Diving blade mystery

[bunst]

I've built my own bandsaw mill (first mistake?) and can't get any consistency in cuts. There are times when I can mill out a whole log with good results and other times every cut has problems. Most often, it is a diving blade issue. When the diving starts to appear, I'll put a new blade on and it is good for a few cuts, but soon will also dive. I know the blade is still sharp and the set is not off, so I'm thinking it could be something else. Everything seems to be alignment.

My first thought is blade tension. My tension is acheived with a screw bolt. I have no way to measure the actual tension; I'm just going on feel. Is there a way to know the proper tension and how could I measure it?

Second thought being the wheels. I'm using inflated tires. They are not perfectly round as I notice a wobble when up to speed. Also they are not balanced. Would I benefit by upgrading to steel or cast sheaves with v-belts?

Thanks in advance.

[bandmiller2]

Welcome Bunst,tough question with no pictures could be many causes.First do you have band guides that the band rides on fixed and movable.If not thats the first step, best to buy,theirs alot in past posts on that subject.Your tires could be taken off and balanced at a tire store.Out of round,if you could setup a grinder to hit the high spots wile its running or try different tires or pressure.I'am sure outhers will have advice shortly,tell us more about how the mill is setup.Frank C.

[bandmiller2]

Forgot to ask where are you located?? Frank C

[fishpharmer]

bunst, welcome to Forestry Forum.  You are at the right place to solve your mill problems.  I couldn't have built mine without the help I received here.  Made some good friends too.

First of all we need pictures to truly assess your problem ;)  I am no expert but will regurgitate some of what I have been told.  It sounds like the blade is not perfectly parallel to the track or log bunks.  That was a problem I had with my mill. You also need some way to determine if the blade is parallel. A blade alignment tool can be made or purchased. Here is one from Cooks Saw
http://www.cookssaw.com/shop/index.php?target=products&product_id=30156

To maintain correct blade alignment you need some good roller guides for the band. This was a major issue for my mill.  Woodmizer and Cooks both make some great guides, although a bit pricey.  Good roller guides will take care of some issues with the tires being a slightly out of round/out of balance.  When building my mill I went through several different tire and wheel sets before getting some that run true. But don't be discouraged about tires for band wheels, lots of people use them for homemade mills, they work fine.  At least one company uses them for the mills they sell (Turner).   

I think tension could be a factor.  Woodmizer, Cooks and several others make tensionometers to check the tension.  Again here is link to Cooks
http://www.cookssaw.com/shop/index.php?target=products&product_id=30148

You can also search these subjects by looking near the top of this page and using the search button.  Also, it helped me to look at the pictures in some of the member photo galleries. 

Don't hesitate to ask any questions, most folks here know way more than me about sawmills.

[robnrob2]

There is what ya call a flutter test, where you remove your blade guides and carefully engauge the blade and bring it up to full speed, and then watch it for fluttering,, tighten up the tension till the flutter goeas away, and then give the tension bolt another full trun,, when lossening up the band when done opperating, count your truns,,
You want your blade guides, to be pressing down on the band about a 1/4"  this will have an effect of stearing your band balde,, also you will want your guides ponting or aiming your blade, streightaway,, nuther words, paralell with the bed,, this is done with a simple to make blade alignment tool, or one could be bought from Cooks saw Mfg,,
Out of balance and nonround tires can cause some of your problems,, but based on what you have described so far, I would say some of your problems is not enough tension, and blade alignment,, You really want the blade tight enough to nearly make a musical note when plucked,,
I think you would benafit from going with say 19" sheeves,and a V-belt isnert, over tires,, although its done lotsa times with sucsess with tires,,

[Magicman]

I can't add to the above advice and recommendations this early on because they nailed the potential problem areas.

But I can say;   Welcome to The Forestry Forum.....

[bunst]

Thanks for the quick replies. I'll post pictures within a couple days even though I'm kind of embarrassed to show what I've done. I used plans I bought off ebay that turned out to be not that good. The guides are adjustable but are fashioned in a redneck manner. Probably you guys will tell me to get rid of them. Anyway, once the pictures are posted we can discuss the issues in better detail.

[pineywoods]

What kind of logs are giving trouble ? If you are sawing pine, you need a bunch of set, new blades out of the box typically have about 20 thousands set. That can be  marginal for pine logs. What blade thickness ?? Thin .035 blades will loose their set rather quickly. If the guides are doing their job, the bandwheels shouldn't be that picky. It sounds to me like you may have a combination of problems instead of just one problem. If it saws ok for a while and then starts diving, What changed ? Most likely the blade.. Dull, not enough set, or not enuff tension. Don't forget. blades will heat up and expand...
From the school of hard knocks,  make sure the problem is not the blade before you go making adjustments on the mill.

Edit   
Where are you located ? There may be somebody like fishpharmer close by, we help each other...

[TblRxDave]

Have you tried a torque wrench to set your tension? I had to experiment with different settings until I got the flutter to stop. At least I have some consistancy for fine tuning. My Oscar 28 starts at 20-25 foot pounds and may go as high as 35 foot pounds.
Dave.

[bunst]

As a matter of fact most of my problems have occurred trying to cut pine. I'm using Lenox .042 blades that come with .021 set. What do expect the set should be for pine or other similar soft wood? And yes, I will experiment with more tension before moving on to the mill itself. For all interested, I'm located in Maine.

[Magicman]

Just a note:  Pine will/could have a considerable amount of "compression" stress in the butt cut which will make a blade do "bad" things.

[Tom]

Your Lennox band should do just fine.   Twenty One thousandths is the accepted "average" band-set. 

The flutter test was developed for Silicone bands and  most everyone's bands, except Timberwolf, are carbon steel and perform best with more tension. There is a homemade device and a formula for determining blade tension that is found on some old posts in this forum.  It uses a dial micrometer and "C" clamps.

Automotive tires have been used with success as bandwheel tires.  the best success comes from balancing and making sure that they are round. There are posts here about that too.

Diving regularly is usually a set problem.  One side set more than the other.

Since you are getting it with new bands, the band might be being damaged on a piece of the saw, flattening one side.  I don't think that the pressure from the rubber tire would do it, but it might.

If the band isn't being damaged, then the other causes are:

1. driving the band too hard and having it follow the grain
2. having too little set and having it follow the grain
3. the buildup of sap on the band, causing too little of kerf which results in too little set.
4. The buildup of sap/resin on one side, dragging the band into a dive.
5. Too little tension will exacerbate #1 and #2
6.  The band needs good and properly adjusted guides to perform up to expectations.

[Chuck White]

Your Lennox band should do just fine.   Twenty One thousandths is the accepted "average" band-set. 

Since you are getting it with new bands, the band might be being damaged on a piece of the saw, flattening one side.  I don't think that the pressure from the rubber tire would do it, but it might.

I agree with Tom.  It just may be that the inside teeth on the band are losing their set due to making contact with some part of the mill!
My guess is either blade guide rollers or rigid (non-roller) blade guide!

With no (or little) set on the inside teeth and good set on the outside teeth, the outside will really be biting in and the inside will just follow their lead!

[ely]

are you cutting green or solid pine... or are they trees that have been standing dead., as in the wood is getting a little bit doady.?

[bunst]

The current log giving me trouble is a white pine that was dead.

[ely]

i would change your log to a hardwood of some sort just to check out and see if it cut well.
i have a manual mill lumbermate 2000. and it will give me living fits when i am cutting the dead pine that has two different consistences of wood in the log. when i throw on an oak or a fresh pine the "problems" seems to dissappear.

if my mill is not 100 % true the dead pine cause me problems, i have learned a few tricks that help me, but i have a friend with a mill like you are describing and it is the same as yours. the best i can tune his is not good enough for dead/doady pine. he can saw fresh pine logs or any hardwood perfect.

[Planman1954]

Being an absolute rookie at this, what I say will probably be scoffed at by everybody here. But I didn't notice anyone mention lubrication of the blade. The first thing that caused me problems was not enough water (with dawn dish soap in it) running on the blade. The detergent and water remove the sap great. Pineywoods uses pinesol. Anyway, if I cut pine without soapy water just one time, the blade will dive soon thereafter. Good luck.

[Fla._Deadheader]

 From experience, using ANY soap, pinesol, Diesel, etc. on inflated tires will more than likely cause blade slippage and tracking problems.

  We had this problem with SYP, Heart Pine, and found just lots of plain old water, and a scraper on the inside of the blade, worked just fine.

  I'm guessing knots and differences of heart-sapwood, and causing enough problems, but, blade set would be the main culprit.

I sharpened all our blades, and followed the deep gullet of Monks blades, even on a couple WM blades with shallower gullet. Moving the sawdust out of the cut makes a difference, also. At least, it did for us.  ;D

[fishpharmer]

Tom,
I just happened to be randomly looking at Larry_Copas mill pictures and found his picture of the homemade tension gage you mentioned in this thread.
IT IS NOT MY PICTURE.
I borrowed it , for the benefit of all.  Thank you Larry_Copas.

[John Bartley]

When I first started sawing I was cutting frozen white pine and it was a disaster. I learned very quickly that if I wanted to keep the cut straight and smooth I needed to do this:

• keep the pitch off the band (pinesol in water w/WW fluid) (solved diving and climbing in clear wood problem)
• keep the set in the teethup in the 0.028" to 0.030" (solved the diving in knots problem)
• keep the set consistent (solved the crosscut marks from an excessive set on one or more teeth)

Once I did these things all was fine.

Also, I found that keeping just enough pressure on the band that the motor started to "work" was a big help in keeping the face of the board smooth and clear of sawdust. I also grind my bands with a Monks depth in the gullet.

just my experience - I hope it helps a bit

cheers

John

[bandmiller2]

Bunst,don't be too hard on your mill mayby you just have "one of those logs".I've got one sitting in the yard now it tipped the scales and got me to go back to circular mills.Later I'am going to throw it on the Chase De Lane and see how the big wheel handles it.Bunst before you go too far get a nice freash pine log and cut it, some logs are just destin to keep you warm.Frank C.

[bunst]

 





Here are a couple pictures of my mill. Hopefully I did the upload correctly. I do have a blade guard but took it off for a better view of the wheels. In response to the great tips I've gotten so far, I will first check/adjust my blade tooth set and apply more tension. I will hold off making any changes to the mill until I hear the criticism...please be kind!

[Magicman]

please be kind! 

Please be kind  ???  You deserve praise !!!  As you work through the suggestions, you will solve your "diving" problem....I like your mill.   

[Fla._Deadheader]

 Shoot yeah !!!!!!  Everyone doesn't have the Cajones to try to build a mill. You done good. It's just yer Garden Variety simple as can be, Band mill.

  As you getRdunn, you can add upgrades for a LONG while.  8) 8)

  I agree with "get a fresh log and try IT". Blade set could be out OR lousy log. We all get 'em.

[Planman1954]

I echo that remark. Good luck! I don't see a water bottle though. I know somebody else said don't use water with wheels. That's a call that is above my pay grade. I hope you do well!

[Fla._Deadheader]

Water with taars is fine. Just don't use soap or any other additive. It gets slimy, and it's all down hill from there.  : :

[laffs]

your logs are frozen,thats some of the problem. in the mid 20s has been the high around here bunst. that whould be a problem around here for any mill. might have to slow your sawing speed down too. or just wait till spring. not a lot of people up here saw in the dead of winter. just dont get frustrated.ya think your having problems now,wait till ya get a nice ash butt log. i had one dive about 4 inches. that will make yer butt pucker when yer blades heading for the bunks.
just keep at it.
brent
by the way nice mill

[fishpharmer]

bunst, Your mill is Awesome. 8)  Simple and functional. Don't be ashamed of that mill.  Forestry Forum members will help you get it cutting well. 8)

[bd354]

  bunst, I'm building a mill very similar to yours (which I haven't finished yet). I know almost nothing about mills but I'll make a suggestion from looking at your pics. The vertical square tubes that hold your roller guides look a little long. You could be getting some flex when sawing. Maybe  braceing them back to the mill would help. I have no idea how much backward pressure is on the guides when sawing so I may be way off base here. Not saying that's the problem but you may want to check for flex.Just my $.o2 worth. Hope this helps

[fishpharmer]

bd, good observation. 8)  If that was happening, it could cause dive, I think.

I can say guides have been my biggest issue with my mill.

[jpickering4468]

Mr Bunst,
I have a homemade mill as well, I bought mine though.  It came with a tire set up and I was running into all of the same problems.  When they come at you all at once it can be pretty overwhelming, and hard to trace back to the source.  I was cutting spruce which acts a lot like pine only worse.  My blade would dive, rise and do anything it could to get around the knots and tough grain.  Make sure your blade guides and blade are perfectly parallel to the bunks; you can do this with a simple straight edge and a good eye.  Correct blade tension is what made the real difference for me.  I was really down on my sawmill and then a friend asked me to come help him saw for a day.  So I went, and the first thing I noticed was that he was applying three times the tension as I was, and he was flying through the spruce and getting clean straight lines.  (Suffolk saw has good tips for cutting pine and spruce and also Cooks who uses Simonds red streak blades.)  The tough part was measuring the tension.  My friend made a tool that measured the tension by deflection on his blade and the sent it to me.  I used this tool to set my tension and I have not had a problem since.  I will try to take a measurement using the slide calipers to get the length of stretch in my blade and then let you know.  
I also had trouble with wobbling tires, first get them balanced and make sure to tell the technician what you are using then for so they do a good job.  Next install them on your mill with out the blade on it.  Take a rigid plank and clamp it to the top of one of your bunks, perpendicular to the length of the bed, and parallel to the direction the blade travels.  The plank should be about six feet long so it extends out past your tires on both sides.  Now take your belt sander with a 50 grit belt on it and turn it upside down and place it on the plank directly under one of your tires.  Clamp it to the board so if you were to turn it on and the tire were touching the belt the tire would be spun by the sander. Are you still with me?  Now with the head raised off the belt turn the sander on. *make sure it is securely fastened and you are not dangling over it.*  Slowly start to lower the head so that one of the tires will slightly touch the turning belt.  Stop lowering and now start to slowly spin the tire on the turning belt opposite of the belts direction.  This will start to remove any high spots that you have.  Make sure your tire is well inflated before you start.  Keep lowering one click at a time until you can go around all the way and your belt is no longer removing high rubber.  Repeat on the other side.  You don't want to take off more than 1/8" because this could affect your blade tracking.  This method worked well for me even though it is quite crude.  The other thing I did to get rid of the wobble was to let some air out,  I was running 60 psi, and I am now running 40 psi in trailer tires.  I found that this lets the band form the tire into the perfect circle; or as perfect as a trailer tire gets.  I hope this helps and I also hope you are still awake after reading this post.  I got excited to hopefully help some one who is in the spot I was in a few months ago.  Take care, Jason

[southpaw]

I can't help, but would like to say good looking mill and I know you keep fine tuning you'll get it cutting  8) ;)  the way you want. Great job and good luck.

[backwoods sawyer]

Take a look at your guides it looks like they may be sticking out past the gullet of the saw, if they are running on the teeth that would take the set out right quick like. However it is hard to see from here.

[bunst]

Wow, great tips. I always thought my guides were the weak link and I'm going to look at improvements. I'm contemplating buying prebuilt ones, but they are pricey and not "homemade". I like the satisfaction of figuring out something myself. Fishpharmer, I notice the picture of your guide upgrade. Are those Cooks guides and did you just buy the rollers or the whole system? Jpickering4468, fantastic ideas about the tires. I will definately goes through that process to make them round and balanced. I'm feeling better about the probability of my milling performing better thanks to this forum.

[bunst]

I've finally had some time to take a closer look at things that have been suggested. Here is what I know/found so far. 1) A couple of you had noticed that the vertical stem holding my blade guides may be too long and flex. They are as solid as can be so I don't believe that to be an issue. 2) I cranked up the tension and experimented with a cut. It was much better. The blade did not dive, but instead rose slightly. Maybe too much tension? Anyway, as a result of applying more tension, the blade/wheel tracking was affected. And I found the cause to be my tensioning device. I have a 2-1/2" square tube sliding inside a 3" square tube controlled by a screw bolt. There is quite a bit of play inside the 3" tube because the inside dimension is actually 2-5/8", leaving 1/8" of space. When I applied more tension it kind of tilted the inside tube, if you can understand. Any ideas on how to firm up the play in the tube and still allow it to slide? I think I'm onto something though...thanks!

[fishpharmer]

bunst, glad to hear your making progress.  Could you put a brass shim of some sort in the space?  Or make adjustment to compensate for the xtra play?  I have seen homemade shims in someones gallery.  Might search "shim"?

Keep up the good work.

[slowzuki]

Also not to be ignored, although your tires should help, on mills with no spring component in the tensioner, as you cut wood the blade heats up and gets longer reducing the tension.

Lube/water helps cool it too.

The last time I was cutting the long fibre buildup folded over the gullet was my problem.  It would rub in the cut and heat up and drive me crazy.  It seemed to be from cutting certain logs that had layed out too long.

[Fla._Deadheader]

Fish has the cure. I would take a piece of steel, just a tad shy of the correct thickness, and pass it through the tube, on the BACK side of the wheel stress side. (Hope that makes sense). bend over both ends, so the shim can't sneak out, and grease with gun grease. Wipe off any excess.

  This way, when you tension the band, the pressure is on the area that does NOT have the shim. It allows a much longer area to guide the adjustment, rather than on the shim side.

[moonhill]

Both Cedar and Pine will clog the gullet and cause a dive.  A good sharp band usually fixes this though.  When cutting Pine in the spring I see a bigger problem with the strings.

Jason, is your mill very similar to bunst's mill?   

Tim

[bd354]

   I've seen worn out hack saw blades used for shims.

[Tom]

These band mill blades make pretty good shims too.

[customsawyer]

Tom beat me to it. ;D

[bandmiller2]

Bunst,your tube within a tube problem drill one or two holes in the outside tube weld on nuts have hand screws loosen to adjust ,then tighten to use.Frank C.

[ladylake]

 Good one Frank, maybe put a little shim in there anyway.    Steve

[mrcaptainbob]

In reply #30, there was discussion of blade tension using a micrometer. Jason, have you had a chance to check that? So far I've read of four ways of checking blade tension: 1. tighten until wobble disappears, then add another full turn, 2. clamp a micrometer to the blade a tighten to a reading (what's a typical dimension on that?), 3. check the blade deflection (how much for a given length?), and 4. 25-35 ft. lb's of torque on the bolt tensioner.