Replies

1. 
   forrestb | Feb 17, 2011 01:21pm | #1

   lost heat treatment

   Usually when you overheat an iron on the grinder you have only damaged a small portion of the tip.  Other than a new iron, you could gently on the grinder remove about 1/4 inch of the tip and re-sharpen it such that you do not burn the tip again.

   High speed grinders can easily overheat iron.  Units like the Tormek are slow watercooled/lubricated for that reason.

   Forrest

2. 
   DonStephan | Feb 17, 2011 08:18pm | #2

   Always being very careful to avoid overheating, I used a grinder to recreate the hollow on plane irons and chisels.  I was literally dunking in water after every two light passes, only a few seconds of grinding.  But I was constantly resharpening the tools because they didn't hold the edge long at all.  Last spring I discussed same at a Lie Nielsen tool show and was told the temper can be affected at 300 deg F but iron doesn't turn blue until 600 deg F. 

   On the advise of LN I switched to "grinding" on 80, 150 and 240 or 400 (can't remember) using Eclipse style honing guide, then hone when needed using water stones. After the first few times my edges stayed sharp for reasonable periods of time.

1. 
   lwilliams | Feb 17, 2011 09:34pm | #3

   Don, I assume you were also

   Don,

   I assume you were also told how great A-2 steel is at the show. Well, you have to heat A-2 to 500º to get the hardness down to RC 60. I assure you you'll see a color change at 500º. I haven't asked LN what temperature they temper their A-2 irons at but I'd guess it's around 350º.

   You can see this on Ron Hock's blog at :

   http://hocktools.wordpress.com/2011/01/31/diy-heat-treatment-of-tool-steel/

   or here:

   http://pmpaspeakingofprecision.com/2010/07/14/temper-colors-for-steel/

   or an A-2 tempering chart here:

   http://www.diehlsteel.com/a2.aspx

   If someone wants to limit themselves to only straight cutting edges, I suppose they can get by with sandpaper but edge shapes required by traditional hand tool work require grinding. Fear of grinding is a huge barrier to hand tool work out there and it shouldn't be. Those promoting that fear would be better served by teaching some basic grinding principles and techniques. It's pretty simple stuff.

1. 
   blopar | Feb 17, 2011 10:10pm | #4

   The last post is dead on, learning to sharpen your tools is the most basic skill  that everyone should master before anything else. I spent years avoding the task because I just didn't know to perform the task properly and the quality of my work paid for it. When I realized that I needed to master the skill Iwent to harbor freight and purchased a set of wood chisels and went at it, they got the hell kicked out of the and were ground down to stubs but now I can hone a chisel by hand in less that a minute and be right back to work.

   The answer is yes it can be repaired, you need to grind past the discoloration first, however if its just the very corner less than 1/16" you will probably notice little if any difference. If I need to grind that much material away to re-establish a cutting edge I will got to the belt sander fisrt, I can remove a great deal of material very quickly without the risk of overheating the edge, keep a pail of water at hand and quench frequently. after that hollow grind the blade and proceed to honing. 

3. 
   lwilliams | Feb 18, 2011 08:57am | #5

   I wish you'd posted a photo. How badly is it over heated? I wouldn't grind off more than necessary, just to the end of where it's discolored.

   Square a line across the iron at the point you want the new cutting edge located. With a well dressed coarse (36 grit) wheel, grind at 90º to the face of the iron.Grind to your square line. After this, keep the wheel dressed and regrind the bevel. As the flat at the end of the iron gets small, slow down and take your time. Grind to where you just have a fine hair-line of that flat left then move to your stones.

   Grinding is a rough shaping operation, do it all with your coarsest grinding wheel and keep the wheel dressed.

4. 
   silkwj | Feb 18, 2011 07:53pm | #6

   photos

   Hi All,

   Thanks for all the tips. I'll grind it down past the discoloration, more carefully this time. Photos attached.

   
1. 
   lwilliams | Feb 18, 2011 08:15pm | #7

   Turners have different ideas about grinding than one finds in more traditional woodworking. I can't really say much about how turners prefer to work but I grind a lot of  bench type woodworking tools. Avoid the white and similar wheels that were actually developed for surface grinding. Get a normal gray coarse wheel, as coarse as you can get. Also get a single point wheel dresser, for a 3/4" wide wheel a 3/4 carat dresser works well. Don't be afraid to get aggressive with dressing, a serrated freshly dressed surface grinds cool and quick. Grizzly sells a 3/4 carat single point dresser for about $11 and this is about the most bang for the buck I know of in woodworking.

   Regrinding a bevel that's been made too acute is an almost guaranteed way to overheat the edge. Always establish the location of the cutting edge by grinding to your layout line at 90º. You can remove metal pretty quickly until you start getting thin material where the cutting edge will be. Thin metal doesn't dissipate heat as quickly as it is generated so you need to slow down and go easy when you approach your cutting edge. Remember, you don't sharpen with a grinder. Grinding is just the shaping operation and all the fine work is done with stones.

5. 
   BruceS | Feb 20, 2011 02:24pm | #8

   No excess grinding

   If you look at back of your  Iron  you will see the lamination of the two different metals  and yours is getting pretty short.  I would re-temper it  and not grind off the 1/4"  (wasted metal).  Heat it to a dull red and quench it in water.  Then hone the back till it is bright shiny clean metal.   Then about 1- 1/2 "  down from the edge slowly start to heat the iron till the "color" starts to work its way to the edge.   You will be looking for a dull straw color at the edge.   When the color is right,  quench the iron again.   You are now ready for honing it to a proper edge.     Why take years of service out of the Iron. 

   Or you could go out and buy a new Hock blade,  which is not a bad Idea.