How to get a nice flat edge using 4x36

Joined
Apr 17, 2021
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2
So I bought a cheap 4x36 belt grinder at harbor freight when I started making. I realise now it's not the most useful of them for knives. None the less it is what I have until I'm able to save for something with variable speed. My question is how can I get a nice flat grind using this grinder? Should I use a magnet? What angle Is the best for my flat of the grinder,and lastly can anyone recommend a good belt grinder I can save for that is not outrageously priced? I have 4 kids and this is a hobby. Thanks Andy
 

A.McPherson

Knifemaker / Craftsman / Service Provider
Joined
Jan 27, 2012
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1,940
Hi! Most 4x36 grinders don't have a really good flat platten to work on, so you're really not going to have great results getting things flat.

Get it as flat as you can, then take it to a known "flat" surface like a granite block or a piece of glass, with some sand paper gluef to it.
Then sand on the DIY "surface plate" till everything you want to be flat, is flat.

Nothing comes off anyone's grinder super flat, at least most folks that is... There are some freaks of nature out there that put us all to shame!

Generally speaking though, if you want it flat, it's not going to happen on a belt grinder.
 
Joined
Apr 3, 2015
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2,464
So I bought a cheap 4x36 belt grinder at harbor freight when I started making. I realise now it's not the most useful of them for knives. None the less it is what I have until I'm able to save for something with variable speed. My question is how can I get a nice flat grind using this grinder? Should I use a magnet? What angle Is the best for my flat of the grinder,and lastly can anyone recommend a good belt grinder I can save for that is not outrageously priced? I have 4 kids and this is a hobby. Thanks Andy
I seen a guy on YouTube that bolted a steel platen to the frame of his 4x36. You won’t get perfectly flat grinds, but it will have to be an improvement.
 

Stacy E. Apelt - Bladesmith

ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
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Aug 20, 2004
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32,846
Use JB Weld to attach a pyroceramic glass platen on the grinder. If that isn't in your budget, use a piece of 3/16" steel. The JB Weld will hold either just fine.

Hold the blade at various angles to the belt andf see what works best for you. Straight across at 90° for most tasks, 45° for some work, and inline with the belt for overall flattening and distal taper. A magnet from HF will help hold the blade. The 30 pound pull one is good enough:
30 lb. Pull Magnet with Handle (harborfreight.com)
The knife supply companies sell magnets in wooden blocks that are great.
https://www.texasknife.com/vcom/pro...=4354&osCsid=b5faab992adeb6649c497d5e3901a6ad
 
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