bandmill blade guides

T_in_SC · December 10, 2003, 02:10:09 PM

I have a homemade mill (13 hp) that uses single roller blade guides. Was wondering if double roller or sandwich type guides would allow me to cut faster without the blade starting to dive. Any observations will be appreciated.

Neil_B · December 10, 2003, 02:39:18 PM

Have you got anything underneath the blade at all? My mill has brass guides under the blade and roller and they are supposed to help the blade stay straight.

D._Frederick · December 10, 2003, 04:15:44 PM

T,
With the blade supported on the bottom, you don't need the 1/4 inch of (press down) that the roller guides require. This will increase your blade life on not having to flex around a small radii. The support under the blades results in less deviation from knots and allow faster cutting rates and increase the quality of the sawn lumber. About half of the sawmill mfg's have this feature on thier band mills, and there are two companies selling after market guides with this feature.

Tom · December 10, 2003, 04:56:01 PM

The down pressure of the guide wheels is actually a function that allows the blade to be controlled horizontally in an invironment where the wheels may not be doing the job. I never thought of short blade life being caused by this extra bend but you may be right, "D". Without the down pressure it's difficult to get the guide to hold the blade parallel to the bed.

While supports under the blade may help, I seldom had any problem with the blade diving off of the guide wheels unless something was drastically wrong with the blade.

Putting another wheel under the blade would keep you from being able to cut close to the bed and may require that your last board be 2" or greater. If you put something under the blade, it would almost have to be a thin, flat piece of metal. Mine are hardened tool steel but so is the top plate. I don't have Wheels for guides on my mill but then, I have a crowned steel wheel too.

T_in_SC · December 10, 2003, 04:58:11 PM

New_sawyer,
My saw has a little steel arm below the moveable guide but it doesn't come into contact with the blade in normal operation.

D.,
Do you recall which companies sell the guides that you are referring to?

woodmills1 · December 10, 2003, 05:01:27 PM

My 93 HD 40 has only the upper roller guides it came with. They have 2040 hours on them and I use very little down pressure, almost neutral. I will say that i think if the blade isn't right no roller in the world will keep it sawing straight. I have seen my blades dive down and less often up. 90 per cent of the time they were dull or had already hit something. However there are those few logs that the blades just seems to follow some grain. But I also bet that at that time I had a blade on that was not real sharp, and/or not set for the log type and cut width I was dealing with.

T_in_SC · December 10, 2003, 05:16:17 PM

Tom,
I hadn't thought about the last board aspect of having a roller on the bottom.
Doesn't the blade sliding on steel plates cause heat buildup and wear. I thought the sandwich type guides used some special material. At Moultrie I was impressed with the Hudson Mills guides that I think are made by Carter.

D._Frederick · December 10, 2003, 07:44:35 PM

T.,
The after market guides with bottom support are made by Cooks Saw and Suffocks Saw.

Tom · December 10, 2003, 07:47:49 PM

"T"
This is my un-educated explanation.

Mills with flat stationary guides depend on the band wheels to keep the blade straight. The guides don't actually touch the blade unless the blade takes off in an errant direction.

Blade guides are really for control of a disastrous failure of the blade to cut straight. They are to bring the blade back to horizontal not to control the blade position all of the time. That is, they don't if the band wheels are doing the job.

Roller guides are a different story. They do control the blade position because the types of band wheels that are on the mills that use roller guides generally have a lessor sophisticated and accurate "Tire" design. V Belts, flat rubber, flat steel etc don't control a blade the same as a crowned wheel. Where flat guides depend on the accurate alignment of the wheels to produce a blade that is horizontal to the mill bed, Roller guides are more forgiving and produce control to aid in the failure of the wheel to do all of the job.

Blade set/sharpness and profile have a lot to do with how the blade runs also. But, the failure or success of a blade would be the same on either guide system. Still either guide system would have to try to correct the failure.

My guides are hard, tool steel and, yes, they will get very hot, wear out quickly and even break the blade if constantly in contact with it.

solidwoods · December 11, 2003, 05:20:36 AM

The back of the blade guides or back roller, keep the blade on location, not the wheels.
1/4" deflection is pointless useless and prematurely wears out the blade.
Flat stock vs. rollers. Rollers sandwich type need to be designed correct. Watch your outside dia/rotational speed, stay within the bearing limitations. A bearing inside a larger dia is what allot of mill use.
Also two bearing sandwiched together to achieve wide surface tend to get dust between them and cause probs. if not watched close.
I would save some lunch money up and get a set of adjustable guides like W/M and other use. One guide, one bearing (greasable) no other guides required. This type of guide is ultra simple durrable and very adjustable.
JIM

Tom · December 11, 2003, 06:13:10 AM

Since I was getting a little confused with the answers and the question, I went to my WM book to get some proper nomenclature and found that it doesn't give any "why's" just "do-it's" Since there are two horozontal adjustments and solidwoods is talking about the one that keeps the band on the wheels. I guess I must change my "horizontal" adjustment word to "tilt'. Under pressure the back wheel does keep the band on the wheel and adds beam support against cutting pressures, though, while not under cutting pressure it should not be contacting the blade.

The down pressure of the guide wheel is to control the catastrophic deflection of the blade. If the wheels are perfect and the blade is perfect then guides may not even be needed. Without some down pressure, roller guides have no way of controlling the "tilt" of the blade.

Since plates are not in direct contact with the blade all of the time, blade "tilt" must be accomplished in some other manner.

It's the catastrophic failure of a blade to remain in the same plane with the bed of the mill that the guide is supposed to correct.

D._Frederick · December 11, 2003, 12:04:03 PM

On Tom's mill with the plate quides, the band wheel have been adjusted so that they are parallel to the log rests, the guides are then postioned so that they clear the blade by only a few thousands of an inch ( 0.010 - 0.015 ). When sawing, the back up roller is supporting the blade, preventing it from springing out of alignment. When the teeth hit something hard like a knot, they tend to want to deflect ( the thinner the blade material the easier they deflect), with both the top and bottom of the blade being supported, the teeth are forced to cut straight. Most of the mill mfg's that are using high horsepower drives have gone to the blade being supported on both sides to allow a faster cutting rate.

danf38 · December 13, 2003, 11:02:35 AM

yes sandwich type guides would be alot better and alow u to cut faster. a baker band mill uses sandwich type guides. 8)

T_in_SC · December 13, 2003, 11:19:37 AM

Thanks everyone for all the interesting responses. I like the idea of the sandwich guides, but since my mill uses trailer tires for bandwheels they may not be the best choice. Has anyone ever used sandwich guides on a mill with trailer tire bandwheels?

Fla._Deadheader · December 13, 2003, 11:55:02 AM

I use trailer tires and bought a used set of roller guides from Solidwoods. NO underside rollers or plates. Jim pounded into my gourd that things HAVE TO BE RIGHT for the saw to work right. Finally wased up and got everything running right. No more diving, dipping, breaking, or whatever happens, UNLESS something is out of whack.
  If ya got good roller guides, take the time to set everything right and yer problems should disappear, ours did. 8) ;D ;D :D :D

  What kinda wood causes the most trouble, sappy ??? ???
  We corrected that also. ;D

DextorDee · December 15, 2003, 06:32:43 AM

This is what came on my mill they work but, I intend to change to some other type when I get the $.

I go through a lot of bearings, to lite I think :'(
Also interested in what you guys have or use.

Fla._Deadheader · December 15, 2003, 07:02:44 AM

Dextor, I built my first roller guides with bearings, actually 3 bearings for the full width of the blade. The blade lube will water down the oil in the bearings and they rust and go bad. I changed to Regular manufactured roller guides and grease them once a day or so, depending on use. So far, no problem.

We cut to 38" opening between the rollers and there is no bottom guide.

Neil_B · December 15, 2003, 07:31:27 AM

http://www.tradegold.com/bandsaw-guides/

There is a site for blade guides. Mostly bandsaws but they do ones for bandmills and resaws too. Not sure how good they are though.

EZ · December 15, 2003, 05:35:23 PM

My mill had flat guides on it when I got it, they worked ok but wore out fast. I went with the single roller guide with the flange on the back. The blade was level with the bunks and I started with 1/8 down pressure and had wavy cuts. I move the guides to 1/4 down pressure and still wavy cuts. The blade was level with the bunks but still wavy cuts with new blade. I called Cooks and they told me my band wheels should'nt be level with the bunks with out the guides on. So I tilted my band wheels back at the top 1/4 inch and leveled the guides with the bunks with 1/8 inch down pressure and it work great.
EZ

Neil_B · December 15, 2003, 06:03:37 PM

QuoteI called Cooks and they told me my band wheels should'nt be level with the bunks with out the guides on. So I tilted my band wheels back at the top 1/4 inch and leveled the guides with the bunks with 1/8 inch down pressure and it work great.
EZ

??? ???
EZ, maybe I'm just not understanding but how do you keep your tracking with the band wheels back that much?

EZ · December 16, 2003, 02:32:03 AM

I think it was 1/8 back tilt now that you mension it. It's been a couple of yrs since I made this adjustment, I dont know if its my age or just all the stuff rolling around in my head that makes me forget things. Maybe both. ;D Well anyways what ever the tilt was it sure did make a world of differance. If you want to make sure call the people from Cooks, there pretty cool. 8)
EZ

Neil_B · December 16, 2003, 04:09:48 AM

Thanks EZ,
I was under the impression that these wheels were supposed to be true in every aspect. Maybe it's just the steel wheels. I'll maybe try Cook's and see if they would help me out.

I tried the no deflection thingy on the blades and just used the guides to level the blade to the bed but I'm getting wavyness all through the cut. It's getting cold out now and logs are freezing so I'm going to try an 8 deg hook on the teeth to see if that changes things. If not I'm going to put deflection back in and see what happens.

D._Frederick · December 16, 2003, 08:31:46 AM

I guess I don't understand this tilt-back of the wheels. On my mill I have found that the wheels should be set so that they are parallel to the log rest and be at right angle to the track. Fine tuning of the blade is then done by the guides.

Tom · December 16, 2003, 09:41:03 AM

Me too ???

Bibbyman · December 16, 2003, 10:17:24 AM

I stumbled onto the Tech Talk section on the Wood-Mizer web site. While it may not provide the answer to your specific question as you've not got a Wood-Mizer mill, it does cover a lot on roller guides.

Also, covered ...

Hydraulic Maintenance
Understanding Roller Block Blade Guides
Engine Concerns
Schedule for Common Maintenance
Refilling your Sawmill's Blade Tensioner
Battery and Charging System: Operation, Testing, Alternator Tests
Battery Do's & Don'ts

Wood-Mizer Tech Talk