Unknown backplate

[Bootlegger BlackyParticipant @bootleggerblacky]

Hello all,I have purchased 3 chucks,3-jaw scrol,4-jaw scroll both 100mm.and an 80mm.4-jaw independant. Bison and Burnerd. I was hoping to use the existing backplates for my Myford ML7.but these are hardened and very well made.so if I knew exactly what I have,maybe I can sell and buy pre-threaded plates. So,looking at the pictures,does anyone have any idea what these are? Thanks in advance.

[Bootlegger BlackyParticipant @bootleggerblacky]

[Mike PooleParticipant @mikepoole82104]

I would be rather surprised if a normal backplate is hardened, the register should be finish turned in position for maximum concentricity. Cast iron or mild steel are popular backplate materials.

Mikr

[DC31kParticipant @dc31k]

Posted by Mike Poole on 11/06/2022 18:03:23:

I would be rather surprised if a normal backplate is hardened

I think you have misunderstood his post.

The photos he shows are the backplates that were on the chucks he bought. He originally intended to modify these to suit his lathe but they are hardened (and ground), so he wants to sell them and then use the money to buy more standard backplate blanks.

If the OP could identify the taper on the ones he has and the drawbar thread inside them, that would give the best lead for finding their origin.

Note the single slot in the spindle-facing side of the plate, for a drive key similar in concept to that found on NMTB taper milling machines.

[Howard LewisParticipant @howardlewis46836]

What is the thread for the drawbar?

Now for a real red herring!

If 5/8 BSW, it is possible that the taper is a INT 30 or 40, and the device is intended to fit onto a milling machine,, located by the taper and driven by the dogs, so that a chuck could be mounted onto mill?

Howard

[Charles JambonParticipant @charlesjambon]

It looks like a backplate for a Myford MG12 cylindrical grinder. A few more indications would be the taper (which I recall is a rather odd one) and the diameter and pitch of the drawbar thread which from memory were Imperial.

[SteveIParticipant @stevei]

My guess based on the taper rough dimensions, the size of the chucks that were mounted, is that the backplates are for a Myford MG12 grinder.

Steve

[DC31kParticipant @dc31k]

Posted by Howard Lewis on 11/06/2022 19:01:04:

Now for a real red herring!

If 5/8 BSW, it is possible that the taper is a INT 30 or 40

Have you ever seen a 30 taper with 5/8" or 16mm drawbar?

It does not take too much effort to find out that the major dia. of 30 taper is 1.25" and 40 taper 1.75" (http://www.tools-n-gizmos.com/specs/Tapers.html) and his caliper measurement is neither of these.

So, no herring there, not even a sardine.

—-

SteveI, however, has pulled up a full net:

MYFORD MG12 80mm Pratt Burnerd 3 jaw chuck & adaptor NEW

 

Edited By DC31k on 11/06/2022 21:48:57

[Bootlegger BlackyParticipant @bootleggerblacky]

Thanks Steve you nailed it.

they are in fact to fit a Myford MG12 grinder. I will be selling these with or without the chucks soon.

best wishes to all.BB.

[Pete RimmerParticipant @peterimmer30576]

You should do well out of selling those parts, they are both desirable and valuable.

[Bootlegger BlackyParticipant @bootleggerblacky]

Now sold,thanks to all.

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