Wearing in or wearing out?

[widgitmaster]

I think it is time to adjust the gibbs on my new Bridgeport clone!
I noticed a strange reaction while dialing a long plate edge on the Y-axis!
When moving inward, the dial was all zero but when moving outward the dial went from -.006 to zero!

I have been pumping gallons of way lube through my machine, so I know its not wearing out, so I guess its time to fiddle with the gibbs! Things like this always happen in the middle of a big project!

Eric

[NC Cams]

Sounds like the gibbs are not perpendicular to each other or the one side that is absobing the thrust from moving in the other direction is NOT parallel to the other.

Could be that the gibbs are loose and you're seeing "table twist" in concert with a lack of parallelism

[widgitmaster]

Actually, i snugged up the gibbs and its tracking perfectly!
I have not experienced any out of square conditions from my mill, actually it has exceeded my expectations for a clone!

I can tram the head, then extend the ram, rotate the turrett, and return it to normal position and find the head is still trammed! My mill has only .005 backlash on x & y axis too! The only gripe i have is that when I ordered it i choose the short table! As it only has 24.29" of travel in the x axis!

Eric

[zoeper]

Ditto ditto!
Yes it only happens when you can't afford to stop the mill!
My 2 gripes with my BP clone:
1. Noticed that when i lift the knee with a dial between the knee and the knee slide on the column and i then reverse direction the guage would drop by 4/100 of a mm. Also when i lower or lift the knee it would sometimes shudder.
I have now tightened the gibs to the point where i am suspecting them of being too tight, but i still get the same problem. What is the proper setup procedure for the knee gibs?

2. The spindle is making a disturbing (hammering) sound when using a rosecutter whenever there is no tooth engaged in cut. It sounds like a key wearing out somewhere in the spindle drivetrain. when there is a tooth in cut the slack is taken up and whenever the tooth exits the material it jumps forward just to be knocked back as the next tooth engages the work...
Any advice to locate the problem with minimum down time would be much appreciated.
PS. I've got the variable speed head version.
Pieter

[mxtras]

I was told to adjust the knee gib so that you have approximately the same resistance going up as you do going down. If your ways are not worn you should have a tight knee by doing this. If the ways are worn, you will likely not have smooth motion on the downstroke.

The noise you hear is coming from the drive splines in the spindle and is quite common.

Scott

[zoeper]

Hi Scott,
If the sound is common there must be a lot of nervous people out there. I can swear mine sounds worse by the day and i don't like it one bit!
I should have another mill in the not too distant future and maybe i must just try and wait till then before attempting surgery!
I suppose the remedy would be replacement parts??
Pieter

[NC Cams]

Problem 1: you can't rely on the knee staying perfectly aligned when you move it vertically. Thus, you are pretty much limited to the quill travel for reasonable Z accuracy. Tighten the gibbs so they just can move with drag is about the best you can hope for.

Problem 2: Root cause is 3 words - drive spline clearance. The normal sine wave speed oscillations in the instantnaeous rotational velocity in the motor and spindle causes the splines to "chuckle". If you put a slight drag on the spindle brake, the chuckle should subside.

A high pole count, skewed armature DC motor tends to spin quite smoothly as compared to AC motors of most kinds. Mills run smoother, grinders grind smooother, all kinds of nice things happen with DC motors. But these are expensive fixes when you consider the drive and all.

Alternatively, you can plate the splines and then grind and lap them for minimal clearance to each other. This should minimize the "chuckle" substantially but is another pricey fix.

[zoeper]

NC,
Are we talking the splines that allow power transmission to the spindle while the quill can be extended?
I am also picking up radial play of about 3/100mm in the quill bearings. Where can i adjust the bearings to take up this slack? (assuming they must be tapered roller bearings)
P

[zoeper]

Chuckle is such a nice word in the English language, but there is really no place for it in my mill!

[motomitch1]

Originally Posted by zoeper Ditto ditto! Yes it only happens when you can't afford to stop the mill! My 2 gripes with my BP clone: 1. Noticed that when i lift the knee with a dial between the knee and the knee slide on the column and i then reverse direction the guage would drop by 4/100 of a mm. Also when i lower or lift the knee it would sometimes shudder. I have now tightened the gibs to the point where i am suspecting them of being too tight, but i still get the same problem. What is the proper setup procedure for the knee gibs? 2. The spindle is making a disturbing (hammering) sound when using a rosecutter whenever there is no tooth engaged in cut. It sounds like a key wearing out somewhere in the spindle drivetrain. when there is a tooth in cut the slack is taken up and whenever the tooth exits the material it jumps forward just to be knocked back as the next tooth engages the work... Any advice to locate the problem with minimum down time would be much appreciated. PS. I've got the variable speed head version. Pieter

1 Real Bridgeport will do the same thing when you adjust the knee, you aways should crank in down pass where you want to go and then crank it back up.

2 thats normal if you cut down the center of a 1/2" plate and have your tool on center you should put your cutter off center to get more than 1 tooth engaged or use a smaller cutter

[NC Cams]

"Are we talking the splines that allow power transmission to the spindle while the quill can be extended?" YES

I am also picking up radial play of about 3/100mm in the quill bearings. Where can i adjust the bearings to take up this slack? (assuming they must be tapered roller bearings) CONSULT YOUR OWNERS MANUAL FOR ANY ADJUSTMENT PROCEDURE> IF IT IS A FULL "CLONE" OF A BRIDGEPORT, THE BEARINGS WILL NOT BE ADJUSTABLE - THEY WILL HAVE TO BE REPLACED.

THERE WAS A RECENT THREAD THAT DEALT WITH REPLACING BEARINGS IN A BRIDGEPORT SPINDLE. ISTEAD OF ASKING THE EXACT SAME QUESTION AND GETTING THE EXACT SAME ANSWER, SIMPLY DO A SITE SEARCH FOR THE THREAD.

[mxtras]

I agree with post #7, problem resolution #1. If you want accuracy, lock the knee tight and don't move it during machining.

Check your saddle for rock, also. The longer table machines typically will wear the saddle faster as the extended table puts more of a cantilevered load on the guiding surfaces.

As far as the noise from the splines - avoid interrupted cuts and the noise is gone. Otherwise, you will have to use good earplugs - I have never run a BP or a clone that did not have that familiar clacking noise.

Scott