Need new / quality backplate for 3 jaw D1-5

[LVLAaron]

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.

 

[woodchucker]

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.

 

[LVLAaron]

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.

 

[LVLAaron]

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.

 

[woodchucker]

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.

 

[LVLAaron]

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.

 

[woodchucker]

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.

 

[LVLAaron]

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

 

[woodchucker]

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

1. spindle plate
2. backplate to chuck
3. chuck
4. rod
5. chuck
6. backplate

I would like to get you to

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

But in reality it's probably going to be

1. spindle plate
2. backplate to chuck
3. chuck
4. backplate that needs truing.

 

[Ischgl99]

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.