Im having trouble with tearout on hard maple on a weinig moulder. Currently using carbide in a 20 degree hook angle cutter head with the rondamat 960 grinder at 25º rough grind and 20º finish grind.
I now have some 12º cutter heads so what angle should I be grinding at?
I have attached an article I wrote that may help you have a better understanding of hook angles. I hope this helps you decide, please keep in mind you will have to sharpen the knives again whenever you change angles.
Also can contact Russ about Super helical heads. These are a curved style knife and really do a great job.
I bought these 2 years ago or so with same problems and really cut down my tear out down to 5-10% on a job and very minor if I do see some. Especially noticed it on resawn lumber really helped cut down that issue when I ran mouldings after resawing it in half. Plus the carbide part lets you run a ton of footage between sharpening is a bonus. you can find on his website in his tooling catalog he has available for download. A great source for any tooling,grinding, or template service you may need.
Thanks for the link, I had found than online the other day. It doesn't actually mention anything about grinding angles of a 12º hook angle knife vs a 20º.
I have set up my machine to experiment today running S4S. Bottom and side heads will be as normal with the 20º hook angle cutter heads and my two top heads will have both a 20 and a 12 degree cutter heads, that I have setup to run as inside and outside, not first and second. Both heads at same height.
So my 70mm wide plank will have 35mm on the inside cut with a 20º head and the outside 35mm will be cut with a 12º head.
This should give me a direct visual comparison.
For now both sets of knives are 25 rough and 20 finish grind. Any suggested variations on this?
The grinding angles do not change from switching hook angles, but experimenting is always an option. If you are just doing straight knives tilt the grinding wheel 5-10 degrees, it will help in directing the wood chips toward the dust collection. As Shaner mentioned the sheer cut cutter heads work well but... you would have to invest in the whole system, carbide, cutterhead, and a tool rest for your Weinig grinder, a costly, but effective solution. I guess you would have to weigh the cost versus how much trouble you're having.
Take care , Have a great week ahead!
Great results from your test, good job!
Those 12 degree hook angle cutter heads will come in handy some day, it was a wise choice for purchase, those problem, hard to run species drive us all nuts from time to time.
Please use filler stock in the slots you are not utilizing to keep the bore round instead of egg shaped.
I dont have a bore, all powerlock cutter heads.
I have filler pieces for use with regular steel knives but none thick enough for carbide and their backers. I used a smaller height knife to fill the gap. Done the job for testing but the proper filler pieces are on the shopping list. Thee ever growing shopping list!
First, hard maple has a lot of swirly grain, so you will be "planing against the grain" in small pockets on most pieces. This grain increases tear out.
Second, moisture contents under 7.5% MC mean that the wood fibers are stronger and so do not cut as easily, but rather break out. The wood is more brittle especially when under 6.5% MC at any time during drying and if the kiln exceeded 160 F degrees.
As mentioned, the hook angle is important. A more slender knife means that the knife acts more like a chisel instead of a plow. With swirly grain, a chisel will result in tear out.
With a planer, we can reduce chipping and tearing with the properly set chip breaker.
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