Difficulty Flattening Chisel Backs

[John Daybell]

I just got a set of Narex Richter Extra chisels and boy do they look great! However, when I've been trying to flatten the backs I am having an issue getting them flat. In particular the 1" chisel has been giving me a lot of grief trying to get it flat near the cutting edge. I've been marking it with a sharpie to see where the low points are and part of the cutting edge doesn't seem to be wearing away. Once it is worn away I re-mark it to make sure that its flat and that same section stays marked when the rest of the markings go away nearly instantly. I know that the part near the tip is the most important and I'm not trying to flatten the whole back, but I've spent 3-5 hours on this one chisel alone and it still isn't flat.

I'm was using 150 grit sandpaper on a granite slab and then stepped up a 325 grit diamond stone, but it is still giving me trouble. Is there something that I am missing? I don't think that one chisel should take this many hours to flatten.

Thanks in advance for any help!

[Robert Engel]

Been there. What works for me is to get more radical with a coarser grit. I would even to to 80 if necessary.

Once you get it flat, the rest is really just removing scratch marks with finer grits.

Concentrate on the first 1 1/2" or so.

[Robert Hazelwood]

Any way you can post a picture? That might help to diagnose what's happening, since its hard to describe in words. Something is wrong, because 3-5 hours of work on a 1" chisel is way, way, too much. Something you are doing is creating extra work. You say the paper is on a granite slab...is it a surface plate or something else? If it's not flat you can chase your tail like this.

Otherwise I agree with Robert Engel, use the coarsest grit you can until its flat, and only then start moving up. I would start at 80 grit, but 150 grit isn't too bad. You need to change the paper often, every few minutes really, to keep the cutting speed high.

[ken hatch]

John,

If the back has a belly it can be difficult to flatten the back because you will have the tendency to "rock" on the belly making the low area lower. It can be self feeding. You have to get rid of the belly first before the back can be flattened.

Good luck,

ken

[Andrew Hughes]

Did you check that your granite slab is flat?
If it’s a scrap piece of counter top it might be flexing or just not flat.
+1 to what Ken says.
Good Luck

[John Daybell]

I went back and did some more work on it. I think it was the diamond plate that was the issue. My granite slab is a certified slab, but the diamond plate is a cheaper plate. I took Rob's advice and made sure to switch out the sandpaper and stopped using the diamond plate. I've worked my way up from 150 - 220 - 400 - 800 - 1200 - 3000 grit sandpaper and the sharpie marks are going away uniformly now. I also started trying to flatten more of the back so I had a bigger area of the chisel to register against. Thanks for the suggestions!

[Jim Koepke]

Good morning John and Welcome to the Creek.

To post images you will have to become a contributor. For $6 it has always seemed like a good deal to me.

You do not mention whether you are trying to remove a hollow or a bump. A bump is more difficult to remove do to the tendency of the blade to rock.

Another problem is the swarf from the piece being worked loading the abrasive sheet. My large bench with a four foot slab of granite has a magnet wrapped in paper to remove the iron swarf every few passes when working items. Otherwise a brush helps to remove the fine iron particles from the abrasive.

Another helper is a way to apply even pressure on the blade being worked:

431735

Note the arrows showing the direction of work.

(DOH! Just recalled while proof reading this that one has to be a contributor to see images.)

Okay, the arrows in the image indicate the blade is being worked in a direction parallel to length of the blade. Working a blade side to side tends to induce rocking.

The item being used to apply pressure is a small circle guide made for another use. A few pieces of scrap can be assembled into an adequate piece to apply pressure for flattening a blade.

One last note, your profile doesn't list your location. You may live near another member who would be willing and able to help you with this effort.

jtk

[michael langman]

John, I have been lookiing into those Narex Richter chisels for myself, and hate to tell you this, but, they were manufactured to very high tolerances and the flatness of them is supposed to be spot on.
The finish is also suppose to be of a very high tolerance.
If there is anything wrong with them in this regaurd then I would send them back for replacement without touching them.
Narex considers them to be the very best in all of these aspects.

[lowell holmes]

I use a diamond hone to flatten chisel backs.

[Mark Hennebury]

Die grinder, works for me.

[Rafael Herrera]

John, it looks from the description of these chisels that they are premium grade. Unless you can diagnose that they're out of flat with a diamond plate or a flat hard sharpening stone, you may just damage them by running them over coarse sand paper.

[Thomas McCurnin]

For flattening the backs of chisels and plane irons, I find that 60-80g sandpaper does a better job than any DMT diamond plate I have, even the new DMT super coarse plate. Norton and 3M have some good cloth backed sheets which are a little over a buck a sheet. Maybe 5 minutes to flatten a cheap Buck Brothers dog food iron, usually only one sheet will do the job. Then move to the a Diamond stones.