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

That's a realistic solution, plus it gives you some future adjustment for wear, which will happen with use. 0.002 is not that much clearance. There is no requirement for a press fit on a back plate anyway. Disposition: UAI (Use As Is)
 
I did the same thing. I had enough thickness in the back plate to machine it a little thinner and machine a new boss. Don't take off the entire old boss. Just make the base of it a little wider. You don't need much of a boss at all in terms of "height" (Z axis). Is there really not enough material?
Robert
 
Since this is generally considered a permanent assembly, there would be nothing wrong with applying a little loctite to the boss and then tap into true using a good, round pin and careful indicator use before tightening the bolts. Most any formula would be acceptable, but by choice I'd use the green (can't recall the number off the top of my head). Of course, this would prevent the future adjustment I mentioned earlier. But it would be a solution.

Just for grins, I'll tell off on a former coworker. We ran multitudes of 'o' ring grooves in fairly small parts (1.5 to 3.o range). He cut one a bit small, and spun the lathe slowly while building the groove up with clear fingernail polish. As long as you didn't mic it to hard and scratch thru it, it would pass inspection. Naturally, being the good inspector I was, I caught him. But it is just lacquer, basically, and relatively hard. You could paint it up with some tough paint and use a little paper to bring it back down. If you miss it again, simply put some more paint on.

I have all sorts of stories where our operators tried to sneak stuff by inspection. Most (I hope) got caught, but I'll never know. I don't recall any rejects from customers on any tricks like that, so I guess all is well. Or if it failed catastrophically I never heard about it. Except for one.....on myself. I shouldn't have been doing that op anyway. I wasn't qualified at the time, but was stuck doing it. As a result, a large portion of a downhole string was lost in hole in Italy by Shell Oil. Our product liability covered the fishing, but I got relieved of doing that op from then on. I was very glad. I wasn't trying to slide anything by QC.....we didn't even have a QC dept at the time. We were too small.....4 man shop, every man for themselves. But we did grow. I got the QC job after a part I failed to deburr properly was rejected. The only inspector we had was called into the main office and terminated. I was called in next, fully expecting the same, but instead was told I was the new inspector. I was afraid to decline. So to QC I went.
 
Ill be honest and say I did the same thing with my 5c collet chuck. In my defense the ID of the bore on the back of the chuck was not deep enough for me to use a mic on so I had to rely on the usually un reliable dial calipers. I did exactly what was suggested and "push" the metal back from the face with a hardened dowel, worked like a champ, the chuck has been running true as can be for years.

There I feel better now having finally told that story.
 
Just thought of a quicker way to swell up the dia so you can return it to size. Take a hammer and beat the undersized edge to swell up the dia then return to size.
jimsehr
 
Short story time -- When I was still working for a living a new guy started in the OD grinding area. The last of three passes made the OD .004 too small. Got a new boss that night also, he asked if they could be fixed with another pass. The set-up man said sure, just let me reset the machine to grind in the opposite direction and they will get bigger. I can still hear the laughter and see the dumb look on the face of the boss. He really thought it could be done. Someone finally told him that there is no grinding machine or wheel that will put material back on.

"Billy G"
 
Maybe try some 0.001" shim between the back plate register and the chuck to fill the gap? I have a CDCO 5-C chuck on my Clausing lathe, had to do a little "tuning" between the backing plate and the chuck to get less than 0.001" total run out. My backing plate was "perfect"; chuck was a press fit going on, but ended up with around 0.003" run out on a 1" piece of drill rod about 4" out of the chuck. It indicated at the collet chuck at <0.001". My set up has a 0.001" or 0.002" shim between the backing plate and chuck at one of the mounting screws, now checks at <0.0004" at the chuck and 6" beyond the chuck.

Bruce
 
Rolling papers are easy to get here. All of the smoke shops sell them. Also there are 5 head shops in the area.

"Billy G"
 
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