[How do I?] Oops ... Now It's Too Small

A

arvidj

Active User
H-M Supporter Gold Member
Joined
Oct 6, 2011
Messages
267
I was turning down a back plate ... this one to be exact ... https://www.grizzly.com/products/6-Pre-Machined-Back-Plate-D1-5/T25218 ... to allow the protrusion to fit into the recess of a 5C collet chuck ... http://www.cdcotools.com/item.php?itemid=404 ...

Things were going along nicely. I was sneaking up on the required 3.74 inch protrusion diameter. I had gone thru several iterations of warming the chuck up in the oven, testing the fit, then taking "just a smidgen" off the back plate. Wash, rinse, repeat.

I'm sure you know how this story ends. The protrusion is now "just a smidgen" too small as the chuck fits without any issues and "just feels loose". I'm guessing the back plate protusion is about .001 - .002 too small. Even thought I knew it was too small I mounted the chuck anyway just to see how bad it was and indeed, there is an unacceptable amount of run out in the mounting.

What are the options to build the protrusion back up 'just a smidgen" so I can take another shot at getting it right?

Thanks,
Arvid
 
You could turn it down to a smaller diameter. Make a press fit ring to go over that turned down step. Then re-do the step as first planned.

Or just leave it alone. And use that wiggle room to fine tune your chuck run-out. Or?
 
Sure you can. Just take a double cut diamond roll and use a 1/4" dowel pin to run it on. Only about 1/16" or so of the rolls I have are chamfered, so you can get to all of it except that corner.

Doesn't need to be heavy knurled anyway.
 
Aside from how do you recover from this gut wrenching error.
Consider what you might have done differently to have prevented the situation in the first place.

I like Tonys idea! I'll need to remember that.
Alternatively, is the plate thick enough that you can face off the shoulder and recut the entire thing?

Daryl
MN
 
was once cutting a board with a handheld circular saw... measured, marked, made the cut... missed the pencil line by 1/8". Made the cut again... missed by 1/16... WTF? One more cut, missed pencil line by 1/16 again...

Looked at the saw baseplate to find a small bit of pencil lead wedged in a screw hole. Do'H!!!
 
there are 2 ways I would fix this. One would be to mount plate on machine ,then use a roller bearing like those used in a steady rest. You only need one of the three. Then running the spindle slowly and with the roller mounted in a tool post . Bring the roller against the undersized dia and with about .100 of the bearing against the plate Push the bearing against the edge and you should be able too swell the dia up. Then return dia to size.

Another way to fix plate is to drill backplate in 4 places and press pins in holes so OD of pins is a bit bigger then needed size then return pins to size.
jimsehr
 
Last edited:
Buy a new piece,do over.
1st parts are just learners unless one gets lucky or has lots of experience.;)
I figure my 4th attempt is going to be the keeper. Just don't get discouraged.:)
 
You must log in or register to reply here.
Back
Top