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View Full Version : Lube ? for knee mill vari-speed



cuslog
03-01-2017, 11:57 AM
So, I have a 6 or 7 year old 3hp (Chinese) knee mill -- its a vari-speed (I now regret buying a vari-speed but its done now).
I've had the motor off ~ 3 times now - it got rattly, I made new bronze bushings for the pulleys, replaced the shaft key (which was nearly sheared off).
First go-round, I put no lube on the shaft or bronze bushings - after a couple years, the pulleys were getting stuck on the shaft and I'd lose the ability to adjust the speed.
Last go-round, I put a light coating of lubri-plate on the shaft - worked nicely for awhile. Now, a couple years later again, the pulleys are sticking on the shaft and no vari-speed.
I haven't pulled it apart yet (again) but looking in some of the vents, it looks like maybe the lubri-plate has dried up and maybe the residue is making the pulleys stick ?
Any suggestions or comments ?

BCRider
03-01-2017, 12:40 PM
I've seen lubriplate dry out and cake like that. If it worked for a while then maybe try one of the all synthetic greases? I've used a tube of Mobil 1 synthetic grease for years now and whenever I run into it on the items I used it on it is still just as greasy as it was originally. And it's REAAAL slippery.

EDIT- To be fair Lubriplate is a name for one brand of lithium grease. I have no way of knowing if the caked grease I've seen was actually Lubriplate or some other generic lithium grease made with lesser components.

lakeside53
03-01-2017, 12:48 PM
Bronze always sounds good idea until this happens... unless you have a way to lube them, you should just use the likes of the plastic bushings and coated key BP used since the late 70's. Sure, they wear out but in a home shop environment it's a lifetime.

If I had to remake mine (I doubt I ever will), I'd use one of the graphite impregnated nylons. I have a bunch I think 2 inch diameter.. pay the freight and I'll ship you a chuck to play with.

BCRider
03-01-2017, 01:07 PM
It took me a moment to realize that this might be helpful to you. Watch it and see if what Joe has for the vari speed setup is similar to what you have...

https://www.youtube.com/watch?v=XIizyhJDzLg

cuslog
03-01-2017, 01:19 PM
Motor off now, yep dried out lubriplate, turned into a hard sludge and seized the sliding pulley to the motor shaft @ about 900 rm location. Took several applications of brake kleen and some scrubbing to get it off.
Lakeside; thanks for the offer but there is a "specialty" plastics place a couple blocks down the street from me where I can pick through their crops bin. Coated key ? hmmm never heard of that before.
Pulling that motor off doesn't seem so bad now, I think I had it off and on the bench in under 15 minutes -- I'd been putting it off for awhile, kind of dreading the job -- I must be getting better at it.:rolleyes:

Doozer
03-01-2017, 01:20 PM
From time to time, the VFD discussion comes up
and again and again people praise the variable speed
Bridgeport head in favor of using a VFD. Makes no
sense to me. Obviously these people do not have to
fix shlt when it breaks, because when it comes to fixing
them, Bridgeport variable speed heads are an abomination
of fudgery. If I was at an auction and a variable speed
Bridgeport was offered, I would pass, because I hate them
so much. Step pulley head and a VFD is the way to fly.

-Doozer

cuslog
03-01-2017, 01:37 PM
Doozer -- agreed, if I had it to do over again I would make different choices-- but I don't --so just have to live with this one:rolleyes:

cuslog
03-01-2017, 01:39 PM
BCRider -- thanks for the link but mine is different just a single rectangular key.

softtail
03-01-2017, 01:39 PM
What BC Rider said... Mobil XHP 222. Designed to stay greasy when used on heavy equipment. It stays so greasy it pisses me off sometimes. Is there a way to figure out a zerk system? Hit it with fresh grease every year?

pinstripe
03-01-2017, 01:42 PM
Doozer -- agreed, if I had it to do over again I would make different choices-- but I don't --so just have to live with this one:rolleyes:

I wonder how difficult it would be to convert? Adding the pulleys doesn't sound difficult, but I have never looked inside one.

BCRider
03-01-2017, 02:27 PM
I wonder how difficult it would be to convert? Adding the pulleys doesn't sound difficult, but I have never looked inside one.

Looking at Joe Pi's setup it looks like the motors are not set up to hinge to maintain belt tension. On the varispeed units the tension would be from the sprung pulley. So for a conversion some sort of tensioning idler would be required. But then the idler would limit the mill to rotating one direction only unless it can be locked in position.

If new grease fixes it then I'm nodding in agreement with the idea of putting in a grease fitting to allow an annual squirt of fresh grease to spiffy things up. It might mean getting creative with some drilling and cross drilling to position the zerk fitting where you can get it and to allow the grease to feed to where it needs to be. But that's why we have a machine shop, right?

lakeside53
03-01-2017, 02:30 PM
I've run and owed both... most problems are "deferred maintenance". i.e run them into the ground then complain when you have worn motor shafts, beat up sheaves etc.

They work fine (cant' speak for "all" Chinese - I've seen some with horrible internals, and some really good versions). Fix it. I've owned several and repaired many that were badly abused. Step pulley versions have their own problems if not looked after - worn top housing for grit/filth/lack-of-oil does number on them. Top bearing set that never get lubed.. lol.. I had one that was literally was pumbled into fragments. Sadly it was in horrible shape right up to the last time the previous guy turned off the power.

I have the best of both worlds - VFD on BP Varispeed. I can wind it down for more torque as I see fit. It doesn't knock, whine or rumble.

lakeside53
03-01-2017, 02:34 PM
I wonder how difficult it would be to convert? Adding the pulleys doesn't sound difficult, but I have never looked inside one.


It's not too bad if you use a VFD and single sheave, but you need to oversize the motor significantly to compensate for the lack of HP at the low end. Poly-vee belts are a good choice.

if you want the same as OEM, you can just take the top section of the a step head and pop them on the lower section of vari-speed - same...

Doozer
03-01-2017, 02:39 PM
If you have a back gear (Like most Bridgeports and clones)
then make up fixed ratio tooth timing belt and pulleys.

-Doozer

pinstripe
03-01-2017, 02:55 PM
So is that what this grease nipple is for? The manual makes no mention of it. I asked the dealer, and they said to put a couple of squirts into it every month. Looks more likely to be for the high/low gear.

http://i1168.photobucket.com/albums/r491/pinstripe2/HSM/Mill_Grease_Nipplejpg_zpsamrowc1y.jpg

lakeside53
03-01-2017, 03:04 PM
That's for the bull gear cavity. Not sure why you'd put it in a couple of time a month unless it's oozing out somewhere. On the vari-speed you fill it (not full!) and forget it - literally... and it has over a full large tube of grease in it. of course it might be pork fat on a non-name import ;)


BTW, your Chinese clone has a bottom bearing support for the driving sheave - BP never evolved to that but most decent clones did - good idea..

pinstripe
03-01-2017, 03:30 PM
Thanks lakeside. So if I ever want to have a peek in there, can I remove the bottom plate, or do I need to relieve the tension somehow?

The manual doesn't say anything about lubrication for the head. Just the oil cup for the quill.

cuslog
03-01-2017, 03:43 PM
I must admit to being the initiator of some of these problems -- I bought this machine new 6 or 7 years ago, was somewhat of a novice at the time. The initial damage was to the motor shaft keyway -- caused (I believe) by my being too aggressive(DOC) with a fly cutter then an indexable face mill which had the cutters hitting the work "square". This hammered not only the key but the keyway too. The key was easy enough to change but a hammered keyway is not.
So, now I am much more conservative with DOC with a fly cutter and I bought a face mill that has the cutters in more of a slicing (rather than chopping) motion.
Live and learn.:o

lakeside53
03-01-2017, 07:13 PM
Thanks lakeside. So if I ever want to have a peek in there, can I remove the bottom plate, or do I need to relieve the tension somehow?

The manual doesn't say anything about lubrication for the head. Just the oil cup for the quill.

What about your spindle or does it have sealed bearings? BP's have quill oil, spindle oil, and a plug to remove to (very occasionally) grease the feed engagement gear.