Reducing collet nut play by electroplating thread?

[BazParticipant @baz89810]

Send it back to Nikken and get the job done properly, all this bodging about is only going to prolong the problem, it’s broke, parts are available so it’s a no brainer, might be different if it’s 50 years old and you have to repair it as makers have gone bust etc.

[Adam Harris]

On Adam Harris Said:

Do you think Loctite could really stop the crack opening when torquing down the nut on the collet?

Well the force appears to be in tension so as I understand these glues, the best use-case.
As someone else said, little to lose, even if it doesn’t work, just a bit of anaerobic glue to clean up!

and considerably cheaper than a factory re-build!

[Michael GilliganParticipant @michaelgilligan61133]

I think this is the one, Adam:

https://datasheets.tdx.henkel.com/LOCTITE-648-en_GL.pdf

MichaelG.

[FulmenParticipant @fulmen]

Glue will be as efficient as chewing gum. 30MPa vs 1000-1500MPa, you do the math…

[Fulmen]

On Fulmen Said:

Glue will be as efficient as chewing gum. 30MPa vs 1000-1500MPa, you do the math…

BUT … Loctite and similar anaerobic retainers do not really work as “Glue” … they are essentially ‘gap fillers’ … So,  in the mode to which I referred,  648 should do an admirable job.

If, however, you are decrying their use for glueing the edges of the crack together, then yes I agree.

MichaelG.

[jimmy bParticipant @jimmyb]

Having dealt with cracked ER8, ER11 and ER16 spindles, plating the thread must be worth a try, but suspect the damage is now done.

 

Good luck with it and let us know what improvements are achieved.

 

Jimb

[Dave SParticipant @daves59043]

Turning down the thread is a simple as installing the speeder in the mill, and clamping an appropriate lathe tool in the vice. Then use table to put on cut and Z axis (quill or knee) to feed.

I can see why the cost makes this a tempting thing to fix at home, I’d be giving it a try – the new spindle cost is t going to change after you try – if you fail you will still need a new spindle.

The external thread on the sleeve can be screwcut on a lathe prior to installing the sleeve on the “turned down” spindle.

[Adam HarrisParticipant @adamharris13683]

Thanks Dave but the spindle steel is hard and the internal gearing would be taking all the resistance against the cutter. If I damage the internal gearing I am stuffed. If I could somehow lock the spindle against the body by clamping the pair of little flats to the body then that could work

[Adam HarrisParticipant @adamharris13683]

I do have a mounting block to seat the BT40 shank in and can put that in a lathe chuck but I still have the problem of locking the spindle nose to the body in order to protect the internal speeder gears

[Robert Atkinson 2Participant @robertatkinson2]

First thing to do is to stop drill the end of the crack to stop it progressing.

That may be all it needs. Loctite is not good under tension.

Robert.

 

[Adam HarrisParticipant @adamharris13683]

I’ve been thinking about my concerns with a cutter catching the edge of the crack on each revolution, but if I clamp the crack closed with a narrow jubilee clip then I could turn the threads down section by section

[Adam HarrisParticipant @adamharris13683]

I am wondering how I might rig up a nose-to-body clamp using the 2 tapped holes in the body that take the pressure lubricant line fitting

[Adam HarrisParticipant @adamharris13683]

I think I should fabricate a cylinder to fit the body snugly, securing it via the 2 above-mentioned tapped holes, with two strips of 5mm thick plate welded to the end that lie over the flats at the base of the nose.

[Dave SParticipant @daves59043]

Given the gearing is good enough to make interrupted cuts with a milling cutter I don’t see that as a problem. Obviously with a gash set up you would not take great big hogging cuts, but all you really need to do is remove 0.5 to 1mm – 10 passes at 0.1mm would not be a great strain IMO.

Hardened steel is relatively easily turned with carbide, especially at high surface speeds (which is more than a hobbiest generally uses…) Not sure how slow it will go, but you want something like 3000rpm I guess

 

[Adam HarrisParticipant @adamharris13683]

Dave your possibly right but I now think actually very easy to make up the clamp as above based on a cylinder around the body. As far as sleeving, I can use an existing ER25 collet holder bored out parallel to double sleeve the turned-down SK10 nose and use an existing ER25 nut with threaded (M32 x 1.5) disc screwed into the nut nose  such that the bore of the disc fits the SK10 collet and also the internal length of the modified ER25 nut replicates the internal length of the SK10 nut. Maybe I should use an ER20 collet holder and nut in order to keep the extra mass down

[FulmenParticipant @fulmen]

@Michael:  I obviously don’t understand the design, I’ve only seen it in photos. And yeah, I was talking about bonding the crack. Sorry for assuming you were an idiot  🙂

[Fulmen]

On Fulmen Said:

@Michael:  I obviously don’t understand the design, I’ve only seen it in photos. And yeah, I was talking about bonding the crack. Sorry for assuming you were an idiot  🙂

Essentially, as Adam has already interpreted my thinking … he would end up with a little ‘reducer’ having the same collet taper at different sizes*: This provides a large surface area for the retainer to act upon, and is not very far removed from the ideal cylindrical pin & sleeve of the classic test piece.

The recommended 428 is low viscosity, and will work in ‘gaps’ as small as a light press-fit, no problem.

I rest my case.

🙂

MichaelG.

*

[quote]
Might be a good idea Michael – they do an SK6 collet which takes up to 6mm cutter which would be good enough for me. I could make an SK6 taper sleeve (same taper externally and internally) and glue it into the SK10 sleeve somehow.

[Michael GilliganParticipant @michaelgilligan61133]

Here’s an indication of the taper:

https://www.cromwell.co.uk/shop/cutting-tools/collets/sk6-2-00-slim-chuck-collet/p/NIK1467510K

 

[Robert Atkinson 2Participant @robertatkinson2]

You are over thinking this.

Stop drill the end of the crack and carry on with it as it is. The nut will stop it expanding significantly. Any run-out due to the crack will bw less than that on any sleeve you can manufacture.
The only issue is if the crack grows circumferentially around the splindle causing the whole collet and nut to detach. Drilling the end of the crack will reduce the stress concentration and stop the crack progressing.

Robert.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

You are over thinking this.

[…]

It’s O.K. Robert … I won’t be doing any more thinking about it until Adam shows us his results.

I’ve had my say; you and others have had different says … It’s up to Adam to do what he thinks best.

MichaelG.

[Robert Atkinson 2Participant @robertatkinson2]

Hi MichaelG,

My comment was about the problem generally not your, or anyone elese’s specific posts.
Sorry I didn’t make that clear.

Robert

[Ian PParticipant @ianp]

Hard to imagine what caused the crack in the first place (other than massively overtightening the collet nut) but as I see it now, the conical bore might clock dead true (without a collet and nut), once a collet, nut and cutter are fitted and tightened up, the crack will open and introduce some eccentricity.

In one sense, one cannot properly ‘tighten’ the collet nut as the slit/split conical part of the spindle will be springing open limiting the amount of grip on the cutter.

For the thread plating idea to work the threads would have to have zero clearance to the point that the nut could not  be rotated.

Since the spindle is toast and dismantling looks a daunting task, carrying out some sort of conversion to a different, probably smaller, collet type might be an option. Even with a fancy carbide or CBN tip I would not want to machine off the existing thread but I would consider grinding it off even it was slow process with a Dremel. Once there is a smooth precision cylinder a custom sleeve (with external thread) could be shrunk on (dry ice for the spindle and a blowlamp for the sleeve). A new oversize nut could be made to fit the existing collets.

Ian P

[Adam HarrisParticipant @adamharris13683]

Thanks everyone for your interesting and helpful comments. I am going to make the clamp I mentioned, turn down the spindle thread on the lathe to 18.6mm with a sharp carbide insert with assistance of repositioning a jubilee clip to keep crack fully closed, modify an existing ER20 collet holder to a parallel bore of 20mm to sleeve it (along with an intermediary sleeve of 20.03 OD x 18.58 ID twixt collet holder and turned down spindle) and modify an ER20 collet nut with an inner disc to match the SK10 collets. Will post photos of progress. Adam

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

Hi MichaelG,

My comment was about the problem generally not your, or anyone elese’s specific posts.
Sorry I didn’t make that clear.

Robert

Appreciated, Robert

Peace !

MichaelG.

[Ian P]

On Ian P Said:

Hard to imagine what caused the crack in the first place (other than massively overtightening the collet nut) but as I see it now, the conical bore might clock dead true (without a collet and nut), once a collet, nut and cutter are fitted and tightened up, the crack will open and introduce some eccentricity.

In one sense, one cannot properly ‘tighten’ the collet nut as the slit/split conical part of the spindle will be springing open limiting the amount of grip on the cutter.

For the thread plating idea to work the threads would have to have zero clearance to the point that the nut could not  be rotated.

Since the spindle is toast and dismantling looks a daunting task, carrying out some sort of conversion to a different, probably smaller, collet type might be an option. Even with a fancy carbide or CBN tip I would not want to machine off the existing thread but I would consider grinding it off even it was slow process with a Dremel. Once there is a smooth precision cylinder a custom sleeve (with external thread) could be shrunk on (dry ice for the spindle and a blowlamp for the sleeve). A new oversize nut could be made to fit the existing collets.

Ian P

I’ve seen ER32 tapers crack from “ambitious” overtightening!!

Is it possible that the crack was already there and unnoticed? we used to get around 2-3 thou runout on a cracked ER11 taper.

 

Jimb

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