Smart and Brown 1.75 8 TPI back plate

[Nigel Turner 3Participant @nigelturner3]

I have a Smart and Brown SAB and I have picked up a 6" 4 jaw chuck. I need a back plate with the spindle dimension 1.75 8 TPI. The internet is full of back plates for Myfords and Boxfords but they are the wrong thread or pitch. The inner recess is 127mm in diameter. Chronos sell one but it is already 127mm so there is no machining wriggle room. I would be happy with a cast iorn blank as long as its bigger than 127mm. Any help graetfully received

[Nigel Turner 3Participant @nigelturner3]

Smart and Brown 1.75 8 TPI back plate

[Martin ConnellyParticipant @martinconnelly55370]

Have a look at this thread, it is relevant to your needs.

Lathe threading tool

A quick check on Ebay turned up this. 

Cast backplate blank

It is easier to make your own backplate than it is to buy one. I and old mart have done this for our machines in the past and Jim Beagley is about to make one as well. 

Martin C

Edited By Martin Connelly on 20/05/2020 22:25:57

Edited By Martin Connelly on 20/05/2020 22:28:00

[old martParticipant @oldmart]

The difference in price between a blank and a 6" Boxford threaded one from Chronos is not much and as long as the boss diameter is big enough on the Boxford one to make it 1.3/4 X 8, it would save a lot of messy machining. I have made a couple of Boxford threaded plates into Smart & Brown ones this way. If your 6" four jaw chuck has front mounting, you can probably use a smaller diameter backplate. It may even be possible to use one backplate for both a three jaw and a four jaw if you are lucky.

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