Bandsaw Roller mod

[BobL]

I know you guys like mods and fab work so here is something I did today.

A few weeks ago I visited the former owner of the BSM I'm using and he gave me the band rollers which he took off the mill because the bearings inside the rollers had seized. He had replaced the rollers with blocks of very hard hardwood and I didn't think anything of it because the mill seemed to be cutting fine. However, I can't help thinking that the rubbing band on wooden blocks has to generate more friction than rollers.

The LHS image is what the rollers looked like in cross section. B1, B2 and B3 are sealed ball bearings
According to the Cooksaw website, band rollers need greasing at least twice a day and clearly that was not going to happen with such a setup. So I proposed to remove B2 to create a cavity and add holes for grease ducts and a grease nipple as shown on the RHS diagram.


When I found out that both Option A and B required drilling through case hardened steel on the main roller surface AND following a suggestion from an Aussie woodworkers forum member I decided to go with the following plan



And here is the real thing
Components 1 and 2 are spacers to hold the roller away from the BSM frame
Component 3 is a lantern ring spacer that has a wide flat groove turned into the inside surface that allows the grease to pass from the bolt hole to the cavity between the bearings.


Now assembled - the arrow is where I drilled holes (not shown in this picture) to allow the grease to pass through the inner bearing on that side.



Here you can see the grease oozing out from the back



Cant try it out yet - maybe Monday.

 

[BIG JAKE]

I know you guys like mods and fab work so here is something I did today.

A few weeks ago I visited the former owner of the BSM I'm using and he gave me the band rollers which he took off the mill because the bearings inside the rollers had seized. He had replaced the rollers with blocks of very hard hardwood and I didn't think anything of it because the mill seemed to be cutting fine. However, I can't help thinking that the rubbing band on wooden blocks has to generate more friction than rollers.

The LHS image is what the rollers looked like in cross section. B1, B2 and B3 are sealed ball bearings
According to the Cooksaw website, band rollers need greasing at least twice a day and clearly that was not going to happen with such a setup. So I proposed to remove B2 to create a cavity and add holes for grease ducts and a grease nipple as shown on the RHS diagram.
View attachment 425036

When I found out that both Option A and B required drilling through case hardened steel on the main roller surface AND following a suggestion from an Aussie woodworkers forum member I decided to go with the following plan

View attachment 425037

And here is the real thing
Components 1 and 2 are spacers to hold the roller away from the BSM frame
Component 3 is a lantern ring spacer that has a wide flat groove turned into the inside surface that allows the grease to pass from the bolt hole to the cavity between the bearings.
View attachment 425038

Now assembled - the arrow is where I drilled holes (not shown in this picture) to allow the grease to pass through the inner bearing on that side.

View attachment 425040

Here you can see the grease oozing out from the back

View attachment 425039

Cant try it out yet - maybe Monday.

 

[BIG JAKE]

Good solution Bob. I use a 50/50 solution of diesel fuel and bar oil in a spray bottle that I spray on the band here and there also. Cuts down on friction and takes the pitch off band and rollers too. Really quiets things down.

 

[BobL]

Thanks for the tip on the diesel and bar oil - I heard about this combo but was not sure of the ratio.

I tried the rollers out today and boy did I get a bit of a run around with them.
The good news is that using the rollers gives me ~100 more RPM which brings the blade speed up from 4600 FPM to 5300 FPM - haven measured it in the cut yet.

I set everything to 0º and the blade was diving under any sort of reasonable cutting speed.
Then I tried a small (0.5º) upward angle on the "blade into the cut" roller - not much of a change. Then I tried 1º then 1.5º - nothing I did could make it climb in the cut.
Then I tried small upward angles (1º) on both rollers and things improved a bit but if I pushed the blade hard it still took a dive.
Then I tried 1.5º on both and finally it was cutting straight BUT the blade was now rubbing on the back rim of the "blade coming out of the cut" roller - this means turning down a spacer on the metal late so back home to do that and by then it was time to cook dinner.

I can understand that the blade flutters even just a small amount so if rollers restrict the upward flutters they won't restrict the downward flutters so maybe thats why its diving.
What I don't understand is why the wooden blocks in place of rollers cut straight. They do have a wider contact area but I don't see how this restricts downward flutters.

 

[BobL]

I adjusted the roller spacer, reinstated everything and tried a systematic variation of roller angle but that blade still dives in the cut.

If I back up and restart the cut slowly it can re-establish a flatfish cut, but if I use the usual cutting speed if anything it's now diving quick than ever.

I then removed the rollers and put the wooden blocks back on and it's no better.

I've been reading about bands bending and needing to be rolled/flattened although I find it hard to believe this would happen to a brand new bimetal blade that has made about 15 cuts in small 8ft long hardwood logs.

The 2 old blades I used and sharpened twice were cutting pretty true.

Anyone have any idea what might be going on?

 

[hamish]

From past experience, I have experienced better luck using sealed bearings (both sides) and not greasing them, just replacing as needed. This is for 2 reasons, we all add too much grease and which will find its way to go elsewhere and ruin some beautiful lumber.

What is your tooth set at? Downward pressure is all that is required on the band, deflection is not.

Most likely you have a bad band, somewhat out of regular specs.

You should consider using something else besides diesel for your band lubricant. Water and Pinesol or Cascade (not sure if either are available in AU but surely you can find similar mixtures).

 

[BobL]

From past experience, I have experienced better luck using sealed bearings (both sides) and not greasing them, just replacing as needed. This is for 2 reasons, we all add too much grease and which will find its way to go elsewhere and ruin some beautiful lumber.

Thanks for the comments.
I'm nNot really worried about grease at the moment, I'd just like to get it cutting straight.

What is your tooth set at?

Set is 0.020"

Downward pressure is all that is required on the band, deflection is not.

You mean by the rollers?

likely you have a bad band, somewhat out of regular specs

.
What does this mean?
This was it started out cutting straight but after about 5 cuts it started diving and now it dives unless I go really slowly and even then its not a flt cut.

You should consider using something else besides diesel for your band lubricant. Water and Pinesol or Cascade (not sure if either are available in AU but surely you can find similar mixtures).

I'm using water while cutting and using the bar oil and diesel mix at the end of the day

 

[hamish]

Yes downwards pressure from the rollers. For you band to consistently dive in the cut you have a set issue (one side has more set in it than the other) or the bed height is not consistent with the band along its travels.
What species are you cutting? You could just be grabbing the grain also.

Are you cutting from the butt or top end?

As you mention slowing your feed rate helps but still is not true, I would steer towards lack of set and/or dullness of the band.

 

[BobL]

Thanks for the feedback Hamish, much appreciated

Yes downwards pressure from the rollers. For you band to consistently dive in the cut you have a set issue (one side has more set in it than the other) or the bed height is not consistent with the band along its travels.

Blade is brand new Lenox Woodmaster bimetal blade from reputable supplier. It made 4/5 good cuts before I noticed
Will check set next time I'm down at the yard.

What species are you cutting? You could just be grabbing the grain also.

It Spotted gum, pretty hard but haven't had a problem with it before

Are you cutting from the butt or top end?

Butt end

As you mention slowing your feed rate helps but still is not true, I would steer towards lack of set and/or dullness of the band.

OK will try the other new band.