bridgeport bed "JUMPHS"

chiefcross · Aug 15, 2020

I have 2 good variable speed Bridgeports, but when I am cutting say .035 thou. bed is smooth one way and sometime jumps coming the other way. Since I usually use small cutters(1/2 and under) breaks lots of milling cutters when it does this. Anyone know what to do to fix. Would new crossfeed nuts take care of the problem? How about tighting the gibs although the bed s are pretty tight now. Any advice would be appreciated. Thanks, chiefcross

talvare · Aug 15, 2020

The jump you are experiencing is likely when you are "climb milling". Climb milling is generally not recommended on milling machines with conventional lead screws and especially when there is quite a bit of back lash. The mill jumps because it is pulling all of the backlash out in one "jump" and of course this puts an excessive load on the tool. Probably best to stick with "conventional milling".

Ted

chiefcross · Aug 16, 2020

Thank you very much for this info. As you can tell, i am not a professional machinist. I have been taking guns apart for about 70 years, and was making a set of claw mounts for a old German Stalking rifle when I broke my 1/4 mill. I will remember this. when i was much younger I had two good machinist working for me in my production shop making gunsmith tools. They helped me a lot but never explained this. Thanks again.

moonlight machine · Aug 16, 2020

chiefcross said:
Thank you very much for this info. As you can tell, i am not a professional machinist. I have been taking guns apart for about 70 years, and was making a set of claw mounts for a old German Stalking rifle when I broke my 1/4 mill. I will remember this. when i was much younger I had two good machinist working for me in my production shop making gunsmith tools. They helped me a lot but never explained this. Thanks again.

You can climb mill if you tighten the table lock a bit. Lots of times you will get quite a bit better finish when you climb mill.

Richard King · Aug 17, 2020

Or replace the feed screw and nut. If you can't afford a new one try moving the work to one side away from the middle where the feed screw is worn the worse. If you want to see how to replace the nut, go to you tube and search H&W machine repair

moldcore · Aug 17, 2020

talvare said:
The jump you are experiencing is likely when you are "climb milling". Climb milling is generally not recommended on milling machines with conventional lead screws and especially when there is quite a bit of back lash. The mill jumps because it is pulling all of the backlash out in one "jump" and of course this puts an excessive load on the tool. Probably best to stick with "conventional milling".

Ted

Good advice. When I was first starting the trade I found out the hard way about climb vs conventional milling. I was cutting with a long 3/4 endmill and everything literally went sideways real fast the first time I tried to climb mill. Part went one way and the Bridgeport head went another. The boss couldn't stop laughing. Fortunately there was no harm done, just a few minutes wasted while we straightened out everything back to normal.

thmachine1 · Aug 25, 2020

Climb millings leaves a nicer finish, you have to be careful and not take to big of a cut. Crash situation can happen fast if the cutter bites in to the work piece and causes the backlash in table to move.

Search

Largest Manufacturing Technology Community on the Web

Search

bridgeport bed "JUMPHS"

chiefcross

Plastic

talvare

Aluminum

chiefcross

Plastic

moonlight machine

Diamond

Richard King

Diamond

moldcore

Hot Rolled

thmachine1

Aluminum

Similar threads