Stupid question on why cutting both ways.

[Greysonvalleyrr]

Since i am still looking for a mill spending hrs on you tube watching everything i can find. Came across a mill that cuts forward and backwards.  Can any mill do it with a blade that has two cutting sides. 

 Other question was seen advertised a Turner hydraulic mill for like 17,000 new that's less than half the price of anyone. .  Not many videos on it and the one that are really don't show much. It says it uses Tires for the band wheels?  Could that be right?   

[Southside]

In order to be able to cut in two direction you need a lot more band, both in terms of width and thickness.  Select saw is about the only portable mill I know of that will cut in both directions.  For comparison the bands are about $250 each - so it's a whole different category.  

[Bruno of NH]

I know someone who bought the turner hydraulic mill
He's changing it to steel wheels and has changed to Cooks guides
Wouldn't  cut to his expectations last I knew he bought a Lucus swing mill

[Woodpecker52]

 I think most thin kerf band mills use rollers that have a flat back which stops the band from coming off the wheels.  That is why one side of the blade is flat.  If you had two serrated edges you would need bigger wheels and a bigger band,  They say auto tires would work but I think that I would rather have them on my truck then slinging resin.  Any who some of the wood engineers around the site could easily rethunk  a new fangled design, just look at what woodmizer has done.  I see a lot of homebuild thing a majig bobs and such on utube.  Oh well If they can figure out the hulla hoop I sure someone can figure out a go to and get away from double welded blade band mill maybe even a wide version.

[moodnacreek]

Double cut bands have been around for a long time, 100 years I would say. The teeth hang off the edges of the wheels. Not all band mills use them probably because they cut their boards on a resaw band. For the little portable I would be afraid unless I was only cutting timber from the woods and was debarking and the mill was a very proven design. The throw away band allows you to play with junk wood. You don't do that with expensive saws.

[Greysonvalleyrr]

Thanks for the information. Not being a sawyer, just an armchair one for now anyway. But being a machinist all my life I am surprised that  no has come out with a blade for even any band sawmill that would cut both ways. Yes it could not have the flat backside to damage the return set of teeth. Why not have the blade with slits in the center and the guides have the exact same spacing for the blade to drop into. And on top of the guide have a plastic roller holding the blade against the guide roller. It would take some mathematical figuring for each size of blade to have the proper spacing and the rollers to match. 
 
For the solid steel drive and idler wheels you would need a wider blade, so as not to have the cutting area on the wheel. If and when I do get one that will be on my things to play with I see what they charge for the guide wheels. I could make them in 10 minutes once programmed on my Haas CNC. Probably 5.00 in materials. 

I gave up on the Baker which I thought was a super heavy duty mill. Called them 5 times in two weeks and they said we will get back to you when the salesman is in. Guess he quit.   Thanks again. 

[SawyerTed]

The cost and relative complexity of the drive to saw both ways offsets the affordability goal of a most portable band mills.  Due to the need for heavier bands there is higher tension which requires heavier frame and wheels.  Heavier bands require more horsepower to pull.  All that adds expense that puts the two direction systems cut out of the price sweet spot for most.

The guides are hardened. Using non-hardened guides turns them into cone shapes in a short time.

[Greysonvalleyrr]

I was not talking heavier bands, the same exact bands you use on say a LT40. Since there driven with a belt under the band I believe (my Opinion ) it would be a easier using that kind of drive system. Would not require anymore horsepower or tension, frame or wheels. Yes the guides are hardened a few hrs in a tempering oven is the same way they make them probably to HRC 55 to 60. It just an Idea floating since I has seen a few machines cutting both ways and the thousands of videos with the mill just laboring back to its home position to cut one way. 

[Southside]

It won't work.  The bands don't have enough backbone to support teeth on both sides, thus why 4" is about the minimum width you see in a double cut band.  

[Woodpecker52]

I have an idea someone  resurrect the, direct drive both wheels at the same time, now with the idea of sawing forwards and backwards.

[hacknchop]

portable sawmills are better now then they have ever been , they are also very convenient having operated a Heartwood double cut mill with 6" band I don't think a band narrower than 4" could handle the stress Southside has explained it well, I like the fact that you and others are willing to entertain different ideas and ask us questions , now if the answer you get does not suit you please don't argue build it try it and if successful tell us about it.  Welcome to the Forestry Forum we look forward to getting a machinist perspective on our projects or repairs.

[donbj]

I have an idea someone  resurrect the, direct drive both wheels at the same time, now with the idea of sawing forwards and backwards.

Ahhh! The ole double drive double cut. It has a ring to it, I think it'll sell!

[JoshNZ]

How do you slot a blade along its whole length without cutting it in half? I'm sure I've misunderstood haha.

Interesting idea anyway. Groove the band? Or a complex toothed guide that could support the opposing gullets hah. Or just accept you don't have that backstop redundancy..

I will say for sure if it added half the price again to the machine I was buying, or blades cost 5x the price, it'd be a pass from me.

[curved-wood]

Some 20 years ago I've look into the Select double cut mill. It was a popular mill around here and people were satisfied with it. As Southside is saying the blade were at $250 a copy, and sharpening is a quite a different ball game. From what I understood (long time ago ), the sharpening is more complex since the blade has to be retensioned and that needs a special equipment. The mill was around double price than an LT40,  but sure the production was there.

[SawyerTed]

The original poster's question was "can any mill do it (cut both ways) with a blade that has two cutting sides."  The short answer is no - any mill cannot cut both ways with just a blade change.

For the sake of a this discussion, forget all of the blade properties required for double cut except blade width.  For efficient cutting,the tooth configuration necessarily has to be existing tooth profiles - so the blade simply has to be wider.

The current design of portable mills just won't support installing a double cut blade.  There isn't clearance on most portable mills in the blade housings or at the drive belt to just install a wider blade that will cut both ways. The drive wheel on Wood-mizers has a groove for the blade belt and grooves for the double drive belt, without some serious retrofit, the driven wheel will mash the set out of the blade and the blade will interfere with the drive belt.  Just the potential damage that could be done by the double cut blade when it breaks would be costly - think cutting drive belts anytime a blade breaks or comes off the wheels.  Blades breaking or coming off the wheels happens often enough.

The controls that control the reverse direction will require retro fit as well.  Most saws have variable cutting speed and one speed for jogging the head back for the next cut.

On the larger mills that have the dragback function, the dragback would require modification yo work both ways.

As much as I'd like to see it work, the gain in production would not justify the cost of retrofit.

[moodnacreek]

And the you would need a drag forward!

[Southside]

Actually just angle the head and bed to about 20° and drop onto a conveyor. So the whole bed would have to become hydraulic. 

[Greysonvalleyrr]

I am just trying to reinvent the wheel .  8)  Well maybe ? 

[Resonator]

With a double cut blade, you get to saw into your backstop going both ways.  ;D

[SawyerTed]

Now that's the funniest thing I've seen on the Internet in a long time! :D :D ;D :D ;D :D :D

[hacknchop]

With a double cut blade, you get to saw into your backstop going both ways.  ;D

I've never cut into the backstop going forward it was always on the way back. ;)

[hacknchop]

Some 20 years ago I've look into the Select double cut mill. It was a popular mill around here and people were satisfied with it. As Southside is saying the blade were at $250 a copy, and sharpening is a quite a different ball game. From what I understood (long time ago ), the sharpening is more complex since the blade has to be retensioned and that needs a special equipment. The mill was around double price than an LT40,  but sure the production was there.

Blades were 250.00 each sharpening was handle by saw filer at local big sawmill usually anywhere between 45.00  to 100.00 depending on what all it needed sometimes cracks needed to be welded . Now the good news yes the production was there 2 men sawing on mill then running through separate Baker portable edger cutting the best and the most out of each log Harwood average about 4000 ft in 8 hrs , softwood 6000 plus  saws generally cut for 4hrs then swap out and if dull taken out of rotation and sent to saw filer. No debarker .

[kelLOGg]

How do you slot a blade along its whole length without cutting it in half? I'm sure I've misunderstood haha.

Interesting idea anyway. Groove the band? Or a complex toothed guide that could support the opposing gullets hah. Or just accept you don't have that backstop redundancy..

I will say for sure if it added half the price again to the machine I was buying, or blades cost 5x the price, it'd be a pass from me.

I think he means slots perpendicular to the band for cogs in the roller guides to mesh.

[Hilltop366]

Other options or crazy ideas.

turn the saw head around at the end of the cut. 

two blades back to back each on there own band wheel with two sets of guides in between them (I'm thinking the trailing blade would get bumped off)

two blades back to back on two separate saw heads that pivot up, one saw head for each direction the other saw head lifts up out of the way.

set of roller guides (one set on the top and one set on the bottom) and flip the saw head on a horizontal axes.

[moodnacreek]

I  think Baker made a resaw that cut 2 boards with one band and somebody did have a turn around head. The sliver tooth band saw blade has false teeth on the other edge to keep from being rubbed off the wheels on the gig back.