Bandsaw Mill Design and Build

[Brackish]

Hi Everyone, 
This is my first post.

I have been poking around the site trying to gather information, I am interested in building a mill.

Im leaning towards:  

4 Post design with a 6 x 2 x 3/16" Main saw beam supporting 19" V belt pulleys with a telescoping tensioning setup.

2" square tube uprights telescoping in 2.5" square tube with ACME rod/bearing hoist. 

A blade length within the range of 150-225"

15-20 HP gas engine.

6"x 3" Log Bed or Frame With 1/4" angle upright to accept casters of saw carriage 20' Track

I will be milling for myself on my own property but may put an axle under it to move about.

I have added a few snapshots of where I am with a design drawing. 
Thanks , Mike



 

 

  

[Ljohnsaw]

Welcome aboard!  Looks like you did your research.  I think 6x3 for your main frame are a bit overkill unless you have a cheap source for that.  Be very careful how you attach your angle to the beams.  I weld-distorted mine a bit.  If I was doing it over, I would have figured out a way to bolt it with the ability to adjust.   (actually, just did...)  How big of wood are you cutting?  With the stoutness of your proposed frame, I'm guessing big so 20 hp would be way better than 15.  I'm running 18 hp and wish I had 25.

[fluidpowerpro]

If it will be on the ground or a fixed base, 6 x 3 is overkill, but if you can swing it, heavier is better.
If you ever plan to make it mobile, 6 x 3 is good. 
Not sure how long of logs you want to cut but with a 20' track you will struggle with a 16' log. I would go about 6' longer than your target length. That way you don't have to have the log positioned perfectly when your pushing the length limits.

[Brackish]

Hi Guys 
Thanks for the responses,
6 x 2 for the saw beam
6 x 3 for the bed
20' length is the length of the stock for 6 x 3 x 3/16 channel, I do want to cut 16' stock maybe I should consider changing the stock to something I can get in a 24' length.

I have done epoxy pour bar tops for a local bar as well as counter tops and other jobs.
in order to get a live edge on top of a 24" deep base cabinet as a countertop you need to have at least 25" to the shortest point of the contoured live edge measured from a straight edge on the back side of the slab. I have been buying slabs and realized in the process that in order to meet that measurement you need a pretty big log. Ive got the epoxy thing down so I think Id like to be able to accomplish that with this mill as well as make dimensional lumber for my own use.

I will consider the method of attaching the angle on the track.
Is the preferred direction for attaching the angle with one leg up as drawn or I see some people with the V facing up?

-Mike

[Ljohnsaw]

Is the preferred direction for attaching the angle with one leg up as drawn or I see some people with the V facing up?

I used 2x3x¼" angle with the 3" side up.  Running wheels on the narrow edge doesn't give sawdust a place to gather.  

My thought on attachment would be to bolt a plate on the side of the angle hanging down to bolt to the side of your 3x6.  With it being 3/16" thick you should be able to thread it, probably 2 bolts.  The ¼" angle would definitely allow for threading, and again, 2 bolts.  Probably do elongated holes in the plate for up/down adjustments.  Then, use washers under the 2" side of the angle to shim as needed.  This way, you avoid welding altogether and any distortion it would bring.  If painting, could have it disassembled to get all sides of the metal.

[fluidpowerpro]

I agree, narrow edge of the angle up. When I built my bed I used the same logic. 6 x 3 came in 20' lengths so that was how long my bed ended up. I often want to cut 16' dimensional lumber and I quickly realized it was too short. I have since added 4'. 
If your careful when welding you should be able to add length without warping. Clamp some heavy steel to each side and tack. Make sure each end is cut straight and when you bevel for welding, leave just a little material so you can butt them up to each other. That way there is no place for it to pull.
(I'm not an expert welder, but that worked for me) 
Also, don't weld the angle on until you have the mill on top so you can roll it down the bed. Just tack it lightly and then when you roll the mill on it you will see if the bed isn't quite true. If it isn't, you can shim the angle iron before you weld it permanently.

[fluidpowerpro]

I just noticed that you referenced 6 x 3 channel. I would use 6 x 3 rectangular tube, especially since you may put an axle under it.

[Brackish]

tube not channel my bad. 

[Hilltop366]

If you bolted or welded the angle to the side of the 3x6 so one part is sticking up above the 3x6 and one part sticking out the side (horizontal) it could be levelled independently from the 3x6 and give you a place to add a safety on the underside of the horizontal leg of the angle iron to prevent the saw carriage from tipping or jumping the tracks. 

[RAYAR]

 Welcome to the forum. A few thoughts on your build. You just need to use the front vertical tubes to guide your saw head. Using the back tubes could be a cause for some binding, it's not needed.

About your carriage wheels, have the wheels on one side of the carriage, probably the left side, so they have some sideways movement (clearance)  to be able to slide side to side on the axles to allow for any slight misalignment and avoid any binding as it rolls down the track. You will be using U groove wheels and at least 3" or more in diameter. On 1/4" angle legs, use 3/8" U groove.

For band blade length, use a standard blade length readily available. 158" is one common length. There are other lengths also. This makes buying blades readily available instead of having to custom order an uncommon length.

[Brackish]

You just need to use the front vertical tubes to guide your saw head. Using the back tubes could be a cause for some binding

I could see that being an issue.

About your carriage wheels, have the wheels on one side of the carriage, probably the left side, so they have some sideways movement (clearance)  to be able to slide side to side on the axles to allow for any slight misalignment and avoid any binding as it rolls down the track. You will be using U groove wheels and at least 3" or more in diameter. On 1/4" angle legs, use 3/8" U groove.

Would bolting the angle as suggested allow for proper alignment?
On 1/4" angle legs, use 3/8" U groove; Rodger that.

I will use a standard blade length, once the design is satisfactory I will figure what to take out of the middle of everything to arrive at a standard blade length.

In determining the width of the saw head at its minimum adjustment for blade tension how much slack should I allow in order to install and remove a blade?

Am I right in thinking I can estimate blade length by taking the distance center to center of the band wheels plus the circumference of one band wheel?

Thank You all
-Mike

[Ljohnsaw]

In determining the width of the saw head at its minimum adjustment for blade tension how much slack should I allow in order to install and remove a blade?

I have about ½" to ¾" adjustment.  More than enough.

Am I right in thinking I can estimate blade length by taking the distance center to center of the band wheels plus the circumference of one band wheel?

Yes

[Hilltop366]

Am I right in thinking I can estimate blade length by taking the distance center to center of the band wheels plus the circumference of one band wheel?

centre to centre x2 plus circumference?

Blade length, speed, and belt length calculator (there are others I just picked one)

https://www.blocklayer.com/band-saw-eng

[charles mann]

My thought on attachment would be to bolt a plate on the side of the angle hanging down to bolt to the side of your 3x6.  With it being 3/16" thick you should be able to thread it, probably 2 bolts.  The ¼" angle would definitely allow for threading, and again, 2 bolts.

If bolting the angle anyways, why bolt a plate to the side of the angle to them bolt it to the frame? Why not just bolt the angle to the frame? Its 1 less step, a lot less holes to drill and tap and less steel to buy. 
Granted my mill bed is 2x6x1/4" wall rec tubing and my 2x2 angle is 3/8", i still bolted it to the bed using 3/8" bolts and drill the holes in the angle with a 7/16" bit to allow for a lil bit of adjustment. 
But i also clamp my angle to the bed, flushing the back/vertical leg to the outside of the bed by butting the vert leg up against a 1/2"x2" flat bar off cut. Once flushed and clamped, i tack welded the angle on both sides and once the entire length was tacked up, i laid the holes out and drilled with a 1/8" bit for a pilot hole, through the angle and into the rec tubing. 
Then i cut the tacks off and proceeded with the drilling and tapping, then using the flat bar off cuts, flushed the angle again and tightened the bolts holding the angle down. 

[Hilltop366]

I believe I have seen some mills that just use a flat stock fastened to the side of the frame it does not give you a safety from tipping the saw head but it does make it easier for you to chose a harder steel for the rails.

[Ljohnsaw]

My thought was to use gravity to your benefit.  The bolts would only be doing light duty for placement but the shims (washers) or direct contact between the bottom of the angle and top of the 3x6 would be supporting the weight of the head.  Just a thought.  But, I suppose bolting through the top would work.  Just not a lot of meat in 3/16" to thread.

[fluidpowerpro]

I welded the angle to my bed and it worked out good. My bed was pretty straight so I only needed a few shims on one end. Whether you bolt it down or weld, you want lots of support between the angle and the bed. If there is too much distance between any shims, the angle will deflect and you will get bounce. I know you wouldn't think that would happen, but it will.

[charles mann]

3/16" thick material is the same on the side (6") as it is on the top (3"). If there is enough to possibly tap the side, there is enough to tap the top. Can always tack a 1/4"x3" flat bar to the top, drill and tap and bolt the angle to that plus the 3/16" of the rec tubing. 

I ended welding on some 1/2" thick flat bar to attach my linear rails to the vert posts of my carriage and to the bottom of the sawbeam/head, giving me 3/4" of meat to drill and tap into. It was probably (75% sure) over kill, but id rather have it and not need it than need and not have. 

[fluidpowerpro]

This sketch shows how I captured my

 mill head to the track to prevent it from falling off.
I welded a second angle iron to the side of the 3" track angle. I then bolted a bracket to the side of the mill structure that hooks around the other angle. If I need to take the mill off of the bed, I can remove the brackets.

[RAYAR]

the distance center to center of the band wheels X2 plus the circumference of one band wheel

Would bolting the angle as suggested allow for proper alignment? >> It would have to be perfect, otherwise, some binding will occur. Better to allow for slight discrepancies and have a smooth and easy rolling carriage.

In determining the width of the saw head at its minimum adjustment for blade tension how much slack should I allow in order to install and remove a blade? >> I would allow at least 1" either way in adjustment.

Also, allow enough length between carriage wheels to avoid the carriage getting too tippy front to back, especially when the saw head is raised quite high.

[charles mann]

Rayar, bolting allows for adjustment a lot easier than welding, which welding needs to be as perfect as can get.
So, unless everything was machined ground, nothing will truly be "PERFECT" with hot rolled/extruded mass produced material. 

Since, im betting most material we and mill manufacturers building these hm brew and factory built mills with is not truly perfect, being perfect is not on the table.

[RAYAR]

Rayar, bolting allows for adjustment a lot easier than welding, which welding needs to be as perfect as can get.
So, unless everything was machined ground, nothing will truly be "PERFECT" with hot rolled/extruded mass produced material.

Since, im betting most material we and mill manufacturers building these hm brew and factory built mills with is not truly perfect, being perfect is not on the table.

It's actually easy to tack weld the track angles straight and parallel to each other. The tack welds should only be about the size of bolts and spaced about 8" to 10" apart. That would keep the heat to a minimum. No adjustments should be needed.

[charles mann]

Then the alignment would have to be perfect as you said.

There isnt a right or wrong way of securing them other than aligned as best as the material will allow.
 Questionable language insinuation deleted by Admin. 

[Brackish]

Hi All
Regarding this talk about the "perfect"-ness of the track, how would that relate to the rest of the log bed. if the track is shimmed wouldn't the cross beams need to be shimmed perfectly too?
Are we more concerned with the tracks being parallel left and right to keep the casters equidistant so the casters don't bind or up and down so the thickness of the board being cut doesn't change?

I like theoretical perfectness but we are "rough sawing" right?

That said maybe bolting the angle to the frame is better simply because you can replace the angle?

How does support of the entire log bed play into this? Jack legs; poured footings below frost line bolted down?

How often do you need to adjust calibrate or tune the trueness of log bed as a whole? 

Do some mills rely solely on the strength and stiffness of the main beams to keep the shape? 

Could you have a mill only on trailer axles and tongue jack that stays true enough wherever you park it?(not my goal)

Thanks,
Mike

[Ljohnsaw]

My mill is long - 50' or so - and sits on 12 jacks.  Four per section (two at 16+', one at 8½' and two sets of 5' sections of angle connecting them).  I do mill a lot of big logs (26"-30") and a few monsters (Mill Reset) that are a lot of work on my manual mill.  My jacks, with ~4x6 pads, were sitting on scraps of wood perhaps 6x10.  The first monster log (20k lbs) sunk those in the ground.  I have reset my mill several times when a log slipped when loading or just rolled a little too friskily. :  I've bent my ¼" angle when dinging it with the forks.  Nothing that a little 12 lb sledge couldn't tap out.  Through it all, my 2x4x¼ frame has withstood it without any bending that I can detect.

My bunks are "registered" to the mill frame and are moveable.  Any bend in the frame will affect them.  I use the 12 jacks and sight down the rails to "level" it up.  A super stretched/tight string is not good enough.  Probably need to set up a laser and a sliding target on the track.  Not concerned with earth-level, just straight.  I'm actually running down hill to make pushing through the log a little easier.  Might seem counter intuitive but the only levelness I really work on is the up/down flatness.  If the track veers to the left or right a little (less than an inch), I don't see that affecting my final product.  That doesn't affect the thickness I'm cutting because it can't - so why fret it?  The left/right straightness only comes into play when the log width is at the max and prevents the head from traveling.