Testing on felt.

[nozh2002]

I just have finished testing using new technic (I read about it on Victor Kuznetsov site http://www.kuznec.com ). It looks like it work very well so far.

I bought piece of 4mm thick felt in Orchid Supplay Hardware, cut it on stripes 1" wide, stuck seven of them together and start cutting like 5mm pices away. After I cut let say 3 top stripes I put them under remained stripes and continue cutting so edge never actually hit the table - it is only felt it is cutting.

I have no spetial way of cutting - just cut it any way possible, but in time blade turn completely dull and is not able to cut at all.

Result of the test - number of cuted off pieces.

I have tested Kirpichev's bulat (see on the picture) and it ends with 801 score. Now I will try something else, but test itself seems working - first time I was able to come to the finish point - it stoped cutting felt at all, clear way to determine end of the test!

It continue to cut wood without problem and I was able few times to cut hanging newspaper (but it fales in most cases) - but felt looks like better indicator.

Thanks, Vassili.

 

[DGG]

That's a test I have never heard of before. I wonder if you had tried cutting rope if the results would have been the same.

 

[Cliff Stamp]

I have no spetial way of cutting - just cut it any way possible...

You can get different results on a draw vs push cut, it is finish dependent on which grit you leave the edge ground, so you want to be specific about the type of cutting.

I have tested Kirpichev's bulat (see on the picture) and it ends with 801 score.

You need to repeat this a few times to check consistency both in the material and the sharpness and have a way to do the cutting so that the number of cuts is counted but you don't know the result, this insures you can't bias the results.

I tried fabric cutting a half a dozen or so years ago, various types, I wound it up into rolls, the problem is that you can keep cutting for a long time if you increase the force you use so you need a way to measure how much force you apply.

A blade has to be really blunt before it won't cut at all and just friction burns the material if you press hard, long past the point most would sharpen it, felt is also fairly soft so this might look at wear resistance fairly strongly whereas a lot of cutting tends to focus on hardness.

-Cliff

-Cliff

 

[nozh2002]

You can get different results on a draw vs push cut, it is finish dependent on which grit you leave the edge ground, so you want to be specific about the type of cutting.

Let say I test ability to cut felt - it is draw cut, my point is that I dont limit number of cuts per stripe.

I just tried push cut, I thought it is impossible with felt because it is too soft, but it works. I'll probably shoud increase number of layers, it is harder to manage not to hit table.

You need to repeat this a few times to check consistency both in the material and the sharpness and have a way to do the cutting so that the number of cuts is counted but you don't know the result, this insures you can't bias the results.

Well, I trust myself... Anybody can try the same - this is the point in "democratic" test which I try to find. Simple test, everybody can do. This way in theory we may have statisticaly good number of tests made by many different knife entusiasts.

I tried fabric cutting a half a dozen or so years ago, various types, I wound it up into rolls, the problem is that you can keep cutting for a long time if you increase the force you use so you need a way to measure how much force you apply.

Felt is different. It was used for sabre testing ages ago. I did applay enough forse and effort to cut - it is 801 cuts. I spnend about hour-half hour a day for three days and it finally stop cutting. Before I pushcut manila rope - I finish after 12 feet 320 cuts because it was not looks like it near the end at all.

Same with oak wood - I whittled out 30cm of it.

A blade has to be really blunt before it won't cut at all and just friction burns the material if you press hard, long past the point most would sharpen it, felt is also fairly soft so this might look at wear resistance fairly strongly whereas a lot of cutting tends to focus on hardness.

-Cliff

I am not sure why felt special - it is wool as I understand, it may have some silicon dust in it or something - like CATRA paper, but I am not sure - anyway I manage to dull the blade, so it stop cutting it.

Thanks, Vassili.

 

[Cliff Stamp]

Well, I trust myself...

It isn't about trusting yourself, it is about evaluating the method. There are random influences which you need to benchmark for comparisons, otherwise you can't tell if a difference is meaningful or just random.

Before I pushcut manila rope - I finish after 12 feet 320 cuts because it was not looks like it near the end at all.

Yes, Busse has done thousands on one inch hemp on a push, Boye has done thousands on a one inch hemp on a slice. I did over 2000 cuts through 3/8" hemp on a slice with a D2 blade and it was still taking ~20 lbs to make a slice.

I am not sure why felt special - it is wool as I understand ...

Natural felt is 100% wool, man made felt is 30% wool and 70% other fibres. I would assume these could change from one manufacturer to another, some fibres can be more abrasive than others.

Interesting result, I would not have thought felt was significantly abrasive, I have a piece that I'll do some cutting on tonight.

-Cliff

 

[Jeff Clark]

My guess is that the individual fibers in the felt are hard, but thin. It feels soft in the aggregate, but at the microscopic level the hairs are hard and flexible. The edge contacts a huge number of fibers simultaneously and those shift as you try and cut them. When you cut a tall stack of felt it furthermore tends to wrap around and pinch the blade. To avoid the pinching effect try extending a single piece of felt off the edge of a board and cut the felt just where the support of the board ends. Arrange it so that the edge cuts past the end of the board, but only by a small distance. Put extra felt under the board to protect your edge after you pass through your test felt. I think that your current test is hyper sensitive to your blade geometry. A blade of the same material, but with a different grind would give you an extremely different measurement.

I have a long haired cat that gets matted fir. Even with a straight razor or razor blades it is hard to slice through the mats. I am not surprised that it can dull an edge. There may also be something gritty used to get the wool to mat and hold its shape.

 

[Cliff Stamp]

I did some cutting last night, 1mm thick felt, cheap, 0.50$ for a sheet the size of a phone book. I cut it in one inch strips, made a stack of ten strips and cut thirty sections, so 300 pieces total.

I used a SAK, reprofiled at <10 degrees per side, finished with 20 degree microbevel on sharpmaker medium rods. The entire blade was used on the draw. The knife was still shaving at the end of the cutting, no significant blunting.

It may be that different man made felt have different fibres and some may be very abrasive, the edge finish makes a huge effect as well, If the initial polish is very high you will lose slicing aggression fairly quickly. You can't slice hemp rope very long with a CrO polished knife for example.

It is fairly hard to cut in that it requires a lot of force and a very sharp blade, it is very demanding in that regard, more so than hemp for example. It is essentially a very compressed material and doesn't fall apart as ropes do when you cut into them.

-Cliff

 

[davmgt]

great idea! that gives you a nice, standard measn of comparison.

 

[nozh2002]

I did some cutting last night, 1mm thick felt, cheap, 0.50$ for a sheet the size of a phone book. I cut it in one inch strips, made a stack of ten strips and cut thirty sections, so 300 pieces total. -Cliff

Cutitng area in your test is 1mm * 24mm * 300 = 7200 mm2
I did 4mm * 24mm * 801 = 77184 mm2

300 cuts on 1mm felt aproximately equal 300/4 = 75 of 4mm felt - not too much.

Also SAK (is Swiss Army Knife?) much thiner. Blade I used probably twice thicker or more near the edge - it is fare to expect it cuts bit better because smalle resistance.

And you are right I polish blade till .15 micron diamond powder. But why it should affect slicing ability?

I checked OSH yestarday - they have felt in 1/8" (4mm) and 1/4" and 1/2" - it is standard things used for thomething in house.

Thanks, Vassili.

 

[Cliff Stamp]

... not too much.

Yes, I was just curious as to the abrasion level, a much smaller number of rope cuts would have produced a significant impact on the SAK blade, I was just benchmarking its blunting ability.

...it is fare to expect it cuts bit better because smalle resistance.

Yes, this however would not significantly effect the edge retention assuming you don't use a cutting board. You would not a difference in the force needed on the first cut, but this difference would be a systematic one throughout the cutting.

[polish]

But why it should affect slicing ability?

As the micro teeth are reduced in size you lose both slicing aggression and edge retention, from a very coarse to a very highly polished edge the effect is very large. Chosing the finishing grit can have a bigger influence on edge retention than the difference between mild steel and the best cutlery steel for example.

-Cliff

 

[nozh2002]

...a much smaller number of rope cuts would have produced a significant impact on the SAK blade, I was just benchmarking its blunting ability.
-Cliff

I did not made same amount of cuts on rope - I gave up on 320, however it was different knife. I should try more rope.

Anyway felt less messy then rope...

Thanks, Vassili.

 

[Cliff Stamp]

Hemp rope is decently abrasive, I rarely do more than 254 cuts in edge retention comparisons any more, you can learn what you need to know on far less cuts, blunting is also nonlinear so the effect of the first dozen cuts is similar to a hundred more after a point. You need to do a few thousand a few times just to confirm the general behavior, but for general testing it isn't necessary on every knife.

-Cliff