Ripped and Torn Shoulders on a Saw Blade- Part 3
In our last blog, Ripped and Torn Shoulders on a saw blade- Part 2, we introduced the problem and gave some insight from some very knowledgeable saw filers on why the problem with ripped and torn shoulders may have been ocurring. In the last blog, we focused on possible causes that centered around the machinery and Automatic Brazers being the most likely cause.
In this blog we are going to discuss various other possible causes, that may have added to the problem of ripped and torn out shoulders.
Here is a little review and background about the problem:
Emily, here at Carbide Processors, got a call from a filer in Canada who had a problem with ripped shoulders. I talked about brazing which is about all I know. He thought there were other factors involved so I sent an email to some filers I had met and they passed it on. That is how I got the incredibly good answers below.
This is the problem the saw filers discussed.
Shoulders ripping out. Filer thinks it is below his chill line. Problem only occurs with Fir. It does not occur when they cut Hemlock. As near as he can tell any kind of Fir causes problems. Saws from X company which can’t give him an answer. Kaehny automatic brazer.
Here is what the Saw Filers had to say:
1. Vibration and timing are major factors. Vibration could be a sprung arbor. Not that the arbor may be bent, but sprung from too tight a belt or possibly new bearings were installed.
2. A cog belt would be preferred to a v –belt.
3. Proper horse power can be a factor.
4. Tooth design is a factor and many people favor an odd number of teeth to dampen harmonic vibration.
5. Of course all the bearings, rolls, clevises, shackles, etc must be in good condition.
6. But more than likely it is timing or clipping. Clipping is when a board is not clear through the edger and the next one is skewed into it. This is a common problem with high speed board edgers and no saw will hold teeth in.
7. It could be the timing is right and possibly, at the out-feed or picker fingers, a flitch or board hits the framework (or a worn spot) from too steep of an exit ramp and is rocketed back into the edger where it hits the piece being sawn and the one in front of that is clipped at the next skew.
8. Also, if the edger has a sharp chain, it may need to be replaced frequently and the hold down rolls may need to be adjusted down so the chain doesn’t slip.
9. If you are cutting hemlock and kiln drying it you may be cutting it heavier to compensate for shrinkage which may help it from slipping on the sharp chain. (Hemlock is softer than Fir.)
10. If press rolls are not timed correctly you will shoot boards. The best thing you can do is devote time to watch boards go through. Watch them skew. Watch them at the out-feed and picker fingers. Bring your programmer and millwright.
Is this on a gang edger or board edger? Sometimes we experience this when press roll time is not correct (Mike west adds “Good point Jimbo, that jerk you get sometimes when a cant jumps will rip out teeth.”)
First thought is feed speed too high.
1. Doug Fir is more difficult to saw than the softer hemlock. Especially if it’s dry. Dry fir is a real challenge under most conditions. I can’t emphasize this enough – dry fir is a real sawing challenge. With that, from experience, I don’t believe it is a species issue. Many questions come to mind.
2. Is it a board edger? They are tough on shoulders either way.
3. If it’s a feed problem like shooting cants/boards or press roll sequencing/timing is may be not bad enough to rip teeth out on hemlock. Possible but not likely.
4. Same with tooth bite. If he is on the edge he may be getting away with it on fir but not on hemlock. He may be over feeding for fir………
5. What has changed recently? If nothing in the mill has changed I would look at something in the filing room.
6. However, I strongly suspect it is none of the above and it is related to welding or annealing with a resulting chill line problem. I have hand welded a bazzilion carbide tips over the years but have never used an auto tipper for carbide. I would start with the machine with emphasis on a hard chill line or simply not getting annealed correctly. Maybe too much heat during the brazing process.
Jeff St Pierre
I assume it’s a board edger by the looks of the saw. I have seen press roll timing play a huge part in this. Any uncontrolled piece slippage will increase tooth bite dramatically for a split second and rip ears out.
That and the fact that they lose their sharp edges and do not carry the sawdust out properly. That is why we gum the gullets out regularly. The work harden part is mostly conjecture on my part, but I know that they certainly seem harder to file after running for several runs.
California Saw & Knife Works
At the wood machining workshop I got to hear Warren bird of California knife and saw speak. He was asked a question about ripped shoulders on saw blades. Warren’s solution was to change the design a bit by removing a couple of teeth. This gives you a little more mass in each shoulder. He also emphasized the importance of shoulder design to get as strong a shoulder as possible.
Now Warren is an incredibly intelligent man and this is just what I remember him saying. If you are really interested or have questions maybe you better contact him directly. In all the years I’ve known Warren I have always found to be very gracious and more than willing to answer questions from anyone, especially saw filers.
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