PM-727m New mill has arrived!

[Sloth2009]

Sloth2009,

Yes, that's what I think is happening. I also noticed that if I leave the quill lock
a little bit tight, just enough to provide a little friction, the quill doesn't jump as
much. I think as long as I have a visual indication on the outside of the hub where
the keyway is, I might be able to use the lock to reduce the jumping. If not, as you
said, maybe milling a new key or even adding brass shim stock in the keyway, possibly
held in with epoxy might eliminate the slop.

Any luck in isolating the source of your quill movement?

 

[fradish]

Not really. The key fits reasonably well in the hub keyway. There is more slop in the shaft
keyway, but I shimed it a bit and it really made no difference. It also didn't slip where I thought
it should if it was key slop.

When I have the quill lock on and the coarse feed hub slightly loosened, I can rotate the hub
a very small amount. This is the key slop. When I tighten up the coarse feed hub and loosen the
quill lock I can rotate the hub more. This makes me think there is slop in the fine feed gears.

I tried adjusting the set screws behind the quill lock, but tightening these seemed to make the
drop more abrupt. I seem to get the smoothest motion from the quill by just leaving the quill
lock slightly engaged. Some day I may disassemble the fine feed mechanism if this bothers me enough
(Or right before my warranty expires...)

 

[TheGov]

Not really. The key fits reasonably well in the hub keyway. There is more slop in the shaft
keyway, but I shimed it a bit and it really made no difference. It also didn't slip where I thought
it should if it was key slop.

When I have the quill lock on and the coarse feed hub slightly loosened, I can rotate the hub
a very small amount. This is the key slop. When I tighten up the coarse feed hub and loosen the
quill lock I can rotate the hub more. This makes me think there is slop in the fine feed gears.

I tried adjusting the set screws behind the quill lock, but tightening these seemed to make the
drop more abrupt. I seem to get the smoothest motion from the quill by just leaving the quill
lock slightly engaged. Some day I may disassemble the fine feed mechanism if this bothers me enough
(Or right before my warranty expires...)

After tightening the set screw, I experienced simular results.
Wish I would have checked that after uncrating to see if this issue was always there or slowly developed.

 

[fradish]

What I eventually want to do is take off the fine feed gear box. Once I marked where the
key is, this is simpler as you don't have to worry about the key falling out on you, but even
if you don't mark it, you can loosen the quill lock and raise or lower the quill by hand until
the key slot is pointing up.

I don't think it would be difficult to take off the fine feed gearbox. I think once you get
the coarse feed hub off you just need to remove a snap ring, then remove the 3 bolts holding
it on and I think it will slip off. What I would be interested in seeing is if there is a damaged
tooth on the worm gear. In any event, I have found that just keeping the quill lock on just
a little bit seems to eliminate, or at least greatly reduce the dropping I was seeing. So at the
moment, I'm not in a huge hurry to tear into this, because today I have a working mill with
an annoyance, but if I tear into it, I might not have a working mill...

Why snugging up the set screws doesn't seem to do the same thing for me as the quill lock,
I don't know... Though as Sloth2009 mentioned, maybe the long set screw is too sticky/grabby.
Maybe if the inner set screw had a nylon or brass bearing surface, maybe it would slide more smoothly.
I haven't tried his trick of polishing the end of the inner screw.

 

[TheGov]

I did polish the inner set screw's face, but without doing the slot it rides in. So now the slop is reduced, but there are some spots in the quill assembly travel that are sticky.

 

[Sloth2009]

What I eventually want to do is take off the fine feed gear box. Once I marked where the
key is, this is simpler as you don't have to worry about the key falling out on you, but even
if you don't mark it, you can loosen the quill lock and raise or lower the quill by hand until
the key slot is pointing up.

I don't think it would be difficult to take off the fine feed gearbox. I think once you get
the coarse feed hub off you just need to remove a snap ring, then remove the 3 bolts holding
it on and I think it will slip off. What I would be interested in seeing is if there is a damaged
tooth on the worm gear. In any event, I have found that just keeping the quill lock on just
a little bit seems to eliminate, or at least greatly reduce the dropping I was seeing. So at the
moment, I'm not in a huge hurry to tear into this, because today I have a working mill with
an annoyance, but if I tear into it, I might not have a working mill...

Why snugging up the set screws doesn't seem to do the same thing for me as the quill lock,
I don't know... Though as Sloth2009 mentioned, maybe the long set screw is too sticky/grabby.
Maybe if the inner set screw had a nylon or brass bearing surface, maybe it would slide more smoothly.
I haven't tried his trick of polishing the end of the inner screw.

I polished up a piece of 1/4" brass rod I had and cut off about 3/8" of it and put it in front of the set screw. It works just as good or better for me as polishing the actual set screw did. 5/16" or slightly bigger would fit the hole better if you have some or have a lathe. Or just remake the whole set screw. Maybe try a piece of delrin plastic. Its always touted as low friction and self lubricating.

https://www.amazon.com/dp/B000FN15K6/ref=biss_dp_t_asn

 

[Sloth2009]

Found another little tweak. My quill lock tightens at about one o'clock for me. To loosen fully it, the handle ends up going half way around pointing down due to gravity. This ends up being a bit too loose in my opinion. I dug around in my parts box until I found a couple washers and played with them until I got a combination I like. Now it tightens at about eight o'clock and still is fully loose with the handle straight down.

 

[Sloth2009]

When I tighten up the coarse feed hub and loosen the
quill lock I can rotate the hub more. This makes me think there is slop in the fine feed gears.

I'm trying to replicate this on my machine. When you see your drop issue, your fine is feed engaged and the quill lock is not engaged? How are you producing the movement and where do you notice it? I did find something similar in the new manual. Do you think this is the same thing?

 

[Sloth2009]

With my PM727 I have occasionally had an issue with the fine feed where I'll be watching the DRO and turning the
wheel and nothing seems to happen, then the quill just seems to jump maybe 10 thousandths rather than smoothly
moving. I had thought that possibly I had not cleaned off the outer barrel of the quill enough or lubricated it
enough or maybe even that I didn't have the quill lock loosened sufficiently and this was causing the quill to stick.

At this moment I have not been able to narrow it down to what is causing it. What I can say is that when I
received the mill the downfeed housing (#2 in the diagram above) was loose and I had to tighten up the bolts (#22). Maybe I need to dig into the downfeed and check the gears that Sloth2009 pointed out. I would hope that I don't
have a missing tooth on #21, but that might also explain what I am seeing, thought I mainly see this between cuts
as I release the quill lock and make depth changes, so maybe I'm just not loosening the quill lock enough.

I'll just have to play around with it some more and see if I can consistently reproduce the issue and if so, figure out
what it causing it.

Well, I think I figured something out. Lock in the hub so fine feed is engaged. Bring the fine feed down a few turns and then reverse it and note the amount of backlash. Mine was nearly half a rotation.

Slightly loosen the 3 bolts holding on the fine feed housing.
Then push or lightly tap the housing down with a rubber mallet. Retighten screws then determine the fine feed backlash again. Mine was way better and slightly too tight. I had to loosen the bolts and readjust again. Made a huge difference. I bet most of us have pulled up on the feed housing during unpacking and setup. I think it just needs a little adjustment to get the worm gears back to meshing correctly. See what you think.

 

[fradish]

I'll have to try adjusting the fine feed housing over the weekend. When I got my PM727 the
FF housing was loose. I tightened it up and after making sure that nothing was binding. I have
tried to loosen and shift the housing forward and backwards, then tightening up on the screws,
but I didn't go about it methodically and didn't notice any difference from my adhoc adjustments.

I'll give that a try and will probably also order a piece of delrin for under the quill set screw. I've been
meaning to for some time, but just never had a project for which I needed any. Now I do!

I don't know where my quill lock lever ends up when loose but still slightly snug, but it must be
somewhere where gravity is working for me because I was able to keep this slightly snug.

I think someday before too long I am going to dissassemble the fine feed gear box just to look
at the worm gear. Without seeing anything, it sort of feels like one of the teeth on the worm gear
might be damaged, but I'm really just guessing at this point. Doing the FF housing adjustment
and the delrin shoe seem like good next steps to take in any event, so I'll probably do those first,
but eventually I think I might have to take the FF apart and visually inspect the gears.