Moderators: Random Orbital Bob, nev, CHJ, Noel, Charley

 Reply
By IWW
#1333612
D_W wrote:.....I'm assuming you mean that it'll wreck the wheel. The iron itself will be about 62 hardness at 350F and still 59 or 58 at 800F. IT has a lot of chromium in it and you don't want any part of it to stay above about 800 degreesF and under 1400F for long, as the chromium will move to the edges of the grains and aggregate and the steel won't be particularly good.


No, what I read implied it could wreck the steel. In my ignorance of things metallurgical, I couldn't see why that should be, but if alloying components start migrating at various temps, it starts to make some sense. I can see how you could alter things drastically either side of the cut. Using a 1mm cutoff wheel to cut unsupported 1/8" thick steel can get it too hot to touch, but I doubt it would get to 426C (800F) anywhere other than a fraction of a mm either side of the cut if the object is firmly clamped in an adequate heat-sink. Grinding off a few thou after cutting should bring me back to "good" metal?

Dunno - I'm tempted to give it a bash, but not with a brand-new, very expensive blade!

Inspector, thanks, yes, I did know Hock does 2 1/4" blades, but I have my heart set on a PM-V11 for this plane. I used to be a Hock loyalist, they were always my first choice for replacement blades until a couple of years ago 'til I tried my first PM-V11. At first I was disappointed with it, I just could not get the edge my oilstones (various grades of Arkansas stones) gave me on the Hocks. A change in my sharpening routine, including a switch to a very fine water-stone made all the difference, & suddenly, I had good edges that stay that way on our nasty woods at least twice as long as the Hocks ever did. So I've switched loyalties....
:)
Cheers,
Ian
User avatar
By ED65
#1333621
IWW wrote:...suddenly, I had good edges that stay that way on our nasty woods at least twice as long as the Hocks ever did. So I've switched loyalties....

That'll do it!
By Inspector
#1333753
Well in that case take your old blade to a machinist so he can visualize what you need, tell him about the PM-V11 that you want to use and see what they think it would cost. Shouldn't be all that much unless they don't want the business and charge you a discouragement fee. If you aren't in a hurry it is the kind of work they can fit in between jobs or when they have the right setup for another job. That way you can decide if you want to take it yourself.

Some metals when cut improperly work harden making it hard to continue or creating a very hard spot. Titanium does that. If it isn't cut properly carbide cutters will disintegrate so fast you can't get to the off button before the cutter is destroyed and the part with it. PM-V11 may behave in a similar manor. It wasn't an alloy we made aircraft parts from so I don't know.

Pete
By IWW
#1334024
Well, just for interest, I contacted Lee Valley & asked them if there was any reason I couldn't grind a bit off a PM-V11 blade. Their reply was to the effect that there is no problem at all as long as I observe sensible practice & don't cook it.

Unfortunately, they didn't directly address the cutoff wheel part of my question, but D_W's post re the migrating chromium has convinced me it may be a good idea to stick with the more tedious but safe method of grinding away the excess. I could get away with just grinding the bottom 10mm to get the blade through the mouth, there's enough room between the sides to take a 2 3/8" blade & allow a bit of wriggle for lateral adjustment. In fact, I replaced the original lever-cap (which had a huge chunk broken off one side) with a modern LC for the 4 1/2 - 7 series and it fits fine without modification. Looks out of place, though, some day I'll have a serious hunt for an oldie from the right era. Then again, the replacement is 20 years old already & part of the plane's rich history. :wink:

I have a year or more heavy use left in teh current blade, so I'm in no hurry - I'll get it sorted eventually.....
Cheers,