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PM-727m New mill has arrived!

Discussion in 'PRECISION-MATTHEWS' started by Sloth2009, Mar 27, 2017.

  1. Sloth2009

    Sloth2009 United States Active Member Active Member

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    I got close to that amount of crud in my first (only) oil change. Have many times you changed it before?

    Looking at the pm-727m's blueprints It appears the coarse/fine feed shaft doesn't go into the gearbox. It goes below and to the back of the quill where those teeth are cut in the back of it. If you look under the head behind the spindle, you can see where they engage.

    If there is slop up and down on the quill and only during fine feed then there might be an issue with the worm gear engagement. Maybe the clamp knob is not in tight enough? Gunk in the worm gear? To me , part (3) and (21) are worth looking at.
    IMG_5368.jpg IMG_5369.jpg
     
    Last edited: May 5, 2017
  2. tweinke

    tweinke United States Active User H-M Supporter-Premium

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    The fine adjust does not go into the part of the mill with the oil in it, is the correct answer. My 727 also has debris in the oil that looks shiny but I'm wondering if its paint because if I stick a magnet in it don't get much on the magnet. I was thinking I should pull the top cover to take a peek and while I'm there flush out the inside
     
  3. fradish

    fradish United States Active Member Active Member

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    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.
     
  4. Sloth2009

    Sloth2009 United States Active Member Active Member

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    I've had similar "slipages" occur. I figured it was due to a combination of the column lock and/or the fine feed locking knob engagement, as playing with those tend to fix it. I wonder if the order in which they are locked and unlocked makes a difference. I will look at mine too and see if I can figure out anything.
     
  5. fradish

    fradish United States Active Member Active Member

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    One thing I just saw tonight is that the quill dro shifts up and down by a fraction of an
    inch when changing direction using the coarse quill feed lever. I probably need to take
    off the knobs and face plate to see if I can locktite the screws holding the dro in. If the
    dro is loose and shifting that might be causing the issue I am seeing.

    Before I go to that trouble, maybe I'll wedge a business card between the dro and faceplate
    to see if that gets rid of it.
     
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  6. fradish

    fradish United States Active Member Active Member

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    Ok, it isn't the loose dro (thought I'll still have to fix that).

    I think it is slop in key #23. I think when there is pressure on the key it turns
    the shaft smoothly, but when the key reaches 12 o'clock or 6 the shaft slips by the amount
    of the slop. I've had hub #18 off once already. I'll take it off again and mark a dot on the outside
    of the hub in line with the key way and see if that is where I'm seeing the quill jump.

    This isn't a big deal but I'd feel better if I knew why this was happening. At least then
    I'll know how to work around it or fix it maybe by machining a tighter key.
     
  7. Sloth2009

    Sloth2009 United States Active Member Active Member

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    That makes sense. If I understand you correctly, the weight and momentum of the handle may cause it to shift on the shaft to take up the slop in the little key. If you can shim it or make T-shaped key you may have your issue solved. The hub does need to slide over the key though to lock to the worm gear, so dont get it too tight. See my below post.
     
    Last edited: May 6, 2017
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  8. Sloth2009

    Sloth2009 United States Active Member Active Member

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    My particular issue I think is just operator error. The way I am understanding it, the worm assembly (3) from the fine feed is always engaged to the worm gear (21). When you tighten the clamp knob it engages the taper on the worm gear and locks it to the hub (18). The hub itself is locked with the quill pinion shaft (1) with the key [fradish] is talking about. When locked you are able to drive the entire assembly with the fine feed wheel.

    I don't think I have consistsntly locked the hub in hard enough. I had actually greased it which likely made it worse. This caused the taper to slip if there was much force on the spindle. Now that I know this, I can watch the outer ring of the worm gear and make sure it is not slipping against the hub when locked.
    There is a lot of backlash in the fine feed worm drive. Is this what you are seeing?
     
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  9. fradish

    fradish United States Active Member Active Member

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    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.
     
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  10. TheGov

    TheGov Reserved Iron Registered Member

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    Had more time to check some things. The up/down slop is also present in the course feed. I noticed that with the quill down any amount, if I push up on it, I see the top of the spindle also move up. (Spindle and drive group).
    Looking at the diagram, I see only 2 different possible loose items. 1-(38) Nut: M25, spanner type. 2-(12) Screw: M5x16, ph HD (3).
    I wouldn't be surprised if the problem was 2 from above as I have found several screws/bolts in hard to get to places loose. (The slop is also less than 16mm)
    Thanks for all the feedback and ideas of other things to check.
     
  11. TheGov

    TheGov Reserved Iron Registered Member

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    As to the oil change, I did one after the initial break in, then this last one after about 20 hrs run time.
    In the pic below is the metalic crud stuck to a magnet.
     

    Attached Files:

  12. Sloth2009

    Sloth2009 United States Active Member Active Member

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    That is a lot of metal for sure. Is that slop measurement supposed to be 1.6mm? 16mm is over a half inch. Yikes!

    This happens when the quill is down. This makes me think the slop is is the top part of the spindle assembly. Because the qill is probably holding the spindle in the correct position when it is up. When the quill drops, I think the spindle assembly may be dropping too causing the slop. If you can confirm that, I would concentrate between the 2 (3) lock rings.

    Does it make a difference with the gear switch in high or low. How about with spindle lock on?

    With slop in the spindle and those metal shavings, I think you will need to look at the meshing gears (7) (8) and and their counterparts (87) and (89) for wear.

    IMG_5383.jpg IMG_5384.jpg
     
    Last edited: May 6, 2017
  13. tweinke

    tweinke United States Active User H-M Supporter-Premium

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    I just had a thought based on my 727, I found that on my mill that if you tightened the draw bar pretty tight that the splines of the quill would have a visible wobble. Upon investigation I found that the draw bar did not center in the quill when tight and I noticed that the quill did not travel smoothly. I would think that might have a tendency to force gear 7 to be pulled out of place but I may be all wet on this theory. I made a new drawbar and a washer that centers into the inside of the quill with a shoulder and that has solved my quill travel smoothness issue.
     
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  14. TheGov

    TheGov Reserved Iron Registered Member

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    Sorry, ment 1.6mm.
    With the quill lock snug, no play/slop, same with it all the way up.
    With the fine feed engaged, quill lock off, the quill and spindle both move the together.
    I stuck a bore scope camera in the housing with no oil to see if the shavings were gone, but couldn't get in that far. (7) prevented this. I will have to find the mirrors that go with the borescope and see if I can see the rings mentioned and gears.

    Thank you for your help and suggestions.
     
    Last edited: May 7, 2017
  15. Sloth2009

    Sloth2009 United States Active Member Active Member

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    I just went out and replicated the same conditions on my mill. I was able to get 0.39mm in upward movement on the dro. I ended up tightening the quill set screw behind the quill lock and was able to get rid of the play. In doing this the coarse feed became so stiff it would not return on its own. I put some anti-seize grease on the quill and in the little slot the set screw rides in. Right now there is no play and quill returns itself to the top position most of the time. I could try to tighten the return spring. I also wonder if polishing the end of the set screw might help.
     
    Last edited: May 7, 2017
  16. Sloth2009

    Sloth2009 United States Active Member Active Member

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    There are actually 2 set screws in the hole behind the quill lock! A short allen set screw and a longer slotted one. I took them out and polished up the mating end a bit. Maybe it will help a little. If I had a lathe I would remake the longer set screw out of something with less friction.

    I have a suspicion what I am seeing with the quill slop and possibly what you [TheGov] is seeing is just play in the gear on the back of the quill and the quill pinion shaft (1) that comes out of the coarse/fine feed. Tightening the quill set screws forces the quill against the shallow end of the splines on (1) taking up any slack. In the bottom rear of the head you can look through a small gap and see the quill gear teeth. When the set screw is loose the teeth slip up slightly. When the set screw tight, this does not happen. Hopefully that is all it is and not something wrong with your gears. See what you think.
    IMG_5400.JPG IMG_5401.JPG
     
    Last edited: May 8, 2017
  17. TheGov

    TheGov Reserved Iron Registered Member

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    You are a god my good man! Finally had some time and checked the set screws. I gave the inner screw a little knudge tighter and the slop disappeared.
    Cross that issue off the list. Now to run for a bit and check to see if the metal particulates came after the first oil change. (This last oil change I flushed everything much more than the first time).
     
  18. Sloth2009

    Sloth2009 United States Active Member Active Member

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    Yay! Glad it worked. Hope your gear box is in good shape.
     
  19. TheGov

    TheGov Reserved Iron Registered Member

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    Yeah, me too.
    I think I just didn't get all the crud out the first time as I only drained the oil.
    This last time I drained, flushed with some more oil, blew compressed air, flushed, blew again followed by sucking, (with a vacuum necked down to drain plug size).
     
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  20. Sloth2009

    Sloth2009 United States Active Member Active Member

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    In a earlier post I showed where I hollowed out a sword scabbard with the mill. Here is result of that project.
    IMG_5419.JPG IMG_5436.JPG IMG_5437.JPG IMG_5443.JPG IMG_5444.JPG
     
    Fitter Bill, wrmiller, jbolt and 5 others like this.
  21. Sloth2009

    Sloth2009 United States Active Member Active Member

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    Any luck in isolating the source of your quill movement?
     
  22. fradish

    fradish United States Active Member Active Member

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    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...)

    :)
     
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  23. TheGov

    TheGov Reserved Iron Registered Member

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    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.
     
  24. fradish

    fradish United States Active Member Active Member

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    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.
     
  25. TheGov

    TheGov Reserved Iron Registered Member

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    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.
     
  26. Sloth2009

    Sloth2009 United States Active Member Active Member

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    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


    IMG_5606.JPG IMG_5607.JPG
     
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  27. Sloth2009

    Sloth2009 United States Active Member Active Member

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    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. IMG_5593.JPG IMG_5596.JPG
     
  28. Sloth2009

    Sloth2009 United States Active Member Active Member

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    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?
    IMG_5611.jpg IMG_5612.jpg
     
  29. Sloth2009

    Sloth2009 United States Active Member Active Member

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    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.
     
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  30. fradish

    fradish United States Active Member Active Member

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    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.
     
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