# SB9 Collet Chuck & Backplate fit.



## graham-xrf (Dec 18, 2020)

We go several steps chasing this one. My SB9s are about 1940 and 1947.
First is a minor confusion about the Morse taper. In all the old catalogues I can find, the spindle taper is listed as *MT 2*. On both my lathes, the (about 1938 - 1943) SB9C and the 1947 SB9A, the Morse taper is very definitely *MT3*. The MT3 test bar fits right up it, as does the MT3 reamer. I don't understand that.
Do we know definitely that the  Morse taper in SB9 spindles is always MT3?

The more important question is about the 1.5" diameter threaded end of the spindle.
5 turns takes up just short of 15.9mm, so looking like 0.625". So 0.125" per turn, which makes it 1.5" 8TPI.

The motivation is to get a ER32 collet chuck, and there are several seen of various diameters from 80mm to 125mm with 3 bolt holes  and a recess to fit over the raised part of a backplate. The picture is of one with 125mm (about 5") diameter




So far - so good. I go after the backplate. Oh boy! I see all manner of rough stuff, from un-machined castings to some with the 8TPI thread in it?
Is the first job to try an cut 8TPI internal threads to make up a backplate?

Confirm - the raised part on it is called the "register"?
Is that what is also known as the "reticule"

I found a couple of backplates with the 1.5" 8TPI thread. In a gorgeous mix of metric and imperial, they are listed sized 100mm and 125mm.
Like this




I am guessing here, but it seems the method is to find a ER32 thingy with a recess smaller than the lump on the backplate, then turn the "register" down until it goes down the hole. If that chuck is to end up with acceptable run-out, that would have to be a _very_ accurate tight fit.

If there is any experience going on how to get this right without purchasing several backplates, it would be much appreciated.


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## Jim F (Dec 18, 2020)

You buy a back plate with your thread, then machine to fit on the chuck, using your spindle, so everything is cocentric to your spindle.
Lots of good youtube videos about it.


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## silverhawk (Dec 18, 2020)

My SB9 "Junior" (sold January of 1930) is an MT3.  Around 1938, they introduced the "toolroom" lathes, which were not the same thing as the previous 9" lathes.  I agree with Jim - do the back plate.  It will be more accurate in regards to repeatability than using a morse taper adapter (the MT collet adapter is what I use on my Junior, and I'm finally upgrading to a true backplate).

On a backplate, This Old Tony on youtube did a video on machining them.  Get one in your thread size, then machine the chuck surface to flat and create the register to match the chuck.  If your back plate doesn't have holes to bolt the chuck to, you will then need to mark and drill them (some need to have those threaded, depending on the chuck), and then simply put it all together.

You really want a semi-machined plate, because it will be as concentric to your spindle turning when you are done, and the only other variables that will make it less reliable would be how precise the collet chuck itself was ground and the collets (which are issues you'd run into with the MT chuck, too, plus the accuracy of the MT grind).


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## silverhawk (Dec 18, 2020)

The This Old Tony video is over at 



 if you are interested.


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## tobnpr (Dec 20, 2020)

What amount of runout is acceptable for your use?
First ops? Second ops?

Like a 3-jaw, fine for most first ops. But, you'll never get acceptable runout for second ops- "collet" accuracy with that method of workholding.

I used my 9A first with a MT3 collet adapter (mine is ER40). For my use- never needed to "feed" stock through the spindle.
Later picked up a Jacobs collet chuck, which provides excellent accuracy, and the ability to feed stock through the spindle.


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## Manual Mac (Dec 20, 2020)

I’m pretty sure your ‘40 & ‘47 SB9 would be the *workshop* style. They will have a 3MT inside the spindle, they were supplied with MT3-2  sleeves from the factory.
I have a reprint of a SB Lathes catalog No. 94 from Feb, 1934, 72 pages listing everything they sold at the time.
There was no mention of A,B, or C configuration. Just the Basic workshop 9” lathe (I suppose this would be called the C model in a couple years of years).
 The 9” junior was still listed & sold then, was a more heavy lathe.
I agree with posts  2 & 3.
I made #3MT arbors so I can use my 2-1/4” 3&4 jaw chucks on my SB9C for very small stuff.
But for my 5” chucks machined backplates on the lathe 1-1/2”-8 spindle.
I just finished a back plate for a new 4jaw chuck.
Even with magnets & shop vac while machining it was very messy. Cast Iron.
But very accurate.
I do not have a collet chuck, i wish I did.
YMMV, cheers


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## Jim F (Dec 20, 2020)

Manual Mac said:


> I’m pretty sure your ‘40 & ‘47 SB9 would be the *workshop* style. They will have a 3MT inside the spindle, they were supplied with MT3-2  sleeves from the factory.
> I have a reprint of a SB Lathes catalog No. 94 from Feb, 1934, 72 pages listing everything they sold at the time.
> There was no mention of A,B, or C configuration. Just the Basic workshop 9” lathe (I suppose this would be called the C model in a couple years of years).
> The 9” junior was still listed & sold then, was a more heavy lathe.
> ...


I made a collet holder and drawbar for 3C collets, pretty easy.


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## Manual Mac (Dec 20, 2020)

Jim, i have a 3/8-16 drawbar for my SB9 to use with the #3MT endmill holders & tiny chuck arbors i made.
I would like to make 3C collet holder.
Any link to plans?
Are we hijacking this thread?
Cheers, Steve


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## Jim F (Dec 20, 2020)

Manual Mac said:


> Jim, i have a 3/8-16 drawbar for my SB9 to use with the #3MT endmill holders & tiny chuck arbors i made.
> I would like to make 3C collet holder.
> Any link to plans?
> Are we hijacking this thread?
> Cheers, Steve


I used 3/4" OD. .095 wall tubing for the drawbar, I used a 12" piece, it was too short for a handwheel, I drilled 4 holes for a pin spanner for my 5C collet blocks.
Hardest part was setting the compound to turn the 3MT.
I used a 4-40 set screw to fit the groovr in the collets.
I used a 1 1/2- 8 nut from Fastenal for the thread protector.


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## Manual Mac (Dec 20, 2020)

Thanks for the write up Jim.
Definitely put this in my “to build” project pile (that’s starting to stack up like cordwood). 
Not to mention a couple projects for She Who Must Be Obeyed.
Then there is the windstorm last 2 nights, limbs brought some of the fence down, need to get the sheep back in main pasture...but I digress....


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## mickri (Dec 20, 2020)

Just make a chuck that fits on your spindle.  That's what I did.  Wasn't hard to do.  It does require a 1.50 metric thread for the collet nut.  Halligan142 has a series of videos on how to make it for a south bend lathe and also has a video on how to cut a metric thread on a south bend lathe.


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## Jim F (Dec 21, 2020)

Manual Mac said:


> Thanks for the write up Jim.
> Definitely put this in my “to build” project pile (that’s starting to stack up like cordwood).
> Not to mention a couple projects for She Who Must Be Obeyed.
> Then there is the windstorm last 2 nights, limbs brought some of the fence down, need to get the sheep back in main pasture...but I digress....


1 thing to add, the internal treads on the drawbar, I made mine 3/4'long, and I used this tool.








						Tool Bit, 1/4" HSS Internal Threading 1895
					

Lathe Threading 1895 This 1/4" square high speed steel tool bit is pre-sharpened for internal threading.  The internal threading tool bit has a 60 deg...




					littlemachineshop.com


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## Jim F (Dec 24, 2020)




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## Jim F (Dec 24, 2020)




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## Jim F (Dec 24, 2020)

I did not anneal the nut I used, should have.........


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## Jim F (Dec 24, 2020)




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## graham-xrf (Dec 25, 2020)

Jim F said:


>


I definitely like the adjustable version!

I know spindles are not supposed to have any significant run-out, but by the time something is threaded on, they do acquire at least a little.
So when one turns up a backplate, everything on it again ends up perfect concentric to that machine axis.
If there was any run-out on the spindle  , then cutting the backplate in effect left it behind in the join. Runout gets removed.

Unless, perhaps, between chuck dismount-remounts??
The result Basement Machinist got was so very good, it brings the 3-jaw to become very respectable. It comes to mind that this adjustable feature could also be used on a backplate that mounts a collet chuck.

*Regarding the metal.*
Basement Machinist mentions how much better is what he called "ductile cast iron" compared to "grey cast iron" in that the ductile version makes little chips, whereas the grey type makes a messy powder. That would be graphite carbon mixed with silicon stuff. The "ductile cast iron" is possibly much the same as "cast semi-steel" that South Bend lathe beds are made of - but I don't really know. His motivation was purely about the messy contamination. "It gets everywhere and is a pain to clean up".




This Old Tony mentions that cast iron is traditionally used for backplates, he thinks to ensure the metal in the thread is not too similar, and so won't seize or gall. Even so, he just uses the steel he has handy, and has not had any problems. Wikipedia mentions grey cast iron is good at damping vibrations.




Like This Old Tony, I more often have to use what I can salvage, score, connive, or have to hand. I has me wondering whether the old brake discs from when I replaced them on my car might be useful. If that is a bad thought, fraught with problems, then please, someone let me know now!


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## Jim F (Dec 25, 2020)

If they are the solid disc, you may find a use, vented ones, not so sure.


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