Precision Ground Stock: Still Confused

M.FREEZE

M.FREEZE

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I am still a little confused on precision ground knife stock when it comes to the surface of the steel. I understand that by precision ground that the thickness dimension is exact, but is the surface smooth? If it is smooth, approximately what grit would you say the surface is? Has precision ground stock been surface ground to a true, level surface? In other words does precision ground stock look like steel that has been run through a surface grinder and is ready for grinding a bevel?
 
I haven't bought any for quite some time. When I did, ity would look like it had small tiney hollows all over it. Yes, you could go right to the grinding thing. Frank
 
I have only used precision ground O1, but I noticed that different suppliers have different finishes. The PG O1 from Aldo looks to be sanded to around 80 grit, while the PG O1 from Sheffield seems to be around 120 grit. They can go straight to the grinder but would benifit from being cleaned up.
 
I would go straight to grinding out your blade and the clean up the flats via hand sanding.
 
You can certainly go straight to grinding your blade but the flats need a lot of
fine grit finishing. This is one reason I've become disenchanted with the advantages
of precision ground for the sort of fixed blades I make. Having the sides smooth,
flat, parallel and with minimal scale is good. Having the thickness *exactly* .093"
doesn't really matter to me and isn't worth the higher price.

I'd probably feel differently if I made folders.

That said, I still use precision ground for A2 and O1 because that's what I can get
easily.
 
I guess I should be clear on my intentions. I do not make folders. So as far as precision thickness goes its not a big deal. I'll let the thickness determine what type of knife I will ultimately make. I'm more interested in the surface of the steel being clean and flat/level. My goal is to determine the grit that the stock has been precision ground to, then match the bevel grit accordingly. I have a piece of A-2 that looks to be smooth, maybe 120 or 220. In the end I will be sandblasting or acid etching with a stonewashed finish. How high of a grit do the flats/bevel need to be to achieve this look?
 
I wouldn't let any High Carbon knife leave the shop with less than 400 grit all the way around (except the tang). More scratches mean more surface area for rust to form. Also, I've never been able to get a good finish with acid or stonewash with less than 400 grit.
 
I agree with Jason and will go so far as to say the same for stainless steel... 400 grit is a good start. Anything less is just asking for trouble, and looks cheap/half-done.

I buy surface ground (not necessarily precision ground) stock whenever possible mainly because it saves me time and belts, not having to grind the tough mill scale off. Most of my stuff has full-flat or full convex grinds, and often tapered tangs so I end up grinding away the "finish" it came with regardless.
 
Precision ground has a decent finish but isn't really held to a specific surface finish. Expect better than Blanchard ground...but don't expect lapped. The "precision" is in the thickness, and most of the time in flatness. I have used a lot of PG stock and may have had one bar over the years that was bowed.
 
I've bought a fair amount of PG flat bar too. The thicker material is usually pretty straight and flat, but here recently I keep getting material that isn't square, but is more of a diamond cross section, so I've been having to square it up (which sort of defeats the purpose of getting pre-finished bars).

In thinner steel like I use for knife work I frequently have to straighten out little bends that I think occur during handling (this pisses me off).
 
Nathan the Machinist said:
I've bought a fair amount of PG flat bar too. The thicker material is usually pretty straight and flat, but here recently I keep getting material that isn't square, but is more of a diamond cross section, so I've been having to square it up (which sort of defeats the purpose of getting pre-finished bars).

In thinner steel like I use for knife work I frequently have to straighten out little bends that I think occur during handling (this pisses me off).
Click to expand...

What good is PG if it's a diamond section?
This is why I like Double Disc.
Flat and parallel.
Add a quick lap to get out the swirls and you've got it all!:)


--just kind of a drag if you're only doing 1 or 2---but that's why we have surface grinders, right?:thumbup:
 
JCaswell said:
What good is PG if it's a diamond section?
This is why I like Double Disc.
Flat and parallel.
Add a quick lap to get out the swirls and you've got it all!:)


--just kind of a drag if you're only doing 1 or 2---but that's why we have surface grinders, right?:thumbup:
Click to expand...

meh

I hate my surface grinder. I'd drag it out onto the street and set it on fire (if it weren't so heavy and non flammable). I really need to convert it to a belt.
 
Nathan the Machinist said:
In thinner steel like I use for knife work I frequently have to straighten out little bends that I think occur during handling (this pisses me off).
Click to expand...

Where do you get steel from? I've only bought from Jantz and Texas Knife, and they both ship the steel taped to a piece of wood to prevent bending. I ordered a 36" piece of rather thin (.093, I think) steel last month that came straight as a laser.
 
Grease your luckier than me. I have received 3/32 from them bowed and taped to wood. As soon ad the tape was removed it was a nice arc. It was fixable with a little tweaking and when I heat treated, but it still can happen. I went to 1/8 and haven't had an issue.
 
Nathan the Machinist said:
meh

I hate my surface grinder. I'd drag it out onto the street and set it on fire (if it weren't so heavy and non flammable). I really need to convert it to a belt.
Click to expand...

:D
Converting to belt is a better idea. Mines been belt for about 13 years.
Even then, I used it mostly for squaring damascus forgings.
 
zachtateknives said:
Grease your luckier than me. I have received 3/32 from them bowed and taped to wood. As soon ad the tape was removed it was a nice arc. It was fixable with a little tweaking and when I heat treated, but it still can happen. I went to 1/8 and haven't had an issue.
Click to expand...

Huh. Yeah, I guess the wood won't help if it gets bent before that. :\
 
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