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Author Topic: Dave's Bandsaw Mill  (Read 4352 times)

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Offline northdesign

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Dave's Bandsaw Mill
« on: November 30, 2016, 11:42:33 PM »
First wanted to say thanks to everyone on this board for providing so much insight into your experiences building mills and trying different designs. Cool to see all of the creative solutions out there and learning.

I'm a designer by trade and hobbyist woodworker. I'm going to take on a mill build and have been studying different designs for a while now. I like to plan stuff out and will research this to death so getting everyones advice will hopefully keep my project moving.

My motivation for building a saw vs buying is mainly for the satisfaction of going through the process and learning, and maybe saving a little money, but I want to build it right. Secondarily looking to improve my welding and fabrication skills.

After a couple weeks of late nights on the internet, here's where I'm heading. Looking for insight on where my plans are flawed.

-36" x 15' log capacity
-18.75" belted sheaves (or larger solid steel band wheels if I can find a decent deal)
-1 1/4" blade
-Acme screws and an electric motor to raise and lower the head
-I already have a nice 25HP Kohler Command engine with electric start off of a retired zero turn mower
-Going to start with a manual feed and maybe add power feed later
-Going to plan so the mill can go mobile eventually
-Will mainly be cutting ash, oak, walnut, maple and cherry

Here are my main questions for ya'll.

1. Do the 18.75" pulleys from Surplus Center work well? Are they balanced well enough? Or should I spend the extra cash and buy actual bandmill wheels from Cooks or another supplier? Are the 18.75" pulleys large enough to handle the size log I'm interested in cutting? Most of what I'll be cutting will be closer to 24" but would like to have the capacity for bigger stuff. I have access to a 50hp Kubota tractor to move logs.

2. Took me a while to figure out the basic design requirements to get the wheels aligned and also to tension the blade properly. I've settled on a drive and idler design similar to the way Cooks mills are set up and have modeled what I'm thinking in CAD.



Any experience with this set up? Seems like a smart design where the wheel can be adjusted in the XY and Z axis to fine tune alignment. I have decent cutting and welding tools and think I can fabricate this without much fuss. Biggest question I have is related to the spring and how much tension/strength it should have. Thinking a 800-900lb spring would do it? I'll buy the springs first and adjust the dimension in the design accordingly but this seems like the area with potentially the most trial and error.





3. Finally, looking for some advice on my lifting design. Thinking about nesting the saw head tubes over the front posts of a 4 post carriage. What do I need to consider to keep the tolerances tight and eliminate any possibility of it binding? Do you try to find the center of gravity for the head before welding the sliding tube on? Seems like too much weight to the front or back would cause binding on the posts. Or should I consider using 4 acme screws instead of 2 to distribute the load?

Thanks for everyones help! Looking forward to documenting my build here.

David


Offline ljohnsaw

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Re: Dave's Bandsaw Mill
« Reply #1 on: December 01, 2016, 12:13:17 AM »
Nice drawing!  Welcome to the Forum.
Just some items I see:

Looks like you have log bunks every 2 feet.  I made mine with cross pieces every 4 feet and my bunks are moveable.  I have 4 bunks now on 22 feet of track and that works quite well.  I plan to make 1 or 2 more when I grow my track to 60+ feet so I can do some long beams for my cabin.

The pillow block set up you have shown - I'd space the bearings as far apart as possible.  There is going to be a LOT of force on those.  What diameter axles will you be using?  Your tension set up, the hinge - make that as robust as possible.  There will be a LOT of side force on that hinge.  I opted for a sliding tube arrangement.  I think you could do it that way as well still using the spring.  I used an Acme thread from a car jack for my tension setup.

Running 1.25" blade (what thickness?), I'd look for larger wheels if you can find them.  The smaller the wheels, the more quickly you fatigue the blade and possibly have a break.

I used car hubs and donut spare tires for my setup.  The tire provides the "spring" in my tension setup.  The hub mounts I made are adjustable to set the toe-in/out.  Blade guides take care of the blade angle.  My tire diameter is around 22 or 23".  I run a 184" band and I have a cut capacity around 32-34".  Biggest cut so far was 26" in dry cedar - tough going with 18hp.  Did some 24" fresh pine and was ok with a sharp blade.
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SkyTrak 9038, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 38" cut Bandmill up to 54' - using it all to build a timber frame cabin.

Offline northdesign

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Re: Dave's Bandsaw Mill
« Reply #2 on: December 01, 2016, 12:49:23 AM »
Thanks ljohnsaw.

=Running 1.25" blade (what thickness?)

Looking for advice from the forum on blade thickness for this setup.

What diameter axles will you be using? 

Was planning on 1 7/16" shaft thickness since that's what those pulleys will accommodate. Is that enough to carry the loads? I think I've seen some mills where they have a 2 inch shaft milled down on one end to fit the pulley. I'm assuming it let's them run a bigger more robust bearing. Based on occasional use, I'm interested to know how well the smaller shaft diameter and smaller bearing will hold up. Related, I noticed huge cost variations for pillow block bearings. Seems the heavy cycle/duty bearings can run as much as $200 each! How much of a difference does it make? Can anyone recommend the best quality/value pillow block bearing?


Offline carykong

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Re: Dave's Bandsaw Mill
« Reply #3 on: December 01, 2016, 01:19:09 AM »
15 foot log capacity? Go ,at least, 16 feet.

Offline fishfighter

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Re: Dave's Bandsaw Mill
« Reply #4 on: December 01, 2016, 04:55:54 AM »
15' and you will be sorry. Have at least room to saw a 16'6" log. Welcome aboard and looking forward to your build.

Offline ozarkgem

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Re: Dave's Bandsaw Mill
« Reply #5 on: December 01, 2016, 05:16:45 AM »
To saw a 16' log on my mill I have to place the log perfect. Give your self some extra room in the length department.  Not much of a fan of the hinge system. Think about it, you use a 1 7/16 shaft for the wheels because of the stress and then go with a shorter smaller shaft for the hinge that has the same stress on it. I prefer something more robust.
I have Surplus center pulleys on mine. Work good. On my mill I found that loose belts on the wheels cause a vibration so I went back to the B56 belts. WM seems to work fine with B57 belts but mine doesn't. Don't know why.
Mighty Mite Band Mill, Case Backhoe, 763 Bobcat, Ford 3400 w/FEL , 1962 Ford 4000, Int dump truck, Clark forklift, lots of trailers. Stihl 046 Magnum, 029 Stihl. complete machine shop to keep everything going.

Offline bandmiller2

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Re: Dave's Bandsaw Mill
« Reply #6 on: December 01, 2016, 07:24:20 AM »
Welcome Dave, no reason you can't build a good functional band mill. First theirs a lot of half truths bantied about most originated from manufactures that want you to believe their mill is ice cream and the next guys is puppy poo. Band wheels 18.75"/ 19" will work just fine, is bigger better, yup but not all that much. Will surplus center pulleys work as well as purpose made, not really, but their not five times better. Many folks even some here will keep parroting these old beliefs. I built my band mill before I even knew about the forums, I looked at many mills and took a little from each  a lot my own design. My mill used the double hinge design and its worked well for about 16 years. Idle wheel pillow blocks are original drive end I just had to replace. Build everything heavier than you think and make everything adjustable ask if your not sure. Frank C.
A man armed with common sense is packing a big piece

Offline Den-Den

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Re: Dave's Bandsaw Mill
« Reply #7 on: December 01, 2016, 08:25:47 AM »
Most of your questions have been addressed.  On the spring rating - I suggest that you plan on having 1000 - 1500 lb of force on the spring.  On the acme rods powered with an electric motor - this is how my mill is set up, it is not the fastest design but is very accurate and repeatable.  I put a home brew set works on mine and love it.
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Offline D6c

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Re: Dave's Bandsaw Mill
« Reply #8 on: December 01, 2016, 09:25:52 AM »
On your power unit I would consider mounting an electric clutch on the crank shaft (similar to what they put on zero turn mowers).  That way you don't have to design any belt tightening mechanism.....just a switch to engage the blade.

I'm assuming your up/down feed will use and elec. motor drive so you'll have power available for the clutch anyway.

If there was room on my LT40 for an elec. clutch I might change it over and do away with the belt/brake arrangement.

Online pineywoods

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Re: Dave's Bandsaw Mill
« Reply #9 on: December 01, 2016, 10:20:38 AM »
My 2 cents...The hinge and spring tensioner setup will probably be a continuous headache. Go with a slider type adjustment and use the hand pump and ram off a cheap floor jack. Drill and tap a hole and screw in a 0-3000 psi pressure gauge. Pics in arnold113's gallery. The 19 inch pulleys with B57 belts have worked fine on woodmizers for nearly 40 years. For up-down, chains running off a worm drive gearbox are about as bullet-proof as it gets. Lends itself well to setworks later. Plan on power feed, even if you don't build it in initially. Don't skimp on the blade guide rollers. They need to be adjustable in up-down and left-right directions as well as in-out. If you don't know about surplus center, check out their web site for stuff like chains, sprockets, motors, etc. 
Blade length...Check with your blade supplier and design to use one of their standard lengths. Yes, most will make custom length blades, but why make things more complex when you don't have to. Also think about blade sharpening, blades won't last nearly as long as you think..
1995 Wood Mizer LT 40, Liquid cooled kawasaki,homebuilt hydraulics. Homebuilt solar dry kiln.  Woodmaster 718 planner, Kubota M4700 with homemade forks and winch, stihl  028, 029, Ms390
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Offline bedway

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Re: Dave's Bandsaw Mill
« Reply #10 on: December 01, 2016, 10:45:30 AM »
I think the best help I can give you is to suggest you go to my gallery and review my build. Any questions feel free to ask.

Offline ReinkeFandS

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Re: Dave's Bandsaw Mill
« Reply #11 on: December 01, 2016, 11:54:04 AM »
Just my 2c, but the bunks on my mill are exactly 4ft, and I have had people bring walnut and cherry logs 3'6"-3'11" wanting to salvage 3ft boards for a woodworking projects or whatever. If I had at least one bunk at 3ft near the front of the mill it would have made those projects way easier.
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Offline Joe Hillmann

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Re: Dave's Bandsaw Mill
« Reply #12 on: December 01, 2016, 01:30:13 PM »
I think your bunks are too close together.  Most logs are not round and being able to drop a crook or knot between two bunks rather than sitting on a bunk can make it easier to roll a log into the position you want to start cutting.

I don't know if your tension adjustment will be strong enough. I have heard  numbers of wanting 15,000 to 25,000 psi of tension on the blade.  If you are running 1 1/4 blades that are .05 thick and wanted 15,000 psi you would need to put 750 pounds of pull on the blade below the wheels and 750 pounds of pull on the blade above the wheel.  So you would want 1,400 pounds of pressure on your tensioning bolt to get to the lower end of what is recommended.  There are also some companies that recommend doing a flutter test and run with as little pressure as you can without the blade fluttering.  So the pressure possibly could be less if that works for you.  On my mill I personally found that the tighter the blade the better the cut and the longer a blade can go between sharpening.


You plan to use a 1 7/16 shaft.  That MAY be strong enough, keep the front bearing as close to the wheel as you can get.  Just to compare that size bearing to something that is in common use, a 3500 pound trailer axle uses 1 3/8 and 1 1/16 inch bearings and each side has to support 1750 pounds plus the extra force of bouncing over bumps so in reality can probably support several times that weight at least for short amounts of time.

Also if you are ordering from surplus center you may want to order a spare pulley, shaft and bearings because I don't think they always have those items in stock and if you have one of them break and have to order parts from somewhere else a pulley of that size will be much more expensive anywhere other than surplus center.


If you want to be able to cut a 36 inch log that doesn't mean you need to have a 36 inch throat between the blade guides.  To cut a 36 inch log you would be able to cut it if you had 26 in opening between the guides and the blade being able to be raised to at least 31 inches.


Offline Kbeitz

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Re: Dave's Bandsaw Mill
« Reply #13 on: December 01, 2016, 06:06:00 PM »
Most of your questions have been addressed.  On the spring rating - I suggest that you plan on having 1000 - 1500 lb of force on the spring.  On the acme rods powered with an electric motor - this is how my mill is set up, it is not the fastest design but is very accurate and repeatable.  I put a home brew set works on mine and love it.

Do you have anything posted here about your home brew set works?
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Offline bandmiller2

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Re: Dave's Bandsaw Mill
« Reply #14 on: December 01, 2016, 07:51:02 PM »
Dave I'am not a believer in a lot of tension on bands, it leads to early breakage. With compression springs you can nest one or two inside each other for more tension. Over tensioning is a crutch to try and force a straight cut, its sharp and proper set that does that. Frank C.
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Offline KirkD

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Re: Dave's Bandsaw Mill
« Reply #15 on: December 02, 2016, 09:17:52 PM »
Most of your questions have been addressed.  On the spring rating - I suggest that you plan on having 1000 - 1500 lb of force on the spring.  On the acme rods powered with an electric motor - this is how my mill is set up, it is not the fastest design but is very accurate and repeatable.  I put a home brew set works on mine and love it.

Do you have anything posted here about your home brew set works?

KB, I think I found it unless he has more info for us.

http://www.forestryforum.com/board/index.php/topic,81708.msg1244796.html#msg1244796
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Offline barbender

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Re: Dave's Bandsaw Mill
« Reply #16 on: December 02, 2016, 11:23:53 PM »
Northdesign, two things I would stay away from- 1. I don't like the hinge tensioner, it looks to me like as you tighten the blade, the bandwheel will climb vertically. It will make it hard to keep consistent down pressure on your blade guides. 2. From my personal experience with the steel tube in a steel tube, don't do it. There is a tendency to bind, water can get in and freeze, if grit gets in there it binds, if it rusts, it binds. I would use a vertical steel tube with nylon or UHMW slide pads sliding on it.
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Re: Dave's Bandsaw Mill
« Reply #17 on: December 03, 2016, 08:06:53 AM »
Northdesign, two things I would stay away from- 1. I don't like the hinge tensioner, it looks to me like as you tighten the blade, the bandwheel will climb vertically. It will make it hard to keep consistent down pressure on your blade guides. 2. From my personal experience with the steel tube in a steel tube, don't do it. There is a tendency to bind, water can get in and freeze, if grit gets in there it binds, if it rusts, it binds. I would use a vertical steel tube with nylon or UHMW slide pads sliding on it.
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Considering post build alignment, wear and tear...generally, adjustments should be linear in the axis of their action, so as not to provide a rotational or tangential component.  Trying to align or fine tune is much easier when the adjustment has only a single component of movement relative to the mechanism being adjusted.
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Offline scully

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Re: Dave's Bandsaw Mill
« Reply #18 on: December 03, 2016, 08:18:00 AM »
Have you considered using a porta-power  type set up for tension ?  I'm no xpert but  spring tension would seem to react to blade entry into the log as well as feed rates .  Nice CAD work !
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Offline ozarkgem

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Re: Dave's Bandsaw Mill
« Reply #19 on: December 03, 2016, 05:08:42 PM »
Considering post build alignment, wear and tear...generally, adjustments should be linear in the axis of their action, so as not to provide a rotational or tangential component.  Trying to align or fine tune is much easier when the adjustment has only a single component of movement relative to the mechanism being adjusted


Man that is deep. I will have to think about that. :D
Mighty Mite Band Mill, Case Backhoe, 763 Bobcat, Ford 3400 w/FEL , 1962 Ford 4000, Int dump truck, Clark forklift, lots of trailers. Stihl 046 Magnum, 029 Stihl. complete machine shop to keep everything going.


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