# Bridgeport Z Axis



## mildot1 (Dec 16, 2014)

I have a 1963 model Bridgeport with a DROPRO 3 axis DRO. The problem I have is very inconsistent reading on the Z axis. Cranking the Z axis lock changes my DRO reading 2-4 thousandths.

I am wondering if the knee gibs are loose?

Where can I find a detailed explanation on adjustment?

Many Thx
Mildot


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## Tony Wells (Dec 16, 2014)

If it only moves 0.003-0.004, call it good. That knee is heavy, and therefore tends to sag. The lock brings it back to true with the world, and hopefully when you swept the head in, you did so with the knee locked.


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## mildot1 (Dec 16, 2014)

Thanks for the reply!

I realize the knee(Z) is heavy, I always try to use the weight of it when moving to minimize backlash or slop in the gibs. I still think that just adjusting the lock should not give .002 from 2/3 tight to full tight.

How do I adjust the gibs to reduce this play?

Thx
Mildot


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## LEEQ (Dec 18, 2014)

Your gib screw is at the top of the knee on the left as you face the machine. You can tighten it up a bit and then see if you still have full range of motion. On worn machines you will have to find a compromise between to tight at the ends and too loose in the middle. Good luck


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## chips&more (Dec 18, 2014)

A +1 on what LEEQ said. And maybe my parts would have a tighter tolerance on dimensions, but have not any study. I do not lock the Z, can’t recall a time of ever locking it? I know some of you are going to roll your eyes. I make parts typically smaller than my fist, maybe that’s why? The BP has a lot of table mass for my size of parts. I do use the X & Y locks. And a bit off topic. When and if you move a BP. Make sure you lock the Z travel. I have seen the Z feed nut get stripped out with the feed screw because of all of that mass/weight hammering on the feed nut. Especially in the back of a trailer on a rough road…Good Luck, Dave.


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## LEEQ (Dec 18, 2014)

I think Keith Rucker has a youtube video on it also.


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