Checking Temper of Old Irons

[Bill Haumann]

Is there an easy way to check the temper of an old plane iron?
I have several old (Auburn Tool, James Cam) tapered irons that are pitted near the edge and I would like to figure out if the blade is tempered beyond the pitting.

- Bill

[David Weaver]

Use a single cut file - a good one, not some imported piece of garbage.

since you're away from the edge due to the pitting, you'll have to file the side. Make sure that you're paying attention to whether you can cut the hard lamination and not what is probably wrought iron above it. If you can just *barely* cut the hard steel or not at all, then it's probably fine.

Don't file the flat back, that'll be misleading. do the sides.

If you can file an appreciable amount away (like the file would cut into a saw plate), no good.

[george wilson]

David is correct. A FINE cut file will be the best choice. A fine cut file will cut harder steel than a coarser cut one. Most likely due to more teeth per inch bearing on the surface to be filed. The file should be in NEW condition,with NO shiny edges at all on the teeth,and NO rust.

I used antique blades for many years in Williamsburg,and did find that the blades that I could BARELY file held their edges the best.

[Bill Haumann]

Excellent! Thank you both.