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Busy Bee CX709 chuck help

M

Marknb

Member
First off, I’m still very new to machining, and might not have all the terms right.

I have a used cx709 lathe I picked up a couple years ago. Yesterday I tried to fit the 4 jaw chuck to it, but the screw holes in the backing plate don’t line up to the holes in the chuck. The 3 jaw is fine, and so is the face plate (they use the same mounting holes).

Can I enlarge the holes in the backing plate to fit, or is there a better option?

Thought I’d ask before I do something I’ll regret.

I’ve attached a couple photos to hopefully show the issue.
 

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If I was doing it I would make a separate backing plate for the 4 jaw chuck. The flat head slotted screws are not the best thing to use to attach the chuck. You want it good and tight and as solid as possible. All the backing plates I have seen are attached with socket head screws. I definitely would not enlarge the holes. You are just asking for trouble there.
 
from the manual
1681230996869.webp

1681231028155.webp


I would consider:
a) 3 new holes in the flange to align with 4J chuck, or
b) 3 new, tapped holes in the 4J chuck to align with the flange, or
c) contacting BB to see if this is a known problem and they'll help with a replacement 4J chuck that fits properly

good luck
 
I'm in the get and fit a new backplate camp.

And I agree with Larry. I'd even use bolts that stick out before I'd use slotted screws. I hate slotted screws. Hate is not a strong enough word. The only time I like them is when they are used as part of the art work for the part. I routinely replace them otherwise.

I'd recommend you get some like this:

Screenshot_20230411_132152_Chrome.jpg
 
Slotted screws?

I think you're seeing the line behind the backing plate when looking "through" the hole.
 
It doesn’t use slotted screws, it uses the pocket head screws.

The 3j attaches using 3 screws and the 4J attaches using 4 with a different set of holes.

The current mounting piece seems to be one piece with the spindle, I haven’t figured out how to get it off yet.
 
curmudgeon said:
from the manual
1681230996869.png
1681230996869.png

1681231028155.png
Click to expand...

I confess that I am shocked that busy bee recommends using the same backing plate for both chucks. It flies against every ounce of common sense I can muster.

To me, it reads like: "We at Busy Bee are hard at work trying to maximize our profits (er, I mean trying to reduce your cost and make our lathes more affirdable) so we found a way to eliminate two of the back plates instead of giving you the three that should have been there."

Anyway, unless I am missing something, I think that by buying or making two more backing plates (one to cover your faceplate too) you can also improve the fit and precision of your chucks and faceplate and also make the faceplate a bit fatter so the screw head has a better fit if needed.
 
Marknb said:
It doesn’t use slotted screws, it uses the pocket head screws.

The 3j attaches using 3 screws and the 4J attaches using 4 with a different set of holes.

The current mounting piece seems to be one piece with the spindle, I haven’t figured out how to get it off yet.
Click to expand...
Looking at the poor diagram in the manual, and reading your description, it sounds like the chucks do not have backing plates; instead they're attached by screws directly to a flange on the spindle with 3 (for 3J) or 4 (for 4J) screws. (total of 7 chuck mounting holes in the spindle flange)

I assume there is a recess on the back of each chuck and a corresponding tenon on the flange; correct? If so, do both chucks fit the tenon snugly? If the 4J does not then it might not be "correct" for your lathe.

As others have suggested you could turn a "spacer/adapter" to act similar to a backing plate including a recess to match the spindle flange, and and a tenon to match the 4J recess. A proper fit on those interfaces is more important than perfectly aligned/centred screw holes IMO.
 
Marknb said:
It doesn’t use slotted screws, it uses the pocket head screws.

The 3j attaches using 3 screws and the 4J attaches using 4 with a different set of holes.

The current mounting piece seems to be one piece with the spindle, I haven’t figured out how to get it off yet.
Click to expand...

Ahhhhh... See, that is why I said "unless there is something I don't understand......"

Yes, I have seen a few lathes with that kind of attachment. I think it was busy bees way of providing a reverse on the spindle without going to the trouble of making a d1-x spindle nose.

I think we all need better pictures of your chucks and the attachment to be able to help properly.

Edit - or maybe @Larry_C9 is already on the right track.
 
I found an old thread that explains the issue much better than I can. I contacted the op to see what his solution was.

Post #16 mentions the issue.

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was just about to share the same...
canadianhobbymetalworkers.com

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