New chuck adapter for SB 9

[mzvarner]

Last posts, I asked about getting a new motor installed and wired. That was successful thanks to all the help I got here!

Been working on trivial projects learning this machine. In doing so I have learned that the 3 jaw that came with it is a bit worn. I have a 5 inch Sanou 3 jaw that I kept from my mini lathe, and figure that would be a nice upgrade.

I have watched a bunch of videos about turning a new backing plate but have some questions. Should I turn down the collar that threads over spindle to get more thread engagement? Currently I have almost a half in of bare threads. Sticking out from the spindle nose. I could remove that portion from the head stock side to get it to sit deeper?

 

[markba633csi]

How much of the spindle thread is engaging is the real question. All of it or part of it?
You want most of it to engage the plate- any unused threads in the plate are just that- unused extra threads
Most spindles have a "register" or non-threaded area behind the threads. You need to measure to see if you can go any closer

 

[mzvarner]

I machined the back of the register to fit. It's just a few thou away from the headstock at this point. All of the spindle threads are engaged. The rest in the photo would be extra at this point.

 

[talvare]

If you are able to move it back closer to the headstock you will have a little less "stick-out" which translates to a little less stress on the spindle bearing. I don't know if the stress reduction by moving it back the 1/2" you have available is at all significant. It can be calculated.

Ted

 

[Chipper5783]

I wouldn’t worry about that extra half inch - so long as it fits up well on the spindle (looks like it closes right up). Machine the register for the chuck, bolt it up and see how the chuck works out. If you are not satisfied with the run out, loosen up the register fit between the chuck and back plate and nudge it over before final tightening of the chuck mounting bolts. If you decide you don’t like the way it fits up, you can always cut off the register fit and try again (that’s why you should keep that 1/2” of material, you get several do-overs).

 

[SLK001]

Thread your adapter in backwards and turn off until you only have one "free" thread. The register is the vertical part of the spindle behind the threads. You want maximum thread engagement for the best registering and repeatablility.

 

[markba633csi]

The plate hub should be contacting the spindle shoulder all around with no gap. If not, then you need to flip
the plate around and cut the plate inner register deeper by a small amount. Use/make a spacer if necessary between spindle and plate
when performing that operation
Use some Dykem, Hi spot blue, or Sharpie ink to verify proper contact

 

[mzvarner]

The plate hub should be contacting the spindle shoulder all around with no gap. If not, then you need to flip
the plate around and cut the plate inner register deeper by a small amount. Use/make a spacer if necessary between spindle and plate
when performing that operation
Use some Dykem, Hi spot blue, or Sharpie ink to verify proper contact

Can you elaborate on the spacer a little bit? I did see Mr Pete use a spacer in his tutorial, but I don't full understand the reason?

 

[SLK001]

Can you elaborate on the spacer a little bit? I did see Mr Pete use a spacer in his tutorial, but I don't full understand the reason?

The spacer is to push out the back plate enough so you don't hit the spindle while facing. Make the spacer somewhat precise, as it's precision will reflect onto your back plate. No big honkin' washer here.

 

[markba633csi]

When you flip the plate around, it will only thread on so far leaving a gap between the spindle shoulder and the plate. This means
the plate will likely be spinning crooked. The spacer enables the plate to snug up to the spindle and run true