Homemade Dimensional Sawmill

[Renze]

When you prepare the pieces for welding (and you will weld-it's more economical and faster to build, not to mention stronger, more about welding later) angle is the surefire way to go for a novice.

For a novice welder that hasnt much experience of how steel structures warp due to heat stress from welding, i wouldnt recommend a trussed structure.
I have worked at a company that made trussed radio masts from round stock, and we allways used a jig to clamp it in tight. No way a truss this long, is going to be straighter than a large single hot rolled square tube... The square tube will also better withstand the torque on it from the offset weight of the saw head....



though i do agree on this point:

If it was me designing this rig, I would consider having the carriage rollers ride on the toe of angles instead of on the flats of square tube.
...If you did this, then you wouldn't need to be as concerned about sawdust accumulating on the horizontal surfaces, since the horizontal surfaces would be 2 or 3 inches(depending on what size angle you use) from the carriage wheels.

 

[Jeremy Maso]

You can always use locking fasteners or a locking compound to secure if welding is a problem.

Yep, we were planning on using locking fasteners.

Square tubing was recommended because of the better strength of a square tube compared to the same amount of metal in an angle.

Jeremy,
I don't want to labor the point past it's due, but you're right-square tube is a better choice , as a stand alone piece of structure, than the equivalent weight in angle.
However, there are a few things for you to consider here:
1) From the illustration you linked, the tube is not being used as a stand-alone structure. It is being used in a trussed structure, where the loads are primarily in one (the vertical) axis, meaning that you could use angle.
Consider, if you will, a radio tower. Very strong, trussed structure. Not much, if any, tube to be found there. Lots of angle

When you prepare the pieces for welding (and you will weld-it's more economical and faster to build, not to mention stronger, more about welding later) angle is the surefire way to go for a novice.

2) All steel sections-tube, angle, I-beam etc- have mill tolerances that allow a considerable amount of dimensional deviation, twisting and bending. You'll undoubtedly encounter this when you're assembling a track that's twenty(?) some feet in length.
Tube, precisely because of it's multiaxial strength, will be much harder to deal with, in terms of rectifying these deviations, than angle.

3) As I mention in my first post, a wheel riding on the toe of an angle, will be two or three inches from the sawdust accumulating on the perpendicular flange, making the clumps of sawdust almost of no effect in terms of accurate, smooth carriage travel.
Compare this with the problem that you acknowledge it will present with tube...

4) About welding your carriage: I understand your concern with adjustability in your carriage. Adjustability is an absolute must, but it should be at controllable points rather than spread over the entire carriage assembly, which is exactly what you'll have with all of those sloppy bolted connections, even if the bolts remain tight.
You need to know that once you align the carriage with the track(using controlled adjustment points/procedures), the entire carriage will remain in alignment with itself,even if you've had slight dimensional screw-ups in welding the carriage together. Once you've established this carriage/track alignment, you can align the saw blade with reasonable confidence that you're building on a solid foundation.

5) About "welding" itself:
Don't be intimidated by the thought of welding. Making acceptable welds (for your purposes) is something that you should be able to master in just a few hours.
It's a valuable skill to build upon, and once you've become more aquainted with it, you'll be able to expand the possibilities of what you can build/design yourself.
Your not building a suspension bridge, a pipeline, or even a radio tower. It's a sawmill, with very simple joint/welding requirements that will be so much stronger and dimensionally stable than bolting, with less effort in the long run.
It could...no, it will ultimately make the difference in whether or not this sawmill will work or be a source of frustration.

I'm trying to help you out.
I've been building and designing steel structures with mechanical interfaces for almost thirty years, so I'm not just guessing about this.

Good luck with your sawmill, and when that works (it will), good luck with the future.

Thanks for the advice! In addition to your points on square tube someone on woodweb also pointed out that the faces of the tube are too thin and will easily be weakened. With angle the thickness can be doubled to strengthen each face with the same weight as square tube. So it looks like angle is indeed the best to use here!

Your project sounds interesting, especially being a former sawmill owner and a senior designer at an engineering company that specializes in the forest products industry. We design sawmills, chipmills, mdf/hdf plants, plywood mills & so forth.

Here are some notes;

1. Mount wipers in front and behind each wheel to push away sawdust. You can even make each one a double wiper. A piece of UHMW plastic cut o fit within 1/16 to 1/32" of the track for the inner, and out in front of that say an inch or so a brush. This way you can really take care or getting the sawdust off the track. Low pressure air can be used in lieu of this or as an added feature. The circle saw mill I owned had wipers either side of the carriage wheels. The wipers should be made such that they push sawdust and debris so that it can drop totally out of the way and not build up in any way to fall back on the track(s).

2. The rollers do not have to be made but can be purchased commercially. Both the flat type and the V rollers are readily available. They can be either with a threaded stud or with a bore hole for mounting on your own shaft or stud. McGill is one bearing manufacturer that makes these. Just google "cam rollers" and a host of providers will pop up.

3. One way, a traditional method, to mount wheels, is based on the following theory. Since metal carriages contract and expand with temperature changes (delta t) one set of wheels is the "V" type and the other set(s) is the flat type. This anchors (more or less) a part of the carriage assembly, while the flat rollers allow expansion in that direction. Studded type shown in photos.



4. For guiding any components or assemblies, the thomson ball bushings and hardened shafts are very good. The shafts are case hardened and come in a variety of sizes, as do the different configurations (pillow block type, cartridge type, flange mounted type) of linear ball bushing bearings. http://www.danahermotion.com/website...r_bearings.php Complete downloadable catalogs are readily available.

Frank Jennings
Senior Designer
Mid-South Engineering Company
mseco.com

Thanks for the information! I'll put some basic wipers on the next design, and I'm going to use V-groove rollers on top and cam rollers on the sides and bottom.

Quote:
Originally Posted by towmotor View Post
When you prepare the pieces for welding (and you will weld-it's more economical and faster to build, not to mention stronger, more about welding later) angle is the surefire way to go for a novice.

For a novice welder that hasnt much experience of how steel structures warp due to heat stress from welding, i wouldnt recommend a trussed structure.
I have worked at a company that made trussed radio masts from round stock, and we allways used a jig to clamp it in tight. No way a truss this long, is going to be straighter than a large single hot rolled square tube... The square tube will also better withstand the torque on it from the offset weight of the saw head....

though i do agree on this point:
Quote:
Originally Posted by towmotor View Post
If it was me designing this rig, I would consider having the carriage rollers ride on the toe of angles instead of on the flats of square tube.
...If you did this, then you wouldn't need to be as concerned about sawdust accumulating on the horizontal surfaces, since the horizontal surfaces would be 2 or 3 inches(depending on what size angle you use) from the carriage wheels.

A good point about the torque, since most other dimensional sawmills that use space frames have the weight more balanced on top of it.

 

[Renze]

A good point about the torque, since most other dimensional sawmills that use space frames have the weight more balanced on top of it.

Dont most sawmill spaceframes use eiter round or square tubing as main runners, for the twist resistance ? I think it would make the blade wobble around the spaceframe axis... But as (yet another) engineer by profession, i'm just a purist and my home built stuff is allways overbuilt and overengineered so i dont get many projects accomplished... As you can see in the thread of the hay trailer build, i just have something with construction with tube

Whatever type of spaceframe you're going to weld, use lots of clamps to hold it down to a level surface, and weld randomly all over the structure, and certainly not the left side first and then the right side. As soon as you're finished with the left side, it will warp hollow on the left side (because of welding the crossbars on one side of the main runners) which wont warp back when putting the same heat (=shrink, tension) in the other side. Allways weld in random mirrored patterns.

 

[towmotor]

For a novice welder that hasnt much experience of how steel structures warp due to heat stress from welding, i wouldnt recommend a trussed structure.

Minor clarification:
Renzo, his drawing indicates a plan to use a trussed structure for the "space frame" (I've been calling it a "track"), no matter what.

 

[Renze]

Minor clarification:
Renzo, his drawing indicates a plan to use a trussed structure for the "space frame" (I've been calling it a "track"), no matter what.

I gave him an advice based on his initial plan. Its a free and honest advice from a guy who has welded a lot of space frames in various applications, 50 meter high antenna masts, commercial trailer frames, and also monotube frames in steered lowboy semitrailers, heavy duty saw jigs etcetera..
I dont know where you're coming from, nor where you're heading to, but regarding your needless "clarification" I assure you that I dont feel offended if the guy rejects my advice based on his personal evaluation, and follows his own ideas. Because i usually do the same unless you can convince me otherwise.

By proposing my ideas, I am not trying to offend his idea, nor yours, just trying to help him, just like you.

 

[Renze]

Will the current design of the rollers/bearings work? Will they have trouble going over sawdust that gets on the track? Are they strong enough to hold the saws and everything(250-300 pounds)? Is it going to be too hard to build the cage to get them to fit on the space frame tightly so it doesn't wobble around and make bad cuts?

I am also working on a band saw mill design, but i decided to use the round tubes i had in mind for frame rails, for the grader blade and buy square tubes for the sawmill because its much easier to weld crossbars to it, and align the tracks on them, than on those round tubes i have.

My thought was, using steel V groove wheels on one side (the carrying side) and then use small wheelbarrow tires on the other end, mount them when they're flat, then inflate them so they push very tight against the steel. That will take out all slop of the entire roller setup... I would do this on the underside, so the V groove wheels carry the weight, but the rubber wheels make sure the saw head cant wobble off its tracks due to its high center of gravity... Just an idea

 

[towmotor]

By proposing my ideas, I am not trying to offend his idea, nor yours, just trying to help him, just like you.

No offense taken. I do feel silly at having (mistakenly) called you "Renzo" , I shoulda' looked a bit more carefully at your screen name before posting.

You do bring up an excellent point-one that I had not taken into account. The weld distortion issue is quite real.
Like you, I've been working with steel for so long that I took this bit for granted.
That's not to say that I feel any less convinced that Jeremy's sawmill frame should (and eventually will ) be welded.

In that case, Jeremy, you should try to enlist an afternoon of help in laying out and welding your space frame (once you decide that welding is the way to go )

 

[Renze]

Towmotor, weld distortion is something that experienced people are so used to that the working technique becomes their second nature. They often forget what will happen if a newbie starts heavy welding from one end: There will be so much tension in a frame that the tacks on the other end will come loose.
At my former employer, we welded the crossbars of trailer frames in pairs of two at a maximum. Best practice was to get two guys welding at each side, running parallel.
If welding 5 by 5, the frame would come back from the galvanising, in an S shape.

 

[Q-Saw]

Jeremy,

Have you tried the Forestry Forum to see if anyone has made one of these types of mills? I know many folks there have made their own band sawmills, but I'm not sure about the Mobile Dimension (circle saw) style.

http://www.forestryforum.com/

My sawmill has brass scrapers in front of the carriage rollers (rolling on angle iron with the angle up - like the letter A). But I've considered replacing them with Lexan, or UHMW scrapers. The sawdust will still collect on the tracks (even with the scrapers), and will pack down and stick to the track (this is particularly bad with resinous woods like white pine). I brush occasionally, and coat liberally at the end of each day with WD40 or fuel oil. The caked on sawdust doesn't seem to affect performance terribly - remember, you're making rough lumber. I have considered installing felt wipers between the scrapers and the wheels to continuously apply a thin coat of oil to the track. I've seen this done and it solves the caking problem.

I would certainly stay away from skate wheels. They probably won't have the needed load capacity, and I would be concerned that they might have enough "give" due to the rubber composition that they may allow the saw to bind up or miscut - this could be dangerous.

Good Luck!

Marty

Portable Sawmill in Michigan

 

[KYErik]

Here's my home built band sawmill I did a few years ago- http://www.tractorbynet.com/forums/build-yourself/74963-home-built-bandsaw-mill.html I used the v groove wheels on the side that the sawdust exits and flat wheels on the "clean" side. I used a 7.5 hp electric motor to drive the band.