View Full Version : impaled on the horns of a dilemma!
loose nut
07-07-2007, 07:57 AM
I need to bore out a .562" hole , in a piece of 2" dia. stock, to a close fit on a shaft to finish machine it ( a one time use collet). I started by step drilling it out to 1/2", I removed the piece from the chuck and checked the alignment and it was within .001 of centre over 2" depth, then I bored it to within a couple of thou. of the finished size and reamed it to the finished Dia. The shaft fit in with a tight sliding fit and when I indicated the shaft near the collet it was only .00075 off of centre, then I indicated it 2" out and it is running off about .005". After that I indicated the hole and it is running off on a curve. Any ideas on what I did wrong. I think I will try boring with an end mill next try 'cuz it can't do any worse. HELP!!!:confused:
Problem could be the reamer......
You said you bored it within a couple thou. Reamers should have more than a couple thou removal.
Rustybolt
07-07-2007, 10:55 AM
I'd have to see the setup you use for checking runout, but i don't think taking it out of the chuck and then remounting it was a good idea. That's probobly where the error occurred.
The reamer, again.....was it in a floating holder or rigid holder? It should be floated to follow the bored hole.
malbenbut
07-07-2007, 11:51 AM
Dont ream it next time just bore it to size.
MBB
John R
07-07-2007, 12:24 PM
DR, could you tell us about a floating reamer holder. I have not heard of that before.
thanks
John R
IOWOLF
07-07-2007, 02:29 PM
DR, could you tell us about a floating reamer holder. I have not heard of that before.
thanks
John R
Huh? kidding right? You probably never heard it called that.
loose nut
07-07-2007, 09:25 PM
OK, third try turned out better. This time I drilled out to 3/8" then mounted a 1/2" end mill in the tail stock chuck and drilled it out, very slow RPM's, and then finished it by boring. the difference in run out this time was less than .0015".
I think the problem was that the boring bar was small to fit the hole (not the best quality) and it was to flimsy to bore straight on a crooked hole. The end mill was stiff and made a accurate hole that the small boring bar could follow. Unconventional but it worked. A reamer won't straighten a crooked hole, and I need a better small size boring bar. Thanks for the advise and any more ideas on this would be helpful.:)
P.S. has anyone seen my red handle Robertson screw driver I had it this morning and now its gone. Damn gremlins!
mochinist
07-07-2007, 10:22 PM
You might want to practice your drill sharpening, you should be able to drill a hole with less runout than that in 2"