Thin edge/low angle M390 Para 2: how low is too low?

[xavierdoc]

I've had positive experience with the M390 mule at low edge angle and a 30deg microbevel. So when my M390 Para 2 arrived I decided to really thin down behind the edge and put a 30 deg microbevel on. I don't know the actual angle as it was freehand.





Thing is, after lowering the angle it was so deliciously sharp I couldn't resist trying it out before putting the microbevel on.

It simply fell through tomatos and carrots and out of curiosity I did some gentle whittling, expecting to see some edge damage. Surprisingly there was none, so for the time being I have decided to leave it as it is. The knife will have to be a "light-use, in line slicer" as any lateral force will surely knacker the edge. I'm not sure how long it will survive but I hope to limit edge damage to that which will be removed by a micro bevel alone.

Anyone care to share experiences of really low angles in M390?

I'd also love to know what hardness the Para 2 M390 is; seemed easier to remove metal than I expected.

(I also posted this query on BF - mods please delete if duplication not acceptable.)

[Niles]

I'd also love to know what hardness the Para 2 M390 is; seemed easier to remove metal than I expected.

I'm also curious about this. Did you find it easier to sharpen than the m390 mule?

[Slash]

Any more than normal sharpening is too much. I would not remove all that good steel in fear of excess chipping.

[xceptnl]

Beautiful edge, but I share Slashs feelings about all the extra steel removal.

[dbcad]

Oh Boy!! Another crazy edge :D Good to hear M390 likes it :)

[Evil D]

It just depends on how you plan on using the knife. I wouldn't go batoning through copper cables or cutting zip ties with it or you'll be taking out so many chips it won't be long before you get so far into the blade that you end up thicker behind the edge than you started with with since you'll be way up into the blade. But, if you use care then it should be that much more of a slicer.

[phillipsted]

...any lateral force will surely knacker the edge.

One of my favorite words in the English language - "knacker". It's a shame that nobody on this side of the pond uses it... :cool:

Nice bevel, Xavier! Please report back in a couple of weeks to let us know how it is holding up!

Cheers!
TedP

[Evil D]

I'd love to see some caliper readings showing just how thin this is behind the edge vs. say a Caly 3. I bet it's not any thinner...it's just like my ZDP Delica i took way down, the bevel looks huge because it's not very thin behind the edge to start with. If you were to put a reasonable micro bevel on this knife i bet it would be just fine. I know my Caly 3 is crazy thin behind the edge and that's straight from the factory, and i've put some lateral force on it cutting all manner of things, and it's not knackered up yet.

[STAK]

:spyder: If I am not fooled by the photos, I think that the angle of your reprofiled edge is way too low, something like 8 to 11deg per side :eek: . . . . I think I am right about this because my current EDC is a PARA2 CTS-20CP reprofiled at 13deg per side and the edge bevel line is not so wide as your PARA2 . . . . I am very satisfied with the 26deg inclusive reprofiled edge of my PARA2 CTS-20CP because all my EDC tasks are done well with no chiping and no regulal touch-ups like other steels :cool: . . . . One thing, reprofiling CTS-20CP is not an easy task :eek: but using my EDGE-PRO (PRO) is very helpfull :D . . . . I noticed that CTS-20CP has a tendency to roll :eek: when the edge is reprofiled at low angles and have no secondary bevel :confused: maybe that enhances the "theory" of consisting real small vanadium carbides, so the 'P' is very true, I do not know how your low reprofiled M390 edge will behave . . . . I wait for my blue PARA2-M390 so I will evaluate the differences between them two in a few days . . . . Enjoy your new SPIDIE with that beautiful mirror polished edge :) . . . . :spyder:

[xavierdoc]

It's getting late for a "school day" but I'll get some caliper readings done when I get the chance (I'm guessing imperial will be preferred?)

The safe-queen will be a useful control.

It is worth noting, the bulk of the metal removed was using stones but I finished by using a convex technique so the final edge is probably an appleseed variation. This will exagerate the appearance of the bevel width and make the edge angle look lower than it really is (compared to truly flat bevels. It also tends to blur the interface line between the bevel and the flat of the blade.

If I hadn't had the experience with the mule, I wouldn't have tried this. I have been very impressed with thin blades recently, but usage does need to be modified accordingly.

[Evil D]

If you wouldn't mind, take readings of both knives just to see what the difference is between them, and if you happen to have a Caly 3 that would be nice too.

[xavierdoc]

Any more than normal sharpening is too much. I would not remove all that good steel in fear of excess chipping.

Beautiful edge, but I share Slashs feelings about all the extra steel removal.

I am sure you are right if you want the knife to be able to do all things you would expect of the standard edge-geometry.

Oh Boy!! Another crazy edge :D Good to hear M390 likes it :)

I didn't go as far as this with the Mule as it gets used as a fixed blade should! I am in new territory for me. I know Phil Wilson goes thin with M390 (and I am very impressed with a K294 knife of his) but I wouldn't want to give one of his beauties a real beasting for fear of damage. They excel as cutting tools with a bias toward slicing, not batonning or twisting out of the cut!

[xavierdoc]

If you wouldn't mind, take readings of both knives just to see what the difference is between them, and if you happen to have a Caly 3 that would be nice too.

That's what I mean about using the safe-queen as a control; I'll use the same point on each blade (take an average of several readings, same distance back from the edge.)

I no longer have a Caly 3 (I'll check, though!) but I do have a Caly 3.5 Super Blue. Unfortunately that has a non-standard edge, too!

[xavierdoc]

Managed to get some measurements and pics done before the light went today.

I measured and marked a point 42mm from the choil.


At this point, on the factory edge, I measured how far from the edge the bevel extended towards the spine ie. where the bevel meets the flat of the blade. The bevel of one side compared to the other were slightly different (Av. 1.00mm v's 1.10mm) so I used the average (1.05mm) to determine how far from the edge to measure the thinned edge.

On the standard/factory edge the blade was 0.72mm thick (average of three readings)
On the thinned edge the average was 0.396mm (0.0140in):
(Photos are illustrative -not the actual readings I used as I don't have enough hands to do that!)


I also measured (arbitrarily) 2mm from the edge on each knife:

Standard/factory edge: 0.8mm thick (average)
Thinned: 0.63mm

The bevel of the thinned blade met the flat 3.99mm from the edge and at this point the blade was 1mm thick:



This would give an inclusive edge angle of 14 degrees but only if the bevel was flat/linear, which it isn't for the reasons described above (I combined stones with convexing).

In fact, using the thickness of 0.63mm at 2mm from the edge yields a predicted edge angle of 17.8deg.

Furthermore: recalculating using the thickness of 0.396mm at 1mm from the edge gives an inclusive edge angle of 22.6deg- not as extreme as the appearance of the bevel suggests and in keeping with the convex nature of the bevel.

Incidentally, I also measured My Phil Wilson Bow River TP (in K294) and Mule M390 (non-standard bevel). The Phil Wilson:


A mere 0.24mm or 0.0095in at 1mm from the edge (it has a 30deg microbevel)!

The Mule measured 0.37mm (0.0145ins) at 1mm from the edge- predicted edge angle of 20.8deg (but also has a 30 deg microbevel)


BTW, I'm really rusty at trigonometry so please chime in if you spot some glaring error in the maths!

I'll keep you posted about performance of the Para 2's edge.

[Bill1170]

Good informative post, Xavierdoc. Thank you.

I've thinned my ZDP Stretch but not my Bento PM2. I am enjoying the factory geometry just fine for now.

[eloreno]

I've had some knives reground to .010 behind the edge, and have had no issues with them.

[Rockcrawler]

That is quite impressive, time to go work on my sharpening skills

[Finedges]

I'd also love to know what hardness the Para 2 M390 is; seemed easier to remove metal than I expected.

My m390 Para came with a wire edge from the factory that stropped out very easily and left a wonderful edge. Much easier to remove than I thought it would be. Hardness would be very interesting to know. Thanks for the info/pics Doc, keep us posted!!

[Cliff Stamp]

II'm not sure how long it will survive but I hope to limit edge damage to that which will be removed by a micro bevel alone.

I would not be concerned.

Edge angles seem to have exploded in this generation, if you read reference material from the last generation they are completely different. For example in Cook's book on axes which is generally regarded as a bible for axes, 15 degrees per side is the angle to sharpen a full size felling axe and it only got that high right at the very edge of the bevel.

It isn't like steel quality has degraded in this generation but for some reason the commonly promoted edge angles are very high. However if you look at older knives, especially very used ones, the sharpening angles were all extremely low - for high cutting ability.

Assuming you are not cutting metals or bone, 10 degrees per side is perfectly functional for most materials including harder woods. If the edge is breaking apart on those materials then either your last name is Kazmaier or the blade was not hardened properly. You should experience significantly greater edge life and ease of sharpening.

If you can damage the edge beyond use of a micro-bevel and you are cutting normal materials it would be an extremely impressive achievement (or an extremely poorly hardened blade) outside of a deliberate side load for evaluation purposes, i.e., cut as hard as you can into a pin knot and then yank the blade sideways.

Very nice even bevel in any case.

[-F1]

Here I go with another "stupid noob" question. First of all, those pics look great; hopefully I'll have my Smurf within a week. The question: Is a 30-deg (15x2) angle reasonable on this blade (the M390 PM2, that is), in a "standard EDC" role? Boxes, branches, occasional rope, in-laws, the usual... Serious question. Sorry for the noobness. This is coming from someone who sharpened his first knife so recently he hasn't had to refill his gas tank since then.