MDF as a sharpening/honing substrate?

[Eshmiel]

I've made a few MDF wheels for use in sharpening (but really just honing a lot) steel edges, mounted in a portable drill clamped to the bench or on the pigtail extrusion of a SorbyProEdge grinding machine. I usually coat them with a honing paste of one "grit" or another, down to one micron diamond paste. They seem to work on my spoon carving knives and gouges in that they make them sharp once more.

However, another discussion prompted me to wonder - what is the "grit of the MDF itself? I have read of people using bare MDF (no paste) to hone and sharpen; and it does have a reputation for blunting tools used to cut it so presumably it does have a degree of abrasiveness.

Does anyone know what "grit" MDF may be?

Do different MDFs have different "grits"?

 

[Jacob]

I've made a few MDF wheels for use in sharpening (but really just honing a lot) steel edges, mounted in a portable drill clamped to the bench or on the pigtail extrusion of a SorbyProEdge grinding machine. I usually coat them with a honing paste of one "grit" or another, down to one micron diamond paste. They seem to work on my spoon carving knives and gouges in that they make them sharp once more.

However, another discussion prompted me to wonder - what is the "grit of the MDF itself? I have read of people using bare MDF (no paste) to hone and sharpen; and it does have a reputation for blunting tools used to cut it so presumably it does have a degree of abrasiveness.

Does anyone know what "grit" MDF may be?

Do different MDFs have different "grits"?

I think you are overthinking this! Be careful you might catch the modern sharpening mania!

 

[Eshmiel]

I think you are overthinking this! Be careful you might catch the modern sharpening mania!

Overthinking? I tried the other mode but found myself wondering if Mrs Thatcher had a point. Or even that Tebbit! No, no - overthinking by the ton for me, please. Too many crazy beliefs are just waiting for an underthinker to open their brain.

Anyway, I caught the modern sharpening mania decades ago. It's my second favouritist hobby*, collecting and playing with sharpening gubbins. It's better than playing darts or watching eejits cavort on the eejit-box, doncha think?

Has someone persuaded thee, lad, to underthink? Have you considered the many strange consequences, such as insisting on hand-sharpening being best for every woodworker then, now and to come?

* 67th favourist, in fact. The other 66 hobbies are even better (including Jacob-stimulating).

 

[mwinfrance]

* 67th favourist, in fact. The other 66 hobbies are even better (including Jacob-stimulating)

[ Frankie Howerd voice ]...Oooh Err MIssus !....You might want to rephrase that one.

or

"Get a shed , the pair of yers ! ".

 

[Eshmiel]

[ Frankie Howerd voice ]...Oooh Err MIssus !....You might want to rephrase that one.

or

"Get a shed , the pair of yers ! ".

Not that sort of stimulating ! But I will rephrase .....

"Jacob-interlocutoring".

I hope that this will calm your imagination and nerves.

Jacob & Eshmiel in a shed, wearing a chisel down to nowt with endless internecine demos of "the best sharpening method".

***********
Will no one tell me the grit-size of bare MDF? There might be a fortune to be made from starting a new WW obsession/trade in MDF slips and other sharpening gubbins. One could probably make hundreds of them out of just one 8 by 4 sheet.

 

[Terry - Somerset]

Sharpening involves the loss of material from both the item being sharpened (call it a "chisel") and the sharpener (call it a "stone").

Normally the "stone" will be harder than the "chisel" - the goal is to reshape the "chisel" with (say) a constant straight bevel.

If the "stone" is softer than the "chisel", the "stone" will tend to deform to that of the "chisel" - clearly not what is intended.

Honing is somewhat different - it removes a very small amount of material from the blade being sharpened. That a soft substrate (leather, MDF) will deform the edge slightly from the ideal required may be an acceptable compromise to get an edge as sharp as it can be.

In truth it doesn't really matter what the grit size of MDF is - it probably varies greatly between the fluffy and cheap from the DIY stores to relatively firm. The key is to try it and see whether it works for you!

 

[Eshmiel]

Sharpening involves the loss of material from both the item being sharpened (call it a "chisel") and the sharpener (call it a "stone").

Normally the "stone" will be harder than the "chisel" - the goal is to reshape the "chisel" with (say) a constant straight bevel.

If the "stone" is softer than the "chisel", the "stone" will tend to deform to that of the "chisel" - clearly not what is intended.

Honing is somewhat different - it removes a very small amount of material from the blade being sharpened. That a soft substrate (leather, MDF) will deform the edge slightly from the ideal required may be an acceptable compromise to get an edge as sharp as it can be.

In truth it doesn't really matter what the grit size of MDF is - it probably varies greatly between the fluffy and cheap from the DIY stores to relatively firm. The key is to try it and see whether it works for you!

Yes, that description of the nitty gritty (ha ha) makes it clearer as to what goes on at the MDF-steel interface.

There's lots of You Tube vids about making & using MDF wheels on buffers and the like. A few use bare MDF on their knives but most involve applying some sort of goo - sometimes a goo containing grit (aka honing paste) but sometimes goo followed by a powdered silicon or even diamond, for more serious sharpening. I suppose my concern is: how much does the inherent "grit" of the MDF affect or even undermine the grinding intentions of putting on honing paste or goo+grit of various sizes/microns?

But you're right to suggest "....try it and see......".

It's noticeable that on the MDF discs I've made, charged with fine grit honing paste and used that the usage seems to make the surface of the MDF disc edge go very smooth indeed - much smoother-feeling than the bare MDF. So maybe my concern is misplaced, as the goo-grit is dominating and that's the grit size that'll be doing the honing, not the "grit" of the MDF. However ....

I use 3 micron and 1 micron DMT diamond paste on these (5" diameter, 34" wide) MDF discs, in a slow-speed hand drill, attached to the bench, with a lot of torque. They do seem to work very well in putting a super-keen edge on to knives I use for spoon and bowl carving, with even very slight damage to that edge (teeny knicks or "lines of light" from hitting a knot, for example) being eliminated if I apply the knife for a bit longer than the time needed for just a hone.

That ability (to de-nick) is what's making me suspect that maybe the MDF itself is doing some grinding, since the diamond paste grit size is teeny-weeny and not meant to be capable of sharpening but only honing. But a wheel in a drill passes a lot of grinding surface over an edge in a very short time, so maybe it is just the diamond grit doing the work.

There - a great wodge of over-thinking for Jacob to bite and chew at.

 

[Jacob]

.....

There - a great wodge of over-thinking ....

Yep.
You could just google and get a wide range of opinions from a variety of lunatics enthusiasts.
n.b. "honing" tends to mean just fine finishing sharpening, not something different - there isn't a step change in the range from coarse grinding to polishing; it's all "sharpening".
There's nothing special about Autosol, any metal polish will do but thicker pastes may be easier to handle than thinner ones like Brasso

 

[Inspector]

Expanding the MFD abrasive theme of this thread. What would the grit value be for various high silica hardwoods? Given that some are reputed to throw the odd spark when cut on a table saw, mitre saw, etc., dulling blades quicker than other low silica woods. One could have a number of sharpening hones made from MDF, domestic and tropical hardwoods, plus paper products. I mention paper because some fountain pen people adjust or break in a nib with brown paper grocery bags.

Pete

 

[Jacob]

Expanding the MFD abrasive theme of this thread. What would the grit value be for various high silica hardwoods? Given that some are reputed to throw the odd spark when cut on a table saw, mitre saw, etc., dulling blades quicker than other low silica woods. One could have a number of sharpening hones made from MDF, domestic and tropical hardwoods, plus paper products. I mention paper because some fountain pen people adjust or break in a nib with brown paper grocery bags.

Pete

erewego!
Some people hone/strop on the palm of the hand. What would the grit values be on different parts of the anatomy?
Perhaps primary bevels on my chin and honing on my botty?

 

[kinverkid]

What grit is the face of MDF?

 

[Inspector]

erewego!
Some people hone/strop on the palm of the hand. What would the grit values be on different parts of the anatomy?
Perhaps primary bevels on my chin and honing on my botty?

That would vary based the individual. Some having spent life at a desk and have hands like a baby, a stonemason's would be rough as cobble and a barefoot hippy chick's would be like boot leather. Butt cracks are perfect for honing gouges and between is just the thing for honing both sides of an axe evenly, so you are on to something.

Pete

 

[JSW]

Some people hone/strop on the palm of the hand. What would the grit values be on different parts of the anatomy?
Perhaps primary bevels on my chin and honing on my botty?

That's going to be way too coarse, in the region of 40 grit I'd wager

 

[Terry - Somerset]

Yes, that description of the nitty gritty (ha ha) makes it clearer as to what goes on at the MDF-steel interface.

There's lots of You Tube vids about making & using MDF wheels on buffers and the like. A few use bare MDF on their knives but most involve applying some sort of goo - sometimes a goo containing grit (aka honing paste) but sometimes goo followed by a powdered silicon or even diamond, for more serious sharpening. I suppose my concern is: how much does the inherent "grit" of the MDF affect or even undermine the grinding intentions of putting on honing paste or goo+grit of various sizes/microns?

But you're right to suggest "....try it and see......".

It's noticeable that on the MDF discs I've made, charged with fine grit honing paste and used that the usage seems to make the surface of the MDF disc edge go very smooth indeed - much smoother-feeling than the bare MDF. So maybe my concern is misplaced, as the goo-grit is dominating and that's the grit size that'll be doing the honing, not the "grit" of the MDF. However ....

I use 3 micron and 1 micron DMT diamond paste on these (5" diameter, 34" wide) MDF discs, in a slow-speed hand drill, attached to the bench, with a lot of torque. They do seem to work very well in putting a super-keen edge on to knives I use for spoon and bowl carving, with even very slight damage to that edge (teeny knicks or "lines of light" from hitting a knot, for example) being eliminated if I apply the knife for a bit longer than the time needed for just a hone.

That ability (to de-nick) is what's making me suspect that maybe the MDF itself is doing some grinding, since the diamond paste grit size is teeny-weeny and not meant to be capable of sharpening but only honing. But a wheel in a drill passes a lot of grinding surface over an edge in a very short time, so maybe it is just the diamond grit doing the work.

There - a great wodge of over-thinking for Jacob to bite and chew at.

My inclination - untested - is that if the edge of a piece of MDF is loaded with goo it first absorbs most into the surface which is fairly porous.

Once the surface is fully loaded the surplus would form a slick around the circumference of the MDF.

Thus is is predominantly the goo and embedded grit which polishes the blade - fairly rapidly given the speed of the drill. Speed of edge of MDF blank 5" in diameter:

5" x 3.142 = 15.7" diameter
Assume 1000 RPM = 15700 inches per minute, = 1308ft per minute - 21ft per second

Much, much faster than back and forth on a piece of leather!!!

 

[Eshmiel]

My inclination - untested - is that if the edge of a piece of MDF is loaded with goo it first absorbs most into the surface which is fairly porous.

Once the surface is fully loaded the surplus would form a slick around the circumference of the MDF.

Thus is is predominantly the goo and embedded grit which polishes the blade - fairly rapidly given the speed of the drill. Speed of edge of MDF blank 5" in diameter:

5" x 3.142 = 15.7" diameter
Assume 1000 RPM = 15700 inches per minute, = 1308ft per minute - 21ft per second

Much, much faster than back and forth on a piece of leather!!!

I am hoping this is the troo picture of reality, as I have no wish to sharpen my V-gouge in a certain ..... declivity 'round the back of Jacob, even if it did fit rather well. Also, my cack hand (so to speak) might result in an unfortunate jab i' the glute, followed by a Jacob-leap, which might cause damage to a workshop when 'e lands.

**********
This arternoon I have been mostly routing slips from wood scraps on which to either stick 3M sharpening papers or, on some, just honing pastes. I'm doing various radii for these slips with various radii bead cutters, for use on the inside bevels of gouges. Tomorrow I'll make a series of MDF panels with variable radii grooves, made with variable radii cove cutters, for sharpening and honing the outside bevels of the gouges. It's cheaper than them Arkansas slip stones!

One day (soon, soon) I might actually carve summick!

 

[Jacob]

I am hoping this is the troo picture of reality, as I have no wish to sharpen my V-gouge in a certain ..... declivity 'round the back of Jacob, even if it did fit rather well. Also, my cack hand (so to speak) might result in an unfortunate jab i' the glute, followed by a Jacob-leap, which might cause damage to a workshop when 'e lands.

**********
This arternoon I have been mostly routing slips from wood scraps on which to either stick 3M sharpening papers or, on some, just honing pastes. I'm doing various radii for these slips with various radii bead cutters, for use on the inside bevels of gouges. Tomorrow I'll make a series of MDF panels with variable radii grooves, made with variable radii cove cutters, for sharpening and honing the outside bevels of the gouges. It's cheaper than them Arkansas slip stones!

One day (soon, soon) I might actually carve summick!

You don't need a set of radiussed slipstones you just need one small enough to do the inside edge of all your curved gouges. They usually have two edges anyway, which helps.
You only need one flat stone for the outside edge of all your gouges. You slide them along the stone sideways-ish and roll it a touch.

 

[Eshmiel]

You don't need a set of radiussed slipstones you just need one small enough to do the inside edge of all your curved gouges. They usually have two edges anyway, which helps.
You only need one flat stone for the outside edge of all your gouges. You slide them along the stone sideways-ish and roll it a touch.

As I lack the motor nerves for doing them steady movements to avoid the multi-facets and other mis-shapes of the bevels, I make the slips with radii close to the sweeps of the gouges, see? I have an alternative plan, which is to capture you and chain you in my shed, which you must then clean of the daily shaving whilst sharpening things in between this essential task. I will watch and attempt to copy but my failures will be blamed on you; and no bowl of gruel that day!

Just now I am planning another sharpening aid - a half-eye steel cradle on a stick that can have it's height varied via a screw thread on the stick, set in a footing that slides about, enabling one to rest a gouge therein to keep the angle constant as one rubs and rotates the tool over a plate of exotic sharpening medium. That's pretty close to hand sharpening, that is. And I'll hold them slips in me paw as well. So there.

Have you removed the synchromesh gears from your motorcar, by the way? And the indicators ? (A hand out the windy is surely better).