PDA

View Full Version : huge Re-saws and rip and bandsaw maintenance



aboard_epsilon
05-12-2010, 12:53 PM
I have a friend who owns a saw mill

he has a couple of huge saws..........tables or trolleys on rails sort of things .. 50- 60 feet long powered by big gardener diesel engines


makes are robinson..and the other dankart or something or other..probably over well 60 years old

all the time he is experiencing trouble with bearings bushings etc .

he uses a grease gun regularly on them ...i have suggested that maybe the saws require oil from an oil gun...like the metalworking machines do

on the instructions on the side of them one of them says grease such and such every so often ..on the same plate is information on the other bearings ...and the words are "charge once daily" ...does charge mean oil ???

my friend looked at me like i was from another world when i mentioned oil ..

i told him that his grease nipples could very well be oil nipples

anyone here know .?

ive also posted this in the OWWM forum

all the best.markj

Tony Ennis
05-12-2010, 01:32 PM
What kind of bearings? Is it possible he's putting in too much grease?

aboard_epsilon
05-12-2010, 01:43 PM
not sure ....

the spindle bearings are open roller bearings, he just had two new ones ...hundreds of .. the spindles, they are about about 6 inches in diameter.

the reversing trolley section has brass bushes or something ..its like a belt driven gearbox under the rails

on the reversing trolley arrangement he has heaps of free-play in the shafts ..1/4 inch in the bearings "wear".....belts are now coming off.

all I'm suggesting is maybe his grease is is not supposed to be grease ..and that oil could prolong the life of the things

all the best.markj

Tony Ennis
05-12-2010, 02:07 PM
he just had two new ones ...hundreds of ..

Where did he get them? Can he ask them for the proper lubrication specs?

Alistair Hosie
05-12-2010, 02:08 PM
Mark , Surely when he gets new bearings they will have instructions with them as to whether they are oil or grease type bearings .It seems as if he's in business he should know that already ,or maybe he did have grease bearings which were swopped for oil a while ago and he wasn't told about the change.Alistair

aboard_epsilon
05-12-2010, 02:31 PM
bearings came from ...not the proper source, company who made the saw no longer exist ..he just got the codes off them ..and replaced them with the same .

so no information weather on this saw they run on grease or oil .

bearings don't come with instructions .

all the best.markj

boslab
05-12-2010, 06:39 PM
when i was in school i worked at a timberyard in neath [south wales] called robinson david, there was a great rack saw of the description you gave, it was greased twice daily with,.. lithium grease not yellow grease, it was black.it may be the grease was the wrong grease? EP greases have been around a while, i dont ever remember a bearing change, as the manager of a local quarry i know used to say, "you cant beat grease boy"
mark

wierdscience
05-12-2010, 07:17 PM
I used to service a McDonough resaw,older unit had copper tubing running up to all the bearings from a central distribution block. One pump per zerk per 8hr shift was all it took.

The other even more important question is what is the preload supposed to be?Roller bearings imply either tapered cone or barrel roller type.Tapered will have a preload spec and barrel will have a internal clearance spec.If either one of those isn't right no amount of grease or oil will work.

Richard Wilson
05-14-2010, 11:30 AM
The new bearings might not come with instructions but at 100s a time, surely its worth a phone call to the bearing manufacturer to ask them what they recommend? There is often lengthy discussion on this site regarding the correct grade of oil for a particular machine. Its the same with grease, different grades, different properties. I bet its cold up where the OP lives? When i got my current lathe, some **** had packed the taper roller bearings with nasty sticky grease, when they were meant to be oiled. Before I got round to dismantling everything and cleaning it out, I went in the workshop on a cold day, and couldn't move the spindle at all. Turns out to have been the grease, gone so stiff with cold, it was solid. Those big saw bearings are normally pretty free running. If the bearing manufacturer can't help, try thinner grease, then oil.

Richard

rohart
05-14-2010, 05:03 PM
You've got to find out why the bearings are failing before you spend any more time getting your shirt spattered with oil and grease.

This link appeared on a post a few days ago IIRC, and I thought it was the bees knees.

http://www.bardenbearings.com/scan%20pdf/Bearing%20Failure%20Brochure.pdf

I guess Timken and others might have similar literature.

The Artful Bodger
05-14-2010, 05:14 PM
I suspect the bearing failure is due more to contamination than incorrect lubricant. Building shields over the bearings may be useful.

Incidently, in really hight contamination applicaitons such as disc harrows they used to use wooden bearings, but that was very low RPM.

Duffy
05-14-2010, 06:36 PM
I read it and reread it and I THINK you are talking about circular saws. If they are indeed 60 years old, goodness knows what bearings are original. In any case, this is a saw mill and the secondary product is SAWDUST. Mix well with lubricant, (your choice,) and you have frequent bearing failure, UNLESS you have a) sealed bearings or b) flow-through lubrication to wash out the gunge. Bearing maintenance in a production sawmill is HELL! I would think that with open roller bearings, you might as well tack the boxes they came in over the ends for a few minutes more life. I would also expect that the bushings on the carriage return, log turner, and anything else that moves, will be worn to a "toss fit," and that is why the belts wont keep tension. If the mill is producing tapered boards, then it is almost time for a rebuild/replacement. Duffy

jkilroy
05-14-2010, 09:36 PM
What kind of SFM do those units run?

Does he keep his blades sharp? I mean as in teeth replaced, blade professionally set, and SHARP? A dull blade increases the load on everything, A LOT.

You should reset a blade every two or three times you sharpen. And you should sharpen every two to four hours cutting! That means you might need to reset and sharpen the blade EVERY DAY. If you are cutting heavy plan on blade swaps frequently. You know your set is off when you get wavy boards or boards that are heavily scored. A blade that has lost its set will dive or climb heavily, killing bearings in no time.

Evan
05-14-2010, 11:52 PM
The brass (or more likely bronze) bushings require oil, not grease. Plane bearings are hydrodynamic bearings. They ride on a film of oil. Grease won't flow well enough to fill the large area of a plane bearing.

wierdscience
05-16-2010, 12:40 AM
I just remembered something,from having built and ran several smaller bandsaw mills the blade tension can also be the culprit.Especially if the tension adjustment is ridgid(not spring or hydraulic dampened)

As the mill is started up and the blade heats up it expands and grows in length.If tension is added once the blade has expanded once the saw is shutdown if the tension isn't released the blade will shrink back to it's normal nominal length once cool and apply tremendous force to the bearings and shafts.Upon startup the bearings and shafts run at much higher loads until the blade expands again.

I had one mill where this force was so great it actually fatigued the shaft at a shoulder and the blade wheel dropped off.That was the first mill I had and it wound up being modified to reply on a spring for constant tension,a definate improvement that solved a lot of problems.

Black_Moons
05-16-2010, 02:32 AM
hmm flow through oil for cleaning..
Random idea for bearings in high contamination envorment:
apply semi sealed surround on one end, apply filtered compressed air, with an inline air oiler device filled with the bearing oil of your choice.

J Tiers
05-16-2010, 08:55 AM
On older equipment, a "grease seal" is sometimes used....... a space which is intended to be full of grease to seal out crud.

The bearings may have an open cover on them which loosely fits the shaft. the grease from the bearing is supposed to ooze out into the space between cover and shaft to form a continually renewed 'seal".

This ensures that new grease pushes out old grease along with whatever dirt is in it. The filler nib may be located to preferentially grease the seal, with some going to bearing.

Alternately, the grease seal is separately filled, and may need to be cleaned and renewed on a schedule.

Then also, greased bearings should be *not full*.... typically the bearing is filled and the cover is filled 1/3 or 1/2. When cover is applied, there is ample grease, but also expansion space, and room for the grease to 'channel", or get pushed out of the way, yet still be available.

When re-greasing, there is often a "drain" hole that is plugged..... you take out the plug, and grease until some flows out.... and then you stop, and replace the plug. Otherwise you may pack the bearings so they overheat.

Has anyone checked temperatures?

On older machines, there is a tendency for parts to disappear, like covers and shields. Any evidence they are missing?

Plain bearings can use grease....... millions of wagons prove that..... the carriages might need either grease or oil, depending on design. Wagons often used grease, railcars used oil. both had plain bearings

if there is 6mm clearance in the carriage bearings, no amount of grease or oil is gonna help.... they need replaced.

aboard_epsilon
05-16-2010, 09:30 AM
YEAH, I suggested to him that he should have bought sealed bearings ...

and the modern way of thinking is that the old adage of pumping bearings full, was old hat and had proved to be detrimental to bearings..
EXPLAINED
The new way of thinking was to buy sealed bearings that are semi filled with superior synthetic for-life lube

.think that would have solved his problems.

He wants me to re-bush his pullyshafts .....the pulley gearbox/ back/ forward/' reverse arrangement...........all i have is brass for the bushings (well i think its brass..i have no way of telling brass from bronze) ..hence me asking in the other thread about using brass as bushings over bronze ..i didn't get a strait answer in this.

I was thinking of doing this and adding myford style machine oilers to them.
...which every other day he could top up with hydraulic oil ...got to be better than what hes been doing before.

all the best.markj

J Tiers
05-16-2010, 09:41 AM
Bronze is pretty much universally considered better, somewhat harder, I think, and the inherent qualities of the tin portion as opposed to zinc.

An oiled plain bearing RUBS until it is up to speed and forms an oil wedge. The inherent lubricity (if I have the right term) of the bearing material is what affects galling and wear on start-up.

AND..... The probable low speed of the carriage very much suggests that grease be used, which does not need speed to build up the "oil wedge", it is active at low surface speeds. (ok, OK, railroads.....but I doubt the saw carriage goes even THAT fast....)

aboard_epsilon
05-16-2010, 09:50 AM
Bronze is pretty much universally considered better, somewhat harder, I think, and the inherent qualities of the tin portion as opposed to zinc.

An oiled plain bearing RUBS until it is up to speed and forms an oil wedge. The inherent lubricity (if I have the right term) of the bearing material is what affects galling and wear on start-up.

AND..... The probable low speed of the carriage very much suggests that grease be used, which does not need speed to build up the "oil wedge", it is active at low surface speeds. (ok, OK, railroads.....but I doubt the saw carriage goes even THAT fast....)

Will see what they are like when they are pulled apart ..have this feeling that the shafts will be worn as much as the bushings ...and will require stevenson type repair on them.

all the best.markj