machinehead61
Titanium
- Joined
- Feb 8, 2004
- Location
- Rochelle,IL,USA
Every once in a while, someone showed me a great little "trick" to fix a machining problem and I'll pass a couple along. Feel free to share your little tricks that someone taught you or you came up with yourself.
Reamer not reaming to size:
An old mold maker I worked for showed me this one. One day I was trying to ream a hole with a rather dull reamer in a Bridgeport. It was a good sized one, say 1". It got to the point where the reamer squeeled and spun in the collet and I couldn't finish the hole. So he showed me a quick fix. Took the reamer out and grabbed a dowel pin. He rubbed the pin along the inside of the cutting surface of each flute. (I've used HSS also) Put the reamer back in and no squeel and the hole was within tolerance.
Turning a thin, long diameter:
I had to turn about a hundred pins from 303 SS hex stock 3/8" with a diameter of a #6 screw and length of 2".
The diameter was too small for our live center. Our smallest center drill was too big for the tip of the part (needed 6-32 threads on end), besides, the lathe tool would not clear the centers we had. We didn't have any box tools so I attempted to turn the pins unsupported with dismal results. Way too much flex. Solution was to take a broken center drill and grind it down to where it would clear the lathe tool and then ground a sharp point on the end. With the parts spinning and the modified centerdrill in the tailstock, I would feed the modified centerdrill into the end of the parts, say .015-.020", just enough to support the end for turning. Put grease in the hole, run the modified centerdrill as a center and it worked great. Just kept coolant on the center to keep it cool. It lasted for the whole order and could do another couple hundred.
Dowel pin location:
Always was told that center drilling and drillindg a hole in a bridgeport was only good for +/- .002-.003" accuracy. Not up to +/- .0005 for dowel pin hole locations. Without a jig borer we went to drilling the hole locations 2 drill sizes undersized. Then "bore drill" with the largest drill available to leave stock for the reamer to clean up. By "drill bore" I mean drill with slow enough feed so that the drill doesn't follow the existing hole but actually bores the hole true to the spindle axis. Stub the drill up as short as possible to get to your depth. If you have an undersized endmill, use that instead. I know that you are still at the mercy of how accurate your Bridgeport can locate, but this has woked for many a parts.
If you guys have seen better ways of doing things, share away.
Steve
Reamer not reaming to size:
An old mold maker I worked for showed me this one. One day I was trying to ream a hole with a rather dull reamer in a Bridgeport. It was a good sized one, say 1". It got to the point where the reamer squeeled and spun in the collet and I couldn't finish the hole. So he showed me a quick fix. Took the reamer out and grabbed a dowel pin. He rubbed the pin along the inside of the cutting surface of each flute. (I've used HSS also) Put the reamer back in and no squeel and the hole was within tolerance.
Turning a thin, long diameter:
I had to turn about a hundred pins from 303 SS hex stock 3/8" with a diameter of a #6 screw and length of 2".
The diameter was too small for our live center. Our smallest center drill was too big for the tip of the part (needed 6-32 threads on end), besides, the lathe tool would not clear the centers we had. We didn't have any box tools so I attempted to turn the pins unsupported with dismal results. Way too much flex. Solution was to take a broken center drill and grind it down to where it would clear the lathe tool and then ground a sharp point on the end. With the parts spinning and the modified centerdrill in the tailstock, I would feed the modified centerdrill into the end of the parts, say .015-.020", just enough to support the end for turning. Put grease in the hole, run the modified centerdrill as a center and it worked great. Just kept coolant on the center to keep it cool. It lasted for the whole order and could do another couple hundred.
Dowel pin location:
Always was told that center drilling and drillindg a hole in a bridgeport was only good for +/- .002-.003" accuracy. Not up to +/- .0005 for dowel pin hole locations. Without a jig borer we went to drilling the hole locations 2 drill sizes undersized. Then "bore drill" with the largest drill available to leave stock for the reamer to clean up. By "drill bore" I mean drill with slow enough feed so that the drill doesn't follow the existing hole but actually bores the hole true to the spindle axis. Stub the drill up as short as possible to get to your depth. If you have an undersized endmill, use that instead. I know that you are still at the mercy of how accurate your Bridgeport can locate, but this has woked for many a parts.
If you guys have seen better ways of doing things, share away.
Steve