Need some advice for regrinding a PM2

J

J-RAY1989

Joined
Jun 14, 2019
Messages
351
Hi all! I'm going to use one of my PM2s for a little regrind project.

My main question is if I should be worried about ruining the heat treat. I'm not going to be doing anything crazy. I'm going to take it to the bench grinder to get the rough profile I want, then I'm just going to do the rest by hand on stones, since I don't have a belt grinder to use.

I've done the same process successfully on a wrench knife I made, but that was just killing some time.

I don't suspect I'll get the blade hot enough to undo the heat treat, but better safe than sorry.

Thanks for any input.
 
just grind at slow speed and keep it cool with a dip in water often ... some steels are affected a lot quicker then you think.
 
JJ_Colt45 said:
just grind at slow speed and keep it cool with a dip in water often ... some steels are affected a lot quicker then you think.
Click to expand...
It's m390 if that helps. I'll make sure to dip it in water often. I'm only grinding off maybe a quarter inch at most at the tip.
Thanks for the advice.
 
bucketstove said:
Hi,
what bench grinder?

Tips: pre chill blade in salty ice water, quick passes on benchgrinder
only dip blade after the grinded part has air cooled enough to where you can touch it with your skin
do not dip a blade that is too hot to touch where it was grinding

bladeforums.com/threads/chilling-blade-before-using-a-powered-belt.1630793/
knifesteelnerds.com/2019/04/08/does-sharpening-with-a-grinder-ruin-your-edge/
bladeforums.com/threads/burnt-edges.1652608/
Click to expand...
Just a DeWalt dw756. Fairly low grit sanding wheels. I'll read that thread, thanks for the info.
 
Now I'm debating fashioning a foot operated water pump, then just pumping water straight on the blade as I grind it I'd think that should keep the blade temp low enough? Really it should only take a couple minutes to get the rough profile.
 
J-RAY1989 said:
Now I'm debating fashioning a foot operated water pump, then just pumping water straight on the blade as I grind it I'd think that should keep the blade temp low enough? Really it should only take a couple minutes to get the rough profile.
Click to expand...
Sounds like that might be fun to watch.
Could you record the vid ?
In all seriousness though be sure the grinder is grounded (electrically). I've been shocked by an ungrounded bench grinder even without drenching everything in water.

And do post photos of the final result. I love knife mods and do them all the time on my factory knives.

. . . not saying there is no validity to the don't dip a warm knife warning. I would have to investigate that further and honestly this is the first I have heard of it
but
I could bore you with a plethora of photos of my frankenknife projects that have been endlessly dipped in water while the edge was a little too hot to touch (I would guestimate ~200°F to ~250°F ((Probably less)) and I have had ZERO problems with micro chipping, chipping, cracking or snapping off. To a knife the edges have all remained durable in actual daily use at work. I don't waste time modding a knife I am not going to use the hell out of.

Better to dip it when it still isn't too hot to touch though

I have not modded one in M390.
These are the alloys I have modded :
Case CV
Case SS
Hand file steel (what is that ? W1 or some such)
AUS-8
VG-10
CTS-XHP
HAP-40
3V

Ohhhhh . . . why not just a little plethroration with a dollop of boredom on topping.
This is 3V : ground (or grinded) from 5mm at the spine down to 2.2mm
IMG_3773.jpg
IMG_3844.jpg
IMG_3916.jpg
Obviously I don't go for pretty just functional. Pretty might come along someday if I get the urge.

Here is a tip mod as well as two more stupid thick blades taken down to smart and full flat. (Since then I have come around to appreciate convex and concave)

Dremel cut off wheel
IMG_4353.jpg
Full flat ground on a white wheel turning fast(ish).
Super frequent water dip every few second. Then very large super coarse diamond file followed up by Shapton Pro120 shown here.
IMG_4379.jpg

The twins
(the long one is the brilliant one because he has an IQ of CTS-XHP but the little guy is incisive in a tight spot even though he is AUS-8)
IMG_4367.JPG
 
Wowbagger said:
Sounds like that might be fun to watch.
Could you record the vid ?
In all seriousness though be sure the grinder is grounded (electrically). I've been shocked by an ungrounded bench grinder even without drenching everything in water.

And do post photos of the final result. I love knife mods and do them all the time on my factory knives.

. . . not saying there is no validity to the don't dip a warm knife warning. I would have to investigate that further and honestly this is the first I have heard of it
but
I could bore you with a plethora of photos of my frankenknife projects that have been endlessly dipped in water while the edge was a little too hot to touch (I would guestimate ~200°F to ~250°F ((Probably less)) and I have had ZERO problems with micro chipping, chipping, cracking or snapping off. To a knife the edges have all remained durable in actual daily use at work. I don't waste time modding a knife I am not going to use the hell out of.

Better to dip it when it still isn't too hot to touch though

I have not modded one in M390.
These are the alloys I have modded :
Case CV
Case SS
Hand file steel (what is that ? W1 or some such)
AUS-8
VG-10
CTS-XHP
HAP-40
3V

Ohhhhh . . . why not just a little plethroration with a dollop of boredom on topping.
This is 3V : ground (or grinded) from 5mm at the spine down to 2.2mm
View attachment 1184021
View attachment 1184022
View attachment 1184018
Obviously I don't go for pretty just functional. Pretty might come along someday if I get the urge.

Here is a tip mod as well as two more stupid thick blades taken down to smart and full flat. (Since then I have come around to appreciate convex and concave)

Dremel cut off wheel
View attachment 1184025
Full flat ground on a white wheel turning fast(ish).
Super frequent water dip every few second. Then very large super coarse diamond file followed up by Shapton Pro120 shown here.
View attachment 1184026

The twins
(the long one is the brilliant one because he has an IQ of CTS-XHP but the little guy is incisive in a tight spot even though he is AUS-8)
View attachment 1184027
Click to expand...
Wow that's awesome. Good job on those. I also go for functional over pretty... In certain instances.

So ill spill the beans on what my full intentions are. The m390 is my heavy use pm2. I have others that I use, but this one is already a franken knife made from parts of 3 other pm2s.

I'm going to make a tanto with belly. Didn't mention that earlier because I know many people on here don't like tantos much.
Ive been patiently waiting to see if Spyderco was going to put their prototype tanto pm2 into production or not. I dont want to wait anymore, and I have a heavy use m390 franken pm2 at the ready to play with. So I'm just going to have some fun with it and see what happens.
 
Id avoid using a grinder wheel, too much friction and chatter, no one grinds blades with a bench grinding wheel.

The ice water thing is BS.


Here's the trick.

Use fresh Abrasives and be proactive with water cooling.

I recommend a 1x30 with 40grit Blaze ceramic belts.

Change belts often, use light touch, be proactive with dunking in water.
 
DeadboxHero said:
Id avoid using a grinder wheel, too much friction and chatter, no one grinds blades with a bench grinding wheel.

The ice water thing is BS.


Here's the trick.

Use fresh Abrasives and be proactive with water cooling.

I recommend a 1x30 with 40grit Blaze ceramic belts.

Change belts often, use light touch, be proactive with dunking in water.
Click to expand...
Using the bench grinder is just because that's something I already have. I could probably pick up a belt grinder from harbor freight for cheap, but it's not something I'm going to use very often. Using a cut off wheel on an angle grinder is an option also. All I need is a rough profile, than the rest I'm going to do by hand.i suppose if it's going to be detrimental to the blade, I could always use a metal file to do it, will just take alot longer.
 
Belt grinder
Click to expand...

Unknown.jpeg
Well ya if you want to take all the challenge out of it.
Next you will be telling me about a VARIABLE SPEED belt grinder. :D
We home hobby modders, we like a little more challenge . . . a little more adversity . . .

Here is a water bath wheel I have. It is so freekin' slow to remove material that it is barely usable for edges. Useless for grinding the side of a knife to a final state within a time frame of, oh say, this millennium. It has a small fast(ish) turning wheel on the side that I have done many of these mods with but I have since moved on to the Norton X Blue wheel shown on the too fast turning bench grinder that also has the paper wheel on it. I have an inexpensive vertical single speed belt grinder for metal but it sucks so bad it doesn't even rate a photo.

IMG_5913.JPG
IMG_4137.jpg
 
DeadboxHero said:
Id avoid using a grinder wheel, too much friction and chatter, no one grinds blades with a bench grinding wheel.
Click to expand...

AAAAAhahahha
I like to be different . . . a mutant spawned in the deep recesses of timeless dark matter . . . cast into a world he never made and barely understands.

eeennnh . . . I work with what I gots.

The ice water thing is BS
Click to expand...
I AM SOOOOOO GLAD you said that.
I strongly suspected it didn't pass the smell test.
 
DeadboxHero said:
Here's the trick.

Use fresh Abrasives and be proactive with water cooling.

I recommend a 1x30 with 40grit Blaze ceramic belts.

Change belts often, use light touch, be proactive with dunking in water.
Click to expand...

errrrr
you are taking for granted he / we are going to go out and buy a belt grinder just for one or two knife mods.

. . . well . . . you know me better (I'm a tool junky that will buy a seriously decent power tool at the drop of a hat) . . . but I doubt the OP will and I must emphasize :eek: the high suckieness level of cheep HarborFreight tools ! ! ! !
You will have more fun sitting and tapping your knee with a hammer.

I do so little of this knife blade work that buying a decent belt sander (multi speed natch ;) ) well . . . even I would be embarassed to say I did that for how little work it would see. :(
 
I'd rather not go buy a belt grinder just for one knife, and I have a bench grinder handy at all times. I think I'll just get some finer grit wheels for the grinder. It doesn't in any way need to be pretty. That's where the finishing by hand comes in. All I need to do is grind the tip flat to the belly. Then I'll put the bevel on by hand.

I could see if I'm going to do this alot to get all the right tools and materials, but this is a quick wham bam thank you ma'am then on to the stones.
 
I think I'll just get some finer grit wheels for the grinder.
Click to expand...
I'm your friend and I'm trying to help and I am sympathetic to the price of decent power tools
but
NO
NO
NO
PLEASE
The fine wheels turned too fast will burn your blades for SURE !
The only hope is doing the coarse heavy lifting with the VERY COARSE grind wheel say 40 ish grit
then polish on something MUCH slower like a bench stone
 
Wowbagger said:
I'm your friend and I'm trying to help and I am sympathetic to the price of decent power tools
but
NO
NO
NO
PLEASE
The fine wheels turned too fast will burn your blades for SURE !
The only hope is doing the coarse heavy lifting with the VERY COARSE grind wheel say 40 ish grit
then polish on something MUCH slower like a bench stone
Click to expand...
Noted. I already have low grit wheels on it. Can't be more than 100 grit. This is going to be a fun project. I'll post pictures for sure. Should be done within the week most likely.
 
full


Rough profile done. Didn't put it on the grinder for more than 2 seconds each time, then doused in water.
 
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