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Cutting Blanks with a Chainsaw


Sawbucks and Log Holders


A chainsaw is the preferred tool for cutting blanks from fairly large and heavy logs, the ones that are too large for a bandsaw.  A skilled operator can remove a lot of waste wood from the blank, and this translates directly to time saved at the lathe.  


What you can do with a chainsaw and how safely you can do it depends largely on your ability to hold the log. Trying to make cuts on a piece that is not held securely is asking for trouble.  The last thing you should consider doing is to stand on one foot and attempt to hold the log with the other.  This is dangerous, and it seldom works for anything but small branches and the like.


A small log is more difficult to hold than a large one.  The weight of the larger log makes it less likely to move around.  On the other hand, touching the chain to a small log may cause it to roll or flip end-over-end, depending upon the direction of the cut.  


Another consideration is keeping the bar and chain out of the dirt. Even a brief encounter with mother earth will take the edge off your chain, and if you happen to hit a rock, you will be in for a major resharpening job.


The easiest way to get the job done depends a lot on where you live. Out in the country, turners frequently have an area permanently set aside for cutting wood.  Closer to town, it may not be possible to have a permanent wood lot.  In this case, the log holder may need to be something that can be set up for use and then taken down after the job is done.


Use the sawdust pile.  Some country turners simply lay the log in a pile of sawdust and shavings and chock the sides of the log, as required, to keep it from rolling.  You can take this idea a bit farther by placing the log aginst two stakes driven through the shavings and into the ground.  The bar of the saw is then inserted into the gap between the stakes to make the cut.


Roll two logs together.  If you have a pile of logs to cut, it is a simple matter to roll two logs together, chock them if necessary, and then place the one to be cut in the valley formed between the two logs.


My super-simple sawbuck.  A simple rig that I’ve used extensively is shown in the following photos.  The log to be cut is placed against two oak strips screwed to the side of a large pine log stood on end. The bar of the saw runs between the strips.  


Crude chocks, actually offcuts from bowl blanks, keep the log from rolling from side to side when I’m cutting parallel to the length of the log.  The vertical strips prevent the log from “lifting” and being pulled toward the saw.  

 

Fabricated sawbucks.   A lot of turners use dimensional lumber to build sawbucks. These take many forms, ranging from very simple to quite elaborate.  


One that’s convenient for urban dwellers can be made from dimensional lumber obtained from a home center.  It consists of a rectangular platform of sorts placed next to two stakes driven into the ground. The details are shown in the diagram at right.


It is quick to set up:  drive the two stakes into the ground and place the platform against the stakes.  A clever user will set it up at the same place every time and make use of the holes for the stakes that are already in the ground.


I made a slightly different version  that uses two limb sections about 4” in diameter and 24” long, plus two pieces of scrap 2 x 4. Decking screws pass through the 2 x 4’s and into the ends of the limb sections.  Two smaller limbs serve as stakes, driven into the ground to hold it in place.


An elevated sawbuck.  Some folks prefer a sawbuck whose working surface is a foot or so above the ground, to take some strain off the aching back while making the cut.  These are a bit more complicated because they need to be fairly sturdy.  


One possibility is shown in the photos below.  It is made from dimensional lumber, joined with 2.5” decking screws.  The vertical strips are cut from a 2 x 2 (actual dimension, 1.5 x 1.5”), but strips cut from a 1 x 4 (cut to 3/4” x 1.75”, actual) work just as well.   The braces, attached to the sides, are 1 x 2’s.  


If you remove the two braces and the top piece, it breaks down into three sections for storage.  If you use treated lumber, you can simply leave it out in the weather.



In the photo above of my prototype, you can see that I used 2 x 4’s for the legs instead of 2 x 6’s.  The resulting sawbuck is plenty strong.  The following diagrams give the details for making the angle cuts.  You can use either option for the legs.


In use, because this sawbuck is fairly short, it exhibits a mild tendency to tip toward you when making a heavy cut on a small to medium-sized log.  This problem can be solved by adding a weight of some sort to the far end or by simply letting the body of the saw make contact with one of the vertical strips while making the cut.  


One solution to the tipping problem is shown at right.  Anything with significant weight can be placed on the board -- a bucket of sand, for example, or a bucket filled with water.  


Do not place a second log on the rear part of the top surface of the sawbuck.  While this at first seems like a good and obvious solution, the risk is that you may hit the second log with the end of the bar and suddenly get a face full of kickback.  


Screwing wood together.  At the risk of offending your woodworking skills, may I mention one detail of joining pieces of wood with screws – drill a hole in the piece the screw passes through so the thread can turn freely in the hole.  The screw will then pull the two pieces tightly together.


Without the hole, the screw will tighten as the head seats, but this is because of the threads engaged in the top piece.  There will be little tendency for it to pull the pieces together.  The diagram at right illustrates this.  


Splitting a Log


After a tree is down and the trunk cut into short “logs,” the next step is to split each log in half, making the cut parallel to the length.  The temptation is to stand the log on end and make a cut straight down through it, but a chainsaw does not work efficiently in this manner.  It will cut, but it’s a laborious process and the sawdust produced has a fine, granular texture.


A much better approach is to lay the log horizontal and make the cut, cutting down into the top of the log.  In this case, long, slender shavings will be produced and if the wood is green and the chain sharp, great globs of shavings will come spewing out.


If the bar of your chainsaw is not as long as the log, begin the cut at the far end with the bar of the saw pointing downward.  Work the cut toward you.  The saw will cut well as long as the angle between the bark and the chain is 45º or less.


There is a minor problem here.  When the chain contacts the log at the far end, it will tend to lift the log and rotate it end over end toward you.  This is at least an inconvenience and the problem is greater with small logs.  The effect can be minimized by keeping the bar nearly parallel to the surface of the log, but what is really needed is a method for holding the log that includes the vertical strips as described earlier.  


Laying out the cut.  The grain pattern in a bowl will be more attractive if it is symmetrical.  For this to occur, the pith must be centered relative to the blank.  This is not an issue if the pith is exactly at the center of the log, but usually this is not the case. Further, if the pith is off center, it is likely that the log will be oval-shaped, elliptical, instead of perfectly round.    


For an off-center pith, there is only one orientation of the cut that will yield two blanks with the pith centered relative to both. If the log is elliptical, this line will be at right angles to the longest “diameter,” in most cases.  It is shown in the diagram at right.  


The price you pay to have the pith centered is that the resulting blanks will not be the same size.  You can get a deep bowl from one but only a shallow bowl from the other.


Dealing with a split.  If the log has been down for a while and has dried out significantly, it may have developed a split down one side that runs most of the length of the log.  This complicates the layout and forces a choice between getting two blanks with the pith off center or just one with the pith centered, and some firewood.  


Rather than to go with a single blank for a deep bowl, an option is to make additional cuts and create multiple blanks which may yield plates, platters, or shallow bowls.


Other factors come into play.  There may be more than one split, or there may be defects in the log that dictate where the best cut line should be.  Your ability to “read a log” will improve with experience if you relate the cut line to the appearance of the finished bowl.  One thing is certain: the design of the bowl begins when you touch the chainsaw to the log to split it in half.  And once you make the cut, there’s no going back.


Removing the pith.  Cracks are most likely to occur around the pith if it is left in the blank.  For smaller logs, the cut is usually made exactly through the pith.  Then, more of the pith region is removed after the blank is mounted on the lathe.


For larger logs, it may be desirable to make parallel cuts on each side of the pith so that it is removed completely.  The resulting slab can then be split to yield two quartersawn boards.  


Removing the Corners from a Blank


Much time and shavings can be saved at the lathe if you remove the corners of the half-log that is about to become a bowl.  The tool of choice is a bandsaw if you have one that’s up to the task and if the half-log is not too large.  However, a chainsaw may be your best option if the blank is really big.  Whether or not this is easy to do depends upon the arrangement you have to hold the blank while you make the cuts.  If you can’t hold it, you can’t cut it, not safely anyway.


The first thing to do is to draw a circle on the flat side of the blank that will indicate where the cuts need to be made.  A collection of thin circular templates is handy to have at this point so that all you have to do is lay the appropriate template on the blank and draw the circle.


If the blank is large, it may be possible to simply lay it on top of a pile of shavings and make the cuts without having it move too much. Smaller blanks will almost certainly have to be held in some manner because they tend to rotate during the cut.  You will be tempted to hold it with your foot, but give the matter some thought before you do.


On the other hand, if the blank is so small that holding it is a problem, the corners can probably be removed with a bandsaw.  If you don’t have a bandsaw large enough to do the job, consider mounting the blank on the lathe and removing the corners with turning tools.  


The best method I’ve come up with is to clamp the blank to the two vertical strips attached to the sawbuck, described above.  A screw passing through a short piece of wood placed across the vertical strips screws into the center of the blank.  When the screw is tightened, it pulls the blank up against the strips and holds it securely.  


If you don’t have a sawbuck with vertical strips, you can drive two stakes into the ground and clamp the blank to the stakes.  Just put a board or a slab under the blank to keep your chain out of the dirt.


After making a cut, loosen the screw a bit, rotate the blank, retighten the screw, and make the next cut.  In most cases I will also make a cut across the back of the blank just to rid the area of bark so that mounting it on the lathe is a bit easier.  


You will observe that removing the corners exposes a new set of smaller corners.  These can also be removed if you wish to take the time to do it and if the accuracy of your cuts is good.  Just be careful not to carry this process too far or you might inadvertently wind up with a smaller bowl than what was originally intended.  



Using a Chainsaw inside the Shop


For obvious reasons, like noise and air polution, this is for electric chainsaws only.  Do not even think of using a gasoline-powered chainsaw in an enclosed area, not even for one small cut.


The major issue is how to hold the piece you are going to cut. This usually requires a fixture made for this specific purpose.  


If you have a sturdy worktable, you may be able to build a fixture that clamps to the top of the table.  This will elevate the piece and make the cutting a bit easier.  


The fixture I built is shown in the following photo and diagram.  It clamps to the plywood top of a table that is weighted down by lumber stored underneath it.  The bar/chain of the saw reaches through the opening between the vertical strips to make the cut.  


If a suitable table is not available, you will have to build the fixture to rest on the floor.  One option is to build an elevated sawbuck, such as the one described earlier.  


Another option is to build a platform similar to the one for outside use, described above.  The problem, however, is how to hold it stationary so that it doesn’t tend to scoot across the floor.  

One solution is to attach the platform to a sheet of plywood large enough for you to stand or kneel on while making the cut.  


The platform may be attached permanently to the plywood or it can be detachable for easier storage, if that is an issue.  My suggestion is to attach small cleats to the plywood to position the platform in the same place every time.  Then the screw (or screws) used to fasten it to the plywood always go into the same hole.  


If you include the cleats, one screw at the rear of the platform should be all that’s required.  Install the screw from the bottom up, through the plywood and into the rear-most 2 x 6.  


Make the plywood sheet large enough so that when you stand on it to make a cut, both feet are comfortably on the plywood.  This is to avoid having one foot on the plywood and the other on the floor; one or the other may slip if the floor is slick, and the presence of sawdust and shavings on the floor should be considered.  Do a bit of experimenting to determine the size best for you, and also where on the plywood the platform should be placed.  


Cutting corners.  Once the logs are split into blanks, you can clamp the blanks to the vertical strips and then use the chainsaw to remove the corners as was described above.  


A minor annoyance, at least, is that the blank will sometimes tend to rotate while you are trying to remove a corner, especially after two or three corners have already been removed.  The vibration from the saw makes this more likely to occur.


A simple solution is to drive another screw between the vertical strips and into the blank, as shown in the following diagram. No damage will be done to the blank because the screw will go into the part that will eventually be hollowed out. Dealing with the screw is a bit of a hassle, but with a power screwdriver it can be added or removed quickly.  


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