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Discussion Starter #1
Recently I bought a used Delta Jointer model 37-190. I knew when I bought it that the knives where dinged up. I did some research and saw some recommendations to only by the Delta knives so I did. Upon receiving them I was inspecting them :detective: to see how straight the cutting edge is. To make a long story short here, I found that the center of all the knives has about a .02” curve to them so that the edges are raised up in a concave way. Is there a reason for this? I was going to build a sharpening jig for the existing set of blades so I have back ups, but was shocked to discover that the “new” blades where not straight to begin with. Now before you tell me that I am being ridiculous here, I work in the tool and die trade and .005” is considered a loose tolerance, am I being too precise here? Should I not worry about it?
:wallbash:
 

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I cannot explain how the knives got the curve. Perhaps stress during manufacture or initial grinding.

When you install these, the gibs screws will flatten out in the jointer, so the only issue is sharpening.

I think a professional sharpening service likely clamps the knives in place so they should be flat whilst being sharpened.

I also have a Delta 37-190. I purchased a replacement set of knives decades ago. I do not recall who made them, but they have worked well.

I also made a quick-and-easy jig to hold the knives so I could sharpen with abrasive paper on a granite slab.

I made a single cut in a scrap of wood with the table saw blade at appropriate angle. Just needed to tweak for the depth of the cut.

Just needs to be tight enough to hold while using the abrasive paper. Works for my needs.

Jig_jointer_knife_sharpening_1317.jpg
 

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If the bow is in the vertical axis, i.e. the ends will be higher than the middle when the knives are installed, then what you have is unacceptable. The cutting edge should be dead flat across the width of the knife.
 

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Discussion Starter #4
Maylar said:
If the bow is in the vertical axis, i.e. the ends will be higher than the middle when the knives are installed, then what you have is unacceptable. The cutting edge should be dead flat across the width of the knife.
That is kind of what I was thinking. I figured that it would make the wood bow outward in the middle. Being I have access to a machine shop I think I will return these and might just make my own.
 

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I think we had this topic come up last year. Somebody had curved blades and checking the straight edge off the machine they were off but once installed the edge was forced straight. When they are ground sharp at the sharpening shop the machine flattens them while they are sharpened. It doesn't matter what they are like off the jointer.
 

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Discussion Starter #7
Steve Neul said:
I think we had this topic come up last year. Somebody had curved blades and checking the straight edge off the machine they were off but once installed the edge was forced straight. When they are ground sharp at the sharpening shop the machine flattens them while they are sharpened. It doesn't matter what they are like off the jointer.
I did push them flat and they where still curved. I checked all of the surfaces and they were not parallel at all. Not the type of quality I would expect for a $60 set of knives. The are getting returned on Monday.
 

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Discussion Starter #9
rrich said:
Yes those will fit my jointer. I've never heard of Jessada before are they a good blade manufacturer?
 

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Yes those will fit my jointer. I've never heard of Jessada before are they a good blade manufacturer?
A very long story . . . .

Jesada was a manufacturer of very good quality router bits. Then FWW did a test of router bits, 1/2" shank 3/4" diameter straight cut. The test was using a CNC machine. The Jesada bits were not designed to be used in a CNC machine. However FWW painted all of their router bits with the same brush and consequently the owner was forced to sell off the business for retirement money.

The business was acquired by RT Razor Tools. Apparently the same people and machines.

BTW - One of the owner's children has reopened a router bit company, Infinity.

I have not used any of the Jesada jointer or planer knives but I am exceptionally happy with a dado blade and many router bits.
 

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I bought a set of Freud knives for my Delta jointer from Amazon about a year ago. They work well for me. I measured my originals & found an exact match. They have many sizes available.
 
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