Tensioning method for homemade bandsaw mill

matt_K98 · May 08, 2016, 04:00:23 PM

Hello,

For the past few months I've been searching around for a concept for a bandsaw mill, I finally settled on a design I liked and started to build it. I am almost finished building it now but I have a few issues and concerns that I thought I should ask,

The main issue I am having is setting up the idle side wheel system, for the wheel system I used 3" square tubing that slides into a 3.5" square tube that's part of the main frame, the 3" tubing doesn't fit very snug and there is a lot of play in it, probably a 1/4", I am having a very hard time getting everything leveled out.

The other issue I am having is trying to setup a way to tension the band, I want to go with something simple but effective, I was leaning towards a bolt and spring tensioner but I don't know if it will work, or how to build it.

I'm hoping someone with more experience could help me, thanks.

Here are a few pictures of the sawmill.

Den-Den · May 08, 2016, 05:56:14 PM

You might weld some thin stock to 2 sides of the small square tube; this would reduce the gap.

pineywoods · May 08, 2016, 06:13:43 PM

The best tensioner on a home-built mill was thunk up by arnold113. Pump and ram off a cheap hydraulic floor jack. Drill and tap a hole in the base and screw a 0-3000 psi pressure gauge in.

Kbeitz · May 08, 2016, 06:16:06 PM

I did this to both sides. You can also see a slack adjusting screw or tracking bolt.

Ox · May 08, 2016, 07:05:33 PM

Drill some holes for bolts in the bigger tubing. Weld a nut over the hole to fit the bolt. Put the bolt through the nut until it just touches the smaller tube when it's in the bigger tube. Put another nut on the bolt first so you can double nut it to lock it in position. Do this for one side and the top. This will push the inner tube over to one side and keep it down at the same time. You should be able to get all the slack out with a little tinkering. Cheap, easy, effective!

The other ideas are good ones too and will also work. I'm just trying to give another option is all.

Magicman · May 08, 2016, 07:22:37 PM

I will yield to the sawmill builders but Welcome to the Forestry Forum, matt_K98. Adding your location to your profile will help with answering questions.

matt_K98 · May 08, 2016, 07:40:34 PM

Thanks everyone for the help, I think I will try to weld some thin steel onto the tube to remove the slack. I will update after I get a chance to try.

Ljohnsaw · May 08, 2016, 08:38:28 PM

Looking good!

One other option is to take some UHMW or Teflon sheet and stick some thin pieces in between the tubes. It will take up some slack and also provide some slick-ness for ease of adjusting. UHMW is what the plastic cutting boards are sometimes made from. You don't need to have it perfect. Once you tension up your band, it will cock in the outer tube and be snug - no wobble.

For tension, stay away from a standard screw/bolt. You will wear them out and they also have a lot of friction. Use a ACME thread - get one from a scissor jack along with the ACME nut. Buy an old jack at the thrift store. Find a VERY stiff compression spring (like a valve spring) and put it in the appropriate place on the screw. However, I did not add a spring. I figure the spring in the tire is enough.

As MM said, you need to be able to adjust the toe-in / -out on each tire to get it to track well. You need it to track where you want BEFORE you put your blade guides in place. The blade guides are ONLY for preventing the blade from going back as you are cutting (and providing about ¼"-½" of down pressure). Even then, the blade should not be pressing much on the backstop. The washer you have on there looks like a normal zinc washer. It will wear out pretty fast. Speaking from stubborn experience, get some Cook's guides and save yourself a lot of headache!

Magicman · May 08, 2016, 09:00:42 PM

ljohnsaw, I believe that some of your reply was directed toward "Picky2016" and his build. ;)

Ljohnsaw · May 08, 2016, 09:15:35 PM

Quote from: Magicman on May 08, 2016, 09:00:42 PM
ljohnsaw, I believe that some of your reply was directed toward "Picky2016" and his build. ;)

Oops, reading faster than my fingers can type, or is it my fingers are typing faster then my brain can think.. :-\

matt_K98 · May 08, 2016, 09:23:16 PM

Thanks for the tips @ljohnsaw, are ACME nuts common?, I know where I can find the ACME rods but I have never seen the nuts for the ACME rods.

Magicman · May 08, 2016, 10:06:37 PM

I believe that bronze Acme nuts would be best. Just do a Google Search.

arnold113 · May 09, 2016, 03:17:03 AM

I used a combo of two of the reply's. I used 4 pieces of UHMW inserted into the larger square tube and then drilled 4 holes on 2 sides of the larger tube, welded nuts over each of the holes and screwed in 1/2" bolts with a second nut on each. With the 8 bolts you can take up all the slack between the inner and outer tubes and have a slick surface for movement. You will have to take up all slack between the 2 tubes, to the extent of it being hard to move the outer tube by hand, or you will have all kinds of problems with your toe in/out adjustments. Don't ask me how I know this. The hyd jack ram with a pressure gauge will give you a easy way to tension your blade to the same point every time without guessing.
Lots of luck with your build and welcome to the FF.

Kbeitz · May 09, 2016, 04:28:57 AM

If you go back up and look at my picture you can see that i used the
slack to my advantage. The slack is what i use for my tracking.
The red arrow is pointing to the adjusting bolt. Works great.

ladylake · May 09, 2016, 07:16:57 AM

I'm not a fan of a hydraulic tensioner at all, no give plus loses tension fast if the blade heat up . I'd go with acme thread and a heavy spring, a valve spring is not near heavy enough. Should be able to find a heavy one a at a machine bone yard or maybe online. Steve

Wudman · May 09, 2016, 09:51:58 AM

Use the air pressure in your tires for the tensioning. I used 2 1/2 inch heavy tube inside of 3" tube for my mill. I put a 3/4 inch tensioning bolt that could move the 2 1/2 inch tube outward. I got it to where it needed to be and tightened and aligned. To remove blade, deflate tires. Install blade and re-inflate to 65 PSI.

Kbeitz · May 09, 2016, 10:40:06 AM

A big rubber donut and two big washers would make a good spring.
Something like a truck body donut off the frame should work.

Ljohnsaw · May 09, 2016, 10:42:22 AM

Quote from: matt_K98 on May 08, 2016, 09:23:16 PM
Thanks for the tips @ljohnsaw, are ACME nuts common?, I know where I can find the ACME rods but I have never seen the nuts for the ACME rods.

There will be one ACME nut in the jack.

In the foreground is the nut in its original bracket from the jack welded to the movable idle wheel mount. Further back is another part of the jack with the slip part of the jack that takes the pressure as you tighten it. It is welded to the frame of the head. The big silver handle is a locking bolt to tighten on to the shaft of the screw to keep it from loosening once set. Behind that is a large washer with a large nut welded to the end of the jack screw. I use a socket wrench to tighten. I suppose I could use a torque wrench to set it to a specific value. I "lubed" the ACME thread with anti-seize compound as it is out in the weather. Figured it would be better than grease as it doesn't attract sawdust as much.

Ox · May 09, 2016, 03:29:11 PM

That there tensioner is a thing of beauty. I love repurposed things.

Joe Hillmann · May 09, 2016, 10:10:42 PM

Quote from: Ox on May 08, 2016, 07:05:33 PM
Drill some holes for bolts in the bigger tubing. Weld a nut over the hole to fit the bolt. Put the bolt through the nut until it just touches the smaller tube when it's in the bigger tube. Put another nut on the bolt first so you can double nut it to lock it in position. Do this for one side and the top. This will push the inner tube over to one side and keep it down at the same time. You should be able to get all the slack out with a little tinkering. Cheap, easy, effective!

The other ideas are good ones too and will also work. I'm just trying to give another option is all.

This is what I did on mine. It it also allows for adjustment for wear.

pineywoods · May 10, 2016, 09:45:57 AM

To each his own, but once you run a mill with a hydraulic tensioner, you'll never go back to springs and screws.. The pressure gauge lets you see what the tension actually is, otherwise you're just guessing... :

ladylake · May 10, 2016, 12:22:04 PM

I'd never go to a hydraulic tensioner which has no give, soon as the blade heats up a little you lose tension. Or if I set up a hydraulic tensioner it would be pushing against a spring to take up the shock load. A spring has give and will keep the tension way better. My TK came with a pressure gauge on the spring setup. Steve

Ox · May 10, 2016, 01:28:00 PM

A hydraulic/spring setup sounds just about perfect, doesn't it? I have a hydraulic tensioner and monitor it closely. On a long, tough cut it'll sag a little. I just give it a small twist up then adjust accordingly afterwards. In normal milling it doesn't change much at all.

matt_K98 · May 10, 2016, 05:35:06 PM

So a little update,

I welded a 1/8" thick steel plate onto the side of the tube and then a very thin piece of scrap steel plate I had lying around for the top. It's a lot better than what it use to be, and i'm sure if I squeeze another plate on the other side it would fit even better.

I found a small scissor jack in my garage so I used a grinder and cut out the ACME rod and nuts, I also found a used compression spring for $5 at a local tractor supply store that I think will work.

I Had to put a new spool of wire in my welder and the wire feed decided to stop working, so I never got a chance to work on the tensioning system. Waiting for my buddy to get off work so I can borrow his welder.

If anyone is interested I can post some pictures of my progress so far.