Assembling the HM 130 Max sawmill - tolerances

[Rene S]

In assembling the sawmill I struggled at times making everything perfect. Being a perfectionist, that bothered me, especially since the manual talks about getting things straight, square, and level.

But having nudged and tweaked different components multiple times and having been unable to achieve perfection, I had to figure out what mattered most and what mattered a little bit less. I was curious to see if others agree or if I am thinking about this the wrong way.

My guiding philosophy was to think about what deviations in saw head movement would affect the accuracy of the cut and by how much.

By the way, this is what I ended up living with.

The rails are nearly straight. Over six feet they are out about 1/16 of an inch. I worked on them for a while and realized I wasn't going to get it any better and it was probably close enough. The saw head moves smoothly, so it seems I am right. Bottom line, I figured very slight side to side movement shouldn't affect the accuracy of the cut. I have two sections of rail on each side and checked at the joint with a six foot level spanning them both.

The rails are nearly square. I couldn't do what the manual said about pulling the diagonal measurements because the log bunks were in the way. So I pulled a 3, 4, 5 triangle and used a framing square on the bunks. With the saw head all the way back at the beginning of the track, it looks like I am out of square around 1/4 inch. Of course, that is true if the saw head carriage is square. I figured that being out of square a little bit shouldn't matter if the rails are parallel to each other.

The distance between the rails is the required 37 inches plus or minus a 1/32. I fiddled with them for a while but here too I found myself bouncing back and forth between being a little too  this way and a little that way, so I settled for this. Since the carriage runs smoothly, I am guessing that I am good. Just like straightness and squareness, I am thinking this won't affect accuracy of cut since all deviations should be side to side. 

The bunks and rails are just about perfectly level. I got the bubble on the level between the hairs with even gaps on both sides. The leveling feet made this task fairly easy and adjustments held while others were made, so there wasn't that sense of bouncing back and forth between too much and too little. And this was a spec that I figured would matter a lot in accuracy of cut. I figured that having the saw head move up and down even a little (more than a 1/32) would affect the accuracy of cut. 

Similarly, I made sure the saw blade was parallel to the first bunk. I got within a 1/32 but nudged it even closer. Took a little time, but I figured this was another important spec regarding accuracy of cut. 

There are a couple of other specs, like the positioning of the blade guides and bearing. I got those real close and then found the adjustable blade guide was out of whack and got to go through them again.  

Closing thought: while this was a lot of work, Woodland Mills did a good job of designing and manufacturing the sawmill, so it felt "fair," meaning I wasn't struggling to achieve results that were impossible to achieve. Also, with their design and quality, it looks like I am going to get some very accurate cuts, which should make cutting with it very enjoyable.  

I'll be glad to hear any thoughts you all have on tolerances and accuracy of cut.

[btulloh]

Sounds good. You've Got a good approach and a good grasp of the important aspects. The rails and bunks are just hot roll mild steel so evenwith the milled top edge they are just going to be perfect without some prodding. Sounds like you've done that pretty well.  It'll require rechecking after a few hours and than occasionally as time goes on.

Making some spacers to get the string above the bunks will help with the diagonal checks and also to check to see that the bunks and rails are all in parallel planes. Having zero Twist in the rails and bunks is critical too, so checking across the rails and bunks with the level can determine this. Bubbles can be hard to judge minor variations but using winding sticks and sighting down the length can be a cheap, easy way to confirm twist. Digital levels can be handy too.  It's not as critical that everything is level, but co-planar is important. 

When everything is perfect with the mill the logs are going to be the variable, but that's what sawing lumber is all about.  If the mill is right you just have to deal with the logs when you have an issue.  Things like bark or sawdust on the bunk, dull blades, belt tension, pitch buildup will always have to monitored. But that's what makes this fun and interesting!

You've got this!  Let us no when you make your first sawdust.  8)

[Magicman]

Similarly, I made sure the saw blade was parallel to the first bunk. I got within a 1/32 but nudged it even closer. Took a little time, but I figured this was another important spec regarding accuracy of cut.

I would be interested it checking and insuring the blade height above each bed rail.  That is what will insure the accuracy of your lumber, not just the first.

[alecs]

Rene,
Sounds like you are not using the trailer, which for me was what gave the most trouble in terms of getting everything lined up.  I cut 2x4s to the 37" dimension and clamped the rails to them using pipe clamps.  After setting things up with the trailer, things got tweaked and I was out to about 37 1/16" in spots.  Woodland Tech Support said that would be fine.  Sounds like you have got it dialed in very well!

You may want to check that the saw carriage posts are perpendicular to the rails, as this will help make the blade parallel to the wood while it is on the bunks.  I measured from the blade to each bunk with a speed square set on the bunk to make sure things were consistent.

I agree with you that the design and manuals were pretty well thought out.  Good luck!

[Rene S]

Similarly, I made sure the saw blade was parallel to the first bunk. I got within a 1/32 but nudged it even closer. Took a little time, but I figured this was another important spec regarding accuracy of cut.

I would be interested it checking and insuring the blade height above each bed rail.  That is what will insure the accuracy of your lumber, not just the first.

Agreed. I thought about that as I was writing the post. (There were a ton of things to check and keep track of, and my poor little brain was at its limit yesterday.)
With all the checking and cross-checking of the bunks that I did, I am hoping that when I do as you suggest, I will get an acceptable result.

[SawyerTed]

Get it the best you can and saw some lumber.  See if the lumber is fairly true.  If so move on.  If not, work on the problems from there.  The key is level tracks with no bumps.  You are correct in thinking about any irregularities in the track being transmitted to the blade and lumber.  A twisted track would be bad.  A C clamp and a piece of angle clamped square to the track should allow you to clear the bunks to pull a diagonal.  

Remember that no matter how smooth and true lumber comes off the mill, it is still green rough cut log run lumber.  If I'm not mistaken 1/16" to 3/32" of variation is typically acceptable for rough cut lumber.  

The truer the lumber the easier planing and jointing will be after drying.  

All sawmills need periodic re-alignment, you will get it right on after some experience with it.  

[Old Greenhorn]

You seem to be off to a good start. Remember that once the mill is loaded with a good sized log, things may change (settle in). After you get a few honkers up there, go back and recheck everything on the bed. Even if your foundation is rock solid, things will settle. Don't let yourself get frustrated. Walk away if that happens.
 I used to set heavy CNC machines as part of my millwright work and these machine weighing up to 25 ton or more would settle in. It could take 2 days to get machines level and running true because the beds would flex as the table moved around and changed the loading dynamic. You had to anticipate these loads and put in some yaw on the beds so the machine would run true. First round was always rough level, second round was to make sure the loading was even, then third round with a lot of moving and checking the table until it was in spec. Then test cuts in all areas of the table. We would then setup a job and run it for a week or two, then I would go back and check everything again after the settling, make minor adjustments and it would be good to go. With many tons of weight involved, concrete will settle in, high spots wear off of cast iron and steel machine pads, and things can move. Your mill is similar, but on a much smaller scale.

 Start with a small low stress log like EWP or something and check your lumber, then go to the bigger heavier stuff. You'll get it because you are on the right track (pardon the pun).

[Jeff]

Also, never forget you are going to be making rough sawn lumber, and ultimately the log is going to determine how good the lumber is no matter how precise the mill is built. One hunk of dirt in the bark on one cut has the potential to make your sawmill cut like it was put together with a blind fold on.  Learn not to stress on any of it. Get it sawing and learn from sawing how to make the best lumber you can from any given log.

[Southside]

Yup - like Jeff said there are factors beyond your control - stress in a log will make a cant bow, crook, and twist on my Super 70, clamped in place with hydraulics, nothing you can do about it but work through the challenges and make the best lumber possible, then re-work what is worth doing so after it's dry.  It's called rough sawn for a reason.  

[rusticretreater]

Having assembled a HM130 Max, I can say you are well dialed in.  This is not a precision machine, its a get it close enough machine.  Still, it will make some pretty nice cuts.

One of the things I did was start it up and move the head to different locations on the track and let it sit there for a bit.  The vibration does things we can't.  I made some adjustments after that exercise.

You can continue tweaking right now but it will all be for naught as folks have already said, it needs to settle in.  Not only the base but also the workings of the mill head too.  

[Patrick NC]

As others have said, it's time to get a few logs on there to get it settled in. You will know if something isn't right. With a sharp blade it should push fairly easy.  About like a half loaded shopping cart or a very light push mower. If things get out of line one of the first things you will notice is extra effort involved to push the carriage.  That's when it's time to check for square and flat. My first mill was set up stationary on a good foundation and it still moved around some from the beating the logs give it. Sounds like your well on your way to making sawdust. Keep us posted.

[RAYAR]

Hi Rene S

As long as you have your tracks straight and parallel (height wise) to each other and the carriage rolls smoothly from end to end, and have the bunks also parallel and aligned to the the tracks both across and length wise, you're good to go. Being out of square a little is OK, what counts is everything being parallel to each other. The next thing is to have the body of the blade parallel to the tracks and bunks in both across and length ways. After that, it's adjustments to belt tension, blade tension etc. The log itself could be the cause of some problems, so don't think there's something out of adjustment on just one log. I believe your mill has cables so they will stretch a little over time, check the blade for side to side level after a bit of use as they may need re-adjustment periodically.

Always use full throttle when cutting.

Have fun making sawdust, it's addictive.

[Rene S]

Thanks everyone, for the kind words and the suggestions. I will be back at it this weekend and will put your suggestions to use. 

I had anticipated some movement from loading logs on the mill and was hoping to minimize it. I hadn't really thought about the weight making the mill settle. Like I said before, my poor little brain can only process so much before it gets overloaded and starts missing stuff.

I do appreciate the responses. They will make the challenges easier to handle.