I Need to Vent About My Precision Matthews Mill

I bought a Precision Matthews PM728 benchtop mill over 2 years ago.

First, a minor annoyance. The oiler leaks. I was advised to remove the check valve, blow some air, and maybe a stuck ball will fix itself. I can’t tell where the leak is coming from, and so I haven’t done this yet. The chip tray is full of oil and a couple of bugs. This is still on my to-do list.

The bigger issue is that the spindle is defective. The R8 taper wasn’t machined correctly, and so it wasn’t holding onto collets properly.

I thought the problem was with my lack of experience, and I spent a ton of time trying to chase down excessive runout.

I finally looked online, found a known issue, contacted Precision Matthews, and they were great about confirming the issue and sending me a replacement spindle. That was 2 years ago.

Replacing the spindle sounded complex, and I avoided it for the longest time. I was still sour from all the time wasted trying to figure out the runout issue, and at some point I was waiting for a free weekend.

I made a point to finally replace the spindle today. First I’d swap the spindle, then test the machine, then plan and build a new stand for it, and finally convert it over for CNC use. This sounded like a plan. I was ready to get back to it!

I got stuck. Removing the quill wasn’t too difficult, until it was time to disassemble it. This step was hard:

The spindle bearings are at either end, and a split nut at the top sets the tension and holds everything together. See Part 38 on page 20.

Advertisement

There are two set screws that when tightened, spread apart the slits in the nut and lock it in place. Loosen the two screws, and then use a straight punch or rod of some type with a mallet to tap the nut loose and then remove it.

Once I realized that the spindle nut was an internal retention nut of sorts, that’s when the fun began and I eventually used a pin punch in an a shallow hole with a wrench for leverage and a quill lock wrench holding the other end immobile. Looking online now, a pin spanner wrench would have helped.

“Tap it loose with a punch and a mallet.” If only that was the worst of it.

Next, with emphasis my own:

Once the nut is off, remove the screws holding the end cap on the tool end of the quill, and then tap the spindle out of that side of the quill. The top bearing will stay behind in the quill, which is fine, but you can remove it by tapping it out the other way with piece of dowel. The other bearing can then be slipped off of the spindle. It should not be such a tight fit that you need a press, as that inner race is held in tension by that nut you removed.

One bearing is loose, the spacer is loose, but the one that needs to move isn’t. I cannot slide them off the shaft. It is NOT a loose fit.

I tried a bunch of things to no avail. I tried to be gentle so as to avoid damaging the bearings.

I sent an email to Precision Matthews’ customer service, but I’m not sure what they can say. Hopefully they’ll have good news or good tips for me tomorrow.

It’s partly my fault for putting this off for 2 years. I bought the premium benchtop mill because it was supposed to be better. Having to work on it from the start was discouraging.

I went through so many disposable gloves handling things. If I can even get these bearings off, I might need to regrease them. PM provided guidance for that too:

The bearings can be inspected, but if you want to re-lube them, you’ll need to clean them out with solvent, and then use an actual spindle grease such as Kluber to grease them. They should not be filled more than about 30% or they will over heat. You can estimate that by filling one third of the circumference of the race all the way, and then spinning the bearing to distribute the grease around it.

I looked up the grease, and wow is it pricey. I hope I don’t need to go that route.

I HATE having to work on new machinery to get them to work. I shouldn’t have to sink hours into new machinery – isn’t that the point of buying new vs old? I also bought a Precision Matthews lathe, and that too required a bit of work and 1 replacement part. It still needs to be tuned and adjusted a bit.

As for reassembly, if I ever get to that part, I was told:

Assembly is the reverse, and the nut should only be tightened enough to remove any axial play in the spindle. Too much tension will also cause it to overheat, and too loose will make more noise. It’s all done by feel and sound here.

I’m not a “feel and sound” type of person, but hopefully it goes smoothly.

Hopefully they get back with some good advice. I’m not convinced – this was a limited problem they dealt with 2 years ago. Maybe the worst case scenario is that I will need to order replacement bearings and the spacer on my dime, even though this was all due to the factory defect.

Sorry, I needed to vent. I thought this would be a simple but time-consuming part replacement. Instead, it’s been time-consuming and I’m not done yet until I get past this part of disassembly without damaging anything. Hopefully nothing is damaged.

Maybe an extra-long bearing puller could do the trick, or a large hydraulic press. I have neither.

I put off replacing the defective spindle because I was sure it was going to be a giant pain. On the bright side, it looks like I was right.

I am 90% certain Precision Matthews will come through for me. But that doesn’t make me feel any better about the situation.

Would I buy the same machine again? Yes. My only regret is that I didn’t deal with all of this 2 years ago.