Round sawmill blades?

[Leroy in Kansas]

I've found an old sawmill, the type with setworks and a round blade. 3' with replaceable teeth. The guy that is selling said he thought the blade was ruined because It had several blue spots. Places where the blade has gotten hot from rubbing on the guide. He stated that he could no longer maintain a line with the saw. It kept running off. The mill is powered by a PTO from a tractor and the guy said it wouldn't run slow enough for this type blade. Can this type blade be repaired? I've heard of hammering blades back into shape. What would be a reasonable cost for blade repair? Sorry I didn't have the camera with when I was there and the phone doesn't take very good pic's. Thanks for the help. Leroy

 

[Mad Professor]

When I worked a commercial mill they sent out the blades to be "hammered" back to trueness. I'm not sure what the cost was, but cheaper than new blade.

They even fixed one that hit 4 horseshoes on a big old oak.

 

[Sethro]

The saw can be fixed. The bluing on the saw in the guide path are from trying to keep the saw in the cut with the guides,Trying to make a saw run true via the guides is bad They are called guides but really don't have anything to do in how a saw runs. The art of hammering is ethier putting tension or taking tension out of a peace of steel.
Go to a local sawmill that has a circular headsaw and ask who hammers the saw blades. Before sending out you saw.
You"ll have to find out what RPM your arbor turns at(600,625,650) and direction(left hand /right hand) the saw runs . Also you should have new shanks and teeth put in. oh and $ just for pressing/hammering is around $200 in these parts

 

[Cowboy Billy]

Here's some info I got from my friends on my tractor site after I got a cordwood saw for my farmall cub.

From Bill Sorensen
Have you ever sharpened a large blade? If not the first thing to do is to look for cracks or metal fatigue. If all is ok you first gum the blade. That is you grind or file off the tops of the longest teeth so that they all are even. Next check for odd ball teeth, either in shape or spacing. Then file for evenly spaced same shaped teeth. You may have to do the front or the back of each tooth to correct previous bad sharpening. Next make all the gullets even and deep enough the teeth are about as long as the longest origional tooth. You may do the gullets earlier in the process if that fits the flow of work. Next you set the teeth or swedge them according to the way the blade was origionally built. To swedge you hammer the top of the tooth to make it wider. To set you bend every other tooth in one direction and the alternate teeth in the other direction. There is such a thing as hammering a blade. To do this you hammer around the blade in a circle to set up stress in such way it runs smother while cutting. It much too much an art for me to describe. For cutting firewood I wouldn't get into hammering.

From George Willer
Here's my take on hammering:

The buzz saw blade is too small for hammering to be necessary. Larger blades have a lot more centrifugal force on the outer rim and that's why it's done. The inner part is peened, stretching it so the blade actually "oil cans", and will probably wobble at low speeds. When the blade is turning at its' rated speed the outer rim is actually stretched a bit by the force and it runs true (unless it gets hot and wobbles like crazy). Properly hammered blades are intended to run at a specific RPM, when centrifugal force, acting more on the outer diameter, cause it to expand and run true. The forces working on the blade must be enormous!

More from Bill Sorensen

I have a horizontal mandrel I put a blade on to sharpen it. A beveled block is then set where I want to put the side set in the teeth. I set every other tooth, turn the blade over and set the remaining teeth. Next I gummit it. That is grind down the tops of the long teeth to meet the shorter teeth. Now that the distance from the center of the blade to each tooth is equal I shape each tooth to match the origional shape when the blade was new. At times i have to take more off the back other times off the front of the tooth to maintain even spacing between tips of the teeth. You want to leave as much beef behind each tooth as you can but you want each to be the same size to keep the blade ballanced. I then mark a circle about the blade in such place that each gullet will be equal when I file to that mark. Re shaping the gullets I feel removes metal that may be stressed to chrystalization and prevents stress cracks as you use the blade.
Some people hammer a blade. Quite frankly I don't know what it is suppossed to help.
You want to keep the blade perfectly round, evenly set, and balanced, with evenly spaced teeth and shaped teeth for best results. When a blade is so it cuts quickly and with less power needed.
It is easier to demonstrate than it is to explain.
There are other blades that are Swedged. For these you hammer the tops of the teeth after getting them the same length so the the tops are wider than the blade and thus cut a wide kerf so that the sides of the blade do not bind.

Thanks George. It must be part science and part art to decide to where hammer and how much. I always take as much from the gullet as i do from the top of the teeth so that metal fatigue and crystalization does't cause cracks. Many newer fancy blades have slots in them to allow for centrifical force. With a large blade it is not the RPM that should be the guide, but the feet per minute. A 30 inch blade travels 91 inches or so in 1 revolution so that is a lot of feet per minute. When you multiply that by the RPM you get a huge number. I hear it sing when not cutting wood. I guess it is cutting air then. I have a Tach that I will try on it next time I cut.

Hope that helps some

Billy