Warning: this is a raw draft. It has not been reviewed yet and may contain misleading information and traces of nuts.
Overhoning is an act of degrading a blade's keenness with excessive honing. Thanks to the lack of its understanding, it is not uncommon for inexperienced honers to blame overhoning for poor sharpness of their razors ("I do everything according to the books and the razor is still dull - I must be overhoning"). Consequently and ironically, the most frequent problem related to overhoning among beginners is the lack of sharpness caused by insufficient honing which is caused by their unsubstantiated overhoning fears.
Causes and impacts of overhoning
It is not easy to overhone most edges, but it is possible. It takes either too much pressure, or an excessive amount of laps to create an overhoned edge. Too many laps produce a wire edge that breaks off leaving a jagged rough edge; excessive pressure takes the edge too far. As a result, it becomes very brittle and chippy and falls apart easily. An overhoned blade feels dull, rough, and is very uncomfortable to shave with.
Test of overhoned edges
Overhoned edges can be usually seen under a 20x loupe and can be detected with the TNT and TPT. Glen/gssixgun advises : "The best way to find an overhoned edge is the TNT but it also can dull a perfectly good edge, so I don't recommend it's use for testing for an overhoned edge. Use the TPT very, very, lightly to feel for a rough spot (using the calloused forefinger tip actually works better for me on this), use magnification to look for a jagged spot." If neither is found then the edge is likely just a bit rough (not overhoned) and can be smoothed out with a .50CrO paste or a fine polisher.
How to fix overhoned edges
Overhoned edges can usually be easily cured with several backhoning (spine leading) laps, preferably on the next coarser grit stone (ie: overhoning occurs on the 8k then drop to the 4k to correct it). Once the burr is removed from a deteriorated edge, proceed with normal honing. Always make sure that the bevel is well set before going to finer grits. As you can see from the last statement this is exactly what the pyramid method was designed for, to avoid an overhoned edge...
Hones and laps
Different hones take different numbers of laps or pressure before overhoning. The generic rule of thumb is that it is easier to overhone with fast synthetic hones than with natural stones. 100 laps on a Chinese 12k stone or on a Coticule will certainly not lead to overhoning, but the same amount of laps may be too much for fast Shaptons or Nortons. Coticules and BBWs are known to never overhone.
If you want to see what it takes to overhone an edge, Glen says: "Use a crap blade and put it on a lower grit synthetic hone and apply heavy pressure and use a circular pattern and stay in one spot, and hone until the edge falls apart... You are going to be very surprised at just what it takes to overhone an edge..."
This topic contains distilled information from several SRP discussion threads. Special thanks go to Glen/gssixgun for his valuable comments on this topic.
- ↑ http://straightrazorplace.com/basic-honing/33218-over-honing.html
--Sparq 01:08, 2 April 2009 (UTC)