Bridgeport spindle deflection

RC99 · May 24, 2010

How much spindle deflection should there be in the spindle on a bridgeport..

The one I have if I put a DTI on the spindle itself and press against the opposite side I get 0.001" movement with moderate pressure... If I put the DTI on the quill and do the same there is no movement meaning the sideways movement is in the bearings... This is for a cold spindle

Is this amount of movement normal??

If it is not normal and since the bearings are not easily adjustable for preload do you grind the inner tube between the bearings a "tiny bit" to get rid of this movement or get new bearings?

abarnsley · May 25, 2010

A bit loose for new bearings. I would give you measurements from mine with new bearings, but my quill is worn more than .001....

The whole Bridgeport is a flexy machine.. Put a DI in spindle (like you are tramming head) and push on the top of head in x and y.... should see more than .001 with moderate hand pressure...

If it still works within your tolerances, use as is. If the bearings are noisy, replace with proper new ones.

jhruska · May 25, 2010

One of the shops Bridgeports would develop chatter when face milling. Changed the spindle bearings,still had chatter.
Tore it down and checked the height of the inner and outer sleeves that are sandwhiched between the precision spindle bearings.
The height of the two sleeves was not identical. I ground the sleeves parallel and reinstalled, problem solved for this machine.
I learned to check the sleeves.
Look carefully at the orientation of the bearings when removing.
New bearings should be purchased as a 'Duplex' pair. Around $250 stateside.
Kluber grease

John

JRIowa · May 25, 2010

Just like John says, if it chatters, fix it. BP had a lot of problems with the first Maylaysian heads. Evidently close enough on the length was good for them.
JR

RC99 · May 25, 2010

jhruska said:
One of the shops Bridgeports would develop chatter when face milling. Changed the spindle bearings,still had chatter.
Tore it down and checked the height of the inner and outer sleeves that are sandwhiched between the precision spindle bearings.
The height of the two sleeves was not identical. I ground the sleeves parallel and reinstalled, problem solved for this machine.
I learned to check the sleeves.
Look carefully at the orientation of the bearings when removing.
New bearings should be purchased as a 'Duplex' pair. Around $250 stateside.
Kluber grease

John

Thanks, I should have mentioned it is not a bridgeport but a clone....The bearings to not appear to be precision bearings, they have the wrong angle (40 degree instead of 15) and while I get no chatter when face milling (63mm face mill), I get boring is near impossible and endmilling/slot drilling loves to chatter...

jhruska · May 26, 2010

Interesting problem here. As long as it is not tool overhang (boring bar diameter/length), tool angle(positive or negative), or drag(tool rubs behind cutting edge) it might be a bearing problem.

The Asian mills used a different setup for held bearings in the quill than Bridgeport.
I saw a diagram, once, and it looked effective but not as solid.

When the Bridgeport machinists had simular problems, this is what I found.

Boring Head: Loose gibs, did not use clamp, dialed in size and backed off screw, bar
overhang, debris in the collet taper of the spindle. Bar diameter poor fit
in boring head.

Cutting tool: Improper geometry for the material, depth of cut shallow, lack of clearance,
tool rubs. Positive tooling reduces 'push'.

Tool: Carbide or High Speed? Magnify the cutting edge. Recheck the geometry.

Depth of cut: Bury the tool and see what happens.

Feed Rate: Low speed and high feed with decent depth of cut.

It could be the bearings or the way the spindle was assembled. Is the spindle tight in the bore of the quill?
Quill tight to the bore of the head?
Nose cap tight? Does the spindle float up and down in the quill?
Head is tight to the ram?
Set up does not 'spring' the part?

Good Luck
John

turbojo1 · Nov 2, 2020

Boring head chatter Bridgeport 2j head with 30 taper spindle

jhruska said:
Interesting problem here. As long as it is not tool overhang (boring bar diameter/length), tool angle(positive or negative), or drag(tool rubs behind cutting edge) it might be a bearing problem.

The Asian mills used a different setup for held bearings in the quill than Bridgeport.
I saw a diagram, once, and it looked effective but not as solid.

When the Bridgeport machinists had simular problems, this is what I found.

Boring Head: Loose gibs, did not use clamp, dialed in size and backed off screw, bar
overhang, debris in the collet taper of the spindle. Bar diameter poor fit
in boring head.

Cutting tool: Improper geometry for the material, depth of cut shallow, lack of clearance,
tool rubs. Positive tooling reduces 'push'.

Tool: Carbide or High Speed? Magnify the cutting edge. Recheck the geometry.

Depth of cut: Bury the tool and see what happens.

Feed Rate: Low speed and high feed with decent depth of cut.

It could be the bearings or the way the spindle was assembled. Is the spindle tight in the bore of the quill?
Quill tight to the bore of the head?
Nose cap tight? Does the spindle float up and down in the quill?
Head is tight to the ram?
Set up does not 'spring' the part?

Good Luck
John

Wondering if bearings is problem on my mill not really noisy but started getting chatter when boring bike cylinders and done everything I can think of besides pull spindle and replace bearings. Would like quality bearings to go back in not China stuff . Any opinions on this problem. My setup is rigid even just taking small cuts .002 or so will chatter . Wondering on the spindle if it may need grind touch up . Had machine for 17 yr and now it wants to start chatter . Any help I would appreciate it Thanks .

CJD · Nov 2, 2020

My BP has no side play in the quill.

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