Go755 Help Needed

negatronix

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Hey everyone! It's been a while since I've been on the forum here.

I am having a nasty issue with my GO755. I recently had the machine grab the part, and lock up which snapped a 7/8" roughing EM.

This crash seems to have knocked my machine out of calibration a bit. The head twisted, and the table seems rather jumpy. The biggest problem seems to be that after I re-calibrated things the machine is really unstable during a cut. The quill bounces up and down and the gearbox sounds really noisy. The cut is straight/true however. The quill bounce happens even if I lock it preventing me from lowering or raising it.

I am not by any stretch an expert with much of this yet, but if anyone has any ideas about what may be causing the instability, slop, and bouncy quill please let me know.

Thanks,
-Kory

Sent from my SGH-T599N using Tapatalk
 
Hey everyone! It's been a while since I've been on the forum here.

I am having a nasty issue with my GO755. I recently had the machine grab the part, and lock up which snapped a 7/8" roughing EM.

This crash seems to have knocked my machine out of calibration a bit. The head twisted, and the table seems rather jumpy. The biggest problem seems to be that after I re-calibrated things the machine is really unstable during a cut. The quill bounces up and down and the gearbox sounds really noisy. The cut is straight/true however. The quill bounce happens even if I lock it preventing me from lowering or raising it.

I am not by any stretch an expert with much of this yet, but if anyone has any ideas about what may be causing the instability, slop, and bouncy quill please let me know.

Thanks,
-Kory

Sent from my SGH-T599N using Tapatalk

Sounds like a hard crash. Could be a bent spindle. Put a dial indicator on the spindle taper and check it for run out. Run out should be less than .0005". If the spindle is bent that would explain the problems you are experiencing.

Tom S
 
Is the quill bouncing or is the spindle bouncing? With the quill locked it really can't bounce unless the whole head is bouncing. It is however possible for the spindle to bounce in the bearings inside the quill. Hitting it that hard could bend a spindle or damage the bearings. It's also possible to have damaged the gears in the head.
 
-Tom- I don't believe the spindle was bent. I checked the spindle and there is no wobble.. at least with my Manager's Special indicator from Grizzly. I also re-indicated both my vise, and rotary table since the crash. I think part of why the crash happened was due to some slop in my table. As my tool was exiting a cut it grabbed and crashed.

-Jim- The quill is moving as is the spindle. If there is any load put on a tool it bounces. As I apply pressure even drilling a hole the downfeed steps with the bouncing. The tooling is sharp, and the cuts/holes don't show any chatter.. ie.. the cuts are clean. It feels like there should be something preventing the tool from resisting the cut by travelling up. When the lock is locked, the issue still happens.

I talked to a tech at Grizzly, and he thinks that a bearing may be the culprit... however there is no wobble or play unless the machine is under load.

The tech felt the next step should be to pull the motor and open up the gearbox to look for a broken gear or the like.... uuuggghhhh

-Question- Has anyone pulled a gearbox apart on a GO755 or similar? Is this a huge can of worms I might be getting myself into, or is it pretty straight forward. Are there special tools required, and will I be forced to replace seals, circlips etc.. finally, is there any form of "timing" for the gears to be assembled, or do they just go in with no specific order/sequence.. I'm just trying to get a visual for the the job.

-Thanks,
Kory

Sent from my SGH-T599N using Tapatalk
 
Jim- The quill is moving as is the spindle. If there is any load put on a tool it bounces. As I apply pressure even drilling a hole the downfeed steps with the bouncing. The tooling is sharp, and the cuts/holes don't show any chatter.. ie.. the cuts are clean. It feels like there should be something preventing the tool from resisting the cut by travelling up. When the lock is locked, the issue still happens.


I would be having a hard look at the quill lock also, it might be damaged. Some careful prying with a prybar might be in order here, you might be able to see where the slack is at.
 
The Precision Mathews forum on this site has a thread on changing seals that gives you the basics on removing the gear box cover so you can inspect the gears and bearings.

Tom S
 
Well... I pulled it apart, and should have stopped at just removing the motor.

Everything inside looks perfect, chip free, sharp, no metal flakes in the oil.

I have noticed that there is backlash/freespin in the spindle. With the motor removed, I could grab the spindle and turn it about 1/8".
I do not recall that being normal.

Any thoughts?

Thanks for the help folks!

Sent from my SGH-T599N using Tapatalk
 
Could have hammered the spindle splines.
 
Not that much. :)

Reason I suggested this is because I put a aftermarket pulley kit on my PM-25 and shortly after I was running a 3/8" carbide rougher, full pass width at a DOC of 1" and hammered the outer splines on the part supplied in the kit. Ended up making a replacement bearing carrier using the original splines that came with the mill. And I ordered a bigger mill to handle the larger jobs. :rolleyes:
 
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