adjust knee gib on bridgeport

[Dave Dahlgren]

I took a look useing the search feature in both this and the bridgeport forum but all I can seem to find is to adjust util there is a little drag. Well i cleaned everything up and put the knee back on and seem to be sending the knee gib to china so to speak. I can still easily raise and lower the table and have been cranking away with no sign of things starting to drag. I was thinking of putting an indicator on the top of the gib with the base on the knee and see if the gib is moving with the knee or if there is some small amout of slack in it still. Will this give any useful info or just keep cranking on the gib til it filally has a little drag. me and my old back are getting a wee bit tired cranking. Only other thought was to put an indiator between the knee and column and see if there is any movement( towards or away from the column) at all when I raise and lower the knee or just give it a good tug.
Dave

 

[aboard_epsilon]

Just put an indicator in the quill.
sweep the quill round
and note the difference when locking and unlocking the knee.

When the knee is locked it takes up all the play.
so when you adjust the knee in unlocked mode you should be trying to get it to show an indicator reading near what it is in locked position .without having too much drag when you crank it...................this position is the optimum setting.
if there is a large difference and you cant do anything about it.
1.there may be dirt under the jibs
2.or you need a rebuild.

all the best...mark

 

[icehd81]

Detecting drag on the knee crank is very difficult, due to the mechanical advantage of the operation. Remember, there are two mechanical steps on the knee, plus a longer crank handle, when you compare it to the table feed or cross feed. Plus the natural droop of the knee will give a false feel. The best way is to tighten the gib til you create more drag than you can handle, almost locked up, then back off until you can acceptably raise and lower the knee with reasonable effort.

 

[Dave Dahlgren]

Got that part done it moves an indicator 0.0002 lock on lock off with little drag on the crank and yes my old bad back does not allow for a lot so that is a good deal as far as i can see. Yes i did mean 2 tenths..
Dave

 

[Dave Dahlgren]

on to the next step. Added a 0.008 shim to the back of the Y axis gib. After cleaning everything very thoughly it was too small go figure. Used paint thinner and scothbright and then cleaned again to get the scotchbright sruff off. i ended up slightly easing one end of the y travel near the column with a scraper to get full travel and it allowed me to get the clearance in the middle to reasonable as well. I know this goes contrary to what might be perfect but seemed to work fine . I did spend a few hours doing it and went very slow blued and moved saddle by hand and found high spots. Eased them off clean and repeat. it was prety tedious but the results seem worth it. In the end it will have to be scraped by someone that knows what they are doing or i will have to get smarter. read most of Connelly's book and don't think I did too much to offend him.

Next question Bijur oil pump. I have cleaned and soaked all the mettering units. With vactra #2 it takes about 1 minute to go from full up on the plunger to bottom and so far they all drip some oil after soaking the metering units a couple of days in paint thinner. Does thei seem about right or do i need to clean further? Waiting for the two feed nuts to arrive so i can get this back together.
Dave