Grease suitable for a lathe chuck scroll

[choochoo_balooParticipant @choochoo_baloo]

I am cleaning up a 7.5" Pratt chuck and want to re-grease the bevel gear side of the scroll wheel.

Unless I've misunderstood, I was lead to believe one should never grease inside a lathe chuck full stop since it attracts and clings to swarf (which makes sense). However as the photo shows this previously unopened chuck is greased but there is (thankfully!) no sign of swarf. I assume grease is used whenever there's a press fit rear chamber to the chuck like here?

Assuming I'm correct, what grease can others recommend? I have marine grease (from a dinghy outboard), but I assume there's something more suited to machine tools?

Merry Christmas to all!

[choochoo_balooParticipant @choochoo_baloo]

[Joseph Noci 1Participant @josephnoci1]

Even all the High-End Chuck mnfrs specify a grease that should be used on the chuck innards – Rohm for example specifies Molykote TP-42 or if not available to you, a Lithium based grease with Molybdenum Disulphide additive. I am not keen on the latter, but it is subjective – The Moly grease is messy – makes everything black when applying it!

The key elements are – a high pressure or high load grease, high adhesion qualities (against centrifugal forces), and of more relevance to production type environments, resistance to wash-out by machine coolants and emulsions.

I have a 180mm and a 250mm 3Jaw Rohm and a 5C Bison Collet chuck for my EMCO 14D, and the innards are well greased.

Regards

Joe

[HopperParticipant @hopper]

I use water-resistant wheel bearing grease designed for boats and trailers inside my chucks. Works just fine.

I don't bother with moly grease because it makes a heck of a mess when it flings out the chuck key holes under centrifugal force in operation. I figure I don't yank hard enough on the chuck key to create extreme pressure forces that require moly either.

On the scroll side, where the swarf can go, I use either machine oil or spray-can teflon motocycle chain lube so it does not stick the swarf to the scroll like grease would.

[Thor 🇳🇴Participant @thor]

I have used moly grease on the internals of the chucks I have cleaned up.

Thor

[Joseph Noci 1Participant @josephnoci1]

Hopper, If it works for you, that's fine..

The HP requirement in the grease has nothing at all to do with how hard you yank on the handle – The grease has to stay in place between the teeth of scroll and pinion, as well as between scroll and jaws. Since contact points are small, and between jaws and scroll there there is a strong wiping action, an HP , high adhesion grease IS needed. If your have the interest, dig on ROHM or P&B sites – they have tables of the tests done on chucks ranging from 80mm diameter up to 900mm showing the effects of grease types, as well as various oils. There aim was to achieve a sufficient grip on the workpiece, with 'normal' human applied T handle torque, but they apply the torque with a machine so it is repeatable for the tests.

ROHM summarise indicating that a 25W50 oil is marginally better than no lube at all, and just as marginally better than a plain wheel bearing grease after 10 tightenings. Moly grease that sprays out the holes is the wrong type – it has no adhesion – as I indicated , a high adhesion grease is needed….

Who am I to argue..

Joe

[choochoo_balooParticipant @choochoo_baloo]

Thanks all who replied.

After looking around rdgtools website, this grease seems most suited to the sealed innards of a 3 jaw chuck: Molyslip MTG. Can anyone else recommend this particular product?

https://www.rdgtools.co.uk/acatalog/Molyslip-MTG-Lithium-Based-Machine-Tool-Grease-Rust-Prevention–MTG.html

the descriptions says:

"…Suitable for ball and roller bearings, particularly medium and high speed, plain bearings, and general machinery lubrication, slides, turrets, spindles, aprons and chucks on metal processing machines."

[MWParticipant @mw27036]

By the looks of the colour, the current state of it looks like molyslip grease has been applied at some point.

Michael W

[HopperParticipant @hopper]

I just overhauled a Myford Burnerd chuck this morning and used some aircraft synthetic lithium grease, rescued from a skip at the local airport. It seems to work very well. Very sticky (yet not too thick and stiff) and did not fling out the chuck key holes on start up, even with a shed ambient temp of 36 degrees C (97F) and gives a very smooth chuck key action. I'm pretty sure automotive synthetic grease would be the same stuff, minus the aviation certification.

Purpose-built high-adhesion moly grease is not readily available where I live so substitutes have to be found!

[Joseph Noci 1Participant @josephnoci1]

@baloo – The Molyslip-MTG looks good from its datasheet has all the correct attributes in comparison to Molykote-TP42, including the same NLGI grade (2). Should work fine.

TP-42 is a Lithium only – ie no Molyb. added, but has other adhesive addititives.

Joe

[Peter KroghParticipant @peterkrogh76576]

Hopper, are there any specification markings for that grease? It sounds just like the kind of grease I've been looking for!!

Thanks,

Pete

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