drilling files

got a few old blunt and broken files.

thinking of making folding knife out of one was wondering how difficult to drill?

does it need any particular drill bit or certain speeds?

Either anneal, drill, shape etc then harden and temper - a good exercise or use a carbide drill.

Would be a bit of a bugger to drill one, kind of like drilling a hole in a stone

The biggest issue IMO would be that a good file will snap like a carrot compared to a well made blade

So a furnace type setup would be essential to do a proper job

edit

saw a chap who makes Claymores on ra TV the other day

It was all soft metal work then heated to straw/cherry hot and dunked vertically into a tube of oil to harden

Then finish ground

I think he used high carbon steel bar

Edited By Ady1 on 18/07/2018 08:58:48

I'm an expert on this after watching 'Forged in Fire' on telly!

Sometimes they use known steel, sometimes they make damascus by mixing metals, sometimes they re-use scrap. Generally the process is to soften the steel by heating it in a furnace and then bashing the billet into rough knife shape by hammering and perhaps some angle grinding. In this form the metal is relatively soft.

The rough knife shape is then formed into a blade and tang by grinding . Once the blade is presentable, its reheated and tempered by plunging into oil. (Water available but rarely used because it makes blades too hard and brittle.)

The blade part is plunged into oil point first. The tang goes in last, and - hard to see - I think the extreme end isn't tempered at all. In consequence I believe that the tang is less hard than the blade, over which a file should skate without cutting.

Even if the tang is less hard one of the more difficult parts of the whole knife making process is drilling holes in the tang so the handle can be pinned. Drills get broken, blood spilt, and metal cracks! Strong men lose heart.

Putting it politely, it seems to me that most competitors aren't skilled on a drill press. Brute force and ignorance, which is surprising considering the impressive skills otherwise demonstrated. I'm confident most model engineers would do better at drilling! No information given about the type of drills used; they look like ordinary blacksmith/jobber HSS to me. No sign of a centre punch either.

I'm not sure if there's a good reason for drilling the tang AFTER the blade's been hardened. They all do it that way. Possibly the hole causes warping if drilled before tempering.

If I was drilling the tang I'd look to a hardened drill, clamp the blade down, go in hard, and apply coolant. I'm sure it's possible to grind a hardened file into a blade without softening first. Much harder to drill holes in it. But another good reason for re-tempering the metal is that files are hard and brittle. Make a better knife if heat treated less aggressively. In practice this can probably be done by tempering in oil. (Hardness and toughness can be tuned by skilled heat treatments. Slow cooling favours toughness over hardness, fast cooling favours hardness over toughness. Oils cool slower than fresh water and salt water cools very quickly.)

This is all armchair engineering!- If someone who's actually done it answers, believe him first!

Dave

If I recall correctly from my technical institute days, to anneal steel you must first heat the part and then let it cool slowly (ie furnace cooling not air cooling) - now it is in its soft state so you can drill, file grind or whatever you want to do to it.

If you forge the blade you will need to stress relieve the part by normalizing, ie heating to red heat and let it air cool, you might need to perform a couple of cycles, but I don't believe you're going this way.

Next comes hardening where you take the part to red heat and leave it there for some time, then depending on what alloy of steel it is you plunge it into oil or water (most often it's oil) Now it is in its hardest state - too brittle for any useful blade so next comes tempering.

Again tempering depends on the alloy you have but basically it is heating at lower heat (150-300 deg c) which you can do in your oven and let it to air cool (no water or oil quench)

At most of the Model Engineering Exh’s I have been to there has been a stand with somebody demonstrating his drill bits by drilling through files.

Perhaps someone can remember the stand name (I cannot).

A few design ideas for you here at Michael Morris but I think you'd need to temper to save snapping the bottle opener.
Make sure your cutting edge is less than 3" if you want to carry it outside of your own property in the UK.

Bill

Tang-hole drilling on that TV show is after the hardened blades have been tempered and we have no idea what they are tempered to.

If the intention by the OP is 'juts' to grind the file to shape then there is the option to avoid holes and bond lugs each side instead or bond the blade part into a carrier. Brittleness of the blade if used as at file hardness might be an issue.

Which causes me to ask the question: If hardened material is tempered to a hardness.. can it be retempered to a softer version without re hardening ( I see no reason why not)

pgk

I've made all sorts of things from old files, tyre irons, knives etc. Just get to red heat, cool slowly. Just use a standard drill, no problem. I did not know about all the technical stuff at the time I did this, so may have helped. Also the old files may well have been a different quality to the stuff available now

"At most of the Model Engineering Exh’s I have been to there has been a stand with somebody demonstrating his drill bits by drilling through files.Perhaps someone can remember the stand name (I cannot)."

I remember the stand & demos well enough and I thought he was selling German Frei drills but advancing age has affected memory [as well as other functions].
I'll occasionally look at the American website "Instructables" - often good for laugh. There are several illustrated postings on making knives from old files:-
**LINK**

(I also remember the short, bearded guy at ME exhibitions who sold American-made diamond files with his animated demonstrations. I succumbed to buying a pack (handle and 3 grades of diamond file). Certainly one of the best buys ever and in constant use.So much so I never used a whetstone thereafter. They finally became worn after a few years but he stopped appearing at exhibitions. Fortunately I located a UK supplier but they're now on Amazon. The files are EdgeCrafter.

(Edit to remove unwanted emoji)

Edited By Fowlers Fury on 18/07/2018 16:45:18

Fowlers Fury - quite correct. The manufacturer had an aitch in the name - Frhei or Fhrei and they were being sold by a company based in Redruth in Cornwall. Bought a set and tried using one medium size on a piece of hardened steel ... Steel 1 Drill bit 0!!

rgds

Bill

Looks like Frhei is gone: **LINK**

https://www.duedil.com/company/gb/02311862/frhei-drill-bits-limited

MichaelG.

I'm still using mine from 20+ years ago, though the 3mm one died.
My middle sized Manchester Rapidor Minor power hacksaw only takes 9" blades, so I drill an extra hole in 12" HSS blades and grind them down to length; plus it gives me a selection of 3" hard scrapers.

There is still an exhibitor at various shows selling something similar, again with a lifetime guarantee on the bits.

Bill

I also watch a lot of forged in fire. One strange thing of this show is that they never show the tempering of the hardened steel. But they do this between the takes. Sometimes they mention something like "now that the blades are tempered ....". In the tempered state the metal is still hard to drill but not as hard as in the fully hardened state.

Tangs are not hardened can be easily bent on some.

Unless drilling close to the file it may be hard there the rest is soft.

I would love to be able to drill files but, after many, many attempts, my conclusion is that the best approach is to temper or anneal. I can't do the carbide approach and I don't think it is reliable enough to try on something you may have invested hours into. To temper, heat to black heat or at least stop as soon as you see any dull glow. You _should_ be able to drill after that. Finish the blade quite well with maybe .5 or 1 mm edge thickness. Harden and temper.

Good files are easy to heat treat to reasonable performance. You need very little soak time. Heating till non-magnetic and quenching in water should do it. Temper in oven for one hour at 180c - if still too brittle, do it again slightly hotter say 200.

Then grind to finish - but don't let it get hotter than the tempering temperature.

A Stellite drill made from a round Stellite rod with a three sided pyramid shaped point will drill though a hardened file or a HSS cutter. It has to be run at high speed with quite a lot of pressure on a machine and it gets red hot. Stellite cannot be softened by the heat and it can be easily sharpened on an offhand grinder. This is a method which I have used many times in the past when a hole is needed through a hardened component. Colin

I have used files to make clock escapement pallets.I heated the file in the fire to red heat and then left it in the shes to cool overnight ,filed to shape and drilled .I then hardened and tempered.Not a problem .

Frank

The idea on which the Stellite method (colin hawes above) relies is sound, and it should work with carbide too. The red heat actually softens the steel as it pushes it aside - which is why it needs a decent column drill and a lot of pressure.

My guess regarding the hole drilling is that the OP intends to make a folding knife, and needs a hole for the pivot. If he also intends to avoid all that heat treatment malarkey, he will find as he grinds the blade thinner at the cutting edge, it is likely to get too hot anyway, and the one bit which needs to hold its edge will be softened in the process.

Cheers, Tim

Decades ago, Asbo 2000 drill bits were advertised with photos of them through files. No idea if they are still available. Seen demonstrated, producing bright red swarf. Sandvik, and others, make bits designed to drill down broken-off taps. They are pyramid-ended, as Colin Hawes describes. For all I know they are stellite. They are not cheap. Orange swarf and sparks!