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Crossfeed Screw Stops and Goes - Help Please

MoronMachinist

Plastic
Joined
Jul 8, 2023
Lathe Model:
Precision Matthews PM1130V

Experience:
3 Weeks so far.
No prior machining experience.
I don’t even mow my own lawn.
That should tell you enough about me.
I am a computer guy and own 2 side business’

Why Machining:
Got into making lanyard beads for knives that I sell online more as a hobby and figured I wanted more control over this side of things so I can make them whenever I want plus I want to learn and come up with other things to do. I come from the EDC World (Everyday Carry). I collect custom knives, beads, and other stuff.

Issue:
I crashed my lathe and busted a piece that rides on the front of that of cross slide. The screws that hold it in place got smushed in and the metal part got bent up but isn’t riding in the ways. There is a felt piece that goes behind and it smooshed out of ever where it could. It actually cleans the ways now as it moves and leaks a little way oil. PM is sending those 2 parts and screws. For now I am leaving it in and there seems to be no other damage from what I can tell and after speaking to PM support going thru some some stuff.

Part 2:
I have only used the cross feed a few times and I had a rod to turn down today and noticed it was stopping for a half a second before it continued on. That’s when I realized something is off. I can’t say that wasn’t there out of the box since I was running it at a high speed the first few times due to being impatience and getting a better turn on the rod. Today I was going slow and that’s when I noticed it was stop and go but it was intermittent and not in the same spots. Sometimes it takes to the end before it goes it sometimes it’s in the middle. It will literally stop for half a second or less and continue on. Now if I turn it up the spindle to over 1k it’s not noticeable or it may not be stopping at all and just ripping thru. If I run it at a slow speed say 600 or less it is very noticeable forward. It doesn’t do it as much going backward.

Additional Info:
I have talked to some people in Facebook groups and I feel like I am from another planet since I don’t understand 10% of the things people are saying to do and check. They provide no details or pics unfortunately. I am impatient and don’t want to wait for PM support on Monday just yet.

Would anyone hear any have any advice with details on what to check? I am happy to FaceTime and send videos over as well. Not sure I can attach to this forum but I will try my hardest.

Troubleshooting So Far:
  1. The crossfeed moves just fine and doesnt get stuck anywhere and am able to cut without any issues manually.
  2. I check to see if that gear that is connected to the crossfeed and underneath cross slide is bent and it doesn’t seem so. I did not take the apron apart to check it but I can look behind there and see if it’s bent. I compared to someone else’s and mine doesn’t look like they. Still looks straight to me. The gears also check out as I check each tooth ok the gear to see if anything got damaged.
  3. I noticed they a hollow pin with a slit in the middle goes into a hole that the lead screw (cross feed screw maybe) connects in the mail box of the lathe keeps coming out of the hole. I don’t know why it’s going they but I keep popping it back in but doesn’t seem to be contributing to the issue (at least I think it doesn’t).
  4. I put some way oil on the screw and they didn’t help. I was thinking maybe it was the backlash from the big wheel on the cross slide but I completely took that wheel off and was still able to replicate the issue. So I put it back on.
  5. I checked to see if the split nut is engaging all the way down and it seems to be just fine but that’s just take a flash light and looking at it from behind without taking the apron apart. Who knows the if that’s the issue. Again this is intermittent and never in the same spots. It might happen twice or 4-6 times the whole way down.
Videos:
Here are some videos that will shed some light on everything I have been saying above. Please forgive my lack of knowledge but in a way this is a good thing to get me to learn stuff a lot quicker. I’m more of a hands on and in person learner vs learning by a book. I don’t read much unfortunately.

Short Videos below of all the above 👆

Video 1:

Video 2:

Video 3:

Video 4:

Video 5:






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The coupler you point to (where the roll-pin keeps coming out) should also have a pin in the other end where the lead screw enters it. I think I can see a misaligned hole there, no pin. If that coupler is not secured both to the gearbox stub and the screw it will slip and not drive the carriage. It might work intermittently under no or light load depending on alignment and tightness of fit, but that will rapidly get worse.

You refer to 'cross feed', but your videos are of the longitudinal feed. Cross-feed is moving front/back across the face of the chuck or workpiece.

Now, if what I've referred to as a 'coupler' is a driving element connected internally to the gearbox, you can forget everything in the first paragraph. The placement of the roll pin makes me think it's a coupler.
 
Maybe you broke a few teeth off of a gear.

If you run in the slowest speed, can you turn off the power while the screw is stopped? If you can, without starting the machine again, disengage the clutch on the apron and try to turn the screw by hand. Does it turn freely? Keep turning it while you inspect the feed gearing, it should be obvious where the problem is.
 
It is really difficult to analyze with not seeing a schematic, stop feeding and restarting is odd.
Did you note the feed screw-stopping?..or just the feed travel?
*Calling the company might be helpful.

Very often small lathes have pins that are intended to shear off/break to avoid breaking something important if something crashes.

If you can, change the title to longitudinal feed

Put a Sharpie line/mark on the feed screw drive collar lined up with a pin or feature.
Put a tab of masking tape with a line/mark, lined up with a mark on the screw.
 
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I called a company once and a nice lady service rep said..I have one right on my bench..and sent me the part for free.
Calling the company can't hurt.
I bought my Clausing used in 1984, but it still had the manual and an envelope of OEM aluminum rivets (shear pins) and push nut retainers. I think I have used two of them so far.

Perhaps a brand new Matthews lathe would have come with spares if it has a shear pin.

Larry
 
I'm confused, you're not trying to use the half nuts for feeding are you? They are locked out from the cross and long feed so they cant both be engaged at the same time. They are only used for threading.They should be lifted clear from the lead screw when using cross or long feed.
 
Well, you used the words ,"smooshed" and "smushed" in describing your issues. This gets you one third of the way to master machinist. You also describe yourself as being "impatient" for support. In my experience, impatience and learning don't mix. Chose a team.
 
The mechanicals on lathes like this are mindlessly simple,
and no different in principle than any other similar machine.
I have a Sheldon now and use a Clausing 5917 (5914?) once in a great while, but had no choice but to buy something like that during the virus to get orders out.
I did the same thing using collets, the rack under the bed wasn't long enough
(Collets allow the saddle to be much, much closer to the headstock than the chuckdoes ) and a few teeth came off a gear. Easy and inexpensive, sold it as soon as I could get back in the shop.
I couldn't quite tell, but if the shaft is stopping, it's something upstream.
don't be afraid to dig in to it, besides all the electronics, there's no voodoo in it.
 








 
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