Sharpening Angle Question for DIY edge guide

[Rengoku]

Hello — New here. I have a blade that I’ve measured to be 22.5 degrees. I used one of those metal edge guide wheels and it’s at 22.5 clean.

I want to make a couple of edge guide blocks out of wood to use as I sharpen. Should they be 22.5 or 11.25 degrees?

 

[Spey]

Your answer will depend on where the guide block is placed on the blade, and the angle qualifier dps or inc (degrees per side or inclusive).

Example:
If for example "metal edge guide wheels" refers to a Richard Kell Bevel Gauge Image below, the gauge indicates bevel in degrees inclusive (inc) vs degrees per side (dps).

Kell Gauge measuring Left (Cold Steel Frontier Hawk) Right (Cold Steel Hudson Bay Hawk)
I ground both these hawks secondary bevels to 30inc aka 15dps (as illustrated in photo below)


If your blade has a flat section where guide will rest A)
If your blade has a primary grind where your guide will rest B)

Your Answer:
A) If your guide block will be resting on a flat on the blade, the block should be at the measured dps of the existing grind (assuming you want to match existing).
B) If your guide block will be resting on a primary grind, you will need to know and compensate for the dps of the primary grind when using a guide block.

If B) Bevel angle you want to grind - primary grind angle = guide block angle

 

[Rengoku]

Your answer will depend on where the guide block is placed on the blade, and the angle qualifier dps or inc (degrees per side or inclusive).

Example:
If for example "metal edge guide wheels" refers to a Richard Kell Bevel Gauge Image below, the gauge indicates bevel in degrees inclusive (inc) vs degrees per side (dps).

Kell Gauge measuring Left (Cold Steel Frontier Hawk) Right (Cold Steel Hudson Bay Hawk)
I ground both these hawks secondary bevels to 30inc aka 15dps (as illustrated in photo below)
View attachment 1900313

If your blade has a flat section where guide will rest A)
If your blade has a primary grind where your guide will rest B)

Your Answer:
A) If your guide block will be resting on a flat on the blade, the block should be at the measured dps of the existing grind (assuming you want to match existing).
B) If your guide block will be resting on a primary grind, you will need to know and compensate for the dps of the primary grind when using a guide block.

If B) Bevel angle you want to grind - primary grind angle = guide block angle

Thank you — helpful. Yes, the gauge looks as your photos. The blade has a flat that I was planning on resting on the wood block.

So, if the inclusive angle is 22.5, I would want a 11.25 angle to rest on, one side at a time.

I’m new to this and am trying it out. Thanks

 

[Spey]

The blade has a flat that I was planning on resting on the wood block.
So, if the inclusive angle is 22.5, I would want a 11.25 angle to rest on, one side at a time.

Yes (22.5inc / 2 = 11.25dps bevel to apex) typically ...

From Post #2
"Your Answer:
A) If your guide block will be resting on a flat on the blade, the block should be at the measured dps of the existing grind (assuming you want to match existing)."

One potential variant consideration would be is said knife is a chisel grind where one side is ground at 22.5°dps and the opposite in unground at 0° making it also 22.5°inc (in this case 22.5°inc would also equal 22.5dps), but I believe when you wrote "one side at a time" to mean there are symmetrically ground bevels to the apex on both sides of the blade).
Chisel Ground Example illustrating one potential variant grind:



By your description (knife with bevel to apex at 11.25dps with a flat unground area above the 11.25dps bevel that extends up to the spine) I am assuming you have a Scandi grind similar to both knives in image below:


If so (Scandi grind), I would comment that with bevels this wide it is typically fairly easy to allow the wide bevel face to self index against a stone simply by placing the blade against stone and applying finger(s) pressure to the opposite side bevel as the blade is run across the stone, sand-paper, strop, etc. using an edge-trailing motion.