Project:
Bandsaw - Log Mill
 Starting Date: September 2012
 Completion Date: September 2012
 Inspiration: The need for something quieter than my earlier Chainsaw Log Mill
 Size: 160" long, 24" large, 38-3/4" tall (Assembled);  120" x 24" x 13" (Disassembled)
 Wood Species: SPF for Table Support, Ash for Rollers, Oak for wheel axis support, and Birch Plywood for Table Top (3/4") and Sled (1/2")
 Finish: None
 Materials Source:
 Additional References: Highland Woodworking Wood Slicer 3/4" Resaw Bandsaw Blade (#1952C)

Spring 2012, and a not so healthy maple tree on my property...

The tree was close to the house, it was not healthy and was threatening to cause damage. It had to go! But I felt less than noble making firewood out of this large diameter straight and tall tree. This is not to say that a quick calculation of the tree's worth in lumber had nothing to do with my decision to build this project!

I had previously used my shop's bandsaw to resaw smaller logs fixed to a plywood sheet. As can be suspected, the important weight of a log and its irregular "round" shape makes precise handling, feeding, and resawing a laborious chore.

The solution offered here is both simple and elegant. It is comprised of: A Support Table, a Roller Table Top, and a Sled.
  1. The Sled is used to securely and precisely support the log as it goes through the badsaw blade;
  2. The Sled easily moves across the Table Top equipped with Rollers to minimize the effort of feeding the wood into the bandsaw blade and allows for the operator to concentrate on a constant feed rate and safe manipulation;
  3. The Sled is precisely guided by a guide bar running in a dado on top of the Support Table;
  4. The Support Table is a free standing structure that is independent of the bandsaw. This makes it easy to adjust for blade drift;
  5. Loading the log onto the sled can be facilitated with a cable winch and a ramp to avoid exertion and injury while handling larger logs; (Smaller logs can be loaded on the Sled manually)
  6. The length of the logs that can be processed is only limited by the available space on the front and on the back of the bandsaw.

The Support Table

As most shop owners, I pay close attention at preserving the shop space available and not cluttering it with stuff that will only be used sporadically. With that in mind, here are some of the options I had for the main guiding principles that would dictate the Support Table's design:

  1. Allow for re-purposing the table for other roles when not used for the Log Mill;
  2. Allow it to be flipped on its side and used as the structure for shelves;
  3. Allow for easy assembly/disassembly and minimize the space required for storage.
The last option was retained, I set out to build a free standing table that could be easily and rapidly knocked-down. The entire table (top, base and legs) is built from 4" X 4" SPF lumber. The base and top are almost identical (see pictures) and assembled with simple L, T, and crossed-frame Lap Joints. The joints are secured with a single 3.5" carriage bolts through their centers. I recessed the nuts and washers in order to hide all connections and make it safer. Even though I do not plan on having to disassemble the base or top, I did not glue the lap joints.



The secret to rapid assembly/disassembly?
Bridle Joints (with no glue or bolts) are used to joint the legs to the base and top. A snug fit is all that is required to ensure sufficient stiffness of the Support Table. If required, additional stiffness could be provided by cross-braces fixed on the legs which would only add minutes to the assembly/disassembly process. In practice, I found that additional bracing was not required.



The Roller Table Top

I originally wanted to use Roller Blade wheels for the rollers, but finally decided to go with more affordable shop made wood wheels. A bolt secures the Ash wheel to the Table Top and serves as the axis. Roller Blades wheels with their sealed bearings would certainly make the sled easier to push, however I am satisfied with the wood wheels which have proved to work better than expected.

The wheels are cut on the bandsaw with the circle jig, and then refined on the wood lathe to their final 2-5/8" diameter. There are two rows of wheels on the 3/4" birch plywood Table Top. The rows are 10-1/4" apart c/c, and the wheels are spaced roughly 7" c/c.

In my case, the shop allowed for processing logs of a maximum length of 84" without having to move the bandsaw. This translated to a 160" long Table Top.

A quick calculation:

  • Maple Density: 39 - 47 lb/ft³ (Source: http://www.engineeringtoolbox.com/wood-density-d_40.html)
  • Volume of Largest size of log to be processed: 60" long, 14" in diameter.
    π * 7² * 84 = 12930 po³ = 7.5 pi³
  • Maximum expected weight: 7.5 * 47 = 350 lbs
  • A rapid test: I mounted one wood wheel in a vise, and tested how much weight it could move. I used a 42 lbs pail of joint compound sitting on a plywood for this test and the result was satisfactory. (ie The plywood supporting significant weight was moved easily on the wheel, the wheel did not slip in contact with the plywood, and it spun freely.) 
  • Conclusion: At any given time, I expect to have at least 10 wheels in contact with the Sled as it travels through the cut, which translates to 35 lbs per wheel. Since my test with 42 lbs was successful, I should not have to worry about the log being excessive weight for the wheels.
(Wheel and their supports viewed from underneath the table)

The available space underneath the Roller Table Top does not allow for Roller wheels to be positioned on top of the Bandsaw's table. (Take a look at the first picture and notice that there are no wheels in the area where the bandsaw table is located.) That was a source of concern with this design and I thought that a UHMW polyethylene skid plate may have to be added to the Table Top in that area for the Sled to slip over. In practice, I found that a skip plate was not necessary. It would definitely help make the sled a little easier to push, and I may add a skid plate in the future.


The Sled and Log Supports

The Sled serves three purposes: Supporting the log and make contact with the Rollers, Securing the log so it does not shift as it is being fed into the bandsaw blade, and travel through a perfect line. The adjustable supports allowing for the log to be screwed at both ends have proven to provide sufficient lateral stiffness and maintain the log secured and stable enough to ensure straight resawing. 

Two UHMW polyethylene guide bars are fixed under the Sled and runs in the Table Top's dado. The guide bars protrude at both end of the Sled to make it easier to locate and insert in the dado.



Positioning the Bandsaw Log Mill

This Bandsaw Log Mill is a free standing structure that is not in contact or attached to the bandsaw.

Use a 4" X 24" piece of scrap plywood in which you will mark a straight line in the middle. Start your bandsaw and cut on the line until you are able to determine the natural drift of the blade. Stop the bandsaw while being careful to maintain the angle that allowed you to follow the line on the scrap plywood. That is the drift angle you will use to align the Log Mill. Timothy Coleman's article in Fine WoodWorking issue #143 "Bandsaw Your Own Veneer" describes how to determine the natural drift angle of the blade using this technique.

The blade should be at least 4-5" from the edge of the Table Top to allow for the freshly resawn board to have support when it "falls" as you complete the cut.

After positioning the Log Mill, you are finally ready for your first cut! Don't be afraid... This first cut will be to cut the edge of your Sled! This is to ensure that the sled runs parallel to the bandsaw blade on its entire length. The edge of the Sled will now provide a reference to precisely locate the line of cut* when securing the log on the Sled.

The thickness of cut can be easily measured by resting a square on the Table Top and on the edge of the Sled. See the video (9:30) to see how this is done. In the video, I am resawing 6/4 boards and one leg of the square I am using is 1-1/2" wide which makes measuring very easy.


A Ramp and a Winch to facilitate loading logs on the Mill

Although not absolutely necessary, adding these features to your Log Mill will greatly improve your experience and possibly prevent injury. This is self explanatory, so I will leave the pictures do the "writing".




The Log Mill Disassembled (with all its pieces)


The Bandsaw Log Mill in Action (Slideshow & Video)




Possible Improvements to the Design:

  • Install cross-braces on the legs to make the Table Support stiffer.
  • Add a second deck to the Sled that would allow for the log to be moved towards the blade and thus provide easy adjustment for the next cut. Graduation tape could even be placed on top of the bottom sled to assist with readjustments. The main benefit of this deck would be to minimize the number of times the log has to be re-attached to the sled and save time. However, this design would subtract the thickness of that second deck to the total possible height of the cut.

Notes:

  • (*) Line of cut: I recommend that you back out the Log Mill by 1/8" to 1/4" in order to allow for the blade to wander without damaging the side of the sled. Make sure to move the Log Mill parallel to the original alignment defined by the Natural drift of the blade.
  • A slower feed rate is necessary to achieve straighter resaw surfaces. The blade has a tendency to wander left and right at higher feed rates and produces a wavy surface.
  • Lower the blade guide close to the log to produce straighter cuts and make the operation safer.
  • The cut surfaces are surprisingly smooth, much more so than regular "rough cut" boards available at the lumber yard.
  • Take the time to remove all dirt from the log before loading the log on the mill, your saw blade will thank you.
  • After felling the tree, take the time to cut the branches as close to the tree trunk as possible. Using a chainsaw makes quick work of that task. If you wait to perform that task in the shop, your tool options will be limited!
  • A dust collector is recommended.
  • Wear your usual safety gear. (Shop glasses, hearing protection and dust mask.)



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