Best file to serrate 420HC Steel knife.

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austin37

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Evening, lookin to add serrations to a folding knife I have. Steel is 420 HC I do believe, yes I understand it can affect and weaken the heat treatment of an already made blade.. but wanting serrations to better suit my needs.
What file would be recommended to DIY

Thank you.
 
You will get a better response if you ask a moderator to move this post to the maintenance/embellishment sub-forum. This is the Custom Knife forum.

By the way, a file will skate off a properly hardened blade. You will need a rotary tool with a diamond cutter to do what you want to do.
 
Any good quality chainsaw file will do just fine, they will definitely cut that steel at knife hardness. They are available in a few sizes at most hardware stores, they usually come two in a pack and are actually pretty inexpensive. You will want to look specifically chainsaw files for sharpening chainsaw chain teeth, they are a straight round file (no taper). You will probably want some high grit sandpaper to polish the serrations after you file them, look for automotive wet dry sandpaper in 600,1000,1500 grits and just roll a piece around the file and pull it through the serrations instead of pushing like you would with the file itself. Good luck , I've done it a few times and it works very well and the results can be very useful.
 
P.S. those chainsaw files are pretty easy to break in the small sizes so be careful, also wear a glove to prevent cuts as you will likely be filing toward an already sharp edge. I suggest practicing on a dollar store knife or two before the real deal, to get the hang of it.
 
thebrain said:
Any good quality chainsaw file will do just fine, they will definitely cut that steel at knife hardness. They are available in a few sizes at most hardware stores, they usually come two in a pack and are actually pretty inexpensive. You will want to look specifically chainsaw files for sharpening chainsaw chain teeth, they are a straight round file (no taper). You will probably want some high grit sandpaper to polish the serrations after you file them, look for automotive wet dry sandpaper in 600,1000,1500 grits and just roll a piece around the file and pull it through the serrations instead of pushing like you would with the file itself. Good luck , I've done it a few times and it works very well and the results can be very useful.
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I’ll have to give it a go on a cheap blade first, think I have some old chainsaw files in dads old toolbox. Thank you for all the prompt help as well.
 
id probably use a Drexel or round file. Wonder how David Mary David Mary does his......maybe he'll pitch in his method......
 
If the blade is harder than 56/7 HRC, a lawnmower file won't cut it. Diamond files will, abrasive bits in a dremel will...but a file will not.

The Rockwell hardness of a chainsaw chain, specifically the cutting teeth, typically ranges from 52 to 55 HRC.
 
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SharpBits said:
I think David uses a rotary tool and very steady hands.
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IIRC , a Dremel .

His serrations are the very best, IMO ! :cool::thumbsup::thumbsup:

But good luck duplicating his work .

He's got the knack ! :cool::thumbsup::thumbsup:

David Mary

How To Post in thread 'Advise needed on how best to sharpen DM's special serrations ! As found on my " Prevalito " .'

Who are you?

{merged post}

Kidding Doc! I will make a tutorial and post it here. Until then, feel free to call me. My number is on my card.

{merged post}

All one take, no edits, a dirty secret revealed, and finally goofiness exposed, please don't judge me too harshly. One clarification: By "ghetto" I just mean, "low tech, high effect".


P.S. I just did half a dozen passes per side on that plainedge S35VN Tenacious and it is no longer snagging at the tip.

{merged post}

Posted this video elsewhere, but adding it here as well, just to show the sheer workhorse my...
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A chainsaw file is should be plenty hard enough to cut 420 unless it was left as quenched. Meaning not tempered and in a brittle state.
 
Hengelo_77 said:
diamond needle file
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This ☝️
Partly because the core of the diamond file is less prone to breaking / does not have to be as hard as a regular file (over the decades I have broken a few "rat tail" files even knowing it might happen) . I have NEVER broken a tiny / skinny diamond file (I use round and square) and I have used them to serrate a few knives up to and including CTS XHP blade alloy .

THAT SAID IT TAKES FOR EVER TO FILE A BLADE AND THE DANGED FILE SLIPS OVER THE BLADE TO WHERE YOU DON'T INTEND TO FILE AND IT IS A GIANT PITA.

PS : also filing a blade by hand is an EXCELLENT way to get cut . . . especially when you finally realize just how long this folly is going to take and you start flailing away with abandon .

as so many before me have said (now that I finally took the time to read all the post ) :
Use some tiny DIAMOND rotary files on a Dremel like high speed grinder at fairly high speed and keep the blade wet / cool .
Unless you just enjoy the meditative experience of spending your day filing .
 
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Put ducktape on the blade and have a cut out where you want the file to cut.
If you have a light touch it can be enough guidance to stop the file wandering all over.
Go one at the time and after cutting a serration move the tape over a few mm's
 
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