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Help! Creating post for shield.

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VBBC

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Hope you don't mind me reaching out, but I've come seeking your advice! I'm producing a bicycle bell for an academic institution and need to attach a hard enamelled shield (15H x12Wx 2D mm) to the top of the brass bell dome. The bell dome has been bought an and is being adapted, so I'm unable to modify that. Having tried various adhesives (very messy) the best solution seems to be to attach an M4 threaded clinch stud into the back of the shield with pro lock. (Please see attached pics). This seems to attach very well. However, as I am gluing on by eye, the stud is not always dead centre on the back of the shield. This is also critical, because the text elements that make up the rest of the logo will eventually be etched or screen printed on top of the dome around it (see production drawings). My thought was to put each shield into jig then use a drill press to drill out a hole and then to recess the pin, with adhesive, into the back of the shield. However, accuracy is critical - as the shield is only 2mm deep. So, is this the best way to go? I also have a MOQ of 300 to do, so this seems like quite a lot of work, unless I can send away for someone to do? Any advice you can give - along with tooling required - will be very much appreciated. Based in Arundel, West Sussex, if this is of use. Thanking you in advance, Dom.
 

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VBBC

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Thanks Paul - yes the adhesive is brilliant (Prolock) but I need to ensure consistency that every pin is centred exactly on the back of every shield.....?
 

Sporky McGuffin

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Yup - some sort of little jig to hold the badge relative to the bell, and a little blob of Loctite 3090 or similar. Other fine adhesives exist, but I am very fond of that stuff. Glue the shield straight onto the bell, unless there's something I'm missing.
 

VBBC

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Thanks Sporky - that's going to be too messy and we've tried that! So, the idea is that the threaded pin has to be attached onto the shield FIRST, then once dry, it passes through the bell dome to screw into a hexagonal spacer underneath the dome - pls see attached pic!
 

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VBBC

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Thanks Droogs - how can I ensure it is correctly centred around the text, other than by eye? Would soldering damage the hard enamel?
 

Droogs

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Make a 3 sided jig - 3 straight bits of wood/plastic etc to form a U shape that the badge fits snugly in.
Clamp the jig to a drill table positioned so that the centre of the drill bit is where the centre of the pin would be on the back of the badge - even hot melt glue or double sided stickytape would do
Drill a small flat indentation 1mm deep in the back of the badge using a Forstner Bit or end mill the same size as the screwhead.
Silver solder the screw to the back of the badge.

Enamel is set by heating in a furnace so the heat generated by the soldering will not affect the badge


hth
 

VBBC

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Thanks Droogs! One last thing before you go...can you recommend any DIY drill press for this job? And lastly, is there anyway of calibrating the jig so it always lines up dead centre underneath the drill bit - as you can tell - this is all new to me.....!
 

paulrbarnard

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Yup - some sort of little jig to hold the badge relative to the bell, and a little blob of Loctite 3090 or similar. Other fine adhesives exist, but I am very fond of that stuff. Glue the shield straight onto the bell, unless there's something I'm missing.
Gluing directly to the bell was what I had meant too.

If the only issue is repeatable alignment, a simple 3D printed jig to put over the bell with a shield shaped cut out to drop the shield through would ensure repeatability.
A dab of super glue beside a dab of epoxy and a squirt of accelerator once put in place would let you reuse the jig immediately
 

Sporky McGuffin

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Yup - lots of fast setting epoxies. The Loctite is a gap-filling cyanoacrylate epoxy; hard in just a couple of seconds, dead easy to apply (self-mixing nozzles), and the bond is astoundingly strong. With a little jig (I like your 3d printed idea) - or maybe three - you could rattle through these very quickly indeed.
 

paulrbarnard

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Yup - lots of fast setting epoxies. The Loctite is a gap-filling cyanoacrylate epoxy; hard in just a couple of seconds, dead easy to apply (self-mixing nozzles), and the bond is astoundingly strong. With a little jig (I like your 3d printed idea) - or maybe three - you could rattle through these very quickly indeed.
I'm going to have to get some opf that Loctite. Sounds like a great product.
 

VBBC

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Thanks All,
Yes, that does sound a great idea - the only danger is it weeping out from the sides of the shield - I guess I would have to be careful with the amount.....but then I suppose I could turn the dome over and glue the threaded stud to the back of the shield through the hole of the dome...
 

Jameshow

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Thanks Droogs! One last thing before you go...can you recommend any DIY drill press for this job? And lastly, is there anyway of calibrating the jig so it always lines up dead centre underneath the drill bit - as you can tell - this is all new to me.....!
A Bosch one will probably be more accurate and controllable than a cheap Chinese one. Otherwise a big cast iron one which is a bit of a sledgehammer to crack a nut.

Cheers James
 

Sporky McGuffin

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Thanks All,
Yes, that does sound a great idea - the only danger is it weeping out from the sides of the shield - I guess I would have to be careful with the amount.....but then I suppose I could turn the dome over and glue the threaded stud to the back of the shield through the hole of the dome...
You only need a teeny amount, and it comes out of the nozzle with good control.
 

Henniep

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Thanks Paul - yes the adhesive is brilliant (Prolock) but I need to ensure consistency that every pin is centred exactly on the back of every shield.....?
A basic jig to place the shield in exactly the same spot every time. Then mount a laser beam device above and aim the beam at the exact location of the pin. Just a thought.
 

Fergie 307

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All you need is two pieces of wood the same height as the dome and joined at right angles. Place your dome in the angle and then attach a cross piece over the centre of it, with either a hole that lines up precisely with the centre of the dome if you intend to drill a hole, or a slot to accept the square end of the shield if you intend to glue it. If you intend to drill a hole then I would make the bridge piece from maybe 5mm thick steel so the hole will also act as a guide for the drill and stop its tendency to wander. Mount the whole thing on a suitable sized piece of ply or similar and you can then clamp it to the table of the drill to keep it in perfect alingnment. You could knock this up in fifteen minutes, people do love to complicate things.
 

Fergie 307

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And for a pillar drill one of the cheap Chinese ones from Wickes, Machine Mart etc would be perfectly adequate for what you want to do.
 
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