Making Test Coupons

CDHumiston

CDHumiston

Joined
Feb 17, 2009
Messages
1,464
I've been doing some heat treating on stock removal blades heated in my forge and quenched in Canola oil. I have been getting pretty good results when testing HRC with my tester. However I am not breaking the blades to look at grain structure.

I want to make some coupons to do the testing on and want to make sure I do it right. From what I have read I should break the coupons and test them after heat treat but before tempering. Is this correct?
 
1"X2" coupons work well.

After the quench, clean them us and hardness test.
Then, break and inspect the grain.
Finally, temper and test the hardness again.
 
Using test coupons is how you can dial in your HT. It will tell you if the steel is getting fully hardened, and allow trying different tempering points to get the desired final hardness.
For the most accurate testing, the coupons should go through the same procedures as the blade.

TIP:
Using a white metal marking paint-pen to write pertinent data on the coupons is wise. The white paint pigment is titanium dioxide, and will survive HT. Sharpie and Markal brands are cheap and work well.
These pens are also great for marking your steel when it arrives so you know what it is later on. I write the steel type and any notes on both sides and both ends of the bars as soon as I unpack them. I have a few bars of 20 year old unknown steel that I got before I started doing this and have no idea what they are now.
Additionally, writing the steel type (and any notes like the customer's name) on the tang of a blade before HT will let you know what steel the blade is and what project it is for. It is easy to set a blade down on the bench and come back a few weeks later and not know which steel it was made from (especially if you do HT in larger batches). This is also really good ID method if you send your blades out for HT.
 
Stacy E. Apelt - Bladesmith said:
Using test coupons is how you can dial in your HT. It will tell you if the steel is getting fully hardened, and allow trying different tempering points to get the desired final hardness.
For the most accurate testing, the coupons should go through the same procedures as the blade.

TIP:
Using a white metal marking paint-pen to write pertinent data on the coupons is wise. The white paint pigment is titanium dioxide, and will survive HT. Sharpie and Markal brands are cheap and work well.
These pens are also great for marking your steel when it arrives so you know what it is later on. I write the steel type and any notes on both sides and both ends of the bars as soon as I unpack them. I have a few bars of 20 year old unknown steel that I got before I started doing this and have no idea what they are now.
Additionally, writing the steel type (and any notes like the customer's name) on the tang of a blade before HT will let you know what steel the blade is and what project it is for. It is easy to set a blade down on the bench and come back a few weeks later and not know which steel it was made from (especially if you do HT in larger batches). This is also really good ID method if you send your blades out for HT.
Click to expand...

Great info! Thanks!
 
Stacy E. Apelt - Bladesmith said:
It is easy to set a blade down on the bench and come back a few weeks later and not know which steel it was made from (especially if you do HT in larger batches).
Click to expand...

This has just recently happened to me...I have a couple blades that I have no idea if they are 1084 or 1095. Same size steel with all the markings rubbed or ground off!
 
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