sticky quill on bridgeport

HI, I have a bridgeport manual mill with a powered draw bar and this last while ive been noticing that whenever i change collets and bits the quill gets tight and sticky, and if i work it up and down for a while it loosens up again , it stays smooth and free until i change bits. any ideas? thanks!

Could be the power unit is rattling some junk into the splines. Probably needs a good cleaning and some lube.

Typical of a lack of oil at the top end of travel. This is a symptom of fines that are carried up between the quill and the bore. If the quill skirt is damaged at installation this will also make the quill tight at full retract.
The head is bored out to two diameters. One is for the quill and the second is for the quill skirt. At the front of the mill where the quill is visible follow the edge of the slot upwards. About where the arrow is pointing is where the bore for the quill skirt starts/ends. Use a squirt can and pump light oil into this space on both sides.

Work the quill up and down and this may resolve the issue. This 'fix' can be messy so have something under the quill to collect the oil.
If this does not work expect to remove the quill and clean it and the bore.
The bottom of the bore will wear to a bellmouth shape because of dirt and debris..
The problem has nothing to do with the drawbar.
John

I would usalley agree with John on this. However I suggest you check your threads on the draw bar as they slowly wear away and for some reason that tightens/bulges the quill sometimes. I never fighered out why...there is no logic to it ...but replacing the bar made the problem go away on more than one machine that I know of.

scadvice said:

I would usually agree with John on this. However I suggest you check your threads on the draw bar as they slowly wear away and for some reason that tightens/bulges the quill sometimes. I never figured out why...there is no logic to it ...but replacing the bar made the problem go away on more than one machine that I know of.

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That's a new one on me I'll agree to disagree as that seems to be unrelated. However, if the operator is overtightening the drawbar i suppose it's possible.
Look for worn threads in the toolholders and drawbars with premature thread failure on the same machine.

Another sticky quill problem is caused by the set screw in the nose cap. This set screw is located on the column side of the cap. If it is too tight the quill will be tight. Be sure to check this!
John

Just to make sure that you are familiar with the drip cup that feeds the quill?
It should be just above the top of the pic shown above.
Those get forgotten about easilly, and could be broken off?


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Think Snow Eh!
Ox

I would loosen the power feed housing bolts and run the quill up as high as it goes and tighten the unit at an even pull. The bad treads makes sense too. does it get tight when you raise it up quill all the way to the top? If it does the set screws on the back of quill that hold the bottom bearing retainer in place were tightened to much and egg shaped the quill. There are 2 set screws in the hole, a narrow one with a through hole that locks the bottom on from moving.

Thanks for this post and the replies! I replaced the index pin on my Bridgeport clone and had the same issue when I was done. Quill did not move freely and stuck at the top of travel. I have now loosened the set-screw for the bearing retaining nut, and it's back to normal. Appreciate those sharing their knowledge!