Project Knobs

[Detrick Merz]

Andy,

I had luck making a plastic knob from scratch a while back.  I needed
a knob for a little Dremel jig I built for creating Manhattan style
PCB pads.  I think my knob was about 2" in diamater.

Basic supplies:
- Polyester plastic casting resin
- Hardener (for resin)
- Mold

The casting resin and hardener can be had at local crafts stores
around here.  I presume it wouldn't be hard to find across the pond
either.  For molds, I have had good luck with Polyethylene (HDPE /
LDPE) and Polypropylene (PP), without using a mold release agent.
That being said, I also cut the mold off, so they end up being one
time use for me.  Mold release (available according to the resin
manufacturer), or a better shaped mold (nice draft angles) might let
you reuse molds.

For my knob, I used an empty plastic single serving fruit cup.  I
wanted a threaded rod coming out of the back of it, so after pouring
the resin in the mold, I gently set a bolt into the puddle of liquid
plastic.  24 hours later, and the bolt is a permanent part of the
knob.  It's not exactly perpendicular to the knob face, but only a few
degrees off, and unimportant for what I needed.  A little work and you
could find a way to embed one and make it square.

Once my knob was done, I faced the back a little bit by chucking the
bolt end into my little drill press.  A little work holding a file
against the back edge, and I shaped it to my liking (flattened it out
a bit, and smoothed over the "corner").

Link to the casting resin manufacturer's site (surely there are
others, but this is the brand I used):
<http://eti-usa.com/consum/index.html> scroll down a little bit

Picture of the style of fruit cups I used for a mold:
<http://tbn0.google.com/images?q=tbn:lBqSO-1t6kwCAM:http://www.packworld.com/thumbsLarge/issues/03.03/images/Features/DelMonte.jpg>

If you go this route, and have more questions, feel free to send me
some mail directly.  I skim this list in digest, so I might miss a
reply sent there.

-detrick
KI4STU

On 7/31/07, [hidden email]
<[hidden email]> wrote:

> Date: Tue, 31 Jul 2007 04:42:32 +0100
> From: "Andy - GM0NWI" <[hidden email]>
> Subject: [Elecraft] Project Knobs
> To: "'Elecraft Discussion List'" <[hidden email]>,    "'Flying
>         Pigs'" <[hidden email]>, <[hidden email]>,
>         <[hidden email]>
>
> Hello to everyone in the group from "Bonnie Scotland"..
>
> I am currently tryin' to source some 2 inch - 2 1/4 inch diameter knobs for
> a project that will be gettin' undertaken in
> The near future..
>
> I am in need of 3 sets of 3 (9 knobs in total) "I think".. although this may
> not be case as I progress
> But better I think to "plan ahead"..
>
> Can anyone on the list give any details of a supplier, ..or possibly some
> ideas from a what type of older
> Radio's in the past might have had this sort of diameter of knobs
> included..?
>
> Think "VFO -Tuning Dial" sort of diameter.. and you'de near a ball-part
> figure/size..
>
> Has anyone in the past home-brewed this size and diameter of knob for a past
> project..?  If so, care to share how you
> Did it..?
>
> I've looked around the internet are lots of places, and there just does'nt
> seem to be anyone out there who stocks
> This sort of thing, both here in the UK and the US and further afield..
>
> Really would appreciate help or ideas on this one folks..
>
> TIA..
>
> 72's 73's                                        [hidden email]
>
> Andy
> GM0NWI
>
> Elecraft K2 "Fully Loaded" QRP S/n 01432
> Elecraft K2 "Fully Loaded" QRO S/n 05469

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