How Are You Mounting Your Pm1340gt Lathe?

[sanddan]

Rio,

This is the same vibration I am seeing. I have run many many tests trying to isolate the source of the vibration, it is in the motor/pulley or input shaft. Some of this is in my other thread http://www.hobby-machinist.com/threads/question-on-aligning-the-lathe-spindle-and-bed-twist.41864/ . As rotating mass is removed the magnitude of the felt vibration goes down but the vibration is still present. The motor by itself runs smooth, either with or without the motor pulley. It is not normal, my Chinese Enco 12x36 lathe does not have a felt vibration at any speed. This is with either the 3 jaw or 4 jaw chuck. It is still running the belts that came from the factory 3 years ago. It is a single phase 2hp motor running a dual belt setup.

Matt,

The upper pulley is as cast, the only machined surface is the bore and keyway. I am pretty sure it is die cast as runout is pretty good, max I measured was .004" and that was on the surface the belt runs on. I haven't tried truing the pulley as I have to machine a mandrel first to keep it concentric with the bore and my other lathe is down. I was focused on improving the stand rather than bolting to the floor , seeing that bolting might not fix the issue I could go back to working on the pulley.

Mark,

You made a comment about the cup of water in the video being on the headstock and maybe not feeling it on the carriage. Other than doing the break in procedure, the first time I ran the lathe was to machine the test bar as part of the headstock alignment and that's when I first felt the vibration. I had my hands resting on the carriage cranks and felt the shake. That led me to looking closer and seeing that it was worse on the headstock. I have run my other lathe enough that I immediately the difference. The carriage has less felt vibration than the headstock but it is very noticeable non the less as you are feeling it through your hands. It is hard to show something like this on a video thus the cup of liquid.

 

[RIO]

As requested:

 

[Muskt]

Looks as though the mystery is lessening.

A few things jump out to me:
1. I do not like that belt flopping about like it does. It doesn't seem to be tight enough, and it doesn't fit the motor pulley very well (Opinions only--I'm certainly not an expert). A flopping belt will have a harmonic (similar to what you are experiencing). The one loose belt on my 12x36 really caused a vibration--even worse than what you are experiencing. Removing the offending belt really helped. I understand that yours only has one belt, but it really flops around.
2 I had a chuck problem on my previous 9x20 in Alaska. It was a 6 inch 4 Jaw. The jaws were different lengths; therefore, different weights. They varied by up to 0.070--This caused the vibration to increase as larger items were chucked up. I should have exchanged the chuck, but did not (Silly Me).
3. You never mentioned (Or I missed it) that you had run the motor with no belt on to determine if the motor might be unbalanced.
4. Are you ABSOLUTELY certain that there is not any junk between the lathe & the base cabinets, or is the bottom of the lathe actually smooth--IE no casting imperfections (bumps or ridges) that may cause the lathe not to sit solidly on the base?

These are just random thoughts, and not intended to be criticisms--moreso additional things to check.

Hope you get it figured.
Jerry in Delaware

 

[joshua43214]

As requested:

I think your second vid is the most informative so far. I wish you had put your hand on things to stop the noise. The doors on these stands are a bit junky, might just be the door rattling? Adjust the lever on the back to make it fit tighter.
I can hit my head stock with the palm of my hand hard enough for it to sting and it just goes "thump." My lathe is just sitting on the adjustment feet it came with.

It sounds to me like the lathe is just not getting a good bed on the stand. I would pull the lathe off the stand and make sure the mating surfaces are flat and free of debris. It is important that the pillars are coplanar as well. I wonder if one of the pillars is leaning at an angle, and the center support is preventing them from being pulled up tight to the bottom of the lathe.
Level the base, install the lathe, level the lathe, tighten the center panel. That way the center panel will not interfere with the base alignment.
You can get heavy gasket paper from NAPA that will make an excellent bed between the lathe and stand. I don't advocate using silicone sealant - it does nothing to bed the lathe, and makes taking it apart a hassle.

 

[Rich V]

That long vibration after bumping the head stock by hand is at least part of your problem. Can you see where the rocking point (pivot point) is when it's vibrating? It could be that you don't have a good flat mating surface between the lathe and the chip pan/bench top. It's also possible that the chuck is slightly out of balance and combined with that long vibration you have it doesn't take a lot to get it vibrating at certain harmonic nodes.

If it was me I would find where that rocking from a hand bump is an correct the cause. That may be you main problem

 

[planeflyer21]

Rio, your post #28 shows there seems to be quite a bit of space between the pan and the base. IMO that is the culprit of the rattling sound. Either the pan needs to be flattened or shimmed to get a better fit with the base.

As to the belt, IMO that is a contributing factor as well: a kind of stacking of tolerances if you will. I had a machine that came with a V-belt that left rubber bits everywhere. Replaced that with a good Goodyear V-belt and was in heaven. Replaced that and the pulleys with the poly round belt style and was in 7th heaven.

IMO in order of fixing, 1-pan to base fit, 2-new belt.

 

[zmotorsports]

I just went out and ran mine again and looked closer at my chip pan and I agree with the two above that the chip pan/cabinet/hard mount is definetily something that needs further investigation. Look closely at where the holes are drilled and see if one of the holes in the cabinet have the center pulled up which would create a high point. If memory serves I ran a chamfering bit around all of mine before assembling.

My stand/lathe setup is rock solid and I can hit it quite hard with my hand and there is no sound but a dull thud and a sore hand. I also noted quite a difference when I replaced the original belt with a better quality one upon the first hour or so of running the lathe. I too would investigate the chip pan first followed closely by the v-belt.

Mike.

 

[sanddan]

I just went out and ran mine again and looked closer at my chip pan and I agree with the two above that the chip pan/cabinet/hard mount is definetily something that needs further investigation. Look closely at where the holes are drilled and see if one of the holes in the cabinet have the center pulled up which would create a high point. If memory serves I ran a chamfering bit around all of mine before assembling.

My stand/lathe setup is rock solid and I can hit it quite hard with my hand and there is no sound but a dull thud and a sore hand. I also noted quite a difference when I replaced the original belt with a better quality one upon the first hour or so of running the lathe. I too would investigate the chip pan first followed closely by the v-belt.

Mike.

Mike,

Could you check the underside of your stand and let me know if it looks like mine? I am referring to the mount the lathe bolts to (see attached pic).

Thanks
Dan

 

[zmotorsports]

Mike,

Could you check the underside of your stand and let me know if it looks like mine? I am referring to the mount the lathe bolts to (see attached pic).

Thanks
Dan
View attachment 119806

Dan, is that sealant/RTV on the underside of the bolts/washers?

Mike.

 

[mksj]

Dan, my lathe cabinet underside looks the same as yours. My drip pan also bows up a bit at the edge of the cabinets. Probably doesn't vibrate because I used some RTV when bolting up everything.

Gates Tri-Power cogged belts. I have both the BX-24 and BX-25. Interestingly the Gates BX-24 has a slightly bigger diameter than the stock B-25. The BX-24 was a little difficult to get off the pulley to change speeds, but that was when it was new. So I am running the BX-25 one on my low speed pulleys for a top end of 1200 RPM at 90Hz. The BX-25 was too long for the high speed pulley set, so the BX-24 is the one I would recommend or get one of each at $6 a piece. It runs much more smoothly, but I do notice the belts will take a set if the lathe is not used for a while. It smooths out after a couple of minutes of use. Changing the belt quieted things down quite a bit, and the stock belt seemed to be throwing a lot of rubber bits all over the belt cover.

Royal Supply has a wide selection of belts, pulleys, etc., there is also SDP/SI when I was looking into pulleys and couplings for CNC.
http://www.royalsupply.com/store/pc/Gates-BX24-Tri-Power-V-Belt-9013-2024-1095p36411.htm
http://www.sdp-si.com/index.asp