Can you sharpen on a firebrick?

[inferno]

I'd say no. unless you are "sharpening" unhardened steel that is.

So today at work i sawed up a hard firebrick for my forge. i used an angle grinder for this. and it took a long time. and the brick ate the first cutoff disc very very quickly. switched to cubitron and then it lasted like 3-4x longer. it still was very slow.

so i figured maybe these firebricks are hidden gems for sharpening. and guess what. they're not.

I tried the light yellow one first. its very coarse. like 50 grit or so. and while it did abrade unhardened steel pretty fast. It did absolutely nothing on my 15n20 blade i'm trying to grind a main bevel on. well it lightly scratched it. thats it.

then i tried the 15n20 on the orange one. and this was was even worse. if thats even possible. Supposedly it a lot of aluminum oxide in these stones. i guess it doesn't really matter.

don't try this at home!

because its a waste of time...

I do however guess these are better than flower pots and probably asphalt and regular concrete. and maybe even better than common garden rocks. but i didn't really do any comparison test here. Not going to either.

 

[Matus]

You should do that comparison test

 

[kayman67]

They look good though

 

[Xenif]

Just stamp it with a Honyama stamp and the performance should improve significantly [emoji13]

 

[Garm]

Looks like some cool renge on the left one..
Maybe use the other as a nagura?

 

[HRC_64]

I'm pretty sure this is why they bothered to mine all those cutting stones back in the day

 

[Cbt]

Your experience reminded me of a video on youtube I never bothered to watch about sharpening on a brick.

Nevertheless here is the link:

 

[Chuckles]

 

[inferno]

i guess my bricks are actually more abrasive than those in the vids. i guess you can do it up to a certain hardness. 62-63 is not it.

 

[jkingrph]

A few years back I was with my wife at her elderly uncle's place. He had several old cheap kitchen knives that were so dull that they would not cut. He had no sharpening equipment. I think what he had was lost when a tornado took out a shed in his back yard, but that's a maybe. I found an old common brick, rubbed it on a concrete drive to clean up and got the knives to where they would cut, not even what i would call a good edge, but much better.