Replies

1. 
   Eef | Mar 01, 2010 12:17pm | #1

   hi matt,

   "...even scratch

   hi matt,

   "...even scratch marks all the way across."

   these marks are not necesarily indicitive of flatness.  the last little while now i have found it important and telling to put a known straight edge across the surface that is being flattened.  try it and see.  be sure you have bright light behind what you're gazing at.

   eef

2. 
   nboucher | Mar 01, 2010 12:23pm | #2

   You might have been rocking the chisel just a tiny bit on the coarser grits, rocking it so slightly that it's not showing up until you get to the higher grit. You might not have to go back to 180, but I'd probably work my way back until you get even scratches again.

   Then, to counteract rocking the chisel, move the back across the width of the stone or sandpaper to generate scratches parallel to the edges.Then flatten the back using both orientations as you move up the rest of the grits.

1. 
   clinton66 | Mar 01, 2010 01:41pm | #3

   Thanks for the advice. I tried putting a straight edge across the width and couldn't see any light poking through. I think my problem might be that I'm using a cheap plastic backed coarse diamond stone. I put a non slip pad on top of my workbench so the stone wouldn't slide back and forth as I worked on it, but I noticed that the stone rocked a little back and forth as the non slip pad compressed under the weight of the chisel. I then put the stone directly on top of my MDF work bench and secured it between the bench dogs and I still couldn't get the high spot in the middle to come down. I think there is something wrong in my technique but I have tried honing across the width of the chisel and the length of the chisel to no avail.

1. 
   Eef | Mar 01, 2010 02:27pm | #4

   matt,

   how wide is your chisel?  it is easier, sometimes, to flatten a wider chisel.  the stone being flat is important, although when first learning, this was not an issue among anyone who taught me, including nora the wood carver.  as the steel of the chisel moves towards the handle,  it is anything but flat.  perhaps you are "rolling" as you stroke/sharpen in that direction.

   also,  is there anyone in your neighborhood that knows how-to?  so many times the direct help of others has advanced me over all of my trying.

   eef

3. 
   SgianDubh | Mar 01, 2010 02:50pm | #5

   It sounds like your stone isn't particularly flat. Your later description of how you're holding on your bench indicates it may be flexing, and possibly flexing in the middle. If this is the case you are likely to be taking more off the edges of the flat side of the blade. Hence when you move to a finer grit which you may be holding on a flatter surface the work is concentrated on the middle of the already worked area.

   How much of the back are you trying to flatten? In most cases you only need about the last 25 mm (1") of the front side (flat side) of the blade flat. You don't really need the whole of that face made flat to micro-engineering tolerances, not even if the chisel is used primarily as a paring chisel. Try just concentrating on the last 25- 35 mm of the blade. It will probably save you a lot of work, and anguish, and you'll almost certainly end up with a perfectly serviceable chisel, assuming, of course, that you can sharpen. Slainte. 

4. 
   clinton66 | Mar 01, 2010 04:58pm | #6

   thanks again for the help. The chisel is 1" wide. I have flattened about 20 or so chisels in my day and this one is proving to be the most difficult. I am not trying to flatten the entire back, just the last inch or so closest to the cutting edge. When I hone with a finer stone, the polished section of the back does not extend all the way to the cutting edge. In my experience that means you have a high spot on the back of the chisel and since the back of the cutting edge is not even, you won't get a truly sharp edge. Since this is a paring chisel that is important. I think my cheap stone is flexing under pressure and rounding the edges off. I am going to glue some 220 grit sandpaper to the top of my table saw and see if that helps even out the back. I have a 220 norton waterstone but I am loathe to use it. In my experience with this particular grit waterstone it wears away too fast, gets out of flat too often and doesn't remove enough material to be of use. Any one else had this problem?

5. 
   RalphBarker | Mar 01, 2010 07:06pm | #7

   Sounds like one of your stones isn't flat.

6. 
   gdblake | Mar 01, 2010 07:37pm | #8

   Clinton:

   It sounds like the back of your chisel is fairly rounded.  This is a common problem.  A good straight edge should be able to show this.  You need to check for flatness both across the width and along the length of the chisel.  The remedy that worked best for me is to use a magic marker to color the entire back so I can see where metal is being removed as I work to flatten the back.  I draw file the center of the backs to quickly work them down.  Then as you have planned, use 220 grit paper taped down to your tablesaw to finish flattening the backs.  For me, abrading the chisel back and forth along the length works better to eliminate a rounded back than abrading side to side parallel with the cutting edge.  Just keep applying the magic marker until the color is removed uniformly across the back.  Also, flatten your waterstones before taking the chisel to them to polish the back once you have it flat.

   gdblake

7. 
   clinton66 | Mar 04, 2010 02:46pm | #9

   I took some 150 grit sandpaper and glued it to may tablesaw top. about 30 minuties later I had a flat chisel back that easily honed to a mirror shine. I think my problem was the cheap diamond stone flexing under the pressure I was applying while abrading and causing the edges to become rounded. The stone itself started to "walk" across the bench while sharpening which should have tipped me off. Thanks for all the advice, Matt.