View Full Version : Mill Head

09-16-2002, 06:57 AM
What is the most stable plate for tramming in a bridgeport mill

Paul Gauthier
09-16-2002, 12:45 PM
Not sure what you mean by "plate" but when tramming in a bridgeport mill one uses the table.

Paul G.

09-16-2002, 03:46 PM
Most make a ring instead of a plate so there is less chance of inaccurate readings because of any damage on the table or tramming ring and/or metal chips (less surface contact). When making one, (think of a washer) it should be the diameter equal to the distance from the spindle center line, to the center of the head tilting pivot pin. If your center line distance is 8", that 8" point should be in the center of the meat of the washer. Making it that size will aid in making Y-axis tramming adjustments.

As to what to make it out of? Any reasonably stable material will do. Just make sure any internal stress are relieved before it is surface ground.


09-16-2002, 06:13 PM
A big ugly Timkin bearing cup - used from the local Caterpillar Dealer (or new). Always a good idea to check it first on a granite flat to insure it is parallal - it is unlikely to be buggered because of Timkins quality control. Timken Bearing spacer rings also work - they are ground on both sides.

09-16-2002, 08:42 PM
I never though of a bearing ring. I'll need to go to the local Cat dealer and check it out. Thanks Thrud.


Uncle Dunc
09-16-2002, 10:11 PM
The point of using a plate or a ring is so your indicator won't have to jump over the t-slots when you're checking the y-axis.

09-16-2002, 11:50 PM
When I was in school I cut a donut out of
1 1/2 inch plate a ground it. It has served me well for years. Using a large bearing cup seems like a great idea though.


Ed ke6bnl
09-17-2002, 08:14 AM
I use bearing races for parrallels when there size is appropriate. Not a good item to hit with tooling though. Ed ke6bnl

Ed ke6bnl
Agua Dulce, Ca.
70 mi. S.E. of Los Angeles

09-17-2002, 02:12 PM
Hi Ed,

I live in Canyon Country, about 10 miles west of you! Small world.


Bob Quale
09-17-2002, 05:36 PM
How big do the bearing rings get and what would I expect to pay for one? GREAT idea!


09-17-2002, 09:53 PM
I have seen 48" bearings. You can buy a shop full of goodies for what one costs. They are rarely thrown out, they usually get returned to the maker and are rebuilt at a substantial savings. There is a a double row 24" bearing welded to a car heater post on the south side of Edmonton - looks cool, but what a waste.

A cat dealer replaces these from time to time in big machinery - if you ask he shop foreman to save you one they usually will. Bring a bag of doughnuts in appreciation after you pick it up if he does not ask anything for it!

[This message has been edited by Thrud (edited 09-17-2002).]

09-18-2002, 02:20 AM
Someone suggested a used brake rotor, I don't remember who...Seems feasable to me, cut out the hub (or use a hubless rotor) and have it blanchard ground flat and parallel. I don't know if the extreme heat cycles would add or relieve stress to the rotor.