How is this chuck mounted?

[Mick BaileyParticipant @mickbailey28509]

Someone nearby has a chuck for sale that has no obvious (to me) means of fitting a backplate as there are no holes drilled. How would this be mounted? It looks similar to the internally threaded light duty chucks for Myfords, but has no thread.

[Robert Atkinson 2Participant @robertatkinson2]

Might never have been mounted on a lathe. Could have been used as a bench vice, on a surface grinder magnetic chuck or held in a larger chuck on a big lathe for a few examples.
I think I can see faint circular marks that could be evidence of stick-on feet. This would support use as a bench vice.

You will need a faceplate…

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

I think I can see faint circular marks…

Given that it is a four jaw chuck, the crop circles you see are the same as nearly every other four jaw chuck: they retain the screws that move the jaws.

[Martin ConnellyParticipant @martinconnelly55370]

It may have been used in a larger 3 jaw chuck to give the 4 jaw utility without having to change a much larger chuck on and off a lathe.

Martin C

[old martParticipant @oldmart]

There is plenty of metal there to drill and/or tap should it need to go on a backplate. Check the thickness in the cavities, there may be enough wall thickness for front mounting. I fitted a very small flange diameter backplate to a 160mm four jaw using 8 small studs just outboard of the register similar to yours avoiding getting too close to the jaw screws. I don’t think the mystery of how the back has no mounts will ever be answered.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mick Bailey, I have a similar or even the same chuck, and a backplate with a short register that fits into the bore of the chuck is fitted into the recess and held by four 3/8″ x 20 TPI cheese head bolts from the front, with the front of the holes counter bored, so the heads are slightly below the chuck face.

As DC31k says, the circles are for pins that retain the jaw screws.

Regards Nick.

[Mick BaileyParticipant @mickbailey28509]

I’m familiar with the mounting method, it’s the absence of such which I wondered about as they’re usually drilled at manufacture.

[Mark RandParticipant @markrand96270]

Sounds like you can make the mounting holes as in Nicholas’s design to suit your choice of bolts. 🙂

[Mick Bailey]

On Mick Bailey Said:

I’m familiar with the mounting method, it’s the absence of such which I wondered about as they’re usually drilled at manufacture.

Maybe it was a special order where the standard drilling did not work with the machine on which the customer wanted to mount it. It would be easy to pull one off the production line before it reached that process – ‘mounting holes by client’. If you could see the disk on the front where the chuck model number is stamped, that might provide some information (e.g. it is unstamped, or has a special number).

[DiogenesParticipant @diogenes]

..there is another reason things don’t complete a manufacturing process.. ..is it cracked in the webs?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, well I guess you could drill and tap blind holes in the back, if you so wished, to fit whatever spindle arrangement your lathe has, so it could have depended on the order as to why there are no holes in it. The backplate in my photo above is a Myford fit, but I trimmed up, drilled and tapped a Boxford backplate for it.

Regards Nick.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, My chuck, No. 34, is on this catalogue page, it doesn’t say if it is pre-drilled though.

Regards Nick.

[Mick BaileyParticipant @mickbailey28509]

There’s no visible makers name in the photos so I’ll go over and take a look first-hand. The question over whether it’s cracked is a good one. There are some signs of use, which is puzzling, as there aren’t any signs of the chuck being gripped.

The specific requirements of industry are infinite, I suppose, and there are some very unusual tools that without specific reference to their intended purpose would be very difficult to identify how they were used.

[mark smith 20Participant @marksmith20]

The no.34 Burnerd chuck sees to have been very popular , especially on boxfords . I have one on my Southbend 9. Also one came with an elliott dividing head i restored.

Some of these dont have the no 34 sticker on them but just a serial no. on the edge of the front face.

[HollowpointParticipant @hollowpoint]

I’ve seen them without holes before. So maybe it was something offered by Pratt Burnerd?

[Mick Bailey]

On Mick Bailey Said:

…

The specific requirements of industry are infinite, I suppose, and there are some very unusual tools that without specific reference to their intended purpose would be very difficult to identify how they were used.

An industry specific need would explain all.  Pay them enough money and companies will make anything the customer wants. Organisations order specials galore, anything from productivity enhancing lathe accessories, to a new  nuclear submarine, better specified than all existing submarines.

My guess is this chuck wasn’t intended to fit on a lathe. Something slow moving, such as a rotary table on a grinding machine.  Perhaps part of a jig or fixture.   We can only guess because the rest of the set-up is missing.

Could the slots double as a bayonet fitting?

If a bayonet fitting, I’d expect the surface behind the edge I’ve highlighted in red above to be a machined ramp, maybe with a register.  Any sign of machining behind, or are the holes just the usual weight saving feature?

Dave

 

 

[Mick BaileyParticipant @mickbailey28509]

Martin C got it in one.

I bought the chuck, it’s a completely unused Pratt Burnerd covered in the original Cosmoline-type protective grease. It is intended for lathe use – they were ordered by the seller’s company for use on larger Harrison lathes. For small jobbing work that needed a 4-jaw the chuck was gripped in the larger chuck, as it was much quicker than changing a large and heavy chuck just for one job. The chucks were offered undrilled at a small reduction in price.

What looked to be signs of use was swarf stuck to the grease from being stored underneath a lathe.

Whilst I would have preferred an internally threaded version, I think it will work out with a backplate for my ML7.

[MichaelRParticipant @michaelr]

Is it my imagination but has there been studs in this chuck there seems to be outlines as though the studs have been machined off as marked by the arrows

 

[Clive Brown 1Participant @clivebrown1]

They are the outlines of the jaw-screw retainers, typical of chucks of this design. Normally more prominent.

[peak4Participant @peak4]

Mick, does the vendor have any more?
I could use a 6″ one for my rotary table

Bill

[BazParticipant @baz89810]

Couple of places I have worked in held small four jaw chucks in much larger three jaw chucks as Mick says, saves all the grief of changing chucks especially when on some lathes a forklift truck may be needed to remove the chuck. The three jaw may have a dedicated set of soft jaws to fit the four jaw in to so concentricity is assured and also no jaw marks left behind.

[Mick BaileyParticipant @mickbailey28509]

Bill, sadly he didn’t have any more. He’d had a clear out and the chuck + a heavy faceplate about 15″ diameter was all that was left. Interestingly, the faceplate mounting was a backplate with 4 screws, the same arrangement as a chuck.

[DiogenesParticipant @diogenes]

..best possible result..

[Mick BaileyParticipant @mickbailey28509]

Nick, if its not inconvenient would you mind measuring the register diameter of your chuck and the PCD of the mounting holes and flange thickness ?

The register in my chuck is too small to fit bolts and I’d need to machine it out and possibly drill and counterbore the chuck body, or maybe drill and tap it from the rear and fit allen bolts.

In hindsight, perhaps I should have obtained a chuck with a Myford threaded body to reduce overhang, and have something ready to fit, but ebay prices are usually pretty steep for this type for one in decent condition.

 

 

 

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mick Bailey, the register on mine is 3.25″ x 3/32″ deep, and the hole PCD is 2.75″, with the holes being 25/64″. The bore of the cuck is 1.625″, and there is a good undercut in the corner of the register.

The backplate has an overall length of 1.04″ that fits on the spindle, and projects into the chuck bore by 0.326″ and a diameter of 1.5″, the flange is 0.488″ x 3.25″, but is only a close fit in the register, the backend has a raised portion of 0.192″, and a diameter of 1-11/16″, and this has a 1/2″ long register for a Myford mount.

Regards Nick.

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