Board run out??

[1harlowr]

I've been playing with the idea of an Alaskan Mill. I haven't used a mill of my own, but have helped at a large mill operation when I was younger. My question is about setting up the first cut to minimize the run out on the boards. I've only seen the Alaskan used on youtube etc. Is it difficult setting up that first cut so all the boards don't have run out especially on logs that are not really flat? Most of the videos shows the person just screwing the rail to log, leveling the rail, then just cutting away not worring about the board run out.

 

[timberwolf]

Easy enough though a little time consuming to shim one end up for the first cut. Set up so the saw is same distance from the center of the log at both ends and there should be little runnout provided log is straight and grain not twisted.

 

[BobL]

Here's a tricky one.

This is how I set my rails up using my log rail offset uprights

A pity I didn't take any more shots that day - anyhow it worked a treat for this awkward shape.

 

[Brmorgan]

So you're basically asking how best to keep the cuts parallel to the center of the tree to avoid grain run-out? If so, here's how I set my guide up:

The end blocks are a set thickness - in this case a 2X6, or 5.5". If I want to make sure I get a pith-parallel cut, I just measure the distance from the pith of the tree to the bottom edge of the end block, and make sure that distance is equal at each end of the log. It has the same net effect of Bob's metal rail/stand setup for the really odd shaped pieces, but provides all the variability I require for almost any fairly straight log I encounter. I have different blocks all the way from 2X4 to 2X12 to accommodate different log sizes.

To keep the guide board rigid for the entire length of the log, I pull a string taut from end to end and drive lag bolts to that depth - this way the board can rest on the lag bolts and be supported over its entire length. The bolts also permit some adjustment of the guide board if it's become warped or twisted. A few guys here don't like this method because it's a bit tedious and time consuming, but it does produce a very accurate cut. Depends on what you're milling for, I guess.

 

[BlueRider]

I think a more acurate goal would to be having the same amount of run out from one side of the log to the other. the nature of trees are that they are tapered and while this may be stating the obvious it is good to keep this in mind when visualizing the lumber that each tree will produce.

A small amount of grain run out can produce some spectacular cathedral grain on flat sawn boards. Also when carving it is desireable to have a bit of even grain run out. For chair and table legs I like perfectly quartersawn boards with no grain run out.

As you can see there are desrable reasons for a variety of differently milled boards.

on the practival side I often end up freehand slabing through the root butress so i don't have to shim as much on the other end of the log. also I always screw the wedges to the log so they don't vibrate loose while I am milling.

 

[1harlowr]

Thanks

I wasn't thinking about measuring up from the center of the log on both ends. Just watching the videos it looked like most people were just attaching the jig and sawing away. Most of them probably were just guessing and sawing though.

 

[timberwolf]

Guys above were clearer than I was, the center being the pith or heart of the log. Can take so visualization to estimate how the heart is located along the length of the log. Straight log makes it easy, but I have cut crooked logs with a bow in the guide to follow the curve of the log. The boards pretty much straighten out when stacked and dried though there is likely some internal tenssion when doing it that way.

Forget about getting runout free boards when dealing with spiecies like hemlock that have a natural tendancy to twist especially if growing in rough conditions. Sometimes the twist shows up in the bark and can be seen other times not.