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Question on attaching the round to the square..... Answered

I need to attach a tube (it is fairly rigid, like a bic pen body), to a box (coming out of the smaller end of the box) and it needs to be fairly secure as there will be wires running through it and a "pickup coil" attached to the end of the device. The box may be plastic, or it may be metal, I haven't decided yet. I had thought about threading the barrel of the tube and just using two nuts to lock it in. Any other ideas would be greatly appreciated.


either direct weld it or cut/drill a hole and epoxy if it isn't under load...

The coil weighs a few onces, and on the end of a pen sized tube (or rather the empty tube from a pen :-) it does needs some bracing. I was just looking for ideas that may accomplish that best. I have been offered a few that may work.

The epoxy would probably do if you give an extra inch and mound it...

That, and / or the same principle on the inside of the box.

Oh sorry i meant on the inside, the combination of support and adhesion should brace pretty well, there's some stuff I bought that I used for making simple parts with, it was a resin + resin stuff that made a nice moldable plastic not an epoxy but works the same.

Tis ok. I have seen several of those kind of epoxies, etc. It may be awhile before I can obtain them :-)


10 years ago

Is this a coilgun?

No, once I get my workbench cleared of my wife's junk, I will be making an ELF detector (Extremely Low Frequency detector). The "coil", which is the pickup coil, will be at the end of a tube protruding from the box. Much like a miniature Metal detector. The first one I made, I didn't make it to look pretty, just functional....and the electrical tape is not starting to peel off :-) so I want this one to be more "presentable" as well as durable.


10 years ago

Sick your tube an extra inch or two into the box, and figure out some way to fix the end of it to thebox as well. That way it's supported in two places along the end of the tube, and less likely to budge. If you have any choice in where to connect the tube to the box, put it all the way in a corner, and let it run along the corner for an inch or so - plenty of space to glue, tie or screw it in place solidly.

Sounds like an idea, I will think about this too, as I search for an "available" (to most) box for this project. Thanks.

Why cant the whole thing just be round

The tube goes into the "side" of a box, which is perpendicular to the tube or squared to it. ;-)

ohhhh, then just thread it and use some epoxy to hold it ehh, sorry the way you said it it sounded just like the tube goes into the end of the box to me X_X'

Yes, it goes "into the end of the box" but because there is a "coil" on the other end, it is pretty weighted and will need attached or anchored somehow to the box, as the sides of a small plastic box are not very strong to start with.

. Could you use the threaded metal tubes that are used in lamps? There seems to be a wide assortment of nuts, washers, &c; available.

Hmm, I could....although I was trying to keep if very very simple (and Bic pen bodies are readily available), if they were metal, they may provide some extra and needed shielding from stray electromagnetic interference from other "sources" including the circuit board itself. Hmmm....it's a thought...

On second thought, shielding would only be marginal if I couldn't find a way to ground it....

Thank you all for your suggestions. I do appreciate it.


10 years ago

A wooden block, about 1/2 to 3/4 in thick, inside the case. Predrill holes in the case and the block. If it's metal, screw the block to the case from the outside....plastic, just glue it. Then glue the 'pen shaft' to the wood..a friction fit might even suffice.

Thanks, I will add that to my list of tings to attempt to see which works best . The end product will look very similar to a miniature version of a metal detector with the box / container being about the size of a small cell phone - i.e. about 5 inches by 3 inches with a "thickness" of about 1 - 1 1/2 inches

That would be my suggestion as well.

Well, the hole will be round. I am so used to dealing with electronics, that I have some troubles with the physical aspect of this: the tube will be pretty snug in the hole, but the weight of the coil will tend to put a lot of pressure on that fulcrum point. I was just wondering if there was a better way then what I came up with.

well if everything is plastic you might be able to use some carefully placed heat (i.e. soldering iron.... lighter.....something like that) to melt everything together.......provided there is enough thickness on the tube. the nut idea might work well but threading sucks balls...........hmmmm.......glue guns are awesome but you gotta make sure it sticks well to the surface your working with......smooth = not so good................

not sure what to tell you......... fancy duct tape work always hods well but it might look ugly

best I can come up with without having it infront of me

Well, the first one I did I used electrical tape on (and some "friction" tape). It held for awhile, but it doesn't really look good, and it does eventually become "unglued" so to speak.

I Like your threading idea.... Provided there is a thickness to the wall.... Perhaps some washes may displace the load... Threading may "suck balls" (Thanks for the that one Chris) but will be the most secure in the long run....

Well, I do have a tap n die set here somewhere (an el'cheapo one got years ago) but that doesn't make it as "do-able" for others. If I can find a happy medium (or, at very least, a "not too sad" psychic LOL - sorry), that would be easily available to most people, I would be happy.

like you are making the hole for the tube in the box and need to secure it? or the round tube is in a square hole?