Saw Blade Ripped Shoulders
Preventing Ripped Shoulders (Short Version)
This is a condensation of a seven-page document based on an e-mail discussion among filers and others. I will be happy to supply the full document upon request. I did quite a bit of editing and any mistakes are mine. Tom Walz, Carbide Processors 800 346 – 8274 email@example.com
There are two major parts to the ripped shoulder problem. First is the condition of the steel and second is the way the saw blade is used.
Condition Of The Steel
If the steel is not brazed or brazed and tempered properly then it becomes brittle and the shoulder will snap off.
As saw steel is used repeatedly it becomes subject to metal fatigue. Metal fatigue increases with additional wear. As the metal becomes more fatigued the saw blade begins to lose its ability to cut straight. As the steel becomes more fatigued, the chances of having ripped shoulders increases.
The Way The Saw Blade Is Run
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. All the bearings, rolls, clevises, shackles, etc must be in good condition.
6. But more then 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.
11. Feed speed too high.
12. Annealing cycle on our Stellite© tipper
13. Board edger? They are tough on shoulders either way.
14. Feed problem like shooting cants / boards
15. Press roll sequencing / timing may not be bad enough to rip teeth out on hemlock but will do so on Fir.
16. Tooth bite. If he is on the edge he may be getting away with it on Hemlock but not on Fir. He may be over feeding for fir………
17. What has changed recently? If nothing in the mill has changed I would look at something in the filing room.
18. Surge problems on the gang feed. We have seen them double stack 2 inch boards into the board edger.
19. It is usually an abuse problem or a mechanical issue.
20. Uncontrolled piece slippage will increase tooth bite dramatically for a split second and rip ears out.
(Based on contributions from: Dick Bernier, Jeff Connie St Pierre, James Davis, Neal Davis, Bruce Maples, Burl Swigart, Mike West)
Variables that have an impact on the life of the steel are:
1. Sharpness of the tool – All the blades pulled out of service before or after they get dull?
2. Impact or force being applied to the body in its application.
3. Machine alignment.
4. Species of wood (or type of metal, plastic, etc) being cut.
5. How well was the carbide brazed? There are many subsets to this topic which include critical temperature of the steel & how well the steel was annealed.
6. Gullet capacity issues.
7. Proper hardening and tempering of the saw plate. In short, is the plate the proper hardness and does it have the proper martensitic structure? (Based on contributions form Steve Hartshorn – Peerless Saw Co.)
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