Question about edge durability on a tapered plane iron

[Joseph Thomas]

I recently finished building my first coffin smoother. Overall I'm happy with how it came out, but I'm finding that the edge on the tapered double iron I'm using is not very durable; I get perhaps 15-20 minutes of nice shavings (using the plane primarily on poplar) before it starts to feel dull.

Some Details:
- I purchased my iron used on ebay and was surprised that the bevel on the iron is 20 degrees; I had expected 25-30 degrees. (There isn't a microbevel.)
- The iron is 2 1/8" x 8", with a small amount of camber.
- I don't think the iron has been overheated by a previous owner; it sharpened about as fast as my other irons.
- I've performed the usual steps to initialize an old iron (removed all rust, flattened the back, checked the fit of the cap iron, etc.)
- The bed angle for the plane is 47 degrees.
- I've been working from the directions in this article: https://www.popularwoodworking.com/projects/smooth-operator/

Is the problem that a 20 degree bevel is just too fragile and I should re-grind to a larger angle? I'd also like to know if there's some reason the iron is set up the way it currently is. (Perhaps it's intended for a different type of plane entirely?)

[Winston Chang]

20 degrees is way too low of an angle. If I were you, I’d try 32 degrees. You could even go a couple of degrees higher, since the bed angle is slightly higher than 45 degrees.

It shouldn’t need any grinding - just hone at a higher angle and the small bevel will grow as you keep using and sharpening it.

[Rafael Herrera]

Are you seeing edge failure in the blade?

If that's the case then, as Winston suggests, sharpen at a higher angle. No need to re-grind the bevel.

Was your iron an NOS item? I've heard that some of those offered on ebay are of poor quality.

I've also bought some irons that have arrived with very shallow bevels, but I have not had a chance to test them.

Nowadays I prefer to buy irons with obvious signs of use just to be on the safe side.

[Joseph Thomas]

Thanks for your help with this.

> Are you seeing edge failure in the blade?

Yes, I think that's what's going on. Right after sharpening, I don't see any light reflecting off the edge. If I plane for a few minutes and look again (from the bevel side) I see a thin, shiny reflection across the edge in the middle of the iron. Unfortunately I don't have a good magnifying setup to look closer.

> Was your iron an NOS item?

I don't think so, I believe it's used. It's stamped "Sandusky Tool Co / Warranted Cast Steel".

Thanks for your suggestion, Winston, sharpening at a higher angle seems like the right thing to try next.

[Rafael Herrera]

I don't think so, I believe it's used. It's stamped "Sandusky Tool Co / Warranted Cast Steel".


I've a Scioto Works jointer with an Ohio Tools iron that kind of falls apart fairly quickly. I replaced it with a Providence Tool Co iron that performs better. Perhaps I should go back and check the bevel.

I try to avoid Ohio Tools and Sandusky irons and choose Sheffield made irons if I can. 2 1/8" double irons show up often on ebay.

[Steve Voigt]

- I've been working from the directions in this article: https://www.popularwoodworking.com/projects/smooth-operator/

Is the problem that a 20 degree bevel is just too fragile and I should re-grind to a larger angle? I'd also like to know if there's some reason the iron is set up the way it currently is. (Perhaps it's intended for a different type of plane entirely?)

Glad to hear you had success following that article! :p Vintage tapered irons can vary widely in quality, but if you are getting 15-20 min at 20 degrees, it's probably excellent steel. As others have suggested, a secondary bevel in the 30-35 range should solve your problems. Good luck with your new plane!

[steven c newman]

May go back and check on my Ohio Tool Co. No. 035, as it has a thick, tapered iron....and a chipbreaker.....

There is an Ohio Tool Co. No. 0-7 iron bodied jointer in my til....did not have a tapered iron....iron did have a "Globe" logo.....

[Joseph Thomas]

Thanks, Steve! Your article is well written. The instructions are clear and I appreciated having a text resource that I could to quickly refer to during the build (rather than searching through a video).

[Jim Koepke]

Hi Joseph and welcome to the Creek.

As was stated earlier the irons of the 19th century were of varying quality. Yours may simply need a slightly steeper bevel or it may benefit from heating and hardening.

One other thing is your iron might be a laminated iron that was beveled on the wrong side. This doesn't occur often, but it does happen.

A simple test with a file will reveal if this is the case.

jtk

[Jim Matthews]

Those older irons varied some, but they're good steel.

Post a photo - if the edge is a blue color.

[Warren Mickley]

I bought a Sandusky trying plane in 1979 and most of the time since have used the original iron. I recommend sharpening at 30 degrees, polishing on an Arkansas stone, and stropping on a clean leather strop.

[John C Cox]

It's worth checking your iron after some use to see if the edge is chipping/rolling or if it's wearing. If it's smooth but worn - it may be the steel.. If it's chipping or rolled, increasing the angle usually helps increase the life.