HT before and after grind effects?

P

Pedro G.

Well-Known Member
Hey guys! I haven't been here in a while but it seems that all the dogs are still as generous as ever with their knowledge ^_^ I'll be back for a while now, hopefully I can help some new people with what i've learned from you guys.

Now to topic:

I after the many knives i've made with my 4x36" grinder and still no funds to get anything better (I've used it heavily for 3 years now and it still works alright). I have been trying to find ways to make the process a little quicker with it, it is a 3/4 or 2/3 HP craftman and I'm not sure the RPM but its not very fast. I'm at the bevel process now but I want to get it perfect this time. I added an 80 grit belt since that's all i could find in the area around me, i heard lower grit belts eat quicker and heat the blade slower. But I also heard that HT blades grind faster and crisper because it is hardened, the only danger is overheating the blade and ruining the HT but as long as you have your bare hands and a bucket of water I don't see that as being to big of a problem. But i have also heard that untreated blades grind quicker too because they are not as hard and are softer so the abrasive claws at it better. I'm using a 1/4 1084 carbon steel bar so I have plenty of steel to grind off. But I don't want to have to take 4 days to make the grinds again either :p

So what can you guys tell me? Any other info that could help me would also be greatly appreciated! :)

Thank you in advance for reading this!

- Pedro G.
 
I my experience hardened and tempered blades grind slower because of increased wear resistance from the formation of martensite. Go to the Jantz site at www.knifemaking.com. They have 4X36" belts down to 36 grit. It's a good idea to watch your heat when grinding both before and after heat treating. Over heating after heat treating can draw the temper back too far but over heating during grinding before heat treating can set up stresses in the steel. Grind with bare hands in either case so that you will know when your steel is getting too hot.

Doug
 
Oh alright! Thank you :) What is the highest grit belt i should go to be safe from overheating with a fair amount of grind time, i heard 400 grit was a round about max.
 
Too many variables to answer that; machine speed, abrasive, force applied to work, and probably a few other things, including the length of the blade. There are those who grind out to a medium fine grit and then change to hand sanding. Do what works for you.

Doug
 
Alright, thank you Doug, I started on the blade without HT anyways. I have an 80 grit belt and i'm trying to put moderate firm pressure. My grinds don't come out very even but i hope it will come out alright, i'm half way done but i'm doing a flat grind half way down the blade. The blade is 5" long and i'm only used to doing about 3" so it's a bit more difficult.
 
80 is to fine to and is one of the steps to finishing.

I start with 36 Grit on HTed steel till I am most of the way there. Then a 60-80 and then a 120 Grit.

Then a 220 Grit or a X65 Norton structured abrasive then I use all four of the Scothbrite belts to get a finish.

Contact www.trugrit.com in Ontario Ca, and get Ceramic 4 x 36 inch belts. the 36 grit will grind well on HTed steel without to much heat build up..

Laurence

www.rhinoknives.com
 
Any specific brand you might recommend for that? and a finishing belt also? I've never finished my knives with a belt, i didn't know you could, I went from 80-120 grit to hand sanding and it did take a long time and a lot of sand paper.
 
rhinoknives said:
36 Grit Ceramic belts
are still the best for Hogging in a bevel and removing unwanted steel.

Laurence

www.rhinoknives.com
Click to expand...

Man do I agree with Laurence! I was doing what you were doing with an 80 grit belt and found it was just a pain and time consuming. I normally use a 36 grit to just hog everything, then 80, 120, 240, 400.

Just recently I decided to try out some Norton Blaze belts. I really really like them. I found that using a Norton Blaze 60 grit works pretty well for the first roughing out of the bevels. Then a 120 Norton Blaze belt, then I move to 240, 400 gator belts. I use them on my craftsman 2 x 48. Thats all before HT. then I do the same thing again after HT just dunk into water more.

I like the 3M Gator Belts for finishing from 240-600 grit. Then I do all my finishing by hand after that.

Good luck.
 
Blaze can be great if they are over the backing problem? Call Scott or Ryan at www.trugrit.com See what the have in your needed size? Ceramic belts are the best bang for the buck. The Ceramic usually only go up to 120 grit.

I use these on Treated or non Hted steel. Then the Gator or the norton X65 for finishing and any hand work you wish after that.

Sell your knives for enough to make at least three more, Then take a third of that and put it in a coffee can until you have enough to get a 2X72" Belt grinder.

Cheers.

Laurence

www.rhinoknives.com
 
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