Eric The Viking
Established Member
- Joined
- 19 Jan 2010
- Messages
- 6,599
- Reaction score
- 76
Planer knives:
My Kity 439 has a two-knife block, roughly 2" diameter, with the knives in the familiar "Z" arrangement and wedges to trap them.
I've been tidying up a couple of teak boards over the w/e, and thought it sensible to swap the going-off knives for my unused spare set - no point in killing them on the teak if they only need light honing to bring them back to top form. They're good quality HSS, not tungsten carbide or anything posh.
New knives = nice results, job done! But...
... I've now got two sets of knives that need work: the set just removed that need honing, and the ones originally in the machine when I bought it s/h, that have been attacked with what looks like a *******-cut file.
The common grinding+honing angle seems to be 40 deg. The newer sets I have (from Appleby Woodturnings) are ground to that, as were the original knives, once upon a time. The bodger that got at those seems to have put a second bevel on at around 50deg, by hand.
My question: what governs the grinding/honing angle on planer knives for hobby machines like mine?
It seems to me the bigger the angle, the stronger the edge, but there must be some issues about the bevel tending to becoming tangential to the block circumference - go too far and it would start scuffing the surface.
Does anyone keep knife sets with a different grind angle for different purposes, and if so when do you use which?
I'll hone the set I've just taken out at 40 degrees, but the original ones are sufficiently damaged to be suitable for experimenting with - if it's worth the effort.
E.
PS: for anyone unfamiliar with this sort of P/T, the knives work like a bevel-down hand plane - I wouldn't be altering the cutting angle (although that might be sensible for teak!*), just the relieving bevel.
*Of course this probably isn't sensible - although you might get to York pitch or whatever, my guess is it would cause increased resistance, straining the motor and heating up the cutter more.
My Kity 439 has a two-knife block, roughly 2" diameter, with the knives in the familiar "Z" arrangement and wedges to trap them.
I've been tidying up a couple of teak boards over the w/e, and thought it sensible to swap the going-off knives for my unused spare set - no point in killing them on the teak if they only need light honing to bring them back to top form. They're good quality HSS, not tungsten carbide or anything posh.
New knives = nice results, job done! But...
... I've now got two sets of knives that need work: the set just removed that need honing, and the ones originally in the machine when I bought it s/h, that have been attacked with what looks like a *******-cut file.
The common grinding+honing angle seems to be 40 deg. The newer sets I have (from Appleby Woodturnings) are ground to that, as were the original knives, once upon a time. The bodger that got at those seems to have put a second bevel on at around 50deg, by hand.
My question: what governs the grinding/honing angle on planer knives for hobby machines like mine?
It seems to me the bigger the angle, the stronger the edge, but there must be some issues about the bevel tending to becoming tangential to the block circumference - go too far and it would start scuffing the surface.
Does anyone keep knife sets with a different grind angle for different purposes, and if so when do you use which?
I'll hone the set I've just taken out at 40 degrees, but the original ones are sufficiently damaged to be suitable for experimenting with - if it's worth the effort.
E.
PS: for anyone unfamiliar with this sort of P/T, the knives work like a bevel-down hand plane - I wouldn't be altering the cutting angle (although that might be sensible for teak!*), just the relieving bevel.
*Of course this probably isn't sensible - although you might get to York pitch or whatever, my guess is it would cause increased resistance, straining the motor and heating up the cutter more.
