I’ve received a lot of email about racing chains since the beginning of this thread. Now is probably the best time to start talking about the different steps that are needed to take place. Although many of the modifications cannot be duplicated without special equipment that I have developed, I can assure you that if the steps are followed correctly, the cuts will drop faster. Once again, I want to remind those people who are interested in making a racing chain that you will not see as much gain if you use it on a saw that hasn’t been modified. These two elements work together, one is not as good without the other.
The caliber of engine modification depends on the proficiency, experience and expertise of the person who does the work. I’ve seen so-called modified saws that are worthless. If you spend anywhere from $300 to $600 in modification to a production model saw, you better know that the person is competent. Rotax types of saws, of course, cost up to $4,500 or more. They are different animal or breed since they are motorcycle or snowmobile engines with a chainsaw bar and chain attached, not a production type of saw. The bottom line is that if you are going to shell out that much money, you better spend a few hundred dollars more to buy a fast chain or learn to make your own.
I now basically make chains for Rotax Robert only and perhaps sharpen a few for my close friends, because I don't want that as my full-time job since I have other interests. I will be glad to answer questions or make a sample of what I use, but that could also get out of hand sometimes. The angles that are used on a chain should fit the type of wood that is to be cut. That is why it is hard to make a fast cutting chain for someone who lives in a different part of the world, and you have never cut the type of wood in their area. I have more expertise on Redwood and Douglas Fir since that was what I cut day in and day out during my first career, although the differences are very slight. There are several chain configurations available, and I have tried them all, in fact even made my own by experimenting in countless ways.
The full skip, as a racing chain was eliminated first of all because it will not cut as fast as a full complement chain, and neither will a semi-skip. For those who still want to argue the point, all I can say is I’ve been there, done it, and then moved on. The only chain that will be faster than a full complement is a custom made chain that has one cutter on either side, one after another with no spaces in between. I’ve only tested it on logs under 20”, and the saw used must be 8 cubes or over and highly modified, but it definitely has the edge over a full compliment chain.
One of the main considerations in chain modification is total weight reduction. The first concern of starting the reducing “diet” is grinding material off all the rivets. Since the rivet hole on the tie straps are counter-sunk, or funnel shaped, removing most of the head will not affect the holding strength of the rivet. Removing most of the rivet heads will gain some kerf clearance so there won’t be any drag created in that area. Removing the material off the top of the drive links that rises above the tie straps is done by a lot of people but it is risky. The reason it is risky, on a 3/8” pitch chain, is that the area above the rivet hole in the drive link has .093” of metal. If you file that area down to the height of the tie strap, so they are even in height, the metal in the area above the hole is only .040”. Very often the chain will fail at this vulnerable spot. As they say, a chain is only as strong as the weakest link. Also some people remove more metal from the end of the drive links where it transverses around the bar nose and that area of the drive link that protrudes. This also adds to the weakening problem. On a ½” pitch chain this can be done without any problem of the chain breaking, if it is run on a modified production model saw. Again, if you file down the tops of the ½” chain drive links on a chain that is used on a Rotax type saw, and the wood is harder than Cottonwood, the chain will break. Rotax Robert will attest to that because it happened to him. His “saw” has so much power that it just pulls the chain apart when under a heavy strain. A ½”pitch drive link has .115” metal on a new drive link above the rivet hole and when it is filed down to the level of the tie strap, it has .058” above the rivet hole.
To be continued.
Art Martin
Thanks alot for all the tips on chisel bit filing I used all your angles,techniques on a couple Carlton square chains and they cut excellent in the White Pines around here I have not tried them in any hardwoods yet but I will as soon as possible.
