Myford/ Drummond M Type chuck back plate.

[David George 1Participant @davidgeorge1]

Just thought I would share drawing of back plate for my M Type lathe. These pictures and need moding to suit your chuck but the spindle sizes are the same no matter which chuck. I also have a C spanner mod on all my chucks and thought it is easy to do.

It's so easy to remove chuck with no damage just tap C spanner with mallet.

David

[David George 1Participant @davidgeorge1]

Myford M Type chuck back plate etc

[JohnFParticipant @johnf59703]

I like the C spanner idea David, this could be incorporated into any chuck backplate or you could possibly use the chuck key hole to locate the C spanner dog on many chucks.

John

[Lee RogersParticipant @leerogers95060]

Another tidy job David. A recent post on the Drummond FB group didn't like that I lock the chuck with the backgear if it's tight, said it could break gear teeth. Any thoughts?

[David George 1Participant @davidgeorge1]

No DON'T USE THE BACK GEAR it will break. I have seen many pictures of broken back gears and attempts to repair them.

David

Edited By David George 1 on 02/06/2019 11:29:02

[colin hawesParticipant @colinhawes85982]

I have machined 24 notches on my backplate for dividing purposes. Colin

[Lee RogersParticipant @leerogers95060]

Posted by David George 1 on 02/06/2019 11:25:04:

No DON'T USE THE BACK GEAR it will break. I have seen many pictures of broken back gears and attempts to repair them.

David

Edited By David George 1 on 02/06/2019 11:29:02

Well that's me told then ! I shall desist.

[John MCParticipant @johnmc39344]

Two slots positioned at 180 degrees would be better for balance? I suppose it depends on what sort of (high) speeds the lathe is run at.

Good advice not to lock the spindle with the back gear, there is often a cast iron gear in the train to quite things down.

How about some ideas about locking the spindle without straining some part of the drive train.

John

[David George 1Participant @davidgeorge1]

I have started machining the back plate ready to mount my new 4 jaw self centering chuck but as I bought it from Myford at the at the Doncaster show as faulty, returned as it ran out written on box. I checked it by holding it in my 3 jaw chuck and after striping and checking it is obvious that the jaws were ground wrong. So I have made a 4 hole cloverleaf jig to grind it when mounted.

Screw cutting the back plate.

Here is the cloverleaf jig.

David

[geoff walker 1Participant @geoffwalker1]

Hi David,

Never seen this before, interesting.

Would I be right to say that clover plate has to made extremely accurately for it to do the job.

I.E. the four outer must be precisely positioned around the inner hole both in angular setting and P.CD.

This will ensure that each jaw exerts equal pressure on the plate when the jaws are closed and set for grinding.

Looks tricky to me, how did you make it

Geoff

[Roderick JenkinsParticipant @roderickjenkins93242]

I don't think the clover plate needs to be made with extreme accuracy: It just needs to resist sufficient pressure to ensure that each jaw is firmly seated against the scroll, taking up the backlash.

Rod

[David George 1Participant @davidgeorge1]

The cloverleaf plate is just to give pressure on front of jaws to make sure that when you grind them they are in the working attitude and will be able to grip on whole width of jaws. The three jaw type are less accurate than a four jaw one as like a three leg stool won't rock but as I have stamped the plate so it can be returned to same position on chuck and I have checked it with feeler gauges and localy filed it till there are no gaps when tightened up. Also it is made from soft mild steel so it will bed down fairly easy. For the other set of jaws j have made a set of rings which will do the same thing but opposite pressure for grinding them as well.

David

[geoff walker 1Participant @geoffwalker1]

Rod, David,

Thanks for the replies.

I get it now, I understand.

The possibility of backlash puzzled me but I can see that as long there is pressure on each jaw that will be enough to take up the backlash.

Very interesting, as I said earlier never seen it before. I have an old 3 jaw which could benefit from a regrind. May try it sometime

thanks again Geoff

[BazyleParticipant @bazyle]

Posted by John MC on 03/06/2019 10:23:03:

Good advice not to lock the spindle with the back gear, there is often a cast iron gear in the train to quite things down.

How about some ideas about locking the spindle without straining some part of the drive train.

Ha ha. ALL gears on a Drummond are cast iron, none of that fancy steel stuff,

For holding the spindle you might be able to with your mandrel handle (the one you are going to make soon) if it grips well. Another suggestion is to make a concave aluminium segment with several teeth that mates with the bull gear to wedge it. The idea is that the aluminium gives enough to align to the teeth and spreads the load over more than one tooth.

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