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Question about files&Plunge lines


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So lets say you have the plunge line on your knife perfect 90 degree right angle, Would that crack in the heat treat? 

If a perfect plunge line does not cause cracking, is it necessary to round the corners of the file you use to make the bevels on your knives? 

Get what im saying?? 

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I get what you are thinking about. There are probably a lot of high tech explanations but I'm a simple guy. The problems that may occur are in sharp corners that go completely through the profile. Surface corners are not a serious but I tend to leave them rather "casually" rounded before HT because they are going to get special attention in the "pre polishing QC check (to make double sure they are square) and in the polish. I do like to get them started while the steel is still soft. If you do a couple of normalizing cycles before heat treat I think, but have never tested, it should be fine.

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7 hours ago, Conner Michaux said:

So lets say you have the plunge line on your knife perfect 90 degree right angle, Would that crack in the heat treat?  

If a perfect plunge line does not cause cracking, is it necessary to round the corners of the file you use to make the bevels on your knives? 

Get what im saying?? 

I get what you are saying, and to be honest about it, I have only seen one person ever get close to a perfect 90 degree corner in his plunge cuts and that was Tim Hancock. He didn't set them with a file either. I seriously doubt you will have any trouble with those corners in the quench. I have always thought the "square corner stress point" was a massively overstated concern, mostly because with the tools we all use, it's almost impossible to achieve. Everything, the files, the belt grinder, the disc and the hand sanding stick, all leave a slight radius behind. There's just no way around it. So go after it. Set it up straight and square. Then get yourself a pair of optivisors or a good magnifying glass and take a closer look at that corner.

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What Josh said.  Japanese swords have a pair of sharp notches in the worst possible place, and they don't break there.  Most firearms have sharp square corners in important places, and they don't fail there.

Now, if you were casting something with a sharp corner at a large change in sectional thickness, yeah, that causes problems. 

I think that's where the idea came from, and it gives you something to blame if you break a blade in the quench.

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Ive been getting my big files for around 30$ All are made in USA and there Nicholson brand, Im wondering if im paying to much, Can I get them cheaper?

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1 hour ago, Conner Michaux said:

Ive been getting my big files for around 30$ All are made in USA and there Nicholson brand, Im wondering if im paying to much, Can I get them cheaper?

What do you consider big?

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1 hour ago, Conner Michaux said:

Ive been getting my big files for around 30$ All are made in USA and there Nicholson brand, Im wondering if im paying to much, Can I get them cheaper?

My parents have always told me and still do “ you get what you pay for.”  So a 30 dollar file compared to a 5 or 6 dollar piece of harbor freight junk, I’d stick with the 30 dollar files.  Yes expensive but they will last you for quite some time.

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Grobet files cost a little more, worth every penny!

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