbar if your collets and drawbar have good threads. But, I keep mine because the drill chucks and boring heads with R-8 shanks always go in the same. So you can put the chuck in and it will always run true and the boring head will cut the same size. My buddy agrees with this and he marks his tool shanks and the spindle nose so they go in the same while at the same time allowing faster tool changes otherwise. But he never forgets to line up the marks. And I would aleays forget. Eric R Snow, E T Precision Machine

Harold sez:

"I guess you might say it's a personal judgment call."

Yeah, Harold and a good call it is. The original designers had good reason to include the pin and it should be left in. IMO, those that rant about the pin not being really necessary are just looking for an excuse to justify their sloppy procedures.

Bob Swinney

[ ... ]

Well ... where it helps, really, is when loosening or tightening the drawbar. It keeps the collet and drawbar from rotating as a unit, without you having to stretch one hand up high to wrench the drawbar while the other is down at the collet, holding it and the took in the spindle firmly enough to keep it from rotating under the influence of the drawbar.

But -- aside from that, it is not really necessary.

I've seen in the MSC flyers from time to time a tool which has three flanges on a handle, to allow you to hold the collet from rotating more easily (without a tool in it), or to allow you to unscrew the collet from the spindle (without an index pin being there). The flanges fit into the three radial slots on the collet's end, to allow you to either rotate it or to stabilize it.

I think that this tool is intended to be used on CNC machines where the collet is tightened by power assist.

Of course, none of my milling machines have such an index pin, because one uses 30 taper, one uses 40 taper, and one uses ER double-angle collets, none of which have such key slots.

The larger lahte (12x24" Clausing) does have such a pin in the (5C) collet adaptor, which is helpful while I'm at the other end of the headstock, screwing the drawbar down to the right point where the lever will lock it. For *that*, I am glad to have the indexing pin.

Enjoy, DoN.

That's more or less that to which I was alluding, Bob, but there are those that feel their decisions are just as valid as mine.

I'm anal enough that I tend to jump through all the hoops when I'm on the machines. I wipe out the spindle and wipe off the collet, then hit both with a blast of air before assembling. I also am heads up enough to avoid engaging the drawbar before the collet is properly seated in the spindle. I'm the kind of guy that always wipes down the ways and oils the machine before beginning work, and then I stop during the day and repeat. The oil on my ways is ALWAYS fresh, never dirty. I tend to preach that concept, but not many appreciate being told, so I don't do it any longer. Hopefully those that didn't do it have learned to do so now. It's very important to the longevity of ways and screws.

The one benefit of not having the indexing pin, and I don't take advantage of it, is that if you use something like a Sjogren collet head (I do) and do considerable heavy work, you tend to get a definite wear pattern from the collet. If the collet had the ability to fit randomly, that would not occur. To me, that is not enough of a reason to remove the indexing pin.

Harold

Chuckle!

I'd question just how "high end" the shop was when they pull tricks like that. My opinion? They should have replaced the guy that screwed up, not removed the indexing pins from all the machines. But I digress. I think it's a personal call, as I've stated, but anyone that worked for me that made that call wouldn't be working for me at the end of the day. I, by far, prefer to have those that have enough skill and talent to not screw up instead of altering machines so they can't do so. To me, it's a sign of a fine craftsman when he can operate equipment properly.

Harold

snip-.

It's been years since I last ran a mill with a 50 taper, but I recall that even they have keys, only in this case they are drive keys. Large mills are capable of turning large cutters, so they can easily overcome the taper drive. The #50's with which I was familiar were used in spindles on Cincinnati, Van Norman and K&T mills. The shoulder at the large end of the taper had opposing slots that accepted hardened drive keys that were a part of the spindle. Do your holders have such slots?

Harold

So after all these comments:

Keep it if you have it, don't worry if you don't?

Regards,

Robin

Have you ever used a machine with a power drawbar? On the ones most of their mills were fitted with when you tripped the handle it took about 0.5 seconds to fully tighten the drawbar. I presume some one was changing the collet and just tripped the handle a bit sooner than they meant to.

I'e used alot of mills in alot of shops and my opinion is if its not there it was never a problem. If its in there and ok leave it. If its in there and sticking out too far take it out.

snip

I think that is a pretty unfair statement. A persons desire to have or not have the index pin is certainly not a reflection of the quality of their work proceedures by any means. Its akin to saying those that use a China made tool to make an item will produce an item that is inferior to an item made with an American made machine. Simply not true as to an index pin in or out reflects on work proceedures or quality of work produced. Visit my website:

expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.

Robin sez: "So after all these comments:

Keep it if you have it, don't worry if you don't?"

Jeeze, Robin. I dunno! After considering all the comments here, I got to feeling guilty and removed the pin in my mill. It wasn't all that hard to get out; about 15 minutes with a rat tail file, upside down, did the trick. Now my mill is as good as anybodys! Only thing I noticed is that now it takes more pressure on the drawbar to make the tooling stay in place.

Bob Swinney

Seem to me that everything will work just fine without it. But you might find it annoying to change tooling because you might need another hand to hold the collet from turning. I will just have to try my "new" machine without the pin for a while and see if it annoys me. If it does, add the pin, but frankly it would have to annoy me a lot to pull the spindle to replace the pin.

Thanks for all the wonderful comments! chuck

snip----

When you've spent as much time working in commercial shops as I have, you'll come to understand exactly what he mean. To the man, those that cut corners, be it in processes or how they approach machine tools, tend to be not great machinists. The problem is that when they're surrounded by people like themselves, there's no one to make them look as bad as they are. Those with the greatest skills and ability deal with the field of machining in a totally different way. If you've ever worked with someone that has that level of skill, you'd know and understand it quite well. They stand out. I've yet to see it any different, and I've been on machines since the late 50's commercially. The very idea that a feature of a machine is eliminated because a worker is incompetent (what else would you call it?) and screws up a machine because they're either in too much of a hurry to do it right, or don't know enough to do so, is a perfect example of sloppy procedure, regardless of the reason. Sorry, I agree with Bob. It does reflect on the work that is produced.

Harold

No, I have not, but under that circumstance I can see how it could happen to anyone. There was no mention of a power draw bar originally. If that be the case, I stand corrected. Still, with just a *little* care, it could be avoided!

I'm from the old school where everything that was done on a machine was done by the operator. Skill level is what sorted out those that could from those that could not. I can see that CNC has changed all that.

Harold