[TXFred]

My mill has sat unused for two years. I'm resurrecting it now and need some help.

I've cleaned the oil system by flushing with WD-40, cleaning all of the oil lines by threading heavy fishing line through them, replacing all of the restrictors, and then flushing with WD-40 again. After all of that, the front X axis dovetail is not getting any oil. The rear dovetail and every other part of the mill gets a flood of oil.

Before you read on, it will help to look at the image I've attached. The yellow oil lines are the ones that don't flow. The green lines feed the rear dovetails from the same splitter, and are working fine.

Here's what I've tried so far.

• Disconnected the oil line and blown it out with a compressor.
• Blown out the drilled passages in the dovetail.
• Cleaned and blown out the banjo bolt connecting the oil line to the dovetail.
• Removed the oil line and pressure tested it for leaks.
• Disconnected both front and rear X oil lines from their restrictors, and operated the pump. Both restrictors released a few drops of oil.
• Swapped restrictors between front and rear dovetails.
• Examined the ferrules on the oil line. They showed signs of being overtightened. But during testing, they don't leak.
• During all of this testing, the Z axis is getting plenty of oil, so it's not a problem with the pump's pressure.

And here's my conclusions.

• It's not the oil line, because I've cleaned and pressure tested it.
• It's not the drilled passages, because I've blown them out and shot WD-40 through them.
• The restrictor for the rear X dovetail will deliver a flood of oil, but only when it's hooked up to the oil line.
• The restrictor for the front X dovetail will not deliver oil, even when it's hooked up to the oil line.
• It's not a bad restrictor, because the problem doesn't move when I swap restrictors.

I'm at a loss to explain what's causing this. Please help if you can.

[GLCarlson]

Had something similar- restrictor seemed to work, offline, worked elsewhere, wouldn't work in place (Z axis). What finally worked was soaking the restrictor in WD40 for a few days.

For what it's worth, a couple thoughts. Maybe there's a piece of junk in a line, acting like a check valve. Enough pressure -or a line- could go past it, but when it's only oil, with other ways out, the oil takes the path of least resistance. I think my next step here would be to plug ALL of the other lines (except front X) and see what happens. If it flows, then there's some kind of differential pressure problem (front X has a higher delta P). If it does not, then there's a plug in the line.

[TXFred]

I've solved this problem, and in the process I've learned a few things about the oiling system.

It turns out that the oiler was working perfectly. The front X dovetail has TWO holes drilled in it, one in the top, and one on the back where I could not see it. I had the table moved out of the way, to see the top hole, which also exposed the rear hole. So when I used the oiler, all of the oil was running out of the rear hole. I didn't see that this was happening because the second hole was hidden below and behind the dovetail.

So it was a PEBKAK issue!

I also figured out why the restrictor wasn't flowing oil when I had the oil line disconnected. The restrictors serve three purposes.

1. Act as a check valve to prevent oil from flowing back down to the oil pump.
2. Act as a restrictor to limit flow.
3. Act as a shut-off valve when flow is excessive. This is the interesting one. When an oil line is broken or disconnected, all of the oil wants to flow out of that line's restrictor. This opens the check valve and compresses the spring to the point that the spring coil binds. The oil can't flow past the spring anymore. This is a nice feature, because it means that if you have a broken oil line, the rest of your oil system will continue to work.

So everything is working now, and I'm going to spend the weekend reassembling the mill!

Frederic

[pickled]

That's great news! Glad to hear that you made it through the madness of troubleshooting the beast! I'm also glad to read that it appears that there was some good engineering thought processes applied to the lubrication delivery system as it was designed. This thread is worthy of reference status now with all the documentation and thoughts that have been expressed :-).

[keen]

I've solved this problem, and in the process I've learned a few things about the oiling system.

It turns out that the oiler was working perfectly. The front X dovetail has TWO holes drilled in it, one in the top, and one on the back where I could not see it. I had the table moved out of the way, to see the top hole, which also exposed the rear hole. So when I used the oiler, all of the oil was running out of the rear hole. I didn't see that this was happening because the second hole was hidden below and behind the dovetail.

So it was a PEBKAK issue!


I also figured out why the restrictor wasn't flowing oil when I had the oil line disconnected. The restrictors serve three purposes.

1. Act as a check valve to prevent oil from flowing back down to the oil pump.
2. Act as a restrictor to limit flow.
3. Act as a shut-off valve when flow is excessive. This is the interesting one. When an oil line is broken or disconnected, all of the oil wants to flow out of that line's restrictor. This opens the check valve and compresses the spring to the point that the spring coil binds. The oil can't flow past the spring anymore. This is a nice feature, because it means that if you have a broken oil line, the rest of your oil system will continue to work.

So everything is working now, and I'm going to spend the weekend reassembling the mill!

Frederic

Thanks for this thread Frederic - very interesting and carefully documented.

When the table is back over the oil holes, the design intention is of course that the holes will lubricate the top flat surfaces and the angular dovetail surfaces. I am interested in how well this works. If you can find time please check the underside flat surface to see if it is receiving a good coating of oil. You may need to wipe it dry, pump oil and inspect to be sure.

Cheers Keen