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Crank Knife edging

4K views 10 replies 7 participants last post by  wrench459 (R.I.P.) 
#1 ·
I finally settled on a machine shop to do my block this week. I'm going to have them bore it and then balance the rotating assembly. I asked them about knife edging the crank while they were at it. They gave me a pice of $100-$150 to do it, which didn't seem all that bad to me.
I have always been told that knife edging made a substantial difference on small, low powered engines, but I have no first hand experience.
Any opinions,
ThanX,
James
 
#8 ·
James,

It's probably obvious, but what exactly is "knife edging", and why do you do it?
Very old post...
First lets look at nature's fastest fish.
Most have a blunt nose with a very sleek taper to the tail.
As far as I know it's the most efficient shape.

So with a crankshaft you'll want to round the leading edge of the counter wieghts
then go crazy on the trailing and cut the beepin' crud out of it. Very time consuming!

Newer engines cranks have very narrow throws for this reason. But that's
another story.
 
#3 ·
Keith, as you probably know by now, I'm a "Jack of all trades, but a Master of none", so I'll do my best to explain knife edging, as I understand it.

Knife edging is grinding an edge on the squared off counter weights of the crank shaft. This reduces the total weight of the crank, but more importantly, cuts down on the area of the counter weight that has to cut through the oil that's returning to the pan. The sharpened edge cuts through with less force required, so HP is saved. I've been told that this is more notable on smaller engines. That's about as good as I can do!
Bestus,
James
 
#6 ·
cant reed it. it says knife-edging reduces power loss from hitting the oil and also removes several pounds of weight from crank allowing higher RPM with reliability.the results in the higher RPM
ranges are startling!

Initial set-up charge--------$100.00
for each counterweight knife-edged---$40.00
(if you do 2 or more identical cranks then only 1 set-up charge)
 
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