Threadcutter From Allan Key ?

[BillWood]

I think I've seen a thread somewhere ....... somebody made a very small very fine single point internal thread cutting tool from an allan key. Used the bend in the allan key to turn the corner.

Have tried googling but cannot find it.

Was wondering if that was done with some fancy heating/tempering/annealing or on the raw allan key.

Bill

 

[4GSR]

You would have to heat the end of the key to bend it. Once done, get the heat back up to cherry red and quench in oil. Then you can grind it like you want. The only porblem would be the cutting edge would not hold up for long due to the material a Allen key is made from. But it would work!

 

[Andre]

I've made lots of cutters from allen keys. I know a guy where I can get an endless supply from, he works at a music store. Most of them are Chinese 4mm keys.

Dovetail cutters, backside hole deburring tool (for deburring the back of a hole in aluminum square tubing), and just recently a hand "router" plane blade. For aluminum and wood they work fine, but as Ken points out they do have to be annealed prior to forming or machining.

I've experimented with making hex broaches with them, but it didn't turn out so well.

 

[RJSakowski]

I think I've seen a thread somewhere ....... somebody made a very small very fine single point internal thread cutting tool from an allan key. Used the bend in the allan key to turn the corner.

Have tried googling but cannot find it.

Was wondering if that was done with some fancy heating/tempering/annealing or on the raw allan key.

Bill

Bill,

Allen keys can be made from a variety of steels. Allen keys are designed to be tough, not hard. You can test the key with a file. If the file bites in to the key, it most likely won't hold an edge as a cutting tool. You can get away with it for aluminum but it will go dull quickly in steel. For a durable cutting edge, you will most likely have to heat treat the key.

You can also run a spark test. touch the end of the key to a grinder. The spark stream will be highly branched if there is a significant amount of carbon. The carbon content is what give the hardness. Use a file tang for a reference. Assuming that you intend to use the existing bend in the key, you can grind your tool to its finished form. Don't worry about overheating during the grinding as you will be heat treating afterward.

Heat the business end of your new tool to a bright red or until it loses magnetism. Quench immediately in water or oil. For a piece this small, either will work. At this point the tool will be hard but brittle.

Now polish the surface from the cutting edge back along the shank. You are going to draw a temper. Under bright light, preferably fluorescent or daylight white LED, slowly heat the far end of the tool. The color of the steel will change from bright white to faintly yellow to a gold to a brown and to a blue to a purple. You want the shank to be a brown to a blue color (spring temper). This gives a tough steel. The cutting edge should just begin to turn that faint yellow. Quench in water immediately. This gives a cutting edge with reduced brittleness without sacrificing too much hardness. If the color is running too quickly, you can quench, re-polish and heat again. If you overrun the tempering process, you can repeat the heat treating process.

When you have tempered the tool, you can complete any grinding and/or honing necessary. Be careful at this point not to overheat the tool as you will soften it.

 

[Rob]

I used one to make some internal ACME threads. I just grinded to shape and size and used it. I was cutting the threads in aluminum. It was also a better quality of Allen wrench. I made a new nut for the Y axis on my Atles Mill and it worked good for the 2 times I used it.

 

[Chipper5783]

I'm sure an allen wrench would work well enough for easy cutting material, but it is no big deal to grind up a piece of high speed steel, or machine and heat treat some carbon tool steel (not really any extra effort). The result will do a fine job of threading that same easy cutting material, and tougher materials, and last a long time. An allen wrench is just a pre-bent piece of pretty good metal??

 

[Tozguy]

Bill, how small do you need to go?
Allen keys are not all created equal. One good enough for cutting metal is worth more as an allen key.
Nails for cement can make good small boring tools. Just grind the head to the shape you need.
Must not heat the nail too much when grinding. No heat treatment required before use.

 

[BillWood]

Thanks for all the responses.

Have noted RJSarkowski response re heating and grinding an allan key etc thanks - and acquiring those skills, plus a gas torch, plus Soldering, brazing and welding will occur at some time in the future. Have saved the post for future reference on my PC.

Concrete nails - never thought of that - thanks, stored for future reference and use..

All my previous internal threads were fairly big and therefore relatively easy grinds.

This one was a bit smaller, and photos of final tool and 28tpi threads are attached. - major diameter of male thread is internal diam of nut is 0.665" tool was ground from 8mm round toolsteel and mounted in a 0.5" square bar - and yes ... I do understand that for some of you this is a trivial job .......... it was a big deal for me.

It was a hassle to grind the tool and get all the clearances working - I do all my grinding freehand and keep promising myself to build some jigs and guides but never get around to it and figure that the freehand grinding must be doing me some good but I will build some jigs one day.

But Gee Whizz I do still enjoy it when I cut a thread and then a nut and they fit together ............ makes me feel all technical.

So ............ its a hollow drawbar + hollow MT3 taper..... soon to become a chuck depthstop from the George Thomas books.


And.......... out of curiousity .............. what is the smallest one of these tools you have made ? and can you use broken HSS drill bits or is the shaft not HSS just the business of the drill is HSS ?

Bill

 

[pineyfolks]

Chipped taps can be ground into internal threading tools for small shallow bores.

 

[Tozguy]

Bill,
HSS drill bits of the garden variety have a soft shank so the drill chuck can get a grip. Just the business end is hardened.

Good quality carbide spade drills like those used for drilling ceramic tiles can be ground into lathe tools if you are equipped to grind carbide.
Beware that the budget quality spade drills with a round shank are not very rigid.

Carbide bits designed for hammer drilling in cement (with a special shank) are stiffer.

Smallest I have used so far is to bore a .300'' hole.