Thread: proper included angle

Whilst poking around a couple of weeks ago, I had read that Hart Steel uses a 14.2 degree angle so that it is a 15 degree when using tape. But for the life of me I can't seem to find that on their website. Maybe it was here. Maybe it was something I had fabricated in my own mind

When the Harts were introduced some of the cognoscenti groused about the thickness of spine to width of blade aspect ratio. They noted that the included angle was 13 and change degrees: too thin, too thin they said and unsharpenable with that delicate O1 steel - all of which makes one wonder how the razor makers were able to get such good edges on them.

I think they look just fine and shave very well.

need to add that so far in my testing that SS razors like a bit more angle then there carbon brothers

I doubt manufacturers actually measured the angle… but throughout the history of making razors, most (if not all) manufacturers adhered to the proportion of the blade about 3.5 times the thickness of the spine.

So for example: 4/8th would be bit over 1/8th inch spine, 5/8th would be 3/16th inch spine, 6/8th razor would be a bit under ¼ inch spine, 7/8th to 8/8th razor would be about ¼ inch or more spine thickness.

I agree with Smythe here. When I make razors I like to stick to these guidelines. most of my razors are 1/4 spine and 8/8 blade. I have found that even a little thinner on the spine makes honing difficult and a couple layers of tape are needed to beef up the spine.

These guys are giving you some good info

Bob @ OCD Razors

So, if I've got a Bill Coffey custom straight that has a blade that is 24mm from spine to cutting edge and had a spine that is 3.2mm thick (7.5:1 ratio), is that out of proportion? If so, that would explain why I haven't been able to hone the damned thing to a shaveable edge.

It sounds as if I need a few layers of tape to get the spine up to around 7mm.


Arrrh, it's been so frustrating trying to get a shaveable edge on it.

Originally Posted by johnmrson

So, if I've got a Bill Coffey custom straight that has a blade that is 24mm from spine to cutting edge and had a spine that is 3.2mm thick (7.5:1 ratio), is that out of proportion? If so, that would explain why I haven't been able to hone the damned thing to a shaveable edge.

It sounds as if I need a few layers of tape to get the spine up to around

Actually, the measurement should be from the lower edge of the honing flat to the edge, not the top of the spine. Notwithstanding that, it sounds like you razor has a very narrow included angle (maybe 8 degrees?).

I'll defer to our more mathematically gifted members for confirmation. FYI, there are a couple very long threads about this very topic that go into great detail.

OK, that still makes it 19.5mm to 3.2 mm or a ratio of 6 times. That's still way out of the 3.5 times.

Originally Posted by KingsRam

Whilst poking around a couple of weeks ago, I had read that Hart Steel uses a 14.2 degree angle so that it is a 15 degree when using tape. But for the life of me I can't seem to find that on their website. Maybe it was here. Maybe it was something I had fabricated in my own mind

The first run of Hart's were 14.2 degrees. That worked great if manufacturing tolerances were kept tight. If the blades got much wider than 3/4" the angle would be too acute and edge holding would suffer.

The current Harts are 16 degrees. That way if a blade is a little too wide, the included angle doesn't go below about 15 degrees.