Sometimes however, you must use a straight knife and the only straight edge knife for me is the Carreducker that I got in 2011. The Carreducker is at about 15 degrees angle, I do not like those knifes at 60 degrees; they are too heavy, too thick, and clumsy.
On my curved edge knife the steel is tapered from handle to point to about half thickness.
They are of course only sharpened on one side and flat on the other.
I use 1/2" 2 sided tape for all my hemming and so I skive the full 1/2"
This 3M tape has ultra thin adhesive so two or more layers don't cause a problem with the sewing machine. Two sided tapes are vastly different, there can be some with very thick adhesive; avoid those. You can use 1/4" tape too.
My approach to skiving is to get there in three passes:
- Take the edge down about 2/3rds thickness and 1/8" in.
- This leaves a ridge to remove so I take that from 1/2 way into the 1/8" skive all the way to the 1/2" line. (I usually scribe the 1/2" line)
- Lastly I take the edge down to a fine edge.
Feeling and looking at the edge is important to know that you have got it down to a nice smooth taper.
Here I use the Carreducker method: a piece of sand paper attached to a plank on one side and a piece of leather on the other. I like to use a high quality 220 paper, if you are only touching up the edge one piece of paper may last years. If you are starting a new blade use 120 grit.
Some people are convinced that you need polishing compound on the strop side... I say no, I never use any. My secret is to us an oil tanned leather for the strop. I have a nice piece of Latigo Side Burgundy it has served me well for years.
What's the point of the strop? The strop is to remove the little burr on the edge of the steel. This little burr referred to as the "wire edge" it will always be there, it easily gets broken off by the repeated stropping back and forth. The burr can be felt with your finger tips. I use the "sticks in your finger nail" method of confirming my success.
Remember also you can look right down at the edge of the knife, if you see any light reflected then you know you have a little more work to do.