Thread: Turning Tools

All the articles I've read about using old files as the basis for turning tools also emphasised the need to know something about the heat treatment of metal.

As I understand it, files are treated to be very hard, and hence are quite brittle, and using them as a turning chisel has the potential danger of the tool shattering.

I've read that the process is (roughly):

1) temper the file, to make it easier to shape. (This can be done by heating in an oven, and letting it cool gradually).

2) transform the file into a new tool.

3) harden new tool by heating red hot, then quickly quenching.

4) temper new tool by heating to appropriate temperature, then quenching again.

Cheers,
Andrew (who has done all this stuff once, so far, to a concrete nail, in order to make an awl )

Hi Andrew

That is probaly very good advice about old files. Mine where never tempered but also have done a lot of turning without any problem, but mind you they are very heavy and thick files.

All the tradesmen where I worked used old files that were never tempered and some of the patterns turned up were very big.

Timber lathes with 6ft centre clearance to the ground with a pit in the floor and an independant tool stand. The steel face plate was 3ft diameter with cross arms bolted to it with a 5ft radius swing.

The best part about them was that they kept their edge for a long time without sharpening.


Regards


Bazza

spade bits also make great small scrapers and cheap too

I've had one scraper made from an old file literally explode when used. It's made me very wary about repeat performances!

Mind you, I was aware of the risks with modified files at the time and it was a borrowed tool of "unknown quality" so I deserved a kick in the butt anyway, but it still made me more aware of that aspect. As Andrew has already said, a file can be made safer by unhandling it then heating in an oven and letting cool naturally. Personally I've found no need to reharden or temper such old files... but then again I'm not expecting 'em to hold an edge as long as my HSS or even good quality CS tools.

They're ideal for the odd job when you want a slightly unusual profile which'll probably never be used again and it's no great loss if you mis-shape it and have to grind more off...

Hardening isn't all that hard - pardon the pun.

However, rather than tempering it in an oven to make it "easy to work", you are far better off heating it to red, then letting it cool VERY slowly (putting it in ash is a good trick to hold in the heat). This anneals the metal.

Now it is easy to shape.

Then once shaped, heat it to red and quench in oil as quickly as possible (you will need to stir it to always make sure that fresh and cool oil is touching the metal). Hold the file with pliers or tongs while doing this and watch out for flash-over - good fun if you are ready for it, bad fun if your head is over the oil can.

If you did it right, a file should not be able to scratch the surace of the metal.

THEN, sand it back to bare metal and put it in an oven and increase the temperature until the metal turns a straw yellow. This is a good hardness for most tools. If it goes blue, it is less brittle, but will lose its edge faster, if it doesn't change colour - you are where you started anyway!

NOTE: The "red" colour is best tested with an extendible magnet. Take the metal up to where it looks reddish, then test it with a magnet slowly increasing the temperature. The actual point you want is about 50 degrees C past the stage where the metal stops being magnetic.

I suppose that this is maybe more than you wanted to know...

However, now you can go forth and make cutlery.

Cam

do u have to heat red heat all the file or just where u want to shape ?

Easiest way to soften a file is drop it in a fire with plenty of hot coals.
Retrieve it the next day and it won't be brittle.

I have set of old turning tools made from old files that belonged to my Grandfather, when I was just starting in woodturning I used them quite a lot, never had one explode, probably would have put me off turning for good. Now that I can afford decent tools they just sit there on the shelf

Originally Posted by Skew ChiDAMN!!

They're ideal for the odd job when you want a slightly unusual profile which'll probably never be used again and it's no great loss if you mis-shape it and have to grind more off...

I posted this comment almost exactly two years ago and re-reading it now I can't help but wonder "I said that? What was I thinking?"



Not that I disagree with what I said - not exactly - but, frankly, using old files scares the crap outta me now. Probably because I'm much more aggressive in my cuts than I was back then, so am putting a heap more stress on the tools. I still use one particular 'recycled file tool' for fine finishing cuts though; an L-shaped hook tool for cleaning out inside bowl rims.

But with cheap chaiwanese turning sets available for under $30- I'd much rather pay the pennies and reprofile them for custom shapes than recycle old files now. I wonder about the steel being used in new files too... I've actually worn out a couple in less than a year, used solely on wood! Definitely not the same quality of steel as truly old ones and I seriously doubt their suitability for use as turning chisels, retempered or not.

Isn't it funny what a difference just a couple of years can make to your attitude? (A coupla nasty accidents along the way probably had something to do with it, too... )

Originally Posted by Skew ChiDAMN!!

an L-shaped hook tool for cleaning out inside bowl rims.

Wouldn't get much use then, I'm tipping...

I'm sort of glad this one was dredged up, 'cause I've just purchased a small cheap lathe and I'd like to use an old broken file as a turning chisel. So theoretically, if I'm taking very small cuts a well sharpened file will be ok without tempering?

Can't speak from explosion experience, but theoretically the notches forming the teeth tend to increase stress on the metal above what would normally be calculated. The term of art is "stress concentration factor." This is why airliner windows now have rounded corners, BTW.

I've successfully used old files as scrapers for hand turning soft metals such as brass and aluminium. Key is to grind the top face to the bottom of the notches from the tip to somewhat beyond the toolrest. This reduces a tendency to shatter.

Joe

That's very helpful Joe, thanks! Being able to work brass is a bonus, because I need to make some ferrules for the chisel handles I'm turning

You can work brass with standard lathe chisels.