Author Topic: What went wrong with my chuck taper?  (Read 7040 times)

Offline John Hill

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What went wrong with my chuck taper?
« on: February 27, 2009, 04:23:04 AM »
I put a piece of metal in the 3 jaw chuck and trued off the end OK.  The I put my tail stock chuck on its taper, put the centre drill in and tried to centre drill the work piece.

For some reason the drill went off centre and the tail stock chuck did a little wobble, so I tried again, same result.  It is the tail stock chuck coming loose on its taper and I could even feel a little wobble when I really tried hard.

So I took my percussion driver and knocked the taper more firmly into the chuck. 

Is it normal to need to do this?
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Offline Darren

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Re: What went wrong with my chuck taper?
« Reply #1 on: February 27, 2009, 04:29:36 AM »
It could be a number of things,

How old is the lathe, is it worn.
Is the tailstock taper clean, it would only take a speck of dirt to upset things

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bogstandard

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Re: What went wrong with my chuck taper?
« Reply #2 on: February 27, 2009, 05:33:28 AM »
John,

As Darren says, it can be a lot of things, but the usual suspect is the chuck taper has released itself

DO NOT HIT ANY PART OF THE CHUCK OR ARBOR  :hammer:

You might already have done irrepairable damage, and the chuck just might not run true again.

Put the chuck on the arbor taper after first cleaning both mating parts, then gently tap the arbor tang onto a solid surface (NOT THE LATHE BED OR ANY OTHER BIT OF MACHINERY), that should then lock both parts together.

What I tend to do is put a very tiny amount of high strength Loctite on both parts before assembly. Not even half a drop of Loctite, just the faintest smear. Don't expect ever to take them apart again afterwards.

John


Offline John Hill

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Re: What went wrong with my chuck taper?
« Reply #3 on: February 27, 2009, 02:50:44 PM »
Dont fret John, it was only a loving tap on the end of the tang! ::) That was after cleaning both surfaces a couple of times, even cleaned it once with alcohol (what a waste) as the surfaces should be dry, right?
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bogstandard

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Re: What went wrong with my chuck taper?
« Reply #4 on: February 27, 2009, 04:56:26 PM »
Is it locked on now John, or are you still having problems.

If it is a guaranteed taper match (there are a lot of different ones) then it could be the taper is a little long and only just allowing the chuck to seat correctly. Just by removing 1mm from the end of the taper can give that a permanent fix.

John

Offline John Hill

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Re: What went wrong with my chuck taper?
« Reply #5 on: February 27, 2009, 05:46:05 PM »
John, if I recall correctly the arbor came from a Jacobs box but the chuck  was 'chucked' in a plastic bin with a lot of others newly arrived from China. They were shop man "gifts" given because I gave the shop man a box of beers for helping me move the lathe home and get it set up in my garage.

I could almost swear there is a subtle difference in the taper as there is a distinct impression that the small end of the arbor is smaller than the hole in the chuck and there were clear bright marks on the arbor indicating the most pressure had been at the other end. So I dont think it is a case of the arbor being too long as that would surely give the wobble at the other end.

It is stuck on right now, I will be checking for centreing this afternoon (it is Saturday and of course it is pouring with rain in sunny Wellington).  If it is out I will be pondering the next step.

I am wondering at this process:


1: put a bar in the main chuck, 1/2", 12mm or whu.
2: skim bar to be accurately concentric with spindle;
3: place the small chuck on the bar with jaws towards main chuch, tighten firmly.
4: put arbor in tailstock
5: put 'something' on arbor
6: bring up tailstock and clamp down
7: use tailstock ram to advance arbor gently into the chuck just until contact is made while turning the lathe by hand
8: withdraw arbor and look for marks.


Question is, what stuff should be used in 5?  I dont have engineer's blue though I guess I could get some, maybe I will try with a felt pen marker.

If the tapers are subtly different can I lap the two pieces together in this rig up?

[Thinks, why dont lathes have a hand grip on the spindle?  Using the chuck key as a tommy bar seems so uncouth and I am sure is not good practice]

« Last Edit: February 27, 2009, 05:48:38 PM by John Hill »
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Offline Darren

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Re: What went wrong with my chuck taper?
« Reply #6 on: February 27, 2009, 06:12:49 PM »
John, if I recall correctly the arbor came from a Jacobs box but the chuck  was 'chucked' in a plastic bin with a lot of others newly arrived from China.




Oh, one of those.
I too have a brand new Chinese chuck with a new arbor and have exactly the same problems. It spins on the arbor... :bang:

I have just bought a Bison keyless chuck to replace it, but yet to get hold of a 6J arbor for it.

You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline John Hill

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Re: What went wrong with my chuck taper?
« Reply #7 on: February 27, 2009, 07:56:09 PM »
Well Darren my chuck seems to be well fixed to the arbor now.  I have just trimmed both ends of a bit of scrap and centre drilled each end without problem.
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Offline sbwhart

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Re: What went wrong with my chuck taper?
« Reply #8 on: February 28, 2009, 01:37:19 AM »
Hi John

It looks like you've got your problem licked. Just to try and answer your ?:-  felt tip marker is fine or just ordinary pencil just rub it up and down on the stub will give you a witness mark. For the stub taper to work the male and female have got to be a dead match, as the length of engaugement is short, and the torque they have to withstand when drilling is high, I've had the same problem, best way to fix it is lap to best fit and use heigh strength loctite or supper glue,:-  that'll stop it breaking wind in Church.
 :ddb:

On the subject of chucks from China the one I got supplied with my 3 in 1 some 5 years ago was next to useless I chucked (pun intended) it in the scrap bin, and replaced it with a UK manufactured Jacobs that are no longer available. The Chines chuck supplied with my Seig mill is a different kettle of fish its very good more like the UK Jacobs  :thumbup: up to yet I've had no problems with it.

Cheers
 :wave:
Stew

A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline John Hill

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Re: What went wrong with my chuck taper?
« Reply #9 on: February 28, 2009, 01:57:24 AM »
Thanks Stew, I will buy some Locktite next week.  The trick though as it has enough clearance to wobble will be to get it stuck while it is in line,  hopefully doing it in the lathe will get it aligned.

Regarding breaking wind in church, there was a funny incident which almost made me laugh at my father's funeral.  It was a long service and right near the end just then the pall bearers were being called to carry him out a side door of the church blew open, I heard one of his brothers behind me say "He's had enough of this already!"
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Offline sbwhart

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Re: What went wrong with my chuck taper?
« Reply #10 on: February 28, 2009, 04:48:59 AM »
Hi John

I bet your father would have found your brothers remark very funny.

If you've got a bit of a wobble sounds like the tappers are not matching up.

Loctite 603 is the high strength one you want to get 10ml will last a long time I've fastened my loco wheels on their axles on advice of the UK Loctite sales manager, I've known him for at least 30 years, he recons they stick full size loco wheels on their axles using this stuff, I found it a bit hard to believe, so once I've got my loco running on air I'll pin the wheels as well.

You can't beat good old belt and braces job  :hammer: .

Cheers
 :wave:
Stew
« Last Edit: March 01, 2009, 05:54:34 AM by sbwhart »
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire