# Need new / quality backplate for 3 jaw D1-5



## LVLAaron (Apr 17, 2022)

Had a need to use the 3 jaw that came with my 1440GT - 8 inch "precision" variety. 

The chuck itself seems nice. 

But the cast back plate- wow. I took the chuck off and put an indicator on the face of the back plate - ~15 thou run out. I skimmed it and got it running true. I marked the position of the plate, took it off, put it back on, weeble wobbles again. The headstock side of the plate is obviously not flat and I don't have a great way to deal with that. 

I have other high quality chucks that I use daily with no problem, so I don't think it's user error. 

Where can I source a quality precision ground backplate for this chuck?


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## LVLAaron (Apr 18, 2022)

Bison Finished D1-5 Adapter Plate 7-878-085F for 8" Chucks
					

Bison Finished D1-5 Adapter Plate 7-878-085 for 8" Chucks




					www.smalltools.com
				





It seems like this would fit. Are the "3 bolt holes" on chucks generally the same?


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## xr650rRider (Apr 18, 2022)

I would probably put my 4 jaw chuck on with a 2" bar protruding 3-4".  Dial it in perfectly.  Put 3 jaw chuck (with backplate attached but pins removed) on backwards clamped to bar.  Check it but then make a skim cut, if I believed it not to be perfect.  Should at least get a true registration surface.  Once that's true to the machine, I would have then made a truing pass on other side.  Hard to believe one slipped thru with that much runout.  On my PM-1340GT with precision 3 jaw, I get around .0015" in 1 position that's repeatable and plenty good with a 3 jaw.  After that first cut, it's true anyway and unless you need to put back in chuck for 2nd op, that's all that matters.


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## LVLAaron (Apr 18, 2022)

Aye, that's a good idea. I've got nothing to lose other than the frustration of cleaning up cast iron


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## xr650rRider (Apr 18, 2022)

Put some rags, paper towels, foil over the ways, use a shop vac.  Not a big deal, it's a tool.


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## LVLAaron (Apr 18, 2022)

Been using a small hospital blanket and shop vac - foil is a great idea.


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## xr650rRider (Apr 18, 2022)

LVLAaron said:


> Bison Finished D1-5 Adapter Plate 7-878-085F for 8" Chucks
> 
> 
> Bison Finished D1-5 Adapter Plate 7-878-085 for 8" Chucks
> ...



That plate looks like it has 6 mounting holes, which would be at 60 degree intervals, if you have 3, then you'd need 120 degrees, so every other one, should be right.................as long as the diameter is the same.   You have a mill.


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## Jake P (Apr 18, 2022)

Did you not just recently get this new from PM?  Have you contacted them about the issue?


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## Firstram (Apr 18, 2022)

LVLAaron said:


> Been using a small hospital blanket and shop vac - foil is a great idea.


Foil is so much safer!


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## woodchucker (Apr 18, 2022)

LVLAaron said:


> Had a need to use the 3 jaw that came with my 1440GT - 8 inch "precision" variety.
> 
> The chuck itself seems nice.
> 
> ...


well if you took off the chuck and refaced it,  it should be true.  What you should do is mark the plate and spindle (with paint) where it should match... then always mount it there.  That should do it.


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## LVLAaron (Apr 18, 2022)

woodchucker said:


> well if you took off the chuck and refaced it,  it should be true.  What you should do is mark the plate and spindle (with paint) where it should match... then always mount it there.  That should do it.


I have all of my chucks (and spindle) marked with a small center punch. The problem with this one is I believe it is badly warped or not flat on the spindle side causing it to mount up slightly differently each time. I can see light in spots between the chuck and spindle when it's mounted.


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## woodchucker (Apr 18, 2022)

LVLAaron said:


> I have all of my chucks (and spindle) marked with a small center punch. The problem with this one is I believe it is badly warped or not flat on the spindle side causing it to mount up slightly differently each time. I can see light in spots between the chuck and spindle when it's mounted.


take out the pins, put it in another chuck and turn that face down, then remount and redo your face.


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## LVLAaron (Apr 18, 2022)

woodchucker said:


> take out the pins, put it in another chuck and turn that face down, then remount and redo your face.



That'll be tonight's project.


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## LVLAaron (Apr 18, 2022)

The chuck side is already flat. I'm going to tackle the original advice and chuck the whole chuck and clean up the spindle side.


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## woodchucker (Apr 18, 2022)

LVLAaron said:


> The chuck side is already flat. I'm going to tackle the original advice and chuck the whole chuck and clean up the spindle side.


it is, but it needs to be redone after you fix the spindle side. *Don't skip this*. For maximum benefit, redo the chuck side after fixing the spindle side.

edit: at least put an indicator on it.  in my mind, if you are out on the spindle side, the chuck side is not true when you fix the spindle side.


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## LVLAaron (Apr 18, 2022)

Put a bar in the 4 jaw, skimmed it so it's true. Attached 3 jaw. ~7 thou tilt in one direction. I'll do the turning later after I have time to put a hazmat suit on the lathe.


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## woodchucker (Apr 18, 2022)

Aaron, just for ****s and giggles, take your readings, then take the chuck off that plate, turn your jaws around on your spindle mounted chuck, mount the plate and see what you get for a reading.

Run out adds up. So while what you are doing is valid, I don't think it's as accurate as spinning less mass closer to the chuck.  I could be wrong.
I think if you move the backplate as close to the spindle as possible you will get a more accurate facing/reading.


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## LVLAaron (Apr 18, 2022)

I agree with you. Not arguing, just talking here, wouldn't it "be better" if it's machined in situ? This aligns the bore of the 3 jaw with the backplate.  - There can be a discrepancy between the 3 jaw chuck and it's backer, who cares, it's about to get turned out.

Edit - I know what I said above relies heavily on how rigid the setup is


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## woodchucker (Apr 18, 2022)

yes, but in this case in situ would be the spindle mount, not the chuck. 
you are way removed from the spindle mount.


spindle plate
backplate to chuck
chuck
rod
chuck
backplate

I would like to get you to 

spindle plate
backplate to out of true    (if we could do that)

But in reality it's probably going to be

spindle plate
backplate to chuck
chuck
backplate that needs truing.


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## Ischgl99 (Apr 18, 2022)

Before you do any turning on the spindle side of the backplate, check for high spots around the counterbore holes.  I bought an ER-40 chuck from PM last year and there was enough of a burr on the spindle side to prevent it from sitting flat on the spindle and left a gap when tightened.  I forget the numbers, but it was in the 0.005” range.  A little polishing with a sheet of sandpaper on my surface plate flattened it up enough.  The runout you are getting now could be from the way you are holding it as well as your first skim cut on chuck side of the back plate.

Keep in mind, if you take a skim cut on the back of the plate, it might not sit flat against the spindle any more since the pins pull it on to the tapered bore and the spindle flat to give dual contact.  If you take too much off the back, it can’t pull in enough to then also sit against the spindle flat and might allow it to sit angled on the taper.  Before doing anything to it, you might want to blue the taper in the backplate and see what kind of contact it is making on the spindle taper.  If the taper is not making good contact, then truing it up is unlikely to help.


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## LVLAaron (Apr 18, 2022)

I got some marking blue just the other day. I should tear this down and check that. Good points.


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## LVLAaron (Apr 18, 2022)

This maybe escalated beyond current comfort level - Skimmed the surface that registers the spindle. Runout was nil. However, this affects two things. 

1. Center registration 
2. Stud "stickout" - If I continue I'm going to need to take enough off the surface to get a full turn out of the studs. 

I'm sure I can figure out the angles for the registration surface and correct them, but I need the lathe for other actual business so it's gonna get tabled for a while.  

Also, I hate cast iron.


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## LVLAaron (Apr 19, 2022)

SK Model 3-Jaw Self Centering Chuck | Di Chun, Worldwide 3-Jaw Chucks Profesionals
					

SK Model 3 jaw self-centering chuck is equiped with hard jaws for heavy cutting and soft jaws for precision cutting, providing accuracy and convenience. Contact Di Chun now for info about our quality 3 jaw self-centering chucks.




					www.auto-strong.com
				







			https://bison-america.com/pdf/Chapter_1/131.pdf
		

Part: 7-878-085F

Measurement K on the backplate seems to align with measurement D on the SK8 chuck. 

Anyone care to double check my work?


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## epanzella (Apr 19, 2022)

LVLAaron said:


> Had a need to use the 3 jaw that came with my 1440GT - 8 inch "precision" variety.
> 
> The chuck itself seems nice.
> 
> ...


The studs on my D1-5 mount are threaded and held in with a setscrew. Pull the studs out and face the headstock side of the backing plate.


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## LVLAaron (Apr 19, 2022)

epanzella said:


> The studs on my D1-5 mount are threaded and held in with a setscrew. Pull the studs out and face the headstock side of the backing plate.



I did that. I need to do it "more" so the studs can go in one full turn, then I'd need to open up the center registration. I just don't want to mess with it. I'd rather turn it into a door stop.


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## woodchucker (Apr 19, 2022)

A machinist will fix what he can... Come on Aaron, this is not trash, it just needs some accuracy. And it's good practice at fitting .. And you'll feel good about it in the end.


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## LVLAaron (Apr 19, 2022)

woodchucker said:


> A machinist will fix what he can... Come on Aaron, this is not trash, it just needs some accuracy. And it's good practice at fitting .. And you'll feel good about it in the end.



I'm confident I WILL fix it... just not right now.


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## epanzella (Apr 19, 2022)

LVLAaron said:


> I did that. I need to do it "more" so the studs can go in one full turn, then I'd need to open up the center registration. I just don't want to mess with it. I'd rather turn it into a door stop.


Grizzly has D1-5 backing plates in 6-8-10 inches.


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## LVLAaron (May 18, 2022)

I got the Bison finished backplate today. It is beautiful and assembled. Perfect fit. The only problem is the bolts are inch and not metric like what came with the chuck. No big deal, mcmaster has a package shipped to me almost every day anyway


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## LVLAaron (May 23, 2022)

Got it all bolted up

3 thou runout at the jaws and 4-5 8 inches out from the jaws. That was just a quick check. Seems acceptable for the type of work I'd put in a 3 jaw.


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## LVLAaron (Oct 21, 2022)

Upcoming work that I'd like to use the 3jaw for... Checked things again and I thought I could get it better than it is...

With my 12 inch test bar, I was getting 3 thou runout at the chuck and 5ish at the end of the bar. 
I removed the chuck from the back plate, and measured... about 1 thou of runout. I took a tiny cleanup cut across the mating surface of the back plate and re-installed and tested. 
half thou at the chuck... 1 thou at the end of the bar. Repeatable. 
Super happy!


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