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Knocking sound coming from headstock on PM1127

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MSD0

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#1
I’m getting a knocking sound from the gearbox on my PM1127 when the power feed is engaged. The sound and vibration sounds like either a tooth has broken off or something has come loose and is catching on a gear. Has anyone opened up the gearbox before and if so, is it as simple as removing the front panel?
 

SamI

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#2
I am not familiar with your particular lathe but I can't see it being any more difficult than that. Bear in mind it is probably full of oil which will need to be drained first unless you want a big mess!
 

MSD0

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I am not familiar with your particular lathe but I can't see it being any more difficult than that. Bear in mind it is probably full of oil which will need to be drained first unless you want a big mess!
Yeah, I was planning on draining it first (which already makes a mess). While I have it taken apart, I might add a drain valve with a hose fitting to make oil changes easier.
 

ttabbal

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#4
Bummer! I haven't had mine open, but please update us with what you find out.

I like the idea of a drain valve and fitting. Trying to get something under there to catch the oil is a bit annoying.
 

MSD0

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5E36DEA0-ED67-4F26-A822-0DA4B96EC722.jpeg
Bummer! I haven't had mine open, but please update us with what you find out.

I like the idea of a drain valve and fitting. Trying to get something under there to catch the oil is a bit annoying.
Didn’t find anything broken, but there was a large burr and lots of grit on the bottom. Was kind of surprised at the size of the gears. Much smaller than expected. 5830DE71-0666-4CA7-8F8A-78F02CAC106E.jpeg
 

Jeff.64

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#6
Does your machine have a feed rod clutch? I remember seeing a YouTube video of a PM1127 that had a clunking sound while making a cut. There was also a slight hesitation of the carriage during the cut when the clutch slipped intermittently. Unfortunately, I do not remember which video. There are 4 ball bearings, springs and set screws on the right. The left side has 4 radial grooves that capture the ball bearings. If there is a crash or some binding in the feed rod, the clutch will slip making a clunking sound. Also, I believe the clutch can be used in conjunction with the carriage stop.

IMG_0252.JPG
 

MSD0

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Does your machine have a feed rod clutch? I remember seeing a YouTube video of a PM1127 that had a clunking sound while making a cut. There was also a slight hesitation of the carriage during the cut when the clutch slipped intermittently. Unfortunately, I do not remember which video. There are 4 ball bearings, springs and set screws on the right. The left side has 4 radial grooves that capture the ball bearings. If there is a crash or some binding in the feed rod, the clutch will slip making a clunking sound. Also, I believe the clutch can be used in conjunction with the carriage stop.

View attachment 277982
I have the older version without the clutch (I think it just has a sheer pin). After putting it back together, I noticed that I was getting a lot of vibration from the belt at certain rpms, so I’m now thinking it might be the change gears that are making the noise.
 

MSD0

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#8
So after cleaning everything up and getting it put back together, I found that the set screw on the motor pulley was loose. I was already getting some vibration from the belt, so I think the noise was a combination of the loose pulley, vibration from the belt, and excess backlash in the change gears. I spent some time getting the gear mesh dialed in and replaced the original belt with a link belt and it’s running like new.
 
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