Thread: Forged razor out of 1084 not performing as well as I hoped trying to figure out why

If i remember correctly you want to be around 3.8-1 from the edge to where the spine contacts the hone for a given spine thickness. 16*-18* included angle. This is a generalization btw. I made one and it was at 3.4-1 after a piece of tape and it shaves well.

What temp did you temper it at? Maybe too soft, at 57rc I suppose your edge could be too flexible to stay on the hone. I’d do what rez said and try a bunch of tape to see if it will hold an edge. First thing to do is to get the edge to follow the shape of the spine, set a bevel then grind to it to clean up your hollows and get the geometry close.

I’m sure one of the resident makers will be along and should be able to sort you out.

Originally Posted by jfk742

If i remember correctly you want to be around 3.5-1 for the edge to where the spine contacts the hone for a given spine thickness. 16*-18* included angle.

What temp did you temper it at?

I’m sure one of the resident makers will be along and should be able to sort you out.

I tempered it at 425 F, which should have resulted in 60 Rockwell, but the oven I used to temper it was not my digitally controlled kiln, as it was still cooling down from 1,500 F at the time, just an inexpensive small toaster type oven that would go up to 500 degrees F or so. I used an oven thermometer, but had a hard time getting the toaster oven to stay exactly at 425 F - dial didn't have exact markings, rheostat style rather than 'punch in a number', small, cheap, etc.

I think for the next one, I'll just wait the two or three hours it takes the kiln to cool down and use it instead, as it's a lot more reliable and easy to use.

Looking at http://www.cashenblades.com/steel/1084.html, it looks like I could have tempered it as 300 F and gotten it to 65 Rockwell. Time to make another then! Thank goodness 1084 is cheap and plentiful. If I'd blown through a chunk of CPM S35VN, I'd be a lot less happy right now

Maybe try putting it in the oven or a couple of fire bricks before it gets to room temp to give your kiln a chance to cool without the blade sitting at room temp too long. Also try tempering it at 400, you can always temper it again if the edge is chippy to bring the hardness down.

I just want to say I’m a complete novice at this and just regurgitating what I learned recently at a meet. I’m very interested in how it all goes though.

Originally Posted by jfk742

Maybe try putting it in the oven or a couple of fire bricks before it gets to room temp to give your kiln a chance to cool without the blade sitting at room temp too long. Also try tempering it at 400, you can always temper it again if the edge is chippy to bring the hardness down.

I just want to say I’m a complete novice at this and just regurgitating what I learned recently at a meet. I’m very interested in how it all goes though.

Yeah, I need to figure out how long I can wait between annealing at 1,500 F and tempering at 300 F. At this point, I'm uncertain as to whether 1084 needs to be tempered the moment it cools to room temp, or if it can stay at room temp for several hours before being tempered.

So austenizing at 1500 should get you about 65rc as quenched, tempering at 400f should be in the 60-61rc area (I’m referencing Kevin Cashen’s website). Maybe your low rc is due to making the edge too thin before ht? ie., losing heat on the way from kiln to quenchant?

60-61 should work just fine at the angles we hone razors at, as I understand it.

Originally Posted by jfk742

Maybe your low rc is due to making the edge too thin before ht? ie., losing heat on the way from kiln to quenchant?

Entirely possible. I did grind it fairly thin before heat treat, definitely thinner than the usual 'thickness of a dime' recommendation. It did hit the oil quench within 5-10s of getting out of the kiln though. A good possibility is that the tempering temp was too high, I believe the small toaster oven hit as high as 450 at points, and with the ah, lack of stability in terms of the tempering temp, that could be another cause.

Is there any issue that you know of with letting a blade sit at room temp for say, 2 hours or so before tempering it? I'm thinking if I can wait for my digitally controlled kiln to cool down from the 1,500 F annealing temp, I'd have a lot more luck with getting an even tempering temp.

I would say go to the thickness of a dime or a little more, it will also help with warping, and then get it to the quench as fast as possible. You’ve got to beat the nose, from 1500f to 1000f in less than 2 seconds if I’m reading the graph correctly. At 400f you can take it out and let it air cool from there to room temp, should give you enough time to cool the kiln if you leave the door open.

You may want to send a pm to bruno, bluesman7, or spazola. The 3 of them have a ton of knowledge. If you do, report back to your thread, as we all like to learn.

Originally Posted by GuyMontag

Entirely possible. I did grind it fairly thin before heat treat, definitely thinner than the usual 'thickness of a dime' recommendation. It did hit the oil quench within 5-10s of getting out of the kiln though.

I'm sorry, 5 to 10 seconds? Did you have coffee first? I know knives let you get away with that sort of thing because they have a lot of thermal mass.
.
that is much too long. I try to keep this time as short as I possibly can: out of the kiln and into the quench in 1 fluid motion that takes a second or so.
A razor has a very low thermal mass. Especially if it is already much thinner than is good, I can pretty much guarantee that this right here is your problem.
A razor's edge works like a thin cooling fin. By the time you hit your quench it was already far too cold.

Originally Posted by GuyMontag

Is there any issue that you know of with letting a blade sit at room temp for say, 2 hours or so before tempering it? I'm thinking if I can wait for my digitally controlled kiln to cool down from the 1,500 F annealing temp, I'd have a lot more luck with getting an even tempering temp.

None whatsoever in terms of end result. The only risk you run is with san mai blades that have a lot of stress in them after quenching.
If you leave those sitting for 2 hours, there is a good chance your razor will become 2 pieces