Heat Treating, Forging, Etc.

[bluesman 7]

There was a recent discussion in another thread about heat treating and I thought it would be good to have a dedicated thread to the subject along with forging, etc. The subject does not have to be strictly razor related, but of course that is how we all got here.

OK, so the quick and dirty on heat treating carbon steel is that when the steel is heated above it's critical temperature (in excess of 1400 F depending on composition) the lattice structure changes from bcc (body centered cubic) to fcc (face centered cubic) The fcc can hold more carbon in the lattice than bcc steel. When the steel is quenched it turns back to bcc, but if done quickly enough the carbon remains trapped in a lattice structure that does not have room for it. This causes stress in the lattice and makes the steel hard (martensite) The steel is brittle hard at this point and can fracture easily, so the steel is tempered by heating (350-500 f depending on the final use) The tempering allows some of the carbon to move out of the lattice reducing some of the the strain and making the martensite softer and less brittle.

This is a very crude description, but I did not want to write a book here. A good book on the subject is "Steel Metallurgy for the Non-Metallurgist" John D. Verhoven

 

[sfeile]

Hopefully we get some more good conversation going. I was enjoying the thread we hijacked.

 

[Hoka Hey]

@bluesman 7, I was a hobby knife maker. Did the HT on carbon, sent the 3v, S30v stainless out. Thanks for the grind info. I was suffering alcohol induced dyslexia. I had an 8 inch wheel, but never used it. Stuck to flat grinds, or stuff off the anvil.

I'd be interested in hearing about forming. Total stock removal? Jigs?

I've come to a realization that making a razor is as different from making a knife as sharpening a razor is considerably different than sharpening a knife. And not just the evil known as trigonometry. A knife you can eyeball, call it good. A razor you've got significant constraints.

I appreciate your input since you have some experience in making razors. Fairly unique, and certainly interesting.

 

[bluesman 7]

And not just the evil known as trigonometry. A knife you can eyeball, call it good. A razor you've got significant constraints.

It doesn't need to be very hard. Yes, the razor geometry is most often expressed as an angle, but an angle can be just as accurately be expressed as a ratio. It's often stated that a width to thickness ratio of 3.5/1 to 4/1 will make a good razor (16.26 degrees and 14.25 degrees respectively). This assumes that the grind comes all of the way to the top of the spine. Now, 14.25 is a bit on the acute side for a comfortable shave, but if you use the 4/1 ratio and don't bring the grind all the way to the top of the spine you will have a very acceptable angle without doing any trigonometry. Using the ratio of 4/1 you would use 1/4" material to make an 8/8 razor and 3/16" material to make a 6/8 razor. Many successful razor makers never go any deeper than this into the angle of their razors.

In one of Charlie Lewis' videos he is seen using a HF digital caliper to measure the thickness of the spine on a forged blank, multiplying that measurement by 4, setting the caliper to this product and using the caliper to scribe a line on the blank where the edge will be, and then just grinding to that line. It doesn't need to be any more difficult than that.


I don't know why the text came out red.

 

[Hoka Hey]

It's cool that way. Once again a mystery simplified. Sort of. How do you do it? I saw your blanks prior to heat treat. More meat on the edge, thinner mid. Anything I come up with is guess or intuition. Not reliable, even if it's right.

 

[Hoka Hey]

And yes, I'm trying to learn enough to ask intelligent questions.

 

[bluesman 7]

It's cool that way. Once again a mystery simplified. Sort of. How do you do it? I saw your blanks prior to heat treat. More meat on the edge, thinner mid. Anything I come up with is guess or intuition. Not reliable, even if it's right.

I built a jig to do the rough grind. I have demonstrated it at meets. It's hard to describe and setting it does involve trig. There is a video of me demonstrating it somewhere on the internet. I'll try to find it tomorrow. My pre HT blanks are actually parallel sided within a few thousandths. The end view may look as if the mid is thinner, but that is just some edge rounding

 

[sfeile]

Thank you for explaining it that way. I'm not forging, but going to do some modification on a GD. It has a little bit of an uneven spine I wanted to fix by thinning. Now I have a better idea of where to go with it since math is not my strong suit.

 

[Hoka Hey]

I built a jig to do the rough grind. I have demonstrated it at meets. It's hard to describe and setting it does involve trig. There is a video of me demonstrating it somewhere on the internet. I'll try to find it tomorrow. My pre HT blanks are actually parallel sided within a few thousandths. The end view may look as if the mid is thinner, but that is just some edge rounding

Ok. I officially love you. Just for being willing to satisfy my couriousity. No voodoo. Any pictures of the jig? If not proprietary.

Thanks

 

[bluesman 7]

Thank you for explaining it that way. I'm not forging, but going to do some modification on a GD. It has a little bit of an uneven spine I wanted to fix by thinning. Now I have a better idea of where to go with it since math is not my strong suit.

Since you will be working with an already ground razor you will be measuring the width to the widest point of the hone contact, NOT the total width of the razor. I assume that you will be thinning the spine by tapeing the edge and using a diamond plate or course stone. Measure your width from the edge to the top of the hone wear that you have made by thinning the spine. Using a ratio of 3.6/1 will give you an inclusive angle ~ 16 degrees. So, your width divided by 3.6 would give you your desired spine thickness for an angle of 16 degrees. A ratio of 3.2/1 will give you an angle of 18 degrees. Anything in between those two angles will shave fine. If you want more help with this just ask.

 

[bluesman 7]

 

[Lmarkow]

Endlessly interesting, even if I can't do math (or hone a razor).

 

[bluesman 7]

Welcome Larry. What are you doing here? First your'e honing, and now your'e reading about heat treating and grinding. Just kidding ,you are more than welcome to join the conversation.

 

[bluesman 7]

After you have established your'e angle you can remove material from above or below the 'land' (the hone wear that you created by thinning the spine) for aesthetics. Just leave a thin line of land to ride on the hone

Since you will be working with an already ground razor you will be measuring the width to the widest point of the hone contact, NOT the total width of the razor. I assume that you will be thinning the spine by tapeing the edge and using a diamond plate or course stone. Measure your width from the edge to the top of the hone wear that you have made by thinning the spine. Using a ratio of 3.6/1 will give you an inclusive angle ~ 16 degrees. So, your width divided by 3.6 would give you your desired spine thickness for an angle of 16 degrees. A ratio of 3.2/1 will give you an angle of 18 degrees. Anything in between those two angles will shave fine. If you want more help with this just ask.

 

[bluesman 7]

I found the video of the jig demonstration. It starts around the 35 minute mark and lasts about 15 minutes


The rest of the tape is from the 2016 North Texas razor makers meet.

 

[sfeile]

After you have established your'e angle you can remove material from above or below the 'land' (the hone wear that you created by thinning the spine) for aesthetics. Just leave a thin line of land to ride on the hone

Thank you! I was actually planning on flattening the top of the spine after I got my correction done anyhow. Wanted to get rid of that big ugly radius on top. It will be my entry for the GD modding contest if you are interested. I'm going to try and make progress reports as I go.

 

[bluesman 7]

I'll follow along.

I would recommend a little material on the spine north of the land. Otherwise any hone wear could make the edge of the spine quite sharp and damage your strops

Thank you! I was actually planning on flattening the top of the spine after I got my correction done anyhow. Wanted to get rid of that big ugly radius on top. It will be my entry for the GD modding contest if you are interested. I'm going to try and make progress reports as I go.

 

[sfeile]

I'll follow along.

I would recommend a little material on the spine north of the land. Otherwise any hone wear could make the edge of the spine quite sharp and damage your strops

Yes, very true.
I didn't want to take it all away. Just try to flatten it to give it cleaner lines. Take it almost to my hone line, leave maybe 1mm to 1.5mm, then break the corners with a file so they aren't sharp.

 

[bluesman 7]

Just heading out to the shop to do a san mai exercise. I've done two san mai razors with mixed results. This is going to be a cleaver. Mostly an excuse to try out some new ideas about keeping the middle layer in the middle.

 

[sfeile]

Just heading out to the shop to do a san mai exercise. I've done two san mai razors with mixed results. This is going to be a cleaver. Mostly an excuse to try out some new ideas about keeping the middle layer in the middle.

Sweet! What are you using on your layers? You going carbon over stainless? Or just different grades of carbon? Also, you taking pics for those of us with no forge to live vicariously through?