Question about using scary sharp process

[Barry Beech]

I have a new set of chisels that I need to sharpen. What grit sandpaper should I start out with and would regular wood sandpaper work?

Also, what is the proper angle that I should put on the chisel. They came with a 25 degree edge but I thought that a higher angle would be appropriate for these chisels, something like 30-35 degrees.

They will be used for finer detailed work like dovetails and such.

Sorry Pic police, no pictures.

I actually still need to post a christmas gloat.

[Cecil Arnold]

IMHO, stay with the 25* angle, you need an assortment of grits and depending on the finish of the chisels the starting grit may differ. You want the black carbonieum (sp?) paper, I range from 220 to 2000 grit. You also need a good flat surface, MDF, glass, and granite are all used.

[Dave Anderson NH]

Like Cecil, I would suggest staying with the 25 degree bevel angle to start. You can always increase the angle later by regrinding or add a microbevel at a higher angle if the chisels won't hold an edge long enough. Since the chisels are only for fine work, the shock of heavy mallet blows shouldn't be a consideration. Paring usually does't deteriorate an edge very quickly. The starting grit for flattening the back depends entirely on how flat the chisel face (back) is to start with. to find your starting point, magic marker the chisel back and then randomly pick a starting grit. After half a dozen strokes you should be able to see the high and low areas as bright shiny metal. If there is a lot to remove to make the backs flat start somewhere arond 100 grit. If the out of flat areas are small and the height difference is minimal, try 220 to begin.

Any abrasive paper will work, the difference is in how long it will last. Aluminum Zirconia (the blue stuff) is best for the lower grits where you need to remove a lot of material quickly and have the paper last. AlZi paper is VEEEERY long lasting, but is commonly available only up to about 220 grit. Aluminum Oxide paper will also work, but doesn't last as long. Above 600 grit, only Silicon Carbide paper is available so there's not really a choice.

[jonathan snyder]

Barry,

For honing I use the micro-abrasive paper from LV 15 micron, 5 micron, & 0.3 Micron IIRC. If I need to flatten the backs or grind out nicks I start with 80 grit (I don't have a grinder or belt sander) 3M sandblaster and then work down through 2000 wet dry paper and finish up on the LV paper.

I find that the 3M lasts longer than other paper

You can get the really fine wet/dry paper at Napa or other auto supply stores.

Jonathan

[Doug Shepard]

Barry,

For honing I use the micro-abrasive paper from LV 15 micron, 5 micron, & 0.3 Micron IIRC. If I need to flatten the backs or grind out nicks I start with 80 grit (I don't have a grinder or belt sander) 3M sandblaster and then work down through 2000 wet dry paper and finish up on the LV paper.
...

Ditto. The LV micro paper works great (as long as you got all the scratches worked out on the bigger grits. I dont even own a strop as I dont feel I need one with the LV stuff. The lower grits 80-220 are usually only something I have to go through the first time for flattening the backs. As long as I don't drop or nick one, I usually never have to go that low on a chisel again. I wouldn't necessarily start at 80 on the backs though. Start off with maybe 220. If you've got a consistent scratch pattern across the full width, keep going and work up. If you can see spots not getting the scratch pattern, start switching to lower grits - how low you need to go depends on how Not-Flat it is. For the bevels I dont think I've ever used anything below about 180. Just my 2¢

[jonathan snyder]

[quote=Doug Shepard]Ditto. I wouldn't necessarily start at 80 on the backs though. Start off with maybe 220.

Doug,
I mentioned starting at 80 grit on the backs. I should clarify that. I have been rehabbing some old flea market chisels, and had to start at 80, as they were in pretty bad shape. I agree you should not need to start out that rough on new chisels.

Derek Cohen posted a Good tutorial on flattening backs a week or so ago
http://www.sawmillcreek.org/showthread.php?t=49164

Jonathan

[Don Naples]

Above 600 grit, only Silicon Carbide paper is available so there's not really a choice.

Dave: A better choice for fine abrasive grits is aluminum oxide which is available to grits as fine as 0.3 micron. These abrasives are known as microfinishing film (to 9 micron) and the finest grits are lapping film. If you use wet or dry silicon carbide paper check to see if it is "P" graded. If so, the grit size is measured according the the FEPA system which means at P2500 you are at 8.4 micron. Since an 8000 grit waterstone is 1.2 micron, you can see why better results are achieved using waterstones.

Silicon carbide in not as effective for sharpening as aluminum oxide as it breaks down too quickly to be very effective. It is in automotive parts stores for sanding paint, not ferrous metals.
Silicon Carbide http://www.manufacturingcenter.com/university/winter2000/glossary.asp
A synthetic abrasive discovered in the late 1800s, which is harder than aluminum oxide. Used in green and black forms, which are distinguished by levels of purity, silicon carbide is typically applied to nonferrous applications. The sharp and easily fractured abrasive grains are also used in nonmetal applications such as the wood and leather industries.

[Bob Jones]

Everything you could want to know about scary sharpening...

http://www3.telus.net/BrentBeach/Sharpen/sharpen.html