M390MK is a b..ch!

[drumlooper]

This frustrating. I just spent an hour on an M390MK Ultratech with a 220 stone to get a burr on one side of the blade. Any advice?

 

[John Phillips]

Do you have the correct angle? What system are you using? I can get a burr on almost any steel with 400 grit stone. Make sure you don’t remove too much steel with the 220.

I’m NOT an expert at sharpening but I’ve gotten a lot better over the past 4 years. I use a wicked edge pro.

 

[drumlooper]

I use the work sharp elite with a 25 angle checked by the sharpie method. With very light strokes.

 

[drumlooper]

I’m using the system according to the manual but the bevel on the tip gets much wider than the factory edge meaning that I had to remove quite an amount of steel on the tip.

 

[rycen]

Welcome

I’m not familiar with that sharpener, but are the angles inclusive?

 

[Ajack60]

From what I’ve read and experience, M390 really doesn’t form a burr.

 

[drumlooper]

Welcome

I’m not familiar with that sharpener, but are the angles inclusive?

There’s an angle indicator on the system.

 

[drumlooper]

From what I’ve read and experience, M390 really doesn’t form a burr.

I can feel a slight burr with the nail of my pinkie.

 

[joesrx]

with 4% vanadium, I would use diamonds if you have them.

 

[Kryme]

If you have to remove a lot of material it's gonna take a while regardless of steel. M390 ain't that wear resistant, but diamond plates help a ton, that's what I use to reprofile. If you're going for 25 degrees combined, that's a lot of material removed before you reach apex. If it's 25 per side you should be feeling a tiny burr pretty quickly, m390/20cv/204 doesn't form that much of a burr. At best it's gonna feel sharper on one side than the other when you run your finger across the blade.

For me the bevels on my Stitch/MSI were even enough to where I didn't feel like a reprofiling is necessary. My Ultratech hasn't seen enough use to warrant sharpening, but it's a drop point version and with a decent factory edge as well, so it won't see reprofiling as well. I just do touch-ups on a fine ceramic/ruby stone on all my knives. It's a pretty fine stone, so it's like a step more aggressive than a strop.

 

[Dutch87]

I use the work sharp elite with a 25 angle checked by the sharpie method. With very light strokes.

I’m using the system according to the manual but the bevel on the tip gets much wider than the factory edge meaning that I had to remove quite an amount of steel on the tip.

Sounds like you are using the original black plastic Prescion Adjust system and not the newer aluminum Precision Pro Adjust.

The reason this is important is that you say you are using the angle indicator on the system, which is just a sticker. The actual sharpening angle is affected be how far the edge extends out from the pivot point of the system, so just because you dial the system in to where the indicator points to the 25 on the sticker doesn't mean that is actually the angle you are grinding at.

You need to use a digital angle gauge to know for sure. You can get an app on your smartphone that will do the job.

25 degrees per side is pretty steep, and I would not expect a relatively thin ultratech blade to develop a wide bevel if it was actually being ground at 25 degrees per side. Wide bevels indicate that you are grinding at a more acute angle than factory.

If your ultratech has a double edged blade, that may also be why the bevel is widening. Dagger grinds tend to be fatter since they taper from the center out and have less distance to taper.

Definitely digitally check your angle, is my advice.

 

[Kryme]

Ultratechs get chunky behind the edge pretty fast, even on drop-point. Can't really have a thin grind when you're working with like 3.1mm stock at 15mm width.

The angle doesn't change this is a myth. It's likely a change in the grind thickness or angle of the bevels of the grind. Main bevel is set perpendicular to the length of the blade, meaning the thickness behind the edge slightly increases once you get past the belly and it begins sweeping up. Measuring my Ultratech mid-way between the tip and the start of the upsweep, and at the heel of the blade, the heel is nearly a 1th of a mil thinner. So with more material towards the tip it's completely normal to end up with a bigger bevel. The difference is so big you can actually feel it with your fingers.

"But why doesn't it have a "smile" from the factory?" You ask? Because they sharpen by hand and compensate for it. Using a fixed angle system in mass production is understandably not a viable or cost effective option.