First chuck backplate turning/setup

GunsOfNavarone

GunsOfNavarone

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So, my G0602z came with a 5" 3 jaw self centering and a 6 .5" independent 4 jaw. I do a lot of rod that is too big for the center hole of the 5" and I can kill 1 5-20 minutes indicating in on the 4 jaw so if course the best answer was to get a bigger self centering chuck. I just received my Shars 6" self centering 3 jaw. Here's my next challenge. It came with a backplate that is a 1.5" 8 tpi
I don't think I will have room to turn that I to the needed 1.75" 8tpi the Grizzly uses, so I ordered a 6.5" plate from them. I really what rumours little as possible and the 2 things I 'm sure I will have to do is turn the register down from the 6.5" Sanou chuck they use to the 6" of the Shars . The lathe will take care of the centering of that so I'm not too worried but I've heard horror stories of turning cast iron. What inserts do I use for cast iron? (Not size shape etc...)
Also, the mounting screws for the chuck to the plate, any secrets to getting those dead on? I remember drilling my welding positioner backplate for its chuck, "dead on" was NOT my end result. I tbought I could run a scratch mark on the larger of the hole circumference placement, but the 120° placement is another issue, but isn't the larger pretty damn close to being a dividing head??
I know you guys have some easier ideas, I'm very interested in hearing them!
Thanks guys
 
If I was gonna do a backplate I would mount a 4jaw on the lathe probably have to flip the jaws. Center your part in the 4jaw off the existing register. I would then cut the threads and the register. For tooling I’d use hss or a positive carbide insert that is sharp. Once the threads and register are cut I’d remove the 4jaw and mount the new backing plate. Once mounted I’d cut the register for the chuck. For the boltholes to mount chuck the easiest would be a rotary table. If you don’t have one and the holes go through the chuck then use transfer punch after the register is cut. Without through holes or rotary table you gonna have to go by cordinants on x&y. Or a index plate on your lathe spindle and a live drill setup on the compound. Good luck.
 
The plate i orders from Grizz will fit into my spindle, so I'll go straight to register cutting. It sounds like I don't need and special carbide inserts for cast iron? Most of mine are pretty basic...maybe TiN coated. I do have a indexing head, but I feel like there is some trick to indexing the lathe, but now that I think I about it, other than finding the 120° spacing positions, there would be no way to drill those holes. I just know there is about ZERO room for error so I'd like to one and done this and my confidence is somewhat low, mostly as I have never done this material or operation before.
 
For the holes you can use transfer screws, screw them into the tapped holes in the chuck with the points sticking above the machined surface, insert the backplate into the recess and whack it with a soft hammer where the screws are, it gives a nice sharp center punch mark to start a center or spotting drill.
 
I guess I'm a bit limited on my knowledge of transfer screws. Being that my register is a 16th of an inch tall (maybe less) I don't know if the transfer screws will allow it to fully engage the register (and be settled dead on center) before the hit the back plate?
 
GunsOfNavarone said:
I guess I'm a bit limited on my knowledge of transfer screws. Being that my register is a 16th of an inch tall (maybe less) I don't know if the transfer screws will allow it to fully engage the register (and be settled dead on center) before the hit the back plate?
Click to expand...
They will screw in to just barely flush, just enough to make a mark.
 
So I just got the back plate from Grizzly. It will fit my lathe and I won't have to machine the threads. I only have about .009 to .010" to take off the receiver..I could probably tighten it down with the mounting bolts and get it to fit. So, what I need to do is;
take a light cut off the surface the chuck bolts down to and the LIGHTEST cut to the circumference of the receiver (if I'm able to take that light of a cut... .0005 off??) Does that all sound right? The new chuck has 3 mounting bolts and this plate has 4 so will have to drill tap new holes. I reaaly want to keep the runout to minimum, with that receiver being onsize..I don't know. Isn't already dead on center (the receiver?) Dead center of a rotating part is dead center? I KIND of understand the light surface cut off mounting leadge having some variable but not center of a rotating mass. (?)
 
By receiver do you mean the register that fits into the back of the chuck?
 
Sorry, yes. Register. I fell asleep about 10 minutes after typing that...12 hour days killing me. I’m just perplexed that the register that is already cut into backplate, would be different if I did a light skim cut. Isn’t centered...centered?
 
I think your best move would have been to practice and get better with the 4 jaw.
Takes me about 30 seconds to center something in the 4 jaw.
No it wasn't that easy from the start but getting familiar with it and comfortable is not that hard.
Can't remember the last time I used my 3 jaw chuck.
I used it all the time when I first got my lathe and was learning, but now It just sits on the bench and it's either 4 jaw or 5c collets for me.
 
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