spope14
Stainless
- Joined
- Jan 29, 2004
- Location
- Claremont, NH
here is the problem. A few weeks back I started having a bit of torquing twist in a bridgeport table in the Y axis. By this I mean that moving the cutter in a slot going Y positive, the slot would machine well. Returning the cutter, moving it .005 offset to climb mill in return, the slot would develop a .013 taper over one inch.
I put two magnetic indicators, 1 inch travel, on the ways and measured the table movement. Moving Y positive (cutter), the table would remain at "0" on both sides of the table. Returning, the table would flex, thus the right indocator would stay at zero on the return over 1 inch travel, but the left side indicator would be .013 behind. This indicated a gib issue, the gib being on the left.
I tried adjusting the gib, but itt only tightened the machine operation. I got it to .003 doing this, but the machine was so tight it acted like it was "locked".
The next step was to take out the gib, clean all things out extremely good and proper on the machine and the gib. The turcite is undamaged from my indication. Tightened the gib,it traveled well beyond the back wiper plate. Thus a .003 shim behind the entire length of the gib (plastic shim) behind the gib. Got it to .001 difference, but still tight. I took another gib out from a similar year /make machine, the measurements are standard between them, maybe .003 difference on the large end.
This issue occured quite suddenly. Two of were teaching in the shop at the time, so I am not sure if the machine was abused during the time the other teacher was there, but I tend not to believe this as he is extremely trust worthy. My other bridgeports (I have six total) measure maybe .001 to .0015" twist/torque.
I also checked the screw mount all around. It is not loose as far as i can check it without pulling the table completely off.
I am in a hiatus where i can really spend some time on the machine fixing it now. I am open to ideas.
I put two magnetic indicators, 1 inch travel, on the ways and measured the table movement. Moving Y positive (cutter), the table would remain at "0" on both sides of the table. Returning, the table would flex, thus the right indocator would stay at zero on the return over 1 inch travel, but the left side indicator would be .013 behind. This indicated a gib issue, the gib being on the left.
I tried adjusting the gib, but itt only tightened the machine operation. I got it to .003 doing this, but the machine was so tight it acted like it was "locked".
The next step was to take out the gib, clean all things out extremely good and proper on the machine and the gib. The turcite is undamaged from my indication. Tightened the gib,it traveled well beyond the back wiper plate. Thus a .003 shim behind the entire length of the gib (plastic shim) behind the gib. Got it to .001 difference, but still tight. I took another gib out from a similar year /make machine, the measurements are standard between them, maybe .003 difference on the large end.
This issue occured quite suddenly. Two of were teaching in the shop at the time, so I am not sure if the machine was abused during the time the other teacher was there, but I tend not to believe this as he is extremely trust worthy. My other bridgeports (I have six total) measure maybe .001 to .0015" twist/torque.
I also checked the screw mount all around. It is not loose as far as i can check it without pulling the table completely off.
I am in a hiatus where i can really spend some time on the machine fixing it now. I am open to ideas.