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here's the thougot:
when maintaining a series of blades at different bevel angles (say for a bevel up plane), one could extend time between grinding by moving a blade "up" a level to a higher angle.
I realize that this may be obvious but it hit me earlier as I was reading an old article on bevel up planes. It would also give you a third angle until you honed back through the previous angle but that shouldn't be a problem right?
Hi Tony
I would disagree with that. The reason for moving to a higher cutting angle is when the grain becomes difficult to plane without causing tearout. The higher the level of interlocked grain, the higher the bevel angle.
A high bevel angle may be achieved by both a BD plane (e.g. HNT Gordon with 60 degree bed) and a BU plane (e.g. Veritas BUS with a 50 degree bevel and a 62 degree included angle).
High bevel angles increase the level of heat at the blade edge (think about burning fingers when pushing a high angled card scraper). This more rapidly wears the edge compared with a plane with a lower cutting angle.
If you are instead referring to honing the same blade at a higher level to maintain the cutting edge, then this is a strategy used by many regardless of the bevel orientation. However it will increase the cutting angle (with a BU plane) and reduce the clearance angle (with a BD plane). Both increase wear rates.
Regards from Perth
Derek
Derek, I was referring to a BU plane where one has more than one blade with say a second blade honed to 38* for difficult grain such as you generally work with. I'm thinking specifically of honing up to that higher angle when the secondary bevel on a "regular" blade reaches a point where one would usually have to go back and reestablish the primary bevel because the secondary has become too wide. I may be over thinking this though.Quote:
Originally Posted by Derek Cohen
hadnt really needed to worry about tear out much in the straight grained walnut and cherry I usually work but a recent delve into flame birch opened my eyes a bit.
The higher angle creates more frictional heating of the blade edge but whats interesting about steel is the strength actually improves with higher temperatures (up to 200 - 300C) after which it drops fairly quickly and about ~400C it is back to its room temperature strength. I doubt we are planing vigorously enough to raise the temperature to the point that self heating is important in the equation of wear.Quote:
Originally Posted by Derek Cohen
Pat, my point is that the heat indicates a higher level of friction. Higher friction equals a condition for higher wear.
Regards from Perth
Derek
I see what you're after, and it'll work but....
So as each blade goes back to the stones for honing you'd bump it up to the next steeper angle. Then the steepest one I presume would be ground to take the place of the lowest one and the circle would continue. The problem in my shop is that I don't use different bevels at the same or even similar rates, so there would soon be too many high angle blades and none in the middle range. I also prefer to use thicker, harder irons for the higher angles, and have them in their own bodies, set up and ready. I hone freehand generally following the existing bevel, adjusting as needed. This circular progression seems unnecessarily fiddly to me with no real benefit. However your mileage may vary- go ahead and run it for a while and report back.
After I thought about it more I came to the same conclusion for most of the same reasons.Quote:
Originally Posted by bridger berdel
I went through this same thought process. If you keep increasing the bevel, youre in for some frustration as your plane blade bevel gets higher. Here is what I do now. I slow grind the primary bevel, hone at that angle on 1000 grit til i have a bur across corner to corner. Then i got to 16000 grit for a microbevel a few degrees higher then do the ruler trick to remove the bur (creating a back bevel). Once that wears out, i hone at 1000 at the original bevel angle until I remove the microbevel and get a bur all the way across. Then back to the 16000 microbevel and back bevel.
True. Higher friction = more wearQuote:
Originally Posted by Derek Cohen