What metal is a telescopic aerial made of

[bugbear]

I want to make a screw extracting tube drill, and matching plug cutter,
to fix a sheared off, tiny, screw.

(as per
https://woodworkersedge.wordpress.com/2 ... en-screws/
)

EDIT; you can even buy them new these days;

http://www.highlandwoodworking.com/set3 ... ctors.aspx

It occured to me that a telescopic aerial might be a plausible source
of thin walled metal tubing in a variety of sizes.

Does anyone know if they're brass, steel, or "other" ?

BugBear

 

[Wuffles]

I want to say chrome plated brass. It's a guess, but I'm sure I've seen brass coloured metal inside them.

 

[IHc1vtr+]

I would go with the above, plated brass

 

[n0legs]

On my little dab radio the last section is magnetic and the 6 hollow sections are not.
Possibly brass, as my honourable fellow contributors have said.

 

[NazNomad]

Just looked at one that I broke (and kept just in case?) and it does appear to be chrome plated brass tubing.

 

[bugbear]

We seem to have a firm consensus - thanks all!

BugBear

 

[ColeyS1]

Best thing I found is stainless steel drinking straw.

Coley

 

[AndyT]

Thinking 'that will never work, the metal will be too soft' I've just done an experiment.
I used a scrap of thin wall brass tube, as sold in model shops, about 3 mm bore. I made two sawcuts across the end and snipped across the corners to make four crude teeth. I put a lost head nail in the other end to stop it collapsing, gripped it in the chuck of a small hand drill and tried it out in some softwood.
It worked quite well - certainly well enough to free a broken screw.

So I reckon your plan is a good one, despite the softness of the metal!

 

[profchris]

I was going to suggest brass tube from a model shop - sold in a wide range of diameters to suit every broken screw!

 

[bugbear]

I was going to suggest brass tube from a model shop - sold in a wide range of diameters to suit every broken screw!

I'm not too worried about fitting to the screw exactly - but the fit of the plug to the resulting
hole needs to be quite good!

BugBear

 

[bugbear]

I've found the full on commercial version, with handy video;

http://www.stewmac.com/Luthier_Tools/Ty ... e_Kit.html

https://www.youtube.com/watch?v=8mvNpCJLBNw

BugBear

 

[profchris]

I was going to suggest brass tube from a model shop - sold in a wide range of diameters to suit every broken screw!

I'm not too worried about fitting to the screw exactly - but the fit of the plug to the resulting
hole needs to be quite good!

BugBear

Then hie thee to a model shop, because the different sizes of tube fit inside each other. I made these friction tuners for a 6.35 inch scale length uke using two different diameters (4mm and 5mm, with 3mm bolts as the centre pillar).

 

[bugbear]

I have made a prototype hole saw; a friend gave me some scrap engine fuel line, which turns out
to be well annealed (so you can bend it) steel. Easy to file.

The OD is 5.5mm, I don't know the ID.

I filed 5 teeth around the circumference, with each tooth face on a radius.

On trial, the problem (shared with the commercial versions?) is that you have a saw with no means of removing the sawdust, so you have to keep withdrawing the bit to brush dust off the bit, and to (try to) blow out the hole.

So I returned to my teeth filing, and with the tube raised high in the vice, used a 45 degree slope to make a VERY large gullet on each tooth for the dust to go in. The dust still has no means of actual escape, but the teeth hold more now. This seems to work OK.

To saw filing experts; any advice on a good sequence to make teeth, given that the one thing I can't do is file straight across (since I'd hit the tooth on the other side).

BugBear

PS Macro photography makes your filing look awful!

 

[ED65]

Very nicely done BB!

To saw filing experts; any advice on a good sequence to make teeth, given that the one thing I can't do is file straight across (since I'd hit the tooth on the other side).

I'd be tempted to do this not with a file but with a bit of some kind in a drill or flex shaft handpiece.

I think I saw something similar done on someone's blog a while back, I'll try to find it again and see how he approached it. His tubing was mild steel if I remember correctly and gave a good enough service life despite this.

 

[bugbear]

Very nicely done BB!

To saw filing experts; any advice on a good sequence to make teeth, given that the one thing I can't do is file straight across (since I'd hit the tooth on the other side).

I'd be tempted to do this not with a file but with a bit of some kind in a drill or flex shaft handpiece.

I think I saw something similar done on someone's blog a while back, I'll try to find it again and see how he approached it. His tubing was mild steel if I remember correctly and gave a good enough service life despite this.

Well, the optimist in us all would hope not to have too many broken off screw stubs...

If my saw last for two stubs, it will have served its purpose, but I suspect it would do far more.

BugBear

 

[Droogs]

Ae whether for large scale use or small telescopic are usually made not from brass but from copper, as this is the most effective and efficient metal for RF wave propagation. Although any conductor can be used to an extent, if it is either 1/16 1/4 1/2 3/4 wave length and depending on the type of signal it has to recieve or transmit - spacewave/groundwave etc. dredged that up from my memories of antennas and propagation lessons as a boy soldier in the 80's, yay another glorious day in the corp

 

[bugbear]

Very nicely done BB!

To saw filing experts; any advice on a good sequence to make teeth, given that the one thing I can't do is file straight across (since I'd hit the tooth on the other side).

I'd be tempted to do this not with a file but with a bit of some kind in a drill or flex shaft handpiece.

I think I saw something similar done on someone's blog a while back, I'll try to find it again and see how he approached it. His tubing was mild steel if I remember correctly and gave a good enough service life despite this.

Well, the optimist in us all would hope not to have too many broken off screw stubs...

If my saw last for two stubs, it will have served its purpose, but I suspect it would do far more.

BugBear

I'm now waiting on a delivery of a box of cheap roll pins; whilst my proof of concept saw works OK, I can't do an actual repair without a matching plug cutter.

So I'll be making at least a plug cutter (just another hole saw), or possibly another hole saw/plug cutter combo, depending on how the sizes work out.

These saws almost can't help cutting "well enough", you're not cutting very deep, and you can exert tremendous pressure, so the teeth aren't at all critical.

I'll be sticking with odd numbers of tooth though - all the commercial examples show this, and I'm guessing there's a reason.

BugBear

 

[ColeyS1]

Drill a hole in some metal and hammer the wood through it. Cheers kev

Coley

 

[bugbear]

Drill a hole in some metal and hammer the wood through it. Cheers kev

Coley

For a good repair I want a cross grain plug - so that the tiny screw holds as well as possible in the mended guitar.

Some more trials with tooth counts and shapes this morning showed that dust clearance is key; almost anything I made cut very well, until the gullets were below the surface, then they slowed down tremendously, some more than others.

I tried even numbers (6) of symmetric triangular teeth (so you can file straight across a diameter) and they didn't cut well - until I made more room in the gullets.

I dropped to 4 symmetric teeth with the same result (although that one tended to shear out the core plug a little early).

So I think it's all about the gullets.

BugBear

 

[Racers]

I guess you need spiral gullets to move the sawdust up and away from the teeth, difficult to do in thin wall tubing.
If you clear some wood from the broken screw can you get hold of it and remove it? you could use some heat from a soldering iron to loosen it, then drill with a normal drill bit it still leaves you with the plug problem, how small? could you turn it on a lathe?

Pete