Tramming a Bridgeport

[scleaf]

HI: scleaf How are you mounting that indicator in the mill? and what are you tramming on the table that is 24"? are you checking the Gib movement?
The digital indicator's I have used had only an accuracy of 0.001 and repeat of 0.0005. Try using an indicator with a needle and graduated in 0.0005 graduations, a Starrett last word works well and you can see the needle movements easily. The indicator holder shown a post back by Jeff in PA is very good it shows the movement of the spindle.
The indicating of the table is fixed. Unless you sweep the table surface for squareness or if you are paralleling the back jaw of a table mounted vice.
I hope I was clear on my questions and partial answers.
dwdw47

I am mounting the indicator in the spindle (picture has a bolt, but the actual tool has a shaft) and sweeping the table the distance of travel. Since I am new to this I found it to work well and though the digital indicator may not be an expensive one it seems to work ok for my learning projects. I got the idea after watching this video http://www.youtube.com/watch?v=JfANyiS8Hs4

 

[Kevin45]

When tramming the head, I always drop the table down and extend the quill down as far as it will go. After doing that and bringing the table up to the indicator, I then lock the knee and proceed to tram each axis in. Also you want to have the bolts a little snug when tramming and not completely loose. If you tram with the bolts completely loose, the head is either tipped front to back or tipped side to side. You want the bolts as snug as possible but not too tight where you can't rotate the head. Then once the axis is tuned in, tighten each bolt in a staggered pattern.

BTW...if you have it within .001, you aren't going to get much better than that, unless you keep tramming each axis all day long.

If possible, and you have access to a wet grinder, make a tramming plate. I always kept one in my bench drawer that was 12" square and 3/4" thick. If the vise happened to be off the table, I would set the plate directly on the table and tram the mill. A solid plate eliminates the error of jumping across the slots in the table. If the vise was on the table, I would set the tramming plate on a set of Gage Blocks set on the vise vise ways, but not tightened up. That way the mill is trammed to where your parallels are going to be setting.