Clarkson autolock help

[SteviegtrParticipant @steviegtr]

When I bought the mill it came with a Clarkson Autolock collet type S chuck. I did nothing with it because it only came with 2 collets that were not the size I needed.

I have been using a ER25 collet chuck up to press with reasonable success. I now have the correct collets for the Clarkson & cutters to suit. Just setting up for tomorrow's task & fitted the Clarkson to the mill.

On using the supplied spanner to tighten & a suitable round bar in the neck of it, the neck unscrewed. It turned all the way up to the MT2 taper flange.

Is this correct as it does seem logical that being like this it gives support to the MT2 taper on the end or nose of it. Just not sure this is how it goes having never used one. Any info appreciated.

Steve.

[SteviegtrParticipant @steviegtr]

[IanTParticipant @iant]

Steve, I'm not sure from your description exactly what's happened – but my Clarkson has a threaded nut that holds the collet in – plus it has a screwed outer sleeve that enables the chuck's MT2 taper shank to be withdrawn from the machine easily.

Is it this sleeve that you are referring too perhaps?

Regards,

IanT

[SteviegtrParticipant @steviegtr]

Yes sorry I was not sure if I wrote it correctly. I have a picture. Basically I fitted the chuck, inserted & tightened the draw bar. Then I fitted a 11/16" cutter to the collet, then screwed the collet in to the main body. The chuck came with a big cast spanner which I tightened the collet in with. But there was no way of stopping the whole thing rotating. I saw it had a collar above the chuck with 4 holes around it. Found a bar that fitted & continued to tighten the collet. But noticed the collar was screwing upwards towards the taper. When it was up to the taper it snugged up against it leaving no gap that my ER25 one does. Picture.

Steve.

[JohnFParticipant @johnf59703]

Steve the chuck you have is made for use on light machines and has a spacial feature – the screw collar at the top of the chuck.

To use insert into your spindle with the collar clear of the spindle nose, tighten the draw bolt on the top of the machine spindle then screw the collar up to the meekest the spindle nose and nip it up.

Insert the correct collet for the cutter and screw the locking nut up by hand then insert the cutter and screw it to meet the location point inside the chuck, then back off the losing nut 1/8 of a turn and screw the cutter to meet the point again, now lock the chuck with the spanner. You can of course screw the cutter into the collet first BUT make sure it is not far enough in to meet the location point. Personally i never do this.

I think i have an instruction leaflet in my workshop for this chuck – will look tomorrow

John

Edited By JohnF on 28/04/2020 23:27:52

Edited By JohnF on 28/04/2020 23:28:49

[not done it yetParticipant @notdoneityet]

John’s instruction might initially seem a bit of a faff, but as the collets are each for one specific size of cutter, you would generally only change the cutter position in the collet when setting it up first time.

[Dennis RParticipant @dennisr]

Go to this site for instructions on Clarkson Autolock chucks.

**LINK**

Dennis

[SteviegtrParticipant @steviegtr]

Thanks guys. I had been told how to insert the cutters by a friend who has a large milling machine. It was that loose collar that had me worried. I now understand when I think it may have been SOD who said they give a MT2 more support. So I will use this now whenever I can. Thanks again.

Steve.

[Steamer1915Participant @steamer1915]

I'm sure we have been here before but you should not back off the nut (not even an eighth of a turn) before screwing the cutter home against the centre point. There must not be a gap between the nut and the body. The cutter will self tighten depending on how high the cutting forces. The cutter will not screw into the body any further when it does this. All that happens is that when the cutter turns, it forces the collet downwards into the taper of the nut and this in turn increases the grip on the cutter. If you have a gap between the nut and the main body, you will most likely (especially on the 6mm or 1/4" shanks) break out the centre in the end of the cutter when the nut is tightened.

(dons tin helmet)

Steve.

[Anonymous]

Posted by Steamer1915 on 29/04/2020 09:51:52:

If you have a gap between the nut and the main body, you will most likely (especially on the 6mm or 1/4" shanks) break out the centre in the end of the cutter when the nut is tightened.

Been there, done that and broken the centre end on a 1/4" cutter.

I'd also agree that there should be no gap between the nut and body. Instructions here:

Andrew

[Nigel McBurney 1Participant @nigelmcburney1]

I was taught (late 1950s) to fit the collet ,screw on the nut,fully home then back off part of a turn then insert the cutter,just tighten the nut by hand , still leaving a gap ,the spanner was only used to remove the nut never to tighten it ,everyone in our shop used this method with no problems or broken threaded ends of cutter,collets in those days collets had two raised driving pegs

[IanTParticipant @iant]

Posted by Nigel McBurney 1 on 29/04/2020 10:20:26:

I was taught (late 1950s) to fit the collet ,screw on the nut,fully home then back off part of a turn then insert the cutter,just tighten the nut by hand , still leaving a gap ,the spanner was only used to remove the nut never to tighten it ,everyone in our shop used this method with no problems or broken threaded ends of cutter,collets in those days collets had two raised driving pegs

I was shown the same way many years ago Nigel – but was taught to have the smallest 'gap' possible (just an easing back) – I still do it that way but clearly it's not what Clarkson recommend…

Regards,

IanT

[SteviegtrParticipant @steviegtr]

Thank again for all the answers given. It seems the collar is unique for MT2 for stability. The only variation in comments is the technique for fitting the cutters. Some say leave a gap, some say snugged up to no gap. The link shows it been snugged up completely to it's shoulder. It then explains how the bit if it rotates will self tighten if needed.

The only downside I can see then is if you have set up to a accurate depth of cut & then the cutter tightens some more. You would then have the wrong depth of cut.

Not a problem for me with the bits I have been doing so far.

Does this mean if you were to do some exact work, 1st do a test pass on some scrap metal to ensure the bit is fully home.

Edit, having read those instructions again it only says that if the cutter tries to rotate is will just tighten the chuck more. The cutter cannot go up because it is already located in its pin. 

Steve.

Edited By Steviegtr on 29/04/2020 11:28:19

[JohnFParticipant @johnf59703]

Steamer & Andrew are absolutely correct according to Clarkson but as Nigel & IanT say I too was taught the same way and never had a problem. Another member messaged me and I replied thus below :—

I have made an album of the Clarkson instructions all in jpg format so you can read it there. It does in fact say as you do in 1. to just screw the cutter up to the location "point" in the chuck and tighten the lock nut — no backing off !

However when and apprentice back in the early '60's we were advised to back off a very small amount so can only assume it was practical experience that was passed on — always did it, still do and its never caused me a problem !

The principle of the Clarkson system is that the cutter is self tightening during use and it cannot be driven into or pulled out of the chuck by cutting forces it works extremely well.

John

[old martParticipant @oldmart]

See the ninth post in the current thread " getting a milling machine ready for use".

[LathejackParticipant @lathejack]

I was also told to back off the the nose piece on an Autolock chuck when I started work almost 40 years ago, but it is certainly not the correct method and is unnecessary and not what the designer and manufacturer intended, and I never do it.

The nose piece with its collet should be screwed and nipped up fully up to the shoulder and left there. Then the cutters are screwed fully in until they tighten up, the collets will fully lock automatically when cutting, hence the name Autolock. The shoulder is also a register to square up the nose piece, and the radial register will centralise it to ensure that cutters run true.

Posiloc milling chucks work on the same principle, but the nose piece is located by a taper at the bottom as well as a radial register. So when the nose piece on these is fully screwed up there is always a large gap below the unused shoulder.

I think the upper threaded collar on Steve's Morse taper Autolock chuck can also be used to eject the chuck by screwing it up against the spindle after the draw bar is released.

 

Edited By Lathejack on 29/04/2020 15:44:43

Edited By Lathejack on 29/04/2020 15:46:46

[IanTParticipant @iant]

Posted by Lathejack on 29/04/2020 15:43:44:

I think the upper threaded collar on Steve's Morse taper Autolock chuck can also be used to eject the chuck by screwing it up against the spindle after the draw bar is released.

That's certainly what I use it for.

IanT

[Mike PooleParticipant @mikepoole82104]

I was taught the Clarkson way of no gap and wondered how the 6mm and 1/4” cutters managed to break the centre end of cutters. The correct method of assembling an Autolock has come up many times on here over the years and the gap method has its followers including JS if I remember correctly. The penny dropped that a large spanner could exert a centre splitting force on the cutter and the mystery was solved. The collet holder has two register faces to ensure concentricity and axial truth for the collet closing cone, I can envisage a tiny misalignment of the cone if the gap is not closed so the register does its job. I always use a rag to screw the cutter in as far as possible so the collet is closed and it is firmly located on the centre pin. I have had no issues with the cutter moving during machining and that is on proper mills rather than the lighter editions most of us use at home. I have an SKF Dormer version of the Autolock and this differs by using a taper rather than the double register so not tightening the collet holder first could result in poor location and the cutter not running true.

Mike

[Clive FosterParticipant @clivefoster55965]

My impression is that the Posiloc type with the inherent large gap are more likely to split the back end of a small cutter than a "proper" Clarkson. Mine will split the back of a 1/4" cutter pretty much every time if you don't snug the nose piece down first. Firm finger tight should be OK but I always give mine a light bump with the spanner after screwing the cutter in.

Got a nice 4 for 2 Brucie bonus when Paul "I used to be a toolmaker" borrowed my Bridgeport and promptly killed the tail end of two cutters. He was taught to use the back off to a tiny gap method on the Clarkson. Most surprised when I showed him a print out of the instructions.

Issue probably arises because folk tend to think the screw on nose is for tightening the collet. Which you'd expect if it were a conventional collet system. Think ER for example. I blame the Clarkson instructions which never make it really clear that the nose piece unscrews so you can get the collet out to change it making it a structural part that has to be kept properly done up.

Clive

[thaiguzziParticipant @thaiguzzi]

Funny old world.

I ALWAYS make sure there is a gap twixt body and nut, been using Autolocks since 1990 professionally on a Beaver and home use on a Tom Senior.

[Martin ConnellyParticipant @martinconnelly55370]

I expect closing the gap on the Clarkson design ensures the collet is in the correct position to be driven by the drive dogs. When the collet is first put in the chuck is it possible to trap it in the wrong place?

Martin C

[Nigel Graham 2Participant @nigelgraham2]

Martin –

It is possible, sort of, to assemble the chuck with the collet up on the dogs rather than between them, but I think it would tell you almost straight away because you would be unable to screw the nut on more than a turn or two.

[Nigel Graham 2Participant @nigelgraham2]

Thank you for this thread – it's helped me, and I've saved the picture of instructions!

'

It's intriguing. all this "I was taught…", against the manufacturers' instructions; and of course an apprentice never questions his superiors' natural great wealth of both skill and experience. *

I was never apprentice-trained but picked it up as I went along, so do stand to be corrected and from time to time do learn such from threads on this site . As here, since I too always thought there was meant to be a tiny gap 'twixt nut and body – it somehow seemed logical. Evidently not, and also evidently being taught didn't always mean being taught the right way; i.e. as the tool was designed to be used!

'

One of my Autolock collets has a broken 1/4-inch cutter shank jammed solidly in it; but snapped across the thread, not split. I didn't break it. It came free with the second-hand collet. I now wonder if it broke thanks to poor mounting technique – perhaps not so much "backed off" as "are we there yet".

Still trying to work out how to remove the broken cutter.

===

* That comment about superiors was tongue-in-cheek but it has had a deadly serious side, such as emerged in the 19C Tay Bridge Disaster inquiry when it considered the shoddy workmanship.

[not done it yetParticipant @notdoneityet]

Still trying to work out how to remove the broken cutter.

Two hopes – no hope and one is dead, as we old ‘uns’ remember.

Drill it out with a carbide drill? Need to get close to the minor thread size to do any good, I would think. Normal right hand drill might loosen it, but likely needs plenty of soaking in release fluid before attempting?

The other (cheaper?) alternative is to dump it, I would think. Your choice.

In my working life, I have come across umpteen discrepancies between operating to ‘the manual’ and operating to get by. Most cost a lot of money for the company involved.

One example was a simple ‘check weigh’ system where what was “reported’ fed to a process (over a weigh-belt) was compared to what was actually fed from a hopper on load cells (material in the hopper was weighed between upper and lower level and calibrated to 0.01 tonnes in nearly 15 tonnes).

The feed-belt result was accepted as correct, even though it usually reported just over 17 tonnes, while only 15 tonnes were actually fed. Unsurprisingly, annual production (by what went over the weighbridge and physical stocks on site) never ever tallied at audit times!

Process operators were contented because it was easier to operate below design capacity and the deficit was annually adjusted in the production figures, without anyone checking how the discrepancy arose. We were talking, here, of around 20,000 tonnes every year which was not produced!

[Anonymous]

Posted by Nigel Graham 2 on 30/04/2020 00:56:49:

It's intriguing. all this "I was taught…", against the manufacturers' instructions; and of course an apprentice never questions his superiors' natural great wealth of both skill and experience. *

Exactly, and that's how better techniques can get ignored, or looked down on. Although at one point I was looking at apprenticeships, due to an impending academic car crash, in the end I'm glad I didn't do one Instead it means I have to work it out for myself, mistakes and all. And I'm happy to try new ideas like CNC.

Andrew

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