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Feed Rate-Circle vs Band

Started by Firebass, February 25, 2008, 12:52:54 AM

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Firebass

Will a bandsaw cut accurately at the same feed rate as a circle saw of the same HP and depth of cut?  Assuming both are setup correctly and have sharp blades.

Firebass

Dave Shepard

What size bandsaw? A 1.25" band can't transmit the horsepower a large circle blade can take. A 6" or 12" band on the other hand can take a lot more power. I have a movie of the AWMV (Wood Mizer) LT300. It is a 30 HP electric, and while it sure cuts fast compared to the small portable band mills, it isn't as fast as a circle mill. I recently purchased a stop watch for timing various activities around the mill, and it has been interesting to find out what your saw can really do. Our Wood Mizer with the 24hp Onan will cut at speeds up to 45 fpm (8" wide pine cut) or as slow as 12 fpm (20" oak cut). I'd like to take some measurements of my friends circle mill, he is running 75hp electric. I've seen it chew up a 20" wide cut by 18' log in just a few seconds. He runs a vertical edger, that can really swamp the tail man having three 2"x6"s flopping off every few seconds. :o


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

bandmiller2

Tough question,you probibly mean swing vs. band.From what I've seen about the same ,band with the advantage on wide cuts swing pulls ahead on narrower cuts.big circle whoops them boath by a factor of three or four.Frank C.
A man armed with common sense is packing a big piece

jason.weir

The rule of thumb for circle mills is 1/8" (softwood) to 1/10" (frozen or hardwood) feed rate per tooth.

Give my blade as an example.

It is a 52 tooth blade that gives me a feed rate of 5.2"-6.5" per saw revolution, lets call it 6".

If I run the blade at 500 rpm that gives me an effective saw rate of 250 fpm...

As with everything else horsepower rules. If you have less horsepower you want to slow the blade down but keep the feed rate the same.  If you slow the feed rate, the saw will cut dust instead of chips and this dust will slip past the shank, causing friction and overheating the blade.

Not sure on the band mills but I would guess the same thing applies.  Any tooth be it band or circle is designed to cut a certain amount.  Forcing it to cut more or less will cause problems.  What changes are made to the band mills when hp changes are made?

If you know how big a cut your blade is designed to cut you should be able to work backwards to get the appropriate feed rate.  Then you can adjust your blade speed to your power available.

Take this as a grain of salt because I've not yet set my mill up, this info is what I have read published.

This has been posted before here but it can't hurt as a refresher.

http://www.fpl.fs.fed.us/documnts/misc/circsaw.pdf

-Jason

StorminN

Funny this should come up now... I was just timing my MD mill the other day.

So my tired (read that... not tuned up in a year, really worn drive belt, and 36 years old to begin with) MD 127 cut 1"x8" western red cedar at about 20fpm with a 12-tooth, 1/4" kerf blade the other day. It's a VW 1,600cc motor, so it's probably about 50hp or less... and yeah, it's edging at the same time (with two six-tooth, 1/4" kerf blades). I'm hoping with a tune-up, valve adjustment and new drive belt, I can make it go a bit faster.

http://www.youtube.com/v/21646yoBm0o&rel=1

-Norm.
Happiness... is a sharp saw.

Firebass

 I had a friend come over and watch my mill cutting.  He mentioned that he had been running a WM Lt thin kerf something...  and said the feed rates he had to use to get good lumber were far slower compared to what my circle mill was cutting,  (comparing a similar pile of framing lumber).  Is this a common fact that gets overlooked by newbies?  Or is his mill just not set up good enough to get comparable feed rates?

Bandmiller2:
I agree with the wide cut is the bandsaw advantage.  I don't want to start a swing vs band war.   It's already been done and the band-millers have popularity edge with votes from 65% of forum members owning thin kerf bands and I'm OK with that.   I'm mainly curios about my friends statement and was looking for some input from the supporters and manufactures for both circle and thin kerf. 

jason.weir:
Thanks for Circle blade rules of thumb.  I'm going to figure mine out and see just how it works out.  Anyone have similar rules of thumb for a band mill or is it the same?

StorminN:
I have yet to see a MD working and I only live 20 miles from the Factory.  I guess I'll have to make a point of it.  There's surely not any bad reviews I've read on them and I would bet that they too are best suited for framing lumber like the swingmill.

Dave Shepard:
Thanks for the input.  My interest is mainly just thin kerf vs circle.   I do a little maint machine work for the local sawmills and one runs a huge band blade that has teeth like my circle blade.  They shove logs thru it so... fast... it's fascinating to watch. 

Firebass

ErikC

  My experience with the band mills is limited, but when I helped a friend run his LT40, and he helped me with my Peterson, The feed was about the same. His LT40 had a bigger motor though. Tomorrow I'll use the stopwatch, but hp for hp I think the circle blade can be pushed a little faster. They just take the abuse better. You still have to treat them nice for best results though....


Erik
Peterson 8" with 33' tracks, JCB 1550 4x4 loader backhoe, several stihl chainsaws

Ron Wenrich

A lot depends on how much horsepower you have going into your system.  I'm running a 125 hp motor on my headsaw.  Thin kerf band mills aren't going to keep up with it.  I'm also running a 6/8 guage saw.

Any info you get from a chart has to be taken with a grain of salt.  That's an optimum figure, and you'll do best if you listen to your saw and let that tell you how fast you should be feeding.  Not all woods will feed the same, even within the same species. 

Your saw should be feeding at a rate that keeps the saw speed at a constant rpm.  If its dying, its not running in an optimum manner.  In circle mills, the saw will open up and lay over a bit, which allows your saw to heat up, and you have a miscut.  Some guys don't worry about that, and keep on putting the wood through at high rates.  They also send their saws out to the saw doc every other month. 

Another thing you have to worry about is filling up your gullets.  It doesn't matter what type of saw you're running.  Run into a wide piece and your gullets will fill up before they can dump, if you're feeding too fast.  Result will be a hung saw.

Knots are another problem.  You are sawing the grain in 2 different directions.  You're going with the grain in normal wood, but across the grain in the knots.  It can make for difficult sawing, and sawing too fast causes knot dodge.
Never under estimate the power of stupid people in large groups.

slowzuki

HP, HP, HP.  Mill up the road is a 4" band with 50 or so electric hp and big honking bandwheels.  Sandborn mill.  Cut rates just like a well powered circle mill.  A little circle mill with 20 hp behind it is not gonna cut fast.  Big mill with 180 hp diesel is gonna cut fast. 

Apples to apples here.  It basically takes so much hp per cubic feet of kerf removed when you are cutting.  There is a bit of difference in blade drag and cross cutting grain vs ripping.

rbhunter

I have a question. I read in the above post the bandmill has four inch blades. I notice msot blades on portable mills to be in the 1.25 and 1.5 range and the baker blue streak has a 2 inch blade. What are the trade offs with the different sizes of blades? Would the wider blade be more stable as far as dipping? Is the width only necessary for the higher horse power? What are the pros and cons?
"Said the robin to the sparrow, I wonder why it must be, these anxious human beings rush around and worry so?"
"Said the sparrow to the robin, Friend I think it must be, they have no heavenly father, such as cares for you and me."
author unknown. Used to hang above parents fireplace.

ErikC

  Just throwin' out a couple numbers for you--FPM with my peterson on 8" cuts, 13 hp honda. I timed several and they were 13-17 seconds for a 10 foot log, ponderosa pine. I get 35-46 FPM at those rates. This was real world cutting, I was doing it all day. I probably could have gone faster if needed, but not consistantly. Maybe someone with a similar powered band mill can give comparitive numbers? On 8" cuts? Not in a race here, just the day to day speed that you could expect.

Erik
Peterson 8" with 33' tracks, JCB 1550 4x4 loader backhoe, several stihl chainsaws

Dave Shepard

Taking cuts off of an 8" cant, my rate varies one side of the other of 35 fpm, oak or pine. If my band is getting dull, or the pine has a particular type of nasty knot I will have to slow down under 30. I am sure I could push even faster under great conditions, but not on a consistant basis. this is with 24HP onan, and 1.25"x.045" bands.


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

StorminN

OK, so let me see if I've got this right... according to the "ideal" book info for softwoods in jason.weir's post... if my MD blade spins at 1,100 rpm (which I believe it does) and I'm using the 12 tooth blade, the feed rate should be about 137 fpm, and with the 6-tooth blade, the feed rate should be about 69 fpm...

(1/8" per tooth x 6 teeth = .75" per rev, x 1,100 rpm = 825" per min / 12" = 68.75 fpm)

I know from practical use, I'm nowhere close to these feed rates, I'm down around 20fpm. Of course, my saw is only 50hp or so and is edging at the same time... but it doesn't seem to be bogging down, and I know I can change a sprocket on my feed drive and speed the whole saw carriage range up... hmmm... more stuff to ponder.

-N.
Happiness... is a sharp saw.

Ron Wenrich

46 tooth saw cutting 8' tulip poplar - 2-3 seconds per cut.  I wouldn't try that in hickory, but have approached some good speeds of 3-4 seconds.  Saw tooth condition also will slow things down. 

My best cutting months are May and October.  Has to do with wood temperature, air temperature and species.

If you want to speed up your process somewhat, wet down your logs and see if that doesn't make a difference.  Rainy days always makes my saws perform better.  Mud is much different than dried dirt or frozen mud.  Debarkers don't remove everything.  ;)
Never under estimate the power of stupid people in large groups.

Firebass

Well again you all have taught me something good.  I've came to the conclusion that I have been babying my mill too much on the feed rate.  Basically I have not pushed it hard enough to get that 1/8 inch per tooth marking.  I guess it's mainly because I've been cutting fairly dry Douglas Fir and thought it was just hard cutting.  I thought is was plenty fast on the feed but I decided to see if I could get a 1/8" bite mark on my boards.  Low and behold my mill cuts way better if I'm loading the gullet with chips instead of sawdust. 

Thanks All :)

Ianab

I agree.

You want to keep each tooth taking decent cuts. It takes almost as much power to shave off 1/32 dust as is does to hog off a decent 1/8 chip.  If you are short of power you are better to cut down the number of teeth and keep driving each one properly. My mill only has 8hp (chainsaw powerhead), so it only has 4 teeth on the blade. That keeps in the 2-3hp per cutter 'sweet spot'. It cant feed as fast as an 8 tooth 24hp saw, but it does OK.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

mike_van

Quote from: rbhunter on February 27, 2008, 12:44:06 PM
I have a question. I read in the above post the bandmill has four inch blades. I notice msot blades on portable mills to be in the 1.25 and 1.5 range and the baker blue streak has a 2 inch blade. What are the trade offs with the different sizes of blades? Would the wider blade be more stable as far as dipping? Is the width only necessary for the higher horse power? What are the pros and cons?
rbhunter, I usually run 1 1/4" 7/8" ts Simmonds Red Streaks, but a few years ago I tried a 2" blade with 1" ts from Suffolk. What I saw, the 2" blade had huge gullets compared to the 1 1/4, I was able to feed a lot faster, the cuts remained nice & flat even after I thought the blade was dull. I run a 10 hp 3 phase electric, with 20 hp, I could have pushed it even faster.  The trade offs are - Each 2" costs at least 3X the price of a 1 1/4", you really should have the 2" guides & bandwheels for these wider blades [lots of $$$$$$]  Also the 2" blade needs to be hammered after you get it dull. [once in it's life was the info I got]  Because it really doesn't matter if I cut 800 ft/day or 1500 ft/day, I couldn't see the extra money. I'm a one man show with very little overhead.  For someone that has to really make sawdust to pay the bills, this blade might be worth it, it just wasn't for me.
I was the smartest 16 year old I ever knew.

bandmiller2

The more I think about this ,as was said by slowski,it all comes down to power to the teeth be they in a circle or straight line.Theirs no replacement for displacement.Wider bands just allow you to use more hp and get a faster cut,same with more teeth in a circle.You want to play you got to pay.
A man armed with common sense is packing a big piece

mike_van

bandmiller2 - You got it, or, put another way - "never ask a boy to do a mans job"  :D
I was the smartest 16 year old I ever knew.

ErikC

QuoteWell again you all have taught me something good.  I've came to the conclusion that I have been babying my mill too much on the feed rate.

   My best cuts are always when I'm pushing just as fast as I can without slowing down the blade speed much. It takes a little while to get a feel for it, but becomes second nature after a bit. Go like heck, and back off a little when it starts to bog down. ;D
   Dry fir is tough to cut sometimes, you may have to go slower for that anyway. I usually do.

Erik
Peterson 8" with 33' tracks, JCB 1550 4x4 loader backhoe, several stihl chainsaws

Dave Shepard

Sometimes you get accustomed to a certain pace. I played around today to see just how far I could push it. 30 fpm in 12" wide frozen pine was my limit. I couldn't get it to dip, but I could squeal the belt. ;D I was also trying to see if I could overlube. It seems like it wanted to slip the belt sooner when I used full lube, but I didn't have enough test data to get a decent answer. I was surprised to find that I could saw that fast with a frozen log, usually get horrible knot waves. I wonder if the alignment I did this summer is making that much difference? I guess we have to be always testing the limits lest we get complacent. :)


Dave
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

StorminN

Speaking of belts... I played hookie today and went and worked on the sawmill instead. I finally got around to replacing two belts and properly adjusting a third, and HOLY COW, what a difference. I had been getting a feed rate of about 20fpm for 1x8's in cedar, and today I cut 1x8's at 43fpm and 1x10's one notch slower, at 37fpm. Cool.

-N.

http://www.youtube.com/watch?v=c4gsbrrkCy4
Happiness... is a sharp saw.

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