Myford VMC rough rise fall Z axis/ knee

Does anyone know if it might be possible to obtain the elevation gears for the Myford VMC anywhere? I suppose best bet is knowing which machines it was the same as (at least in respect of the gearing for Z axis). Mine has some roughness when lowering the knee and, although better on raising, still not perfect. You hear a click click click on when lowering. Everything has been cleaned but i cannot see any way of adjusting the gears.

Wondering if they are all like this?

Photo of gears cleaned up and with the retaining washer and nut removed. All greased up with fresh grease but no different.

Nice photography, John

Nasty-looking gears though.

MichaelG.

Don't know the machine, but are you sure that it's the gears? Is there, say, a thrust bearing taking the thrust on the leadscrew or on the drive spindle?

I suppose the Warco and Chester versions may have the same gears but there have been many small changes made over the years and I believe some machines were made in Taiwan and some in China so it could be a real lottery whether the gears would fit from any other source. I doubt that Myford of today carry spares for the mills but it might be worth a phone call.

Mike

The gears look ok to me; I'd be looking for a problem elsewhere.

Andrew

I defer to your wisdom, Andrew

… but they don’t look a patch on what you have shown us of yours.

MichaelG.

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If the clicking is only on the downward direction, I would suspect that the gears are continually changing from loaded to unloaded (or loaded in the opposite direction). The table mass should keep the gears driving on the same surfaces while raising or lowering. I suspect it is not working as it should.

I believe that the Myford VMC is essentially the same as the other "makes" referred to by Mike Poole, above. My Warco version has a slight tendency to make a similar noise if I forget to loosen the Z-axis lock before moving the knee. I your case, I would loosen off or completely remove, the gib strip ( not forgetting to support the knee ) thoroughly clean the gib and its bearing surfaces, re-lubricate, reinstall and adjust. If that doesn't make a difference, only then would I consider further investigating the gears.

John

Edit: For clarification, what I'm trying to say is "is it a sticky gib"?

Edited By John Hinkley on 16/10/2022 07:59:31

I have a Myford VME and doubt that you could buy new gears with any certainty but I too don’t think that is the problem, more likely to be a tight gib.

Tony

John, do they have tapered gibs or plain? If tapered and not restrained at either end that can also cause the gib to tighten in one direction so you end up pushing the knee down and it jumps a bit, then push again, etc which may be the gears clicking in and out of load.

Thanks everyone. Everything is freshly assembled and lubricated after full strip down when I got the machine. It did the same before i started but i hoped to improve it. It is most prominent on the downward but still faintly there on the upward travel. I'll check gib adjustment again, and also the positioning of the threaded boss at the bottom of the Z screw. I did wonder if, given how small the meshing surface is, whether the gears could be reversed to use 'fresh' surfaces.

It would be good to hear from other Myford owners if they have the same thing going on (I know of one).

If its not solved as above then any suggestions - ranging from not worrying about it to something else?

There's a screw against either end of the tapered gib so i don't think its moving within its channel. The sound is very much related to the rotation of either the handle or the lead screw (is it called a lead screw on the z axis?).

I'll check that its falling rather than being pushed down when descending as you suggest.

John, in this earlier thread

Advice.. ..DRO on VMC..

You mention

"I've been cleaning everything ready for assembly and fitting the DRO. The worm gears on the vertical lead screw/ knee rise/ fall were caked in old grease and dirt. I removed the knee and cleaned with petrol. Does anyone know how to remove the worm gears to be able to get to the bearings (the one on the vertical lead screw and the ones at either and of the handle shaft)? I am worried that by cleaning all around there that i will have flushed the lubrication out of the bearings. Should I replace the bearings or is that a pain?.." ...

..it'd be useful to know whether you progressed any further with the stripping here, did you disturb the gears in any way?

..even if you just had a investigative 'pry' at them, you may have just shifted them enough to disturb the original 'meshing' points slightly, leaving it feel a bit rough, as areas previously not in contact are now being asked to run together.. ..if all is 'as was', then use might ease them, they don't look like tey have done much work..

The gears look a bit worn, but there don't seem to be any dings or damage that would cause intermittent action.

Skew helical gears are not the best choice in this appication as there is significant sliding action rather than simple rolling action of the teeth. The flanks of the lower right gear appear to be quite worn. A gentle pass over the tooth flanks with needle files or wet 'n' dry may help remove any small imperfections due to wear.

Andrew

I didn’t disturb or dismantle further than knee off and washer/ nut removal. The gears were solid on their shafts. The noise / feel was present before starting any of this so not related to the strip down - but I’d love to improve it as the rest of the machine is in such nice order. I’ve seen another myford that does exactly the same, hence wondering if it’s standard or common.

Here’s a clip of the noise action with free play first, then down, then up: https://youtu.be/O9QiMO3fSYg

Edited By John D on 16/10/2022 10:01:23

I might try reversing one of the gears on it's shaft to present new faces for bedding in and check both thrust bearings while they are accessible with the knee propped up on a wooden block.

EP 90 gear oil as lubricant might also impart some improvement.

Brian

Edited By Brian Wood on 16/10/2022 10:10:40

For convenience:

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John D, are you using a feed motor to raise and lower the table? Having heard the video we can all tell it's not the gib but my X table travel will sound like that when the motor gear comes a bit out of mesh.

Tony

Hi Tony, no it’s just me turning it by hand.

My one sounds the same as the one in the video, has always been like it since I bought the machine new from Myford. It hasn’t got any worse over the years and will most probably see me out, I have always put the noise down to poor machining tolerances, I believe the Myford machines were manufactured in Taiwan.