Circular Mill Alignment

Advice on fine adjustments to a circular sawmill for accurate cutting performance. February 12, 2007

Question
I am having trouble with my circular sawmill. I recently purchased it and moved it to the current location. While doing that, I was careful to be sure the tracks are level and straight, and that the carriage/head blocks run true. When setting the husk, I squared it using the head blocks to measure the amount of lead at the tail end of the blade (currently 1/8).

The problem I am experiencing is I am seeing a taper in the cant after squaring it off. The taper measures 1 inch in 18.5 feet with the thicker end on the tail end of the cant. Could this be a problem with too little lead? In my mind, to create this taper, it seems the blade wants to run out of the log to the board side. Keep in mind when experiencing this problem I had a fresh set of teeth in the saw.

I was told by the previous owner that the blade was tensioned for 500 rpm, and I found it ran true at approximately that speed. It is a 50 inch saw, and when disassembling it, I did find that both of the lug pins had been sheared at some point, and the saw does show a slight dish on the log side when idle.

Is it simply a blade tension or collar problem? Possibly an alignment problem? Any advice would be welcomed.

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
You need to read Circular Sawmills and Their Efficient Operation by Stan Lunstrum. I do believe that your blade is dished incorrectly, as when it is not spinning, it should be dished away from the log. It is likely, unless the blade was hammered wrong, that the collars are causing this dish. You should have one flat collar on the mandrel and then a slightly concave collar on the "bolt" or log side. Lunstrum shows how to check the trueness with chalk.



From contributor R:
A saw hammering might be in order, but I would try a few other things. One thing is to make sure that your head blocks are the same distance from your saw. I would measure the distance from saw to head block #1. Then move the carriage forward to head block #2 and measure. Do the same for all head blocks. If there is a difference, either your head blocks are off, or your track is out of line. If they're all the same, then it's something else.

It could be that you have too much lead. Too much lead will have you digging into your log. Just because a book says it should be 1/8" doesn't mean that is what it has to be. My lead is less than that.

You may have your saw guides out of adjustment. I adjust mine on a moving saw. You must use extreme care when doing this. One bad move can result in injury. I keep my guides adjusted so I just see light between my guide and the saw, when running. If there is too much room, your saw may dig in. If you are pushing with your boardside guide, you are putting more lead in your saw. If you don't want to do the moving saw adjustment, set your adjustments with an idle saw, but inspect them with a running saw.



From contributor J:
If you are getting 1 inch of taper in 18 feet, you have a problem with the knees, or rather one of the knees is not in alignment with the other knee or further away from the blade. To correct this, you need to get the knees "in time" with each other. If you have 3 knees, you would notice one of them is gapped on a cant... another indication that is where the problem is. I seriously doubt you could get the lead off enough to produce a 1 inch taper that didn't cause a tremendous heating and drag on the blade. I run 5/16 lead and the blade when stopped dishes to the log. I set the saw guides at 1/32 off the blade with a feeler gauge. This works great for me, sawing both cedar and walnut.