A little edge geometry help please

[-Jack-]

A little background first. I've been shaving with a Parker Shavette for 10 years now. I primarily use Astra blades which have an edge averaging 16.5°. I also make custom knives as a hobby and decided to try my hand at my own straight razor.

Here's the rub... After getting it sharpened to what I believe (if I'm doing the math correctly) is 16°, I can't seem to even begin to cut hair with it. I have really thick, coarse facial hair, and very sensitive skin of course, so I'm looking for something pretty dang sharp.

heres what I have so far...

Spine - .25"
Total Height - .9"
Bevel height - .79"
Legnth - 2.5"

I'm brand new to sharpening these, so hopefully someone on here can tell me what I've messed up. I started with a 400 grit stone, and progressed with 1000, 3000, 8000.

 

[DrStrange]

2 * asin(0.25 / 2 / 0.79) * 45.0 / atan(1)


I get 18.2 degrees.

I used radian trig functions.

 

[Darth Scandalous]

Based on the numbers you've reported, that would be more like 18 degrees, and I'm not sure your measurement of the active width (i.e. top of spine wear to apex) is accurate based on the photo. If the active width is shorter, the angle will be more obtuse.

18 degrees, properly honed, should shave, even with coarse whiskers, so I suspect it may be a honing learning curve. (16 degrees will likely cut better, though).

 

[rbscebu]

Knowing the steel type and heat treatment process you used would be a help. Some steels, even very good knife steels, will not take a shave-ready edge.

Knowing your grinding process would help. Also, was it done dry or under constant flowing water? If some high carbon steels get to just 200°C while grinding, the shaving ability can be adversely affected.

If your measurements are correct you have a bevel angle of about 18° (9° in knife terms). This can be a good bevel angle for a SR of the correct steel, properly heat treated and honed.

Most experienced knife sharpeners do not know how to properly hone a SR. Properly honed off 8k should shave but not comfortably. If you know how to properly hone a SR, it would be better if you took it up to at least 12k or even higher.

Your whiskers are not as tough and your skin not as sensitive as you think. It is your shaving technique that has you thinking that way.

 

[Sando]

Great looking blade. I hope you get the honing sorted.

 

[-Jack-]

Thanks for the feedback! I used O1 tool steel, normalized at 1400° for 15 minutes, then quenched at 1600° in veg oil. Ive got Parks AAA, but thought it would be too fast for O1. I hand grind on a 2X72 bare handed so I don't let it get real hot during the grind. As for the photo of the active edge, it's a bit deceiving. I triple checked that measurement, but needed a third hand to hold the blade, caliper, and camera .

Guess I'll go back to stones
Thanks again

 

[Darth Scandalous]

What synths are you using? Not all 8k are created equal.

 

[rbscebu]

Thanks for the feedback! I used O1 tool steel, normalized at 1400° for 15 minutes, then quenched at 1600° in veg oil. ....

Do you temper the steel after this?

Your O1 steel should work for a straight razor.

 

[Doc226]

Have you honed a straight before? Different than a knife for sure.

Nice start to the blade, so you have scales on it?

 

[-Jack-]

Wow! So many replies and questions! This is awesome . (1) I have to admit I don't even know what synths are. (2) I did temper it at 375° for two hours. (3) I have not honed a SR before, but did stay at a Holiday Inn once, and watched a bunch of YouTube how to's (thanks Lewis Razors & Jacob Ray Razors). & (4) No, I haven't made scales yet. I want to make sure I get it shaving before I go to that much more work.

You guys are great

 

[JaggardJ]

Synth = synthetic stones, man made. Vs natural stones, jnats etc.
I'm watching this thread expecting some excellent info.
Can you explain what stones you used for the honing?

 

[Bevel]

First off, if that's your first attempt at a straight razor, it is a fine attempt. I love handmade things so I'm looking forward to seeing you getting this shaving.

A few observations:

1. You've shaved with a shavette for 10 years so I'll assume your technique is fine.
2. You mentioned 400, 1k, 3k, 8k stones so it's safe to assume these are synthetic stones and a good start.
3. As others have said your angle is 18.21° and that's a good angle and will shave perfectly fine.
4. On the metallurgy front your material choice and process seems fine but I'm no expert on that so I'll assume you're good.

Next steps:
Your bevel isn't set properly yet so everything below is getting to that point, pun intended.

Before you do anything you need to flatten the cutting edge so it's perfectly straight.
If you look at the picture below the heal of the blade looks to be protruding and as a result you're not getting the first third of the blade at all so you need to fix this before anything else. Just breadknife it, set a bevel and see where you are.

The protruding heal is lifting it up and, while you're missing the first third, all the pressure it should be getting is being transferred to the toe end resulting in the excess wear encircled below. It might be an idea to check the spine geometry with a known straight edge. Some closeup pictures of the spinewear so far might help, both sides. The honewear should be an even line right the way along both sides. (Easier said than done but once you have it shaving, you're obviously good at grinding so, you'll be able to go back and fix the uneven honeware with a light regrind)

Once that's fixed do you have any sort of magnification?
A cheap 30x loupe will do. If so use it to see if your current scratch pattern goes all the way to the edge. You can clearly see that's not the case in the above picture but check if the breadknifing exercise fixes this.

If you don't have magnification wet your thumbnail, point your thumb about 30° downwards and pull the blade from heal to toe over your nail using only the weight of the blade. If it falls off your bevel isn't set. If it drags all the way it likely is set but I'm willing to bet it will slip off somewhere along the length. You'll also feel any imperfections or chips in the blade.

If this seems ok, look at the edge under a strong light source, edge on, and see if you can detect any reflections of light or flat spots in the very edge. Again magnification would be useful here. Moving the blade around while perpendicular to the light should show up flat spots if they're there.

It's difficult to tell from the pictures but the heal end of the spine seems to have very little honewear compared to the rest.
Anyway flatten it try set a new bevel and come back to us.

 

[-Jack-]

Jaggard - Thanks for the clarification. I use a couple DMT diamond stones for the lower grits and some unknown softer stones that were given to me. Sorry for being clear as mud.

Bevel - that's a whole lot of awesome stuff you gave me! And you're definitely right, my hone wear really showed off the imperfections. I didn't want to "fix" that before I shared the pictures here. I figured someone like you would be able to help me see where I need to make improvements. I went back to the grinder yesterday and fixed those uneven grind areas, pulled the hollow grind much closer to the spine, and took care of that proud heel. I also went back through all the stones, but unfortunately I shaved that morning so I'll have to wait a few days to find out if I've fixed any yet.

I'll definitely be on the lookout for some magnification equipment .

 

[Gamma]

"....I have not honed a SR before...."

Coarse whiskers are not the issue, it's your bevel set that is the issue.

Not all hones are good for honing razors.
Not all stones have accurate grit ratings. Just because the box said 8000x, that doesn't mean it's really 8k.
Hones for honing razors should be dead flat.

Learn to set the bevel. Learn to set it so you can shave with it. When you can do that, you are on your way.
It won't be the best shave, but it should not hurt or tug badly.
Until you get that down pat, don't go forward.

The bevel is the edge, No bevel = no edge.
My bevel stone of choice right now is a 1.5k Shapton Pro - works well.

An 18 deg bevel on a well made 01 blade can probably shave just fine when it's been set correctly.

Did you strop the blade? I didn't see that mentioned.
If not, you'll need to do that.
You might consider an abrasive compound on a strop for finishing... 8k isn't all that fine and I suspect your 8k isn't even really 8k to begin with.

1st things first, learn to set the bevel.

How's your lather? Canned stuff or soap/brush? You'll need really good lather to shave with a straight.

But get that bevel set first... no soap in the world will fix a bad bevel.

 

[MileMarker60]

Jaggard - Thanks for the clarification. I use a couple DMT diamond stones for the lower grits and some unknown softer stones that were given to me. Sorry for being clear as mud.

Bevel - that's a whole lot of awesome stuff you gave me! And you're definitely right, my hone wear really showed off the imperfections. I didn't want to "fix" that before I shared the pictures here. I figured someone like you would be able to help me see where I need to make improvements. I went back to the grinder yesterday and fixed those uneven grind areas, pulled the hollow grind much closer to the spine, and took care of that proud heel. I also went back through all the stones, but unfortunately I shaved that morning so I'll have to wait a few days to find out if I've fixed any yet.

I'll definitely be on the lookout for some magnification equipment .

Jack, I have a some experience with making razors
I'll send you a Pm.

 

[Doc226]

Jack, I have a some experience with making razors
I'll send you a Pm.

This is like Bach saying "I've done a little music" I will try to help out