[Brett]

Wandering through the big box hardware store this morning, an odd item caught my eye.
Metal polishing compound for 6 bucks, 3 flavors in one blister pack.
Black which is a grit similar to fine emery cloth, yellow which is a hard metal polish
and white which is used for highly reflective finishes. At 6 bucks, such a bargain.
If you wander the web like I do, I'm sure you've run into folks using MDF lumber
as a tool to sharpen most any edged hand tool you can think of.
Well, I had a chunk of 3/4 inch thick scrap in the odds and ends pile, so why not.

3 inch hole saw/drill and a couple minutes cut 3 disks out of the scrap MDF.
3 inch 1/4-20 screws, washers and nylocks made shafts to fit into the drill.
With a disk snugged up in the drill chuck and rotating at medium speed
some 100 grit sandpaper smoothed out the saw kerfs. Dusted off the disks
and applied a different compound to each disk, black/yellow/white.

Guess what? That is the fastest I've ever put a razor edge on any knife.
Not only did I do my EDC Buck 110, along with my 2 fillet knives, I did all the
fancy kitchen knives the wife keeps in a block on the counter,
in less time than it would take me to use my diamond stone to work a fillet knife.
Abso-freaking-loutely amazing how fast it worked and how sharp they are.

Hmmmmmm...hand plane could use a touch up, as could my axe...machete...chisels...

Ya'll be good, this could be an interesting afternoon in the garage.

 

[hipshot]

Don’t overheat the metal

 

[BassFlats]

In carpentry apprentice school (40 plus years ago) our instructor showed us how to sharpen chisels . You chould shave the hair off your arm when finished. 1st step ,rough wheel on the grinder (if needed). 2nd step, fine grinding wheel. This creates a fine burr on the end of the chisel. 3rd step,deburr the cutting edge with a cotton wheel with buffing compound applied to it by pointing the cutting edge down and lightly pushing the cutting edge to the buffing wheel and turning the chisel 180 degrees several times to remove the burr. Step 4 shave arm hair. Pretty simple if you have the right set up. This also works on plane irons.However, my knife sparpening method needs help.

 

[Brett]

Overheat the metal?
Unlikely in a handheld drill using MDF and wax based compound.
This is a 3 inch diameter disk running at maybe 100 rpm,
not a bench grinder with a 6 inch disk running 2000 rpm.
The fine grit and hand held blades don't even get warm.
Doesn't even melt the wax, just hones the edge.
Think of it as a rotary paper strop.
Very effective method of touching up the edge on a blade.
Cheap too.

 

[hipshot]

I stand corrected. I assumed you were using the bench grinder in that video that I didn’t play.

I use stones, then 1000 or 1500 grit diamond rods if needed. I finish them with a leather strop and the green compound. Daily touchups are with the leather. My EDC knives have a steeper taper; they will almost shave, but that edge won’t turn so easily. My hunting and skinning knives will shave handily.

When the bride was alive she used to abuse her kitchen knives, and I spent a lot of time retuning chipped and dinged blades. I finally bought a Work Sharp machine for her kitchen knives; it would do a really quick job of regrinding the edges, and I’d just have to finish them up on the strop. But I won’t use that machine on my good knives.

It’s funny; I buy cheap knives for rough work so I won’t have to abuse my good knives, but then I won’t abuse my cheap knives either. I have some cheap knives that are so soft I just can’t get a good edge on them. But I’ve picked up a few cheapies that will take and hold a shaving edge.... Some blades with good steel aren’t properly tempered, and don’t hold an edge well. I also see blades of lower grade steel, properly tempered, that exceed all of my expectations.

 

[WC53]

It is not overheating the whole blade, just the edge, even if cool to the touch you can lessen the temper at the edge. It can be recovered after subsequent sharpening to get out of the affected area.
Ask me how I know...

 

[Brett]

Quick follow up.
Overheating the edge with these 3 inch diameter disks
spinning in a small hand drill doesn't happen.
Can't apply enough pressure or generate enough friction
or remove enough metal to create heat.
I sharpened all my chisels, couple of machetes, axe, hatchet
along with an assortment of old pocket knives.
The disks won't put an edge on a butter knife
but it will restore the edge to a previously sharp tool.

 

[PeteS]

Name of big box store and polishing compound please

 

[Brett]

https://www.homedepot.com/p/RYOBI-Hard-Metal-Cleaning-Compound-Set-3-Piece-A04HM11/205642393

 

[Seymour fish]

Wandering through the big box hardware store this morning, an odd item caught my eye.
Metal polishing compound for 6 bucks, 3 flavors in one blister pack.
Black which is a grit similar to fine emery cloth, yellow which is a hard metal polish
and white which is used for highly reflective finishes. At 6 bucks, such a bargain.
If you wander the web like I do, I'm sure you've run into folks using MDF lumber
as a tool to sharpen most any edged hand tool you can think of.
Well, I had a chunk of 3/4 inch thick scrap in the odds and ends pile, so why not.

3 inch hole saw/drill and a couple minutes cut 3 disks out of the scrap MDF.
3 inch 1/4-20 screws, washers and nylocks made shafts to fit into the drill.
With a disk snugged up in the drill chuck and rotating at medium speed
some 100 grit sandpaper smoothed out the saw kerfs. Dusted off the disks
and applied a different compound to each disk, black/yellow/white.

Guess what? That is the fastest I've ever put a razor edge on any knife.
Not only did I do my EDC Buck 110, along with my 2 fillet knives, I did all the
fancy kitchen knives the wife keeps in a block on the counter,
in less time than it would take me to use my diamond stone to work a fillet knife.
Abso-freaking-loutely amazing how fast it worked and how sharp they are.

Hmmmmmm...hand plane could use a touch up, as could my axe...machete...chisels...

Ya'll be good, this could be an interesting afternoon in the garage.

Bret, this is interesting. Are you doing this hand held or mounting /clamping one part of it in a fixture. The direction of rotation must be away from the edge else it might bite thus this must be a polishing operation. Do you find any signs of “pulling a burr” off the edge ? Have you tested the edge produced on hardwood to spot any tendency to roll? Experience with belt grinders is that coarse grits remove metal without rapid heat buildup in the blade, whereas very fine polishing grits build heat quickly, and especially at the tip where metal is thin. Another “ask me how I know” deal.

 

[Brett]

No true hardwoods in my pile,
only white pine and plywood at this time.
From what I see the results are the same as extended stropping.
It produces a highly polished convex edge.
Unknown as to how long the edge will hold up.
I found that clamping the hand drill to the end of the work bench
with the upper portion of the disk rotating away from me provides a stable working orientation.
As you said, the rotation has to be away from the edge,
as is also stated in all the videos I watched.


MDF wheels have been used for quite a while, many videos on YouTube.
Some of those folks are nuts.
No way would I be running a large diameter disk at high rpms.
Small diameter at low rpms, yes.
Unlikely to come apart due to centripetal loads.
Can you imagine an 8 inch disk exploding at 3600 rpm?