1st Time Making a Backplate

J

JPower6210

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Hi All- so I picked up a Sjogren 5C chuck for my 1236. It did not come with a backplate so I am planning on ordering a plain D1-4 backplate and machining to fit. The check has a recess in the back with a lip that is about .250. Here is my newbie question- I assume that I want to machine the backplate so that it hits the lip and the surface of the recess on the chuck at the same time? Looks fairly simple to do since there is no taper to worry about. My plan would be to make the “spigot” on the backplate a little larger than it needs to be, get the diameter to be a nice fit and then face very gradually to get contact on both surfaces using some Dykem to check. Is that the right way to go about it? Am I missing something really obvious? (Wouldn’t be the first time)

Thanks all-

JP
 
JPower6210 said:
Hi All- so I picked up a Sjogren 5C chuck for my 1236. It did not come with a backplate so I am planning on ordering a plain D1-4 backplate and machining to fit. The check has a recess in the back with a lip that is about .250. Here is my newbie question- I assume that I want to machine the backplate so that it hits the lip and the surface of the recess on the chuck at the same time? Looks fairly simple to do since there is no taper to worry about. My plan would be to make the “spigot” on the backplate a little larger than it needs to be, get the diameter to be a nice fit and then face very gradually to get contact on both surfaces using some Dykem to check. Is that the right way to go about it? Am I missing something really obvious? (Wouldn’t be the first time)

Thanks all-

JP
Click to expand...

That's not what matters. You do NOT want the face of the backplate boss to touch the inside of the chuck, because the inside surface of the chuck is typically not precision machined, while the outer mating surface of the chuck is precision ground. You want a diameter that perfectly fits the recess so that the chuck runs concentric to your spindle. Face the mating surface of the backplate just enough so that it's square with the spindle and carefully turn the diameter of the "spigot" to fit the chuck as perfectly as you can make it. Some people make it a slight interference fit and heat the chuck to mount it.

My very first job after I got my lathe was machining the backplate for an ER40 collet chuck, and it's still the chuck that I use the most.
 
Hopefully some experienced machinists will come around soon, but I had an issue with a D1-4 chuck and as I recall there is a taper on the "spigot".
There are several people here that are really knowledgeable that helped me, In fact due to my inexperience they saved me from disaster.
Have a good day
Ray
 
Briney Eye said:
carefully turn the diameter of the "spigot" to fit the chuck as perfectly as you can make it.
Click to expand...
This refers to the backplate spigot that is likely not tapered and not the D1-4 spindle spigot that is tapered. You do not want to modify the tapered spindle spigot!
 
Thanks all- I definitely won’t mess with the spindle at all. Sounds like it will be easier than I expected. The Sjogren chuck recess looks like it is ground and that was throwing me off. I’ll machine the backplate to register to the recess but not touch both surfaces.

JP
 
My previous lathe (chinese) had a D1-4 mount and the runout would change if I mounted the chuck in different holes.

I would blue the backplate and check its mounting on the spindle before you machine it. You can always use a bit of emery cloth on the backplate (NOT THE SPINDLE NOSE) D1-4 mount to get the fit better.

When you machine the backplate mark it for indexing and always put it back in the same position. This will ensure (hopefully) that it repeats.
 
On my Grizzly G4003G the spindle has a witness mark from the factory to insure the chucks are always indexed the same. The 4 jaw, 3 jaw and faceplate all have matching witness marks.
 
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