Quick action locking nut

[ChrisBParticipant @chrisb35596]

Came across these type of nuts : **LINK** and wondered if they could be used for holding a lathe chuck. The WM280 chuck is very awkward to mount for persons with large hands!

Edited By ChrisB on 04/06/2017 12:57:55

[ChrisBParticipant @chrisb35596]

[John HaineParticipant @johnhaine32865]

Personally I wouldn't like to be anywhere near a lathe chuck held on by just those!

[Clive FosterParticipant @clivefoster55965]

Probably even more fiddly as you have two thin nuts linked together which need to be turned 180° relative to each other to close the slot before being tightened up. I share Johns doubts as to security.

Proper answer is a bayonet ring style as per DIN 55027 / 55022 (?) with keyhole slots in a bayonet ring floating behind the flange. Nut and thread are reduced in diameter relative to the stud so the nut can pass through the flange and the round part of the keyhole slots in the bayonet ring. Ring is turned so the threaded part of the studs passes through the straight part of the keyhole slots. Nut scan now be done up tight to hold chuck on. To release nuts are loosened just enough to permit the bayonet ring to be turned to align the round part of the keyhole slots with the studs and nuts. Chuck can now be pulled off with the nuts still on the studs.

Maybe modification is possible. Probably have to pull the spindle tho'.

Clive.

Edited By Clive Foster on 04/06/2017 14:41:37

[SillyOldDufferModerator @sillyoldduffer]

I'm not so sure. Does anyone know how strong chuck bolts need to be? I would guess not very. Many lathes mount cast-iron chucks coarse threaded directly on the spindle without problems : wouldn't even cheap steel bolts be stronger than that combination? ChrisB's link says the special nuts are Strength 6, which is about the best that you could expect from an inexpensive nut. Not strong but not the weakest available either.

Happy to be shot down in flames – I have smallish hands and don't need to risk it!

Dave

[JourneymanParticipant @journeyman]

I find the easiest solution is to use smooth face flange nuts and do away with the washer. Not so much to juggle in the limited space.

Also make sure to trim all the studs to a sensible length, they tend to be too long.

John

[ChrisBParticipant @chrisb35596]

I was thinking 600mpa was what most common nuts are, the ones which came with the chuck are not marked, but I'm not confident they are of a better quality. From what I could gather there's not much fiddling involved to put that nut on, drop it on the stud and tighten, then lock the nut, just a quarter turn back. If they were rated higher in strength I would be tempted.

Clive your idea is good for a nice project, but I'd rather not mess with the spindle flange for now.

I like your solution John, simple and effective…

[BazyleParticipant @bazyle]

I have this problem on my Hobbymat. If one nut is put on and done up too much the other studs are too close to the headstock to get the others on, though this sort of helps as one can trap a nut while fiddling with the spanner orientation.

I'd like to suggest a competition for the 3D printer people out there. A device, specific to each lathe type probably, held I your left hand that positions all the nuts in the right places then when the chuck is put in place pulling/pushing a lever on the device gives each nut a couple of turns to pick up the thread.

[Clive FosterParticipant @clivefoster55965]

Seems penny wise – pound foolish not to make the lathes with a DIN style bayonet ring in the first place. Accepting that these are a relatively low cost machine, so hard choices have to be made as to what features can be included and what compromises accepted to fit the customers wallet, the standard nut and stud fitting seems almost militantly unsuitable. How much extra can an adequately thick piece of sheet steel with suitable piercings cost?

Clive

[JasonBModerator @jasonb]

Then you need to add on the larger dia billet the spindle has to be cut from as the enlarged holes would come right to teh edge if cut through the existing flange.

Luckily I have quite small hands and don't find it too much of a problem, My Emcomat 8.6 had a similar DIN fitting with nuts on the back but the spigot was a short taper rather than parallel and I manages on that for 20yrs before I got teh Warco.

So long as you think ahead a bit you can save having to swap chucks too often, also helps if you have a few parts on teh go at once so all the work in one type of chuck can be done before swapping to another.

[SillyOldDufferModerator @sillyoldduffer]

I'd never heard of DIN bayonet fittings before and did a search. Very nice engineering but chucks to fit that standard seem to be high-end ; the first I found was £530.64 plus VAT, the second €1915! I like the idea of owning a chuck costing more than the lathe though.

[JasonBModerator @jasonb]

I was looking at a Warco 290 at Ally Pally earlier this year and that had the bayonet ring, just holds a basic backplate on and the standard chuck fits to that

[Clive FosterParticipant @clivefoster55965]

SillyOldDuffer

That would, I think, be integrated chucks including fitting. Which are always high end. Backplates probably comparable to cam-lock types as being essentially the same except for thread ended studs instead of cam scooped types.

Owning a chuck costing about the same as the lathe is a nice feeling. Did that with a brand spanking new Pratt Bernard precision three jaw for my Southbend Heavy 10.

Clive.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Clive Foster on 04/06/2017 18:36:16:

…

Owning a chuck costing about the same as the lathe is a nice feeling. Did that with a brand spanking new Pratt Bernard precision three jaw for my Southbend Heavy 10.

Clive.

Yes please! Drool…

[opochkaParticipant @opochka]

One of those sites where you only get to know the price you paid after you have entered your credit card details

[Howard LewisParticipant @howardlewis46836]

A while ago, MEW had an article by a chap from Oz or NZ, going by the nickname M2Z. (He says that his name is too unpronounceable otherwise)

He described a simple mod to a bit of steel strip, or banding strip, to hold the nut on a mini lathe, for fitting or removal, to prevent the nut falling down, and having to grovel around under the chuck to retrieve it (them)

It works! Could be scaled up for larger nuts / machines.

The object is to generate sufficient clamping force for the friction between the chuck and the mandrel to prevent slippage under load.The nut/stud combinations, Camlock fittings, and king size castelated nut arrangements do this.

(If there were to be any relative movement the studs would soon wear and shear off) The friction between the threads, and / or flange, on a lathe with a screw fitting chuck, does the same thing.

Howard

[ChrisBParticipant @chrisb35596]

Posted by opochka on 04/06/2017 20:06:55:

One of those sites where you only get to know the price you paid after you have entered your credit card details

The site I linked is the manufacturer, they don't normally sell online and give prices…. but you can find similar stuff on online shops with pricing : **LINK**

[Clive FosterParticipant @clivefoster55965]

Assuming suitable machine dimensions and clearances it might be practical to make a DIN bayonet ring style fitting in sections for easy retrofit. As the actual stress on the ring is low glued joints between sections should be fine. There is no metal to metal support directly under the new, smaller, nuts so the ring needs to be quite thick. Maybe something like 3/16" or 1/4", 5 or 6 mm.

I'd use three identical sections. One for each keyhole slot. Mill the ends down to half thickness to provide an over lapping glue area. Not forgetting to do top and bottom on opposite ends keeping the correct hand so things go together. Probably something like 1/2" or 10 mm overlap would be sufficient. Glued joint gives a bit of wiggle room when assembled in in situ using fitted alignment studs in the round hole part to ensure the small nuts on the new studs will go through.

New studs with smaller threads on the ends should be straight forward turning. Best to have the plain section long enough to be only minimally below the flange face. Just enough clearance to ensure the nuts pull the ring tightly against the flange without touching the stud.

Prudent to do a trial fit with double sided sellotape or similar easily broken adhesive in the joints. Going straight to high strength loctite or epoxy could lead to unfortunate language if the sizing isn't quite right. Obviously use cling film, insulation tape or similar easily removed protection on the flange back face before sticking to ensure the ring doesn't bond to the flange.

Clive.

Edited By Clive Foster on 05/06/2017 11:33:07

Edited By Clive Foster on 05/06/2017 11:33:55

[JasonBModerator @jasonb]

Easier to make the ring "C" shaped so it just slips over the spindle as it exits the headstock. Without measuring I think it should work. Just the drilling of the spindleto enlarge the nut holes insitue to sort out.

[Perko7Participant @perko7]

Clive Foster's description of the 'bayonet ring style' chuck mounting system is exactly how the chuck on my Sieg C6 is arranged.

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