Mosaic pins

[keith_beef]

Martyn, I saw the thuya burl skinner with mosaic pins that you posted on BushcraftUK.

Very nice work.

How about explaining how you made the pins?


Keith.

[Martyn]

No problem Kieth. It's messy though, and time consuming.

For reference, here's the pins Kieth mentions...




Materials:
Some 1/4" outside dia tubing.
Variety of capiliary tubing (or whatever for the innards)
Slow cure epoxy
Epoxy die
rubber or latex tubing with 1/4" inside dia.
small pot for mixing/containing epoxy.
variety of clamps.

somewhere to make a mess.
First you have to decide on your pattern, go to a hardware shop and locate some tubing, I used 1/4" dia nickel silver tube, but brass or anything will do. The nickel silver worked well for me as the walls of the tube were quite thick and so had good mechanical strength (it's the same tubing I used for the thong hole in the above knife).



Then you need to find some smaller tubing, I used brass capilary tubing from B&Q - but it's just a question of trial and error cold fitting the pieces so they fit. Try and buy your materials as straight as possible, anything with kinks in, discard as the fit inside the tube needs to be clean and straight.

Then cut your pieces into 10" or 12" lengths and dry fit them, make sure they are clean and straight. These pieces must make a good friction fit to avoid gaps appearing in the mosaic and the straightness ensures continuity of the pattern and correct orientation through the tube. Any twists or kinks will throw the patter off and you wont be able to match the sides and orientate the pin properly in the knife. I cant stress the importance of this enough. If the small inner pins are twisted, even a little, then the mosaic face of the pin will change from one side to the other of the knife handle. Trial and error again.

One everthing is dry fitted you can go to the messy stage. Make sure one end of all the tubes are flat against a surface. Place the rubber or latex tubing over the opposite end. The idea is to use the latex tubing to suck up the epoxy through the mosaic pins - harder than drinking a McDonalds milkshake I assure you. Now at this point I should mention a health warning. I have no idea if there are any toxic fumes given off my the curing epoxy, so you do this at your own risk.

Mix up the (slow cure) epoxy as normal and add a small amount of die. Probably best to experiment, as the die affects the consistency, cure time and hold of the epoxy. It will take a few minutes to suck the epoxy up the tube, so you need to have it fluid enough to last that long. You need to work fast too, once the epoxy starts to cure, that's as far as you get.

Mix your epoxy close to where you are gonna work (mix plenty - enough to do the whole job in one go) and immediately place the end of the tube into a little puddle of it and start to suck on the rubber tube. It'l take some effort, but it *will* climb the tube - even the tiny capiliaries. Keep sucking untill either epoxy bleeds out the top of you pins (visible through the rubber tube) or until it starts to cure, whichever comes first. Clamp the rubber tube to hold the vaccuum. and you're done.

On my first attempt, I managed about 8" of usable mosaic, but results would vary depending on the consistency of your epoxy. Experimentation will bring better success.

[keith_beef]

Originally Posted by Martyn

No problem Kieth. It's messy though, and time consuming.

..snip..
Mix your epoxy close to where you are gonna work (mix plenty - enough to do the whole job in one go) and immediately place the end of the tube into a little puddle of it and start to suck on the rubber tube. It'l take some effort, but it *will* climb the tube - even the tiny capiliaries. Keep sucking untill either epoxy bleeds out the top of you pins (visible through the rubber tube) or until it starts to cure, whichever comes first. Clamp the rubber tube to hold the vaccuum. and you're done.
..snip..

Great, Martyn. Thanks a lot.

I wondered about using a syringe to fill the tubes. Cut the tubes to around 6" lengths and assemble them; block up one end; fill from the top using a syringe and fluid epoxy. This way, you could perhaps use several colours.

What do you think?


Keith.

[Martyn]

Use the syringe to suck rather than push would probably work better, but I'd be interested to hear your results. It would work if you filled the smaller capilliarys individually first (& left to cure), then assembled the full pin and use the above method to fill the gaps.

[Colin KC]

Achully just had an epiphany based on what Keith just posted.

How about filling the little tubes first, then assembling & filling the whole with a different colour?


OMG, I think it might work

[Colin KC]

:doh: Just read Martyn's post nob

[Dave Barker]

May I suggest that the epoxy is warmed slightly. Not enough to start curing. If you warm it it becomes more fluid, I did this when I used epoxy for gluing blades.And still do if ... like now I run out of shellac!

[PS_Bond]

There's a few makers have a hotbox (cardboard box with a 60W lightbulb in it!) for keeping the epoxy fluid prior to mixing it.

[Colin KC]

Be warned though, that heating the epoxy (to thin it) also speeds up cure time, swings & roundabouts

[Martyn]

get the 24hr cure stuff and problem solved. If anyone is worried about sucking epoxy fumes, you can get 50ml syringes (like a turkey baster) will a bull nose that would work perfectly. Also, if you get an air buble which forms a dimple of the finished surface, it can be invisibly filled with superglue. I was lucky and didn't get any.

[keith_beef]

Now, I could find out by trial and error, but I would like to find out how to mathemagically determine the OD of the small tubes to fit into the large tube...

Common sense tells me that I can fit two 5mm OD tubes inside a 10mm ID tube. But to fit three or four inside this 10mm ID tube, what OD small tube do I need?

As I see it, the radius of the small tube needs to be such, that the centres describe a triangle (in the case of three tubes) or a square (in the case of four tubes) or a pentagon (in the case of five tubes), with sides equal to twice the radius of the small tube.

There must be some relationship between the radius of the small tube (r), the radius of the big tube (R), and the number (n) of small tubes that fit in the big tube...

Can anybody help me out, please?

I hope my little drawing makes this clearer...


Keith.

[ugug]

Can anybody help me out, please?

errr.. buy your 'pre-calculated geometry' mosaic pins from brisa? :p

[keith_beef]

Originally Posted by automated ugug

errr.. buy your 'pre-calculated geometry' mosaic pins from brisa? :p

Thanks.

Got any more helpful hints ike that?

Keep 'em to yourself :p


Keith.

[PS_Bond]

Keith -

For the 3 tube example, you want the distance from the centre of the small tubes to the centre of the circle. Call it x...

x = r/sin(30 degrees)
Add r on to x and you have the internal radius of the large circle.

I *think* this is scalable for other shapes (square - 360/(2*4) degrees, pentagon 720/(2*5)), but I'm not sure - working on building a port of ucLinux just now, so a bit distracted.

[Dave Barker]

Another flash git!