Thread: How easy is it to harden a plane blade?

We get that a lot in the shop ( antiques) when ppl want to sell us stuff, "its old, its grandma's, so it must be good and worth a lot of money!!"

WRONG!!!!

They made Krap years ago too. :eek:

Al

greetings Richard

Back in the dark ages [70s] as an aprentice saw doctor with
spear & jackson we used steel from royal albion and it was reliable and always top quality. from dim memory to harden bring to chery red / quench . to temper light straw/ quench in oil good luck.
gordon.

What cookyboy said about hardening but only the tip (first 3mm). You have nothing to lose. When tempering use an oxy torch from about 100 mm away and heat the area 20 mm or so below the tip and (as the metal is blued from hardening) heat gently and watch the heat rainbow colours travel towards the tip. You can often stop heating before the tip gets that straw colour and it will still travel up. Immerse in any mineral oil but only about 10 mm of the tip and allow the rest to air cool.

You can practice this on an old chisel, screwdriver or centre punch.

Good Luck and Cheers

the question is, were all the old steel blades lovingly handcrafted by greaet forgers, or were some not so great after all?

The blade probably started out good and hard. But then lost its temper through poor grinding techniques.

Here is a link to DIY heat treating: http://www.hocktools.com/diyht.htm

Regards from Perth

Derek

p.s. Vic, how is the #7 blade?

Outstanding!

Thanks for all of your replies folks...what a helpful bunch and what a great forum this is (being a relative newcomer)!!

I have hardened and tempered a few small things (scribers, screwdrivers and the like) but the link from Derek mentions about splitting and warping, which I guess is what I was afraid of. Quenching in oil sounds like the way to go - you learn something new every day - I had never heard of that!

Thinking about Derek's comment about grinding, sounds quite likely. I tried running an old chisel across the back of the blade and, although it was pretty obvious where the "hard" steel began, it still was far less hard than the chisel (and it isn't a very hard chisel either). I think the previous owner has had a go at grinding off the rust which must have pitted the blade slightly and in the process completely ruined a good blade.

Thanks again all - I'll try re-hardening/tempering the blade in a couple of weeks when I get access to an oxy acetylene torch and post the results .

Incidentally, does anyone regularly use this kind of plane? The one I have is stamped EMIR 404 London 21/4 inch. It feels a bit cumbersome compared with a metal plane to me. However, the modern Clark and Williams planes look similar in a catalogue so there must still be some call for them. What is the little leather bit on the front top for?

re. hardening/tempering smallish blades, you might try to find your local blacksmith as a coal fire seems to give a better result.
cheers g.