CLARKSON AUTOLOCK CHUCKS

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CLARKSON AUTOLOCK CHUCKS

This topic has 16 replies, 8 voices, and was last updated 19 October 2015 at 12:15 by Steamer1915.

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30 June 2013 at 16:35 #123500
RICHARD GREEN 2
Participant
@richardgreen2
A while back I bought a TOS universal mill, and with it came loads of spindle tooling, all 40 INT taper, including 2 large Clarkson Autolock , and 1 large Osborn Titanic collet chucks. all with 1" and 1 1/4" collets,

The Osborn chuck body runs true, also any cutter I put in runs true,

But the 2 Clarkson chucks both run out of true by about 2 thou on the chuck body, and any cutters I put in run out even more , the longer the cutter the worse it is,

These chucks are a " chunky " lump of steel, but could they have been strained at some point during use ?

There is a centre point inside each chuck body, I have removed one to check for any damage, the point looks "used" but not too bad,

I have a new ish Vertex ER40 collet chuck which runs "spot on " in the TOS mill, so the machine and spindle are OK.

Has anyone got any ideas , or should I scrap the Clarksons and move on ?

Richard.
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30 June 2013 at 16:35 #12153
RICHARD GREEN 2
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@richardgreen2
30 June 2013 at 18:39 #123505
Steamer1915
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@steamer1915
Hello Richard, How are you tightening the Autolock? There is a common mis-conception that there must be a small gap between the nose piece and the body. This is incorrect.

Steve.
1 July 2013 at 07:30 #123525
john kennedy 1
Participant
@johnkennedy1
Steve, can you please elaborate on this. I have 2 Autolocks and I am labouring under this misconception,I allways leave a small gap,believing that if the nut 'bottoms' the collet wont close.Everything runs true though..John
1 July 2013 at 08:06 #123526
Michael Gilligan
Participant
@michaelgilligan61133
Andrew Johnston kindly posted Clarkson's assembly instructions, on this earlier thread.

MichaelG.
1 July 2013 at 09:05 #123527
Bazyle
Participant
@bazyle
The critical point is to understand that if the chuck is assembled tight with a collet but without a tool in it then it will not be tight enough to close down say on a bar of the appropriate size. It takes the thread on the tool interacting with the collet and the centre point to push the collet up into the nose.
This means the nose piece can bed right down on the flange to register truely. The centre point must be the right length/condition to push the right amount.
1 July 2013 at 09:17 #123528
RICHARD GREEN 2
Participant
@richardgreen2
I've now tightened the chuck as Clarksons suggest and the cutters now run straighter than they did, but the shanks are still running 2 thou out on a dial gauge, I've tried a 1" collet also 3/4" and 32mm, all about the same, am I being too fussy ?

Richard.
1 July 2013 at 09:27 #123530
John Stevenson 1
Participant
@johnstevenson1
Clarkson is old hat nowadays, for a start many cutters are made with the shank size the same as cutting size like 5mm

No collets exist for this size in Clarkson and you will always be paying a premium for the threaded shank, more so if using carbide.

Industry has moved onto ER's you never see Clarksons used in production these days.

One reason is the way they tighten. Yes I know this is going agaist how Clarkson say but they never had the machinery then we have today.

Put a cutter in like Clarson says, put it on a jig to measure the tool length offset and enter this into the tool table.

Now run the chuck and the fact the cutter tightens it's self up then makes any measurements in the tool table useless.

The ONLY way on a CNC to keep the correct length off set is the tighten the cutter into the collet, then tighten the bnut so you have a small gap showing.

Totally against what they say but the only practical way to do this.
1 July 2013 at 12:40 #123542
Steamer1915
Participant
@steamer1915
John,

I'm struggling to see how the cutter moves out of position when it tightens itself. Isn't this the whole point of the Autolock chuck? i.e. It can't go any further in than the centre point will let it?

Steve.
1 July 2013 at 15:29 #123550
Another JohnS
Participant
@anotherjohns
Posted by John Stevenson on 01/07/2013 09:27:06:

…Industry has moved onto ER's you never see Clarksons used in production these days.

I gave away my clarkson autolock, it came with my mill and I had never used it.

As the other JohnS says, metric and clarkson are difficult, and the ER collet holder is what is on my mill 99% of the time.

I know, not very helpful…

The across the pond JohnS.
1 July 2013 at 15:57 #123552
Michael Gilligan
Participant
@michaelgilligan61133
For info:

Here is how they explained the locking action, in 1942

MichaelG.
1 July 2013 at 16:35 #123555
RICHARD GREEN 2
Participant
@richardgreen2
I've been playing with these chucks this afternoon, and have come to the conclusion that the tightening procedure is quite inportant to maintain any sort of accuracy,

I now screw the nut up by hand , until it touches the main chuck body, then screw the cutter in until it contacts the centre, then gently tighten with the spanner,

They seem to run quite nicely using this method, perhaps Clarksons knew what they were talking about,

I always used to leave the nut uncsrewed about 1/4 turn and then tighten, but when you think about it all you are doing is squeezing the hardened cutter even harder against the centre, doing it as Clarksons suggest is less damaging to the centre,

Richard.
1 July 2013 at 18:42 #123575
Steamer1915
Participant
@steamer1915
Hello Richard

This was my point exactly. I was taught the "incorrect way" in the mid 70's at an engineering training centre where all the local companies sent their first year apprentices. Despite breaking out the centre of a 1/4" dia end mill, I carried on in this manner until there was an exchange of letters in the Model Engineer magazine in the 90's (I think) and only then did the penny drop. I have discussed this point with many people and the general concensus is that most of us were taught incorrectly. At the risk of incurring John's wrath, I would still say that if the cutter was inserted correctly i.e. hard up against the centre, then it shouldn't be able to move "a few thou" when it is used for a heavy cut. All that should happen when the cutter rotates under cutting torque, is that the collet will be pushed down into the taper within the nose piece and grip the cutter more tightly, therefore preventing further rotation. This is surely the ideal situation – the cutter will only be (self) tightened as much as it needs to be. Despite being in the Autolock wilderness for too many years, I now firmly believe the Clarkson people had it right all the time.

Steve.
1 July 2013 at 19:04 #123581
Mike Poole
Participant
@mikepoole82104
I was taught the Clarkson recommended method. It now becomes clear how the small 1/4" 6mm cutters get their centre ends broken, following the Clarkson procedure this has never happened to me.

Mike
1 July 2013 at 20:12 #123586
Michael Gilligan
Participant
@michaelgilligan61133
For anyone who cares …

Here is the Patent

MichaelG.
1 July 2013 at 21:54 #123593
RICHARD GREEN 2
Participant
@richardgreen2
Steve,

I fully agree.

Richard.
19 October 2015 at 12:15 #208458
Steamer1915
Participant
@steamer1915
Wrong thread – sorry.

Edited By Steamer1915 on 19/10/2015 12:16:05

Edited By Steamer1915 on 19/10/2015 12:24:19
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