Please help me with Spyderco GB1 Geometry

Z

Zenturio

Joined
Aug 7, 2017
Messages
174
Hey all together,

I was not interested that much in the newer knife designs.Then I was extremely lucky to buy a GB1, unused. I disassembled, cleaned and polished it up a little bit, perfect in every way.

I sharpened it and it got extremely sharp with no effort. Then I checked the blade geometry with calipers. And that is when things are going ridiculous. Thickness bte is 0,0125in, and 10mm up from the cutting edge my calipers are showing 0,033in. This is extremely thin, has to be much thinner than my GB2.






I am so pleased, but a little bit afraid to use it hard. I think that the CPM M4 is heat treated well because of how sharp the edge got with no effort. I sharpened tons and tons of knives, this GB1 is another level.

Are your GB1 that thinly ground too?

Looking forward to hear your experiences.

Best regards,
Oliver
 
my gb2 feels like that... incredibly nice hollow grind, I've only ever used a strop on it
I need to get myself a digital caliper, thanks for reminding me
 
My spyderco mantra is .4 mm bte. it's not a hollow grind but it's in m4. Got other knives that are thin like that and it's a thing of beauty. Manly peak and a rukie 191 (too bad its got 8cr steel instead of sandvik). Oh another one I got, and this one is hollow ground, is CS code 4 in xhp, but i think it's an anomaly. It's a wicked slicer, although the spine thickness on it is comparable to a thick bushcraft knife.
And yeah the m4 is fun to sharpen. One time it almost started whittling hair just coming from spyderco brown stone for me.
What angle did you sharpen at?
 
The GB2 is a fantastic slicer, probably due to that high thin grind and the excellent M4 steel. These are users.
 
I would not worry.
Though I have not carried my GB1 in a while I never once thought it was too delicate for any tough cutting.
 
.0125in behind the edge you say? I like it. I like them even thinner, but I'm crazy like that.

When you get that thin there are limitations to what you can do, but as long as you use some sense it will be ok.

You have experienced one of the great joys of a thin edge: they sharpen much more easily than thick edges. Much less material to remove on a thin edge.
 
No issues with mine even when ground thinner


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That succulent geometry is what made that model so significant. Use it and you may be surprised to find out it may be fine to even go thinner. Only way to find what's right for you and your specific application(s) is to use it and learn what you may have been missing out on ;-) Any pocket-knife ≥ 20-thou BTE is a tanker for those with little practical experience (IMHO), or for those who pry/lever vs cut with their pocket-knife.

Consider yourself extremely lucky to have lucked into such a situ ;)
 
Thanks for all the answers.

That helps me quite a bit. I like my knives that thin, I did quite a bit of regrinds to get thin geometries (but only flatgrinds because of the flat platen I use on my Beltsander) . What makes me wonder is not the BTE thickness, but the thickness of 33thou 10mm behind the cutting edge, due to the hollow grind.

marthinus marthinus : Your GB1 is ground even thinner?

Br Oliver
 
Zenturio said:
Hey all together,

I was not interested that much in the newer knife designs.Then I was extremely lucky to buy a GB1, unused. I disassembled, cleaned and polished it up a little bit, perfect in every way.

I sharpened it and it got extremely sharp with no effort. Then I checked the blade geometry with calipers. And that is when things are going ridiculous. Thickness bte is 0,0125in, and 10mm up from the cutting edge my calipers are showing 0,033in. This is extremely thin, has to be much thinner than my GB2.






I am so pleased, but a little bit afraid to use it hard. I think that the CPM M4 is heat treated well because of how sharp the edge got with no effort. I sharpened tons and tons of knives, this GB1 is another level.

Are your GB1 that thinly ground too?

Looking forward to hear your experiences.

Best regards,
Oliver
Click to expand...
Spyderco takes their m4 pretty high in hrc and at the higher end of h/t the metal can really support a thin grind without rolling and will naturally flex under pressure when taken even thinner. I believe its known as "ductility". I love the mantra 1 so much I have bought two and the second one tested at 65 hrc. I don't believe I tested the first one before it was lost. I digress, while 12 thou is very thin for a production folding knife it's not in the world of custom knives and sub 10 thou bte thickness on performance steels is preferred for many enthusiasts. Use it and learn to love that slicey geometry without fear. It will support hard cutting just fine as long as you are not twisting hard during cuts which should be obvious to anyone that using a blade with a slice grind.
 
Zenturio said:
Thanks for all the answers.

That helps me quite a bit. I like my knives that thin, I did quite a bit of regrinds to get thin geometries (but only flatgrinds because of the flat platen I use on my Beltsander) . What makes me wonder is not the BTE thickness, but the thickness of 33thou 10mm behind the cutting edge, due to the hollow grind.

marthinus marthinus : Your GB1 is ground even thinner?

Br Oliver
Click to expand...
I will have to do some measurements for you but it will have to wait until the weekend when I can get the callipers out but yes I did regrind mine quite thinner.

I did some experimentation with M4 at low angles many years ago that led me to do the regrind.

CPM-M4 at low angles. My experience recently.

I have been decreasing the edge angle on my Gayle Bradley using the shoulders as a guide. Finally finished with it and the edge is around 5 Degrees Per Side (DPS). Finished it up on a Spyderco UF stone. The edge was shaving sharp in both directions and felt very crisp to the touch...
www.bladeforums.com www.bladeforums.com
 
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Mine is 0.012-0.015 thin behind the edge and 10mm up from the edge thicker than the original at 0.054 of an inch.

Quite surprising to see throughout the years it is now very similar to that of the original.

I measured the amount of steel removed compared to my original I still have and there is around 1.5-2mm of steel that has been sharpened off.
 
marthinus marthinus
Thanks for your work. I measured again because I could not believe that big difference at the 10mm measuring point. I repeated that and precisely measured 42 thou. 12mm behind the edge (imagine that I ground 2 mm off the edge) it stands 52thou. That means that our two knives have quite the same geometry, doesn`t it? If yes I will no longer hasitate to use my GB1 harder ;)

BR Oliver
 
Zenturio said:
marthinus marthinus
Thanks for your work. I measured again because I could not believe that big difference at the 10mm measuring point. I repeated that and precisely measured 42 thou. 12mm behind the edge (imagine that I ground 2 mm off the edge) it stands 52thou. That means that our two knives have quite the same geometry, doesn`t it? If yes I will no longer hasitate to use my GB1 harder ;)

BR Oliver
Click to expand...

Seems like it. I was surprised. Thought mine was thinner than it was.

You might find the below interesting if you are still on the fence

Gayle Bradley Hard Use

So, in addition to the strong build of the Gayle Bradley collaboration knife, the M4 steel is highly lauded for its wear resistance. That's one of the reasons I bought it, so today, it had the chance to show what it was good for. My wife and I fixed fence today, and used some old electric...
www.bladeforums.com www.bladeforums.com
 
I was cleaning out my nightstand this weekend and I found my long lost GB1. The blade needs a touch up, but it’s one of the old solid liners. It made me a firm believer in well heat treated M4 and it was my trustworthy work horse, before it was usurped by a Sebenza 21. I need to put it back into the rotation.
 
Helped a buddy move. He had a trailer and the trailer had post holes in the corners. We had 3/4 that came with the trailer but didn’t have the last. We grabbed a 2x4 and I used my GB1 to chop and whittle it down to fit it. Cut like a demon before and afterward.
 
I've had my GB1 for nearly 8 years (August I believe) and it has never chipped, rolled, etc. Very easy to touch up. Never had to use more than the medium sharpmaker stones. Guess I'll have to carry mine tomorrow.
 
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