Waterstones : why 2 for plane blades and 3 for chisels ?

[pompon44]

Hi,

Forgive me for what maybe a stupid question, but in either DC's or Cosman's DVDs, when it comes to sharpening chisels (as opposed to plane blades), a third waterstone (a medium one, complementing the coarse and super-fine used for plane blades) appears. What is the rationale behind this ? Is this medium step really mandatory ?

Thanks,

PS: I'm pretty sure the explanation is not given in the DVDs, but well, I might have missed a few seconds here and there ;-)

 

[Philly]

Pompon
The jump from coarse to fine makes it difficult to remove the deeper scrathes from the coarse stone. A medium stone remove the coarse scratches, and the fine stone then succesfully polishes away the traces of the medium stone.
If you go from coarse to fine it is difficult to achieve a truly sharp edge.
Hope this helps
Philly

 

[pompon44]

Hi Philly,

This I do understand, but why then should this medium step be skipped for plane blades ?

 

[Anonymous]

Good question. Guess its just a preference. Can see the idea behind it....

but, IMO, you only need two stones for any type of blade.

I'd get at least two fine and two medium stones though, to speed up flatterning though.

 

[Pete W]

In the Rob Cosman DVDs he uses three stones, but two are 1,000-grit and one is an 8,000-grit; there's no intermediate stone.

One of the coarser stones is used to flatten the other two.

 

[David C]

Pompon,

Answer, the ruler trick. and the three bevel method.

Chisel backs need to be minutely concave or flat and well polished near the edge.

This takes three stones as the jump from 800 to 8000 is too far for the 800g scratches to be polished out. I use King 800, 1200, & 8000. It would do no harm to include 4000 in the series but I have not found this to be essential.
If using Norton stones the series is 800, 4000, 8000.

For bevel side of both chisels and plane blades, I use 800g to get wire edge, then raise angle by two degrees and polish edge with 8000.
Because of the change of angle it is very quick and the deep scratches at cutting edge get removed after 4 gentle strokes.

The flat side of plane blades and most other blades except chisels can be flattened on 800 g. Then because I use the ruler trick, I am imposing an angle of 2/3 degree on the edge of the flat side and this makes it possible to go straight from 800 to 8000 to get a polished edge. The polish is only visible and present on the last 1/2 to 1 mm of the blade back, adjacent to the edge. No intermediate stone needed!

Rob Cosman has embraced the ruler trick with enthusiasm.
He has said it is the only original technique he has come across in his lifetime.
It has reduced his plane blade set up/prep time to a matter of minutes.

Soon, Chris Schwarz has an article on Hand/card scraper preparation and he has deduced that the ruler trick is very helpful here too. We have been doing this for some years but I had not written about it yet....

best wishes
David Charlesworth

 

[pompon44]

Thanks David.

Now I get it. It's related to the surface to be polished then : the bigger the more important intermediate grits are. I'll buy that argument.

While I'm at it, another small question : would an extra-coarse DMT suitable to flatten waterstones ? Is it flat enough and does it stay flat long enough to justify the expense ?
I did try wet&dry on a float glass, but it seems this will cost me a fortune in wet&dry, as the latter does wear really fast (or is it just a question of wet&dry quality ?)

Regards,

 

[engineer one]

dc has given a very decent explanation of the jumps, and the fact that more of the chisel has to be flat than of the plane blade.

some people now use a rotating wheel of mdf on a grinder with leather as a strop that is filled with rouge etc to get the polish, and i have found the tormek leather wheel quite useful once you get your angles right.

however what many people in both the uk and us use for flattening water stones is the plaster board gauze which smooths the joints. certainly available in uk sheds. i only looked at one after seeing what philly was able to do at the get together.

paul :wink:

 

[David C]

Wet & dry method does have an accumulating cost.

Drywall screen also wears out.

I have used DMT and Eze-Lap diamond stones, Eze-lap significantly cheaper than DMT I think. Also based on stainless steel so less rust issues.

Kingshott used DMT and had not worn his out though this thought does worry me a bit.

David C

 

[Anonymous]

Well, I go from 800 to 6000 on a regular basis on backs and bevels.....and I feel my blades cut more than adequately.

Still think its a question of preference, and less so importance.

Backbeveling a good concept for plane blades I agree........that same concept of speeding up backing off, is applicable in sharpening the bevel as well.......ie. raising the bevel slightly between grits to speed the process up, because less surface area to remove as the bevel goes up.

uno....something like.......25 degrees off grind, 28 off 800, 31 off 6000(or 8000). The only angle of importance being the last at the polish. (31 in this case)

Anything to reduce sharpening time the better......means less wear to your easily worn waterstones......means less re-flatterning

A flat grit is very important......the stones shape at any one time, will transfer to your blades edge.......not such an issue if your lapping blades that require feathered edges, which is mostly the case (bench planes) but if your using jointers, or rebate planes and dado planes etc and CHISELS you want a dead flat stone. Thats when waterstones are a pain in the buttocks.

So, thats why I think one should get many of each type. Ideally something like 3 x 800's and 3 x 6000's ( or whatever). And don't store them in the water. Gives them time to dry out properly......and when there dry flatterning is very quick....like chalk off a blackboard.....Can see without having to wipe water and squint with a ruler, exactly where your removing the grit because of the lighter shade your lapping causes to the stone.

Having many means its likely you'll always have one stone thats dry enough to flattern quickly, dunk for a half a minute or so in the water, and use immediately knowing its dead flat.

If you store them in the water there harder to flattern.....slows things right down. Has me wishing diamond stones to be cheaper.

Whatever you do....be mindful with those chisels to not raise the handle even slightly when flatterning the backs off any stone. Doesn't take much of a lift to screw it up.

 

[Philly]

David
I've found the dry wall screen to be very quick cutting and long lasting. Still on my first sheet after a year (although you sharpen a lot more than me :wink: )

I find going from 800 to 6000 does not remove the wire edge completely. Maybe it's just my stones (King) but since I included a 4000 I now have a more repeatable fine edge. It also lasts longer, convincing me that this approach actually works. I found going straight to the 6000 the edge broke down quite quickly.
Hope this helps
Philly

 

[David C]

Philly,

What grade of screen are you using please?

David C

 

[Philly]

David
240 Grit. I find it takes 5 or 6 strokes to level an 800 stone.
Norton brand, from B+Q.
Hope this helps
Philly

 

[David C]

Interesting.

Thank you.

I go 800 to 8 or ten thousand now and the 2 degree change of angle is the key. My wire edges frequently fall of on the sponge cloth I use to wipe the blades. I think removal of wire edge is absolutely controlled by the state of the flat back, and whether or not it is making good contact with the polishing stone at the critical area.

David

 

[bugbear]

I think removal of wire edge is absolutely controlled by the state of the flat back, and whether or not it is making good contact with the polishing stone at the critical area.

Yes - one of the reasons (*) I flatten the backs of blades so carefully is that it is the only way to ensure that you can reliably take of the burr (AKA wire edge) on the finest grit (I'm using 2500 grit SiC) with the blade dead flat, and no sneaky lifting

BugBear

(*) The main reason is a bad case of OCD, which also leads to very flat plane soles

 

[Paul Chapman]

The main reason is a bad case of OCD, which also leads to very flat plane soles

So now we know - but do you flatten plane soles because you have OCD or did the OCD come from flattening too many plane soles :? :lol: :lol:

Cheers

Paul

 

[George_N]

I think removal of wire edge is absolutely controlled by the state of the flat back, and whether or not it is making good contact with the polishing stone at the critical area.

Yes - one of the reasons (*) I flatten the backs of blades so carefully is that it is the only way to ensure that you can reliably take of the burr (AKA wire edge) on the finest grit (I'm using 2500 grit SiC) with the blade dead flat, and no sneaky lifting

BugBear

(*) The main reason is a bad case of OCD, which also leads to very flat plane soles

OCD...WTF :?:

 

[Paul Chapman]

[
OCD...WTF :?:

Obsessive Compulsive Disorder - could also apply to matters concerning honing guides :roll: :lol: :lol:

Cheers :wink:

Paul

 

[Colin C]

could also apply to matters concerning honing guides :roll: :lol: :lol:

Cheers :wink:

Paul

I dont know what you mean Paul :shock: :^o :^o 8-[ :-$