Roller guides

[JoshNZ]

I just had a couple of questions about roller guides and how the band should interact with them. Ive watched a couple of vids including cooks about where on the wheel the back of the band should ride.

One question I have is, should the band be relying on the back (shoulder) of that guide while it's in the cut? Ever? Sometimes? Or should you be riding far enough forward on the guide that the natural deflection never reaches the shoulder.

Second question what sort of angle should the shoulder be at to the back of the band? I.e. if you lay a ruler across the top of your guide square against the shoulder, parallel with the band, I assume the angle should be slightly open between the blade back and guide shoulder, on the incoming side? Or are you better square?

I was running my mill today with the band sitting quite far back on the guide and saw the blade jump up onto the shoulder several times. As a result the teeth have marked the front of the guide and probably not been great for the blade either, I'll pull it and have the set checked.

So I'll be turning some new guides sometime soon, last question is should the shoulder be higher! Or am I doing something wrong if they ever make it that far back anyway. Funnily enough I still got a nice flat cut with the blade carrying on like that. But I doubt I would again

[Chuck White]

The back of the band will contact the shoulder of the blade guide roller while in the cut!

If the blade guide roller didn't have that shoulder, the blade would be pushed completely off of the rollers as you enter the cut!

[Banjo picker]

I have Cooks guides.  Ideally you want:
 1.  About 1/4 inch down pressure from bottom of guide more than band wheel
 2.  When the band is turning 
, I like a good 1/8 inch from back of blade before it hits the flange on back of roller guide.  Really if properly tensioned the band will only hit the back flange of the roller guide if your pushing the mill pretty hard or encounter a knot.  The back flange of the cooks guide ( I have the megs rollers) is close to 1/2 inch high.  I have never had a band jump up on it.

3. If you let the band run against the back flange of the roller guide all the time, you will have short band life.

4. Chuck must have a different guide than mine...no way the blade will come off the back of a Cooks guide.

You'll have to get other opinions about the angle of the rollers you speak of.  Tim

[ladylake]

  (If you let the band run against the back flange of the roller guide all the time, you will have short band life)


 Real short life, I run my flange 1/4 " back of the blade. You could get by with 1/8 if you don't push hard and run a higher hook angle.  When I hear the blade hit the flange it's time to put a sharp one on.   Steve

[scsmith42]

I have Cooks guides.  Ideally you want:
1.  About 1/4 inch down pressure from bottom of guide more than band wheel
2.  When the band is turning
, I like a good 1/8 inch from back of blade before it hits the flange on back of roller guide.  Really if properly tensioned the band will only hit the back flange of the roller guide if your pushing the mill pretty hard or encounter a knot.  The back flange of the cooks guide ( I have the megs rollers) is close to 1/2 inch high.  I have never had a band jump up on it.

3. If you let the band run against the back flange of the roller guide all the time, you will have short band life.

4. Chuck must have a different guide than mine...no way the blade will come off the back of a Cooks guide.

You'll have to get other opinions about the angle of the rollers you speak of.  Tim

This is also how I do mine on my Baker (Cooks guides)/

[JoshNZ]

Thanks for the responses. I should mention I'm not using cooks guides I'm using fabricated guides. I think it must have been 40mm 4140, as it was what I had on hand. Obviously slightly under sized already so I only turned down to 38mm leaving maybe a 2mm shoulder.

Sounds like starting again will be good. Larger diameter and taller shoulder.

I've set my band forward 1/4" to try it out today. Obviously the space between the shoulder and the front of the guide cant be more than the space between the back of the band and gullet, so I've lost a bit of support from the front of the band like this. We'll see.

Is it quite an obvious noise it makes hitting that flange?

[ladylake]

 
 Your blade will be pushing back some when sawing so you wont lose much support on the front of the band. On my mill its easy to hear when the band hits the flanges. Make sure your running 1/4" down pressure which gives good control on the blade.  Steve

[Hilltop366]

Wondering if a back bearing or roller would be any advantage over a roller guide with shoulder, the bearing/roller would have to be large enough to prevent over spinning past its rated RPM. I'm thinking it could be made to be shimmed up or down with washers as it wears a grove to extend its life or perhaps the bearing would give up before then?


Also I have seen pictures or video of ceramic guides with a block of ceramic for the back.

[YellowHammer]

I have Cooks guides.  Ideally you want:
1.  About 1/4 inch down pressure from bottom of guide more than band wheel
2.  When the band is turning
, I like a good 1/8 inch from back of blade before it hits the flange on back of roller guide.  Really if properly tensioned the band will only hit the back flange of the roller guide if your pushing the mill pretty hard or encounter a knot.  The back flange of the cooks guide ( I have the megs rollers) is close to 1/2 inch high.  I have never had a band jump up on it.

3. If you let the band run against the back flange of the roller guide all the time, you will have short band life.

4. Chuck must have a different guide than mine...no way the blade will come off the back of a Cooks guide.

You'll have to get other opinions about the angle of the rollers you speak of.  Tim

This is also how I do mine on my Baker (Cooks guides)/

That's the same way I run my WM, except the shoulder isn't as tall.  

[JoshNZ]

Wondering if a back bearing or roller would be any advantage over a roller guide with shoulder, the bearing/roller would have to be large enough to prevent over spinning past its rated RPM. I'm thinking it could be made to be shimmed up or down with washers as it wears a grove to extend its life or perhaps the bearing would give up before then?


Also I have seen pictures or video of ceramic guides with a block of ceramic for the back.

Just got done a day milling, and rushed back here to ask this exact question. Why do we not run a roller guide/bearing against the back of the blade? Do any commercial mills have this?
I'm having a world of trouble with my guides at the moment. I picked up a bar of 60mm 4140 on the way home so I'm set to make some proper guides this weekend but it has got me thinking... Obviously the blade needs support on the back, surely a surface rolling against its spine is better than a flat shoulder 'wiping' against it in an arc...?

[JoshNZ]

This is the sort of carry on I'm dealing with at the moment. That's several minutes of clean wood into a brand new blade. Maybe a 200mm wide walnut cant. Might be a bit knotty but still, thats really bugging me.

I think what is happening is my band is deflecting and there doesn't seem to be any way to stop that happening with the woods I cut, they're usually knotty and I like that. Then it blips up onto the shoulder, scuffs the teeth crossing the nose of the guide as it does, and with that group of teeth having a wrecked set the problem quickly compounds and wrecks the blade.



 

I see my old tanner band saw in my woodshop has a bearing supporting the bands spine, but facing it, i.e. wiping across it as shown below. This is essentially the cooks guide concept working but with the shoulder on a different bearing. There must be a reason they've chosen to do this?



 

This design makes a whole lot more sense in my mind - just the concept of a radial bearing or roller, rolling against the blade spine . But I'm not an engineer... I would love to hear some opinions before I go and turn this 4140 into chips.

[ladylake]

 
 The best bet would be to get some Cooks roller guides and run 1/4 down pressure.  Those little bearings  wont last long.   Steve

[Mapleman]

If you haven't done this already, you might want to check the alignment of your blade guides.  They need to be set at a slight angle so that the back of the blade contacts the flange of the guide on the side that would tend to pull the blade up into the guide as it rotates and not on the side that would tend to pull the blade away.

[JoshNZ]

I'm not meaning use bearings Steve I just meant the concept. I've turned mine out of 4140 and they're just a bit small and not a big enough shoulder but I'm really wondering if a shoulder is the answer or if a roller like in the last photo is a better idea. 

mapleman I've spent 5 minutes thinking about your comment just now, I've got them set the opposite direction, with the intention of exactly what you mentioned but Ive got myself backwards. That won't be helping at all =/. Thanks!

[teakwood]

I had the same problem and did all the adjustments cook advises. the rollers are very important, mine where conical. so a machine shop made me new ones, after turning them they heated the steel to red and then rectify them again. all works perfect now.
 

[YellowHammer]

I run the WM high performance blade guides.  With my old LT40, which didn't come with them, I used to have the band deflect occasionally enough to come over the shoulder and cause issues, even with down pressure.  I converted over to the HP blade guides, and never again.  My LT70 comes with them as stock equipment.  They are retrofit metallic pads set adjacent to the existing rollers, and spaced about .010 from the top and bottom of the band which constrain the band from lifting off.  They do not touch the band in normal operation, but they act as "bumpers" to the band if it deflects more than the clearance distance and tries to raise off the guides.  With them, it's physically impossible for a band to climb the shoulder.  They also significantly decrease wavy cuts.  

As mentioned, the blade guide roller should be set at a slight angle to the band so that if the shoulder is contacted, the angle will push the band back down to the roller guide, and not up and over.  If it's set the wrong direction, it will naturally try to get the band to climb and will dismount it like a tire off the rim on an automotive garage tire changing machine.  

[Banjo picker]

 Why do we not run a roller guide/bearing against the back of the blade? 

If you run it against the back of the roller guide.  After you have run it for a while ,run your finger and thumb among that back edge....you will start to feel where the band is increasing in thickness.  As several of us have already told you.  It will soon break.  I have already went down that path, Those little rollers you showed on the small woodworking saw aren't running the speed of a saw mill nor do they get the pressure exerted when yo hit a hard knot.  Tim 

[JoshNZ]

Yep, all understood. After bringing the guides back the other night I put a ruler on them and set the angle with that very thought in mind. After reading these comments I got a mental picture of what the ruler looked like and realised it was backwards. Was late in the evening shouldn't have been playing with it.

I'm quite sure setting this right is going to improve my cut no end, I've never seen the mill cut this poorly before today. But Ive been meaning to replace the guides with larger diameter ones anyway, and add some shoulder height. I'll look into the sandwich setup if it still gives trouble.

Photo of my current guides below. Standby for 2.0..

Makes perfect sense Tim thanks



 

[Banjo picker]

No problem.  The bigger the guide is the slower it turns, which leads to longer life.  That's why I got the Mega guides on mine.  The down side is they as a pair are 2 inches bigger than cooks regular, and that cuts my width between the guides down to 28 inches, which sometimes means I have to get out the chain saw to get them to clear.  Tim

[RAYAR]

Hi JoshNZ, Mine uses a pretty slick set-up, three bearings stacked on a common shaft, two 6205-2RS and a 6305-2RS. The 6305 being 10mm larger in diameter acts as the back stop for the band, being 5mm higher than the 6205 bearing diameter. These bearings work great for 1-1/4" bands.

[JoshNZ]

No problem.  The bigger the guide is the slower it turns, which leads to longer life.  That's why I got the Mega guides on mine.  The down side is they as a pair are 2 inches bigger than cooks regular, and that cuts my width between the guides down to 28 inches, which sometimes means I have to get out the chain saw to get them to clear.  Tim

You can have my old guides, if you want xD.
I appreciate the suggestions for cooks guides too but being here in NZ by the time I convert the dollar and pay international freight... I've learned over the years it's usually better not to entertain the idea =/.
Is the idea in the yellow flap to reduce the amount of dust going under the guide rayar?

[shenandoahsawmill]

I designed and fabricated roller guides "borrowing" from the best features of everything I could read online in this forum and gained from graduation from the school of hard knocks. Here is what I have come up with. I'm using 4" dia. 4140 steel x 5" long with high speed bearings and a center shaft that is 1" dia.  These blade guides are offset from the top of the saw blade down from the bottom face of the wheels by 1/4". I am using a 4" dia x 1" tall 4140 steel back up rollers for the back edge of the band. These rollers also have high speed bearings in them.  They  mount on a bar that rotates through an arc and is adjustable to allow me to use from 2" wide bands to 5" wide bands. They have light tension springs to always keep the rollers against the band to eliminate flat spots in the back stop rollers when the band hits it at full speed. I run 42" dia wheels that are 4" wide, 90" between blade guides at widest setting and 120 HP.  

 

 

[RAYAR]

Is the idea in the yellow flap to reduce the amount of dust going under the guide rayar?

Yes, it is and I'm thinking about installing a piece of plastic or something on that to get closer to the blade yet. There's still a fair amount of sawdust squeezing through there and it tends to get caked on the bearings and drive belt.
I've also formed and welded a piece of rod on that yellow flap you mention as a blade guard. It extends about a 1/4" below the blade to catch the back stops before the blade does.

[JoshNZ]

Great idea. I've been meaning to do that but my backstops are set quite far in from my outter blade guide. Do you not find them interfering with nobs/limbs and bends on some logs? That's why I moved my backstops out further in the first place...

I got finished up with these replacement guides today, the lathe gods were good to me, the bearings all seat nicely with a tap. I could have gone a tad higher on the shoulders yet but I think if the blade is climbing over that thing I've got bigger troubles. No doubt setting up the angle correct is what will make the difference. Quite looking forward to running them!



 

 

[Ljohnsaw]

They look nice.  So did you harden them?