Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Ed Caffrey reground a sabre/hollow ground blade I had made by Blade many years back. He used a full convex profile and tapered to an edge was was 0.005" thick and had a secondary v-ground edge bevel. After many years of use this secondary bevel had widened to about 0.070" wide (~1/16") and was reducing sharpening efficiency.
To fix this I used a 1" belt grinder to first apply a flat grind using the platen at about 4-5 degrees to the blade which basically hit the last half of the primary grind. I brought the edge down to about one third of its origional width. This took a long time, about 10-15 minutes because I was using a worn 80 grit belt. I didn't want to grind it much thinner because this is a heavy use wood working blade.
I then ground in the slack belt region, basically flat to the blade and removed the secondary edge bevel. This was another very flat grind of about seven degrees per side and it started when the blade was about 0.025" thick. For a pure paper/utility blade I would have taken the primary flat grind down much further but it would then have had issues with knots. This left the final edge bevel barely visisble at < 0.005" thick :
The dark region is the new grind, the dull region is the patina on the existing grind. Note if you have nice belts then you can do this dual flat grind in one step using the slack region above the platen. The belt I had was not abrasive enough to cut at a low pressure and when you press hard the curvature increases so I had to use the platen.
The main purpose of this post is to illustrate how the regrinding focused on the cross section not the curvature. I wanted a specific thickness and angle to get the necessary cutting ability and ease of sharpening. I wasn't thinking convex vs flat but a specific cross section.
-Cliff
To fix this I used a 1" belt grinder to first apply a flat grind using the platen at about 4-5 degrees to the blade which basically hit the last half of the primary grind. I brought the edge down to about one third of its origional width. This took a long time, about 10-15 minutes because I was using a worn 80 grit belt. I didn't want to grind it much thinner because this is a heavy use wood working blade.
I then ground in the slack belt region, basically flat to the blade and removed the secondary edge bevel. This was another very flat grind of about seven degrees per side and it started when the blade was about 0.025" thick. For a pure paper/utility blade I would have taken the primary flat grind down much further but it would then have had issues with knots. This left the final edge bevel barely visisble at < 0.005" thick :
The dark region is the new grind, the dull region is the patina on the existing grind. Note if you have nice belts then you can do this dual flat grind in one step using the slack region above the platen. The belt I had was not abrasive enough to cut at a low pressure and when you press hard the curvature increases so I had to use the platen.
The main purpose of this post is to illustrate how the regrinding focused on the cross section not the curvature. I wanted a specific thickness and angle to get the necessary cutting ability and ease of sharpening. I wasn't thinking convex vs flat but a specific cross section.
-Cliff
