Mill quill has become very stiff *Problem fixed*

[JustBen]

Hello,

I recently picked up barely used Bolton Tools ZX32GP (similar to a PM-727M or Grizzly G0795 bench mill). As the story goes, the previous owner purchased the mill and passed away. It has a 2017 date stamp on it, so it has sat for some time.

Grizzly parts diagram: https://www.grizzly.com/products/g0795/parts
Grizzly Manual: https://cdn2.grizzly.com/manuals/g0795z_m.pdf

I had been using it for some test cuts and noted the quill seemed stiff. It seemed to progressively get worse and now the quill will stay in position even with the return spring disengaged.

Things I have tried so far:

• Removed the fine feed worm gear assembly and cleaned it. The grease present was very stiff. Cleaned it all up and put new grease in place. Bearings for the worm gear are not smooth but they rotate by hand. Will do the bearings in the future. Slight change in the quill feel but obviously only when the fine feed is engaged.
• Fully extended the quill and degreased the outside. Worked the quill up and down to hopefully dislodge any debris. Oiled the quill body with a light oil (Starrett oil I had around). Greased the splines on the back of the quill for up/down movements. No change in quill movement feel.
• Greased the quill spline to see if the pin that rides in the groove is binding as I found in this thread. https://www.hobby-machinist.com/threads/pm-727m-new-mill-has-arrived.57473/page-12 . No change in quill movement feel.
• Removed the quill lock assembly completely (Edit: I realized later that half the lock was stuck in the head and was the issue). No change in quill movement feel.
• Dropped some Vactra #2 way oil down the top of the toothed spline shaft for the spindle. Ran the quill up and down. No change in quill movement feel.
• Disengaged/removed return spring. Made no real difference. The quill will stay in whichever position it was moved to.

What should I try next? What causes this type of binding to occur?

Thanks,

Ben

 

[JustBen]

Ok. I went ahead and dropped the quill out. A little dirty but nothing crazy. Felt around for any burrs and didn't find anything notable. I did note the pin for the quill spline is not sliding smoothly by hand. The spline has chamfered edges in the bottom which do not match well with the squared off pin. I am rounding off the pin slightly to help it match the profile of the chamfer in the spline/slot.

 

[JustBen]

Hole in the head for the quill.

 

[jwmay]

Well I was gonna say not to take anything apart yet. But too late for that. Lol

Did the quill fall right out when you removed the splined shaft?

 

[JustBen]

Update: Quill is fixed and better than before.
It ended up being a combination of things.

1. The quill locating pin (not sure of the official name) that goes in the vertical slot and prevents rotation needed to be polished and edges rounded over a bit to match the profile of the groove. It would not slide smoothly otherwise.
2. I think a combination of sitting and me spraying it down with some Starrett M1 before shipment (worried about rust) may have made it sticky. I read some other posts about the wrong lubricant causing sticking in some cases. I am now running what I have which is some Starrett instrument oil which seems light enough.
3. The main reason for the stiffness is the quill lock. When looking at the head the left side of the quill lock was not releasing. I noticed the issue during reassembly. I would install something and test movement, then repeat. The right side would slide free. When looking at the machined part, it was clear the finish was poor and there was a noticeable step from where it was machined. It seems like someone machined half of the round tube, flipped it around and machine the other half while leaving a step from the misalignment in the lathe. Filing, stoning and polishing it down made a huge difference and now it doesn't stick.

Quill locating pin.


Quill lock. Note the visible step on the round tube near the handle.


Cleaned up quill lock part:


Opportunity for improvement. The quill locating pin was not able to be removed when this plate was in place. It is a pain to deal with the return spring. I notched a hole in the plate to allow the pin to be accessed and removed if necessary.

 

[JustBen]

Well I was gonna say not to take anything apart yet. But too late for that. Lol

Did the quill fall right out when you removed the splined shaft?

LOL. It was bugging me and I couldn't stop pulling things apart. To answer your question, no, the quill had to be pulled down with some force a half inch at a time into some wood blocks to prevent dinging the table/spindle nose.

 

[jwmay]

Yeah I had the same problem, but I’ve just been wracking my brain all day trying to remember what it was. What I knew for sure was that I didn’t have to take all that stuff apart to fix it. Anyways it was exactly the same problem and exactly the same solution…At least regarding that half of the quill lock.

Congratulations on NOT having to depend on my crappy memory, and on fixing it yourself.

 

[matthewsx]

Yep

Bolton = Many opportunities for improvement.



John
FBO (Former Bolton Owner)

 

[JustBen]

Yeah I had the same problem, but I’ve just been wracking my brain all day trying to remember what it was. What I knew for sure was that I didn’t have to take all that stuff apart to fix it. Anyways it was exactly the same problem and exactly the same solution…At least regarding that half of the quill lock.

Congratulations on NOT having to depend on my crappy memory, and on fixing it yourself.

Well, if you solved it earlier, then all those parts would still have the old grease and dirt on them. Fresh and clean now.

Yep

Bolton = Many opportunities for improvement.



John
FBO (Former Bolton Owner)

It is a bit of a project for sure.