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BigBoy1
05-07-2007, 10:15 AM
I have a Chinese made MT3 taper socket and bought a Polish made MT3 shank to use in the socket. Both are new with the oldest being 3 months old so wear is not a problem. The tapers do not "lock" as one spins in the other. Could this be due to each being at the opposite end of the tolerance range? I tried to shim the shank with a wrap of paper to see if that would snug them up. It helped but still did not lock them tight.

The shank has a shoulder on it and is appears that this shoulder touches the shoulder of the socket and prevents it from seating deeper. If I took several thousands off the shoulder on the shank would that help solve the problem? Thanks.

Bill

SGW
05-07-2007, 10:28 AM
That sounds like a reasonable thing to try (machining off the shoulder). If the shank can't fully seat in the socket, it certainly won't hold.

You may have to take more than "several thousandths" off the shoulder, but I assume even a tenth of an inch wouldn't be a problem.

TGTool
05-07-2007, 10:33 AM
If the shoulder is preventing further entry of the taper that could certainly account for the problem you're seeing. I'd want to see clear daylight there. Take off 30 thousandths or so.

I also have a Morse taper chuck shank that shows a small step in the middle. It was obviously plunge ground in two steps, but the operator missed the infeed by a little. I called the supplier on that one and they credited that one and I bought a Jacobs, which did have a good shank.

J Tiers
05-07-2007, 12:46 PM
Before you get a-cuttin........

I'd suspect the Polish one of being right, and the chicom one of being wrong..... This may not matter in the end, since you just want them to fit.

First thing is whether the angle seems wrong, or whether the depth is wrong. If the angle is wrong, it will be tighter at one end than the other, and will consistently mark that way using chalk or blue. If the depth is wrong, it won't mark consistently anywhere.

if teh chicom socket is wrong, take off a bit of the end, and it will be OK. That will likely be easier than machining off part of the shoulder, and also probably messes with the cheaper part (always a good idea).

LarryinLV
05-07-2007, 01:15 PM
Big,
There's no hard and fast rule on if shanks should have shoulders, and your socket might be a perfect taper; only starting about a few fractions from the hole opening.

In other words, you won't "ruin" anything by narrowing the shoulder or trimming the lip of the socket. Depends on what you want and how it mates up to other tools.

Does the shank have a tang on the end and the socket slotted to accept the tang to lock them up? Many times the knockout slot is narrowed sufficiently to seat the tang and prevent rotation but I have seen Chicom sockets with the slot off center or not extended close enough to the lip to allow engagement or the taper was ground too deeply or not deep enough.

Try some other sockets or shanks and combinations before you start cutting. Ideally you only want to trim one piece (either the shoulder of the plug or the lip of the socket) so that most other combinations mate easily rather than trimming the wrong one and then having to trim every following like piece.

edited: Looks like I was composing when J.Tiers was sending - I think we're saying the same thing.

matador
05-07-2007, 05:44 PM
@TG Tool:the "step" in the middle is supposedly there to avoid the very problem under discussion,e,g. slightly mismatched tapers.
@ bigboy:I would try blueing the shank and stoning the high spots before doing any cutting.It doesn't take much to correct an odd taper.I only had to stone of 2 spots to stop this problem in my tailstock.You can of course shorten the shoulder anyway.YMMV.

BigBoy1
05-07-2007, 05:53 PM
As a test I tired to get a slip of paper between the shoulders and it would not fit. I took off about 0.005" off the shoulder per try and finally I was able to get the paper to slip between the two shoulders. Once this fit was obtained, twisting the shank in the socket caused the two to grab. With a tap from my rubber hammer seated them so tight I had to use the removal key to get them apart. Thanks for the help.

Bill

TGTool
05-07-2007, 09:07 PM
@TG Tool:the "step" in the middle is supposedly there to avoid the very problem under discussion,e,g. slightly mismatched tapers.


Sorry, matador, but with two different size sections I'd only get a fit into the socket on less than half the length. Not a good hold and a potential for axial play, especially if it's only seating toward the tail. I have some good taper shanks and can tell the difference when I see it. I wouldn't accept that as good quality, no matter what explanation I heard for why it was there.

matador
05-08-2007, 03:07 AM
Sorry tg,I just noticed the "step" part.What I thought of was a "relief"in the middle of the taper,e.g.a section with the diameter turned smaller.I have a couple of these.
I have never seen a "step" in the taper,and agree that it's hard to think of a purpose for one.i will go 'n bang my head on the vice as penance:D

TGTool
05-08-2007, 11:11 AM
Sorry tg,I just noticed the "step" part.What I thought of was a "relief"in the middle of the taper,e.g.a section with the diameter turned smaller.I have a couple of these.
I have never seen a "step" in the taper,and agree that it's hard to think of a purpose for one.i will go 'n bang my head on the vice as penance:D

No need for that, but a special prayer for a micrometer wouldn't hurt.

Actually I pulled out the dud to refresh myself on what I was seeing, and I think what happened is that the wheel dressing was done at too steep an angle. So the shank has a sawtooth form that large at the top, tapers down, steps out a little larger again, and tapers further to the small end.

I didn't intend to actually use it on a chuck, but to set it up between centers as a gauge for setting the compound for cutting a #2 Morse taper. It's obviously not going to do that with any accuracy. It will go into the museum collection of machining curiosities and hopefully not confused with a "real" item.