Thread: My first go at hollow ground

I use the time recommendation for my soak time in the forge, after bringing it to critical and letting it come back down to black at least once to relieve stress in the steel from forging & grinding. Most of the time I will simply soak at critical for 8-10 minutes and quench for O-1 or 1095. I believe most of us will temper for one hour at a set temperature, I double temper at 350F personally. I could be wrong, but all of my customers have been very pleased. Keep in mind that mind that I mostly sell knives, but have a handful of razors in our SRP member hands.

Originally Posted by 3Drew101

The place I get my steel from recommends the following for tempering

Tempering:
150C (300F) Rockwell C62
200C (400F) Rockwell C60 - 61
232C (450F) Rockwell C58 - 59
290C (550F) Rockwell C56 - 57

Hold at tempering temperature for about one hour per inch of thickness


so figure for 4mm thick temper time = 9min
5mm = 12min
6mm = 14min

so as I use mainly 5mm that has lost a little width while I'm working on them I'd go for 10min, if i'm wrong please tell me so i can adjust accordingly.

Hi guy’s I’m going to go through my heat treating process so you know exactly what I’m doing.

1. Normalizing I take the blade up to critical temp (until its no longer attracted to a magnet then let it cool back down to black. I do this three times just to ensure that it has the same structure all over.
2. Heat treating take the blade up to temp again until its no longer attracted to a magnet then let it soak for (depending on thickness) 4mm = 5min, 5mm = 6min, 6mm = 7min. this is working off the information from my steel supplier who recommend 30min per 25mm (1”) thick. Then quench in hot oil until the bubbles has almost stopped then back in the forge for another two rounds.
3. Tempering as soon as the last quench is done and the blade is still hot it goes into the oven at 150c for depending on thickness 4mm thick temper time = 9min 5mm = 12min 6mm = 14min

The reason why I heat treat three times is to ensure that the crystals have all become the same size, this is something my granddad taught me to do, he was an engineer and tool maker and during WWII he worked with Barnes Wallis on the casing for the bouncing bomb so I don’t know if its over engineering for a razor but it seems to work, doesn’t take that much longer in the grand scheme of thing so I’m going to keep on doing it.

I’ve added the info from my steel supplier, this is for 01 tool steel and I’m not sure if it varies for other steels.
If I am doing something wrong please point it out so I can correct my process.

Drew

Hardening Heat slowly and if possible pre heat at 300-500°C before raising to the hardening temperature of 780-820°C. Pre heating is especially desirable for complex sections. Soak thoroughly allowing 30 minutes per 25mm of ruling section before quenching. Light sections should be quenched in oil from the lower end of the hardening temperature range. Tempering is always necessary after hardening.
________________________________________
Tempering Temper between 100°C and 350°C. Soak well at the selected temperature and soak for at least one hour per 25mm of total thickness.

Temperature [°C] 100 150 200 250 300 350
Hardness [HRc] 64-63 63-62 62-61 60-59 58-57 56-55

Originally Posted by 3Drew101

Evening all,

This is my fist crack at a hollow ground razor, it’s nearly 10/8” fixed blade with a natural horn blade guard fixed with pewter wedges and brass pins.
And it shaves as good as it looks!
Attachment 179923Attachment 179924Attachment 179925Attachment 179926Attachment 179927Attachment 179928


And these are three Did a little while ago

Attachment 179930Attachment 179931Attachment 179932
Attachment 179933Attachment 179934Attachment 179935
Attachment 179936Attachment 179937Attachment 179938

I'm still enjoying myself too much to call making these razors work, and I can't see that changing any time soon!

Beautiful works of art, I've read a few comments regarding your tempering times. If it holds a good edge and shaves well then your doing something right dude. Soak it up and keep doing what your doing and enjoy. The world is full of experts ha ha

Nice smilers those.
Next one I make, I will attempt to do a smile grind for the first time.
Joe

Tempering for 10 mins seems a bit short.
As it is intended to relieve stresses, longer is better. I use at least 1 hour.
Also, 62 is a bit too hard for comfort. Most people go for 60-61 because that allows for a very fine edge that it not too brittle, and not too hard to hone. 64 would be silly. It would make honing truly onerous, and result in an edge that would chip out almost by looking at it.

Originally Posted by Bruno

Tempering for 10 mins seems a bit short.
As it is intended to relieve stresses, longer is better. I use at least 1 hour.
Also, 62 is a bit too hard for comfort. Most people go for 60-61 because that allows for a very fine edge that it not too brittle, and not too hard to hone. 64 would be silly. It would make honing truly onerous, and result in an edge that would chip out almost by looking at it.

Agreed,
A good temper is as much a function of time as it is temperature regardless of how small the section is. I start with an hour and have never had to go to two. If I struggled to hone I would temper for a further 30 mins to 1 hour. Some guys go straight for two hours in the oven.

Joe

Originally Posted by Bruno

Tempering for 10 mins seems a bit short.
As it is intended to relieve stresses, longer is better. I use at least 1 hour.
Also, 62 is a bit too hard for comfort. Most people go for 60-61 because that allows for a very fine edge that it not too brittle, and not too hard to hone. 64 would be silly. It would make honing truly onerous, and result in an edge that would chip out almost by looking at it.

Bruno-I was talking about "as quenched" hardness up to 64 with a proper soak in o1, not suggesting to aim for 64 as an end result. and Bruno- the statement on tempering as a stress relief- i agree wholeheartedly. its not just a matter of reducing the hardness, its about equalizing internal stresses as well. I do think ease of sharpening is better for anyone interested in maintaining their own blades. it seems a lot of folks have become obsessed with highest degree of hardness rather than ease of maintenance. it doesn't take an ultra hardened blade to achieve keenness and edge holding. sometimes its more a matter of ingredients in a particular steel that affect the ability to achieve keenness. sometimes its the manner of heat treat that means the most. will the particular steel benefit from multiple quenches or not in order to refine the grain size? lots of factors, but as hipsley said, if it takes an edge and shaves successfully then the proof was in the pudding. optimal does not mean essential by any means. the shave and ease of maintenance are the test of any blade.

Originally Posted by silverloaf

Bruno-I was talking about "as quenched" hardness up to 64 with a proper soak in o1, not suggesting to aim for 64 as an end result. and Bruno- the statement on tempering as a stress relief- i agree wholeheartedly. its not just a matter of reducing the hardness, its about equalizing internal stresses as well. I do think ease of sharpening is better for anyone interested in maintaining their own blades. it seems a lot of folks have become obsessed with highest degree of hardness rather than ease of maintenance. it doesn't take an ultra hardened blade to achieve keenness and edge holding. sometimes its more a matter of ingredients in a particular steel that affect the ability to achieve keenness. sometimes its the manner of heat treat that means the most. will the particular steel benefit from multiple quenches or not in order to refine the grain size? lots of factors, but as hipsley said, if it takes an edge and shaves successfully then the proof was in the pudding. optimal does not mean essential by any means. the shave and ease of maintenance are the test of any blade.

Precisely,

This is why I go only for a 1 hour temper to start. Its because I can't be sure how optimal the hardening has gone. The hone always informs me. This is purely a practical consideration over theory. If I get a very hard edge, one hour would not be enough and would relinquish more martensite. Chippy edges are another real problem if they are too hard, I can vouch for that.

Joe