Pozilock Chuck

I have a PoziLok chuck which uses threaded collets. If I make a new collet
without the thread, provided the collet is properly dimensioned for the
chuck/cutter, I should still be able to grip the cutter securely. Or
should I?
Advice gratefully received.
Steve
Reply to
Steve
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I have one as well. (Well, three actually if you count the INT30, the MT2 and the replacement myford thread chuck that I made when I discovered how flexible MT2 was)
I have made collets to hold non-screw thread cutters with no trouble at all. You can use lock screws for cutters with a flat, my preference for cutters without a flat is to Loctite the cutter into the collet.
I use FCMS for the collets and make a handful of blank collets at a time, then drill/bore/ream (as appropriate) the blank collet to fit the cutter, while held in the chuck. This ensures the best concentricity that I can get. To do this, I remove the centre-point from the back of the chuck to give room for the drill/reamer to come out of the back of the collet.
Hope some of that made sense.
Mark Rand RTFM
Reply to
Mark Rand
In a word - NO!! There is no difficulty in making threaded collets - they ALL have a 20tpi Whitworth form thread (unless of the metric- wash-my-mouth-out variety!) I've both a Clarkson and a Pozilok, and for the former, which has the older, round-base, collets, I even used a 20tpiUNC tap to make the thread, not having a Whit one, and it works fine. The thread helps to make the cutter self-tightening, up against the inner central point location. Without the thread, the cutter will creep down out of the collett. Disaster the next stop!
Dave.
Reply to
speedy
Thanks for the reply, have you tried a "threadless" collet in the pozilok? I'd been told prior to posting that the thread is for locational purposes rather than gripping the cutter. When I looked at my chuck, the reason the collets don't grip straight shank cutters is because the collets aren't quite long enough in the chuck body.
The Whit/UNC thing raises another question. I told my mentor that the drawbar on my mill was 3/8W - spec from supplier. He said UNC has been a machine tool standard since the ark, so it's more likely to be UNC. He also said you can't tell them apart by eye so don't worry about it!
Steve
Reply to
Steve
Very clear thanks for the tips.
Steve
Reply to
Steve
so don't worry about it!
I can see how that works, thanks.
Steve
Reply to
Steve
You were misinformed about the purpose of the thread. Any tendency for the cutter to slip forces the collet down thus tightening the collet..
Tom
Reply to
Tom
Bollocks:
The way these chucks work is that you fit the collet into the chuck and tighten the locking ring so it's about 1 to 2 threads from being closed up. You then screw the endmill into the collet until it locates on the pip at the bottom. THEN you tighten the locking ring. You must have some space between the ring and the body. Any attempt for the cutter to spin will force the collet down and grip more.
If you tighten the locking ring fully and allow the collet to press down against this it makes it hard to release. Because of this pip and thread action these chucks in their ORIGINAL form can only hold threaded cutters.
As you have noticed the collets are too short to grip a plain cutter and tighten up.
There are two ways to hold plain cutters SAFELY in a posilock. First one is to make a collet with a thru bore to hold a plain cutter but is longer so it can tighten up not onto the pip but the base of the body and the locking ring.
Second way is to insert a cup grub screw into the end of the collet to mimic the threaded portion of the end mill. This will allow it to hold the collet down but in both cases you will loose the self tightening action.
In place of a grub screw you could use part of the threaded portion of old cutters cut off with a dremel and having a screwdriver slot cut in.
I have used this latter method for many years with no problems at all using both imperial and metric collets and all sizes of cutters.
I can post photo's if needed of these and also long reach collets that hold small throw away cutters. -- Regards,
John Stevenson Nottingham, England.
Reply to
John Stevenson
Thats great thanks John. I've been given a couple of cutters with imperial plain shanks and my threaded collets are metric, the obvious answer seemed to be to make a collet without threads.
Best Regards
Steve
Reply to
Steve

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