[sdiy] embarrassing noob needs to mount some pots

[David G. Dixon]

If one wants to be really fancy, one could cut about half of the tab off,
and then drill a hole only part way through the panel using the stop on a
drill press (like when you countersink a screw hole).

Of course, I always cut mine off too.  :)

David G. Dixon
Professor
Department of Materials Engineering
University of British Columbia
309-6350 Stores Road
Vancouver, B.C. V6T 1Z4
Canada
 
Tel 1-604-822-3679
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> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of peter edwards
> Sent: Monday, March 09, 2009 9:07 PM
> To: Horton
> Cc: Electronics_101 at yahoogroups.com; Synth DIY List
> Subject: Re: [sdiy] embarrassing noob needs to mount some pots
> 
> I think Laurie's answer is a good one, but I strongly disagree with
> his casual stance on the anti-rotation tab. :-)
> I do a lot of repair and salvage and I have seen plenty of problems
> stem from the lack of proper utilization of the anti-rotation
> tabs....really. People very commonly cut the tab off and I always
> recommend that they do not. Using the tab makes for a more solid
> interface. And think about it, the knobs are your connection between
> you and the functions of the device you're tweaking. This interface
> should be as reliable as you can make it with a reasonable amount of
> work.
> 
>   The quickest way to drill the hole for the tab is to A) measure how
> far the tab is from the center of the pot shaft and mark a hole that
> far from the main shaft hole on your faceplate.
>   or B) First drill a hole for the main shaft of the pot. Then press
> the pot through the hole so that that tab is pressed against the face
> plate and turn the pot back and forth a few degrees. This should make
> a little mark showing you where to drill the hole.
> The tabs are usually flat on smaller and/or cheaper pots. I used to
> try to make rectangular holes for the tabs to stick through which was
> really silly and time consuming. Now I just measure across the width
> of the tab and drill a hole that size. They're usually around an 1/8"
> wide.
> if the hole is a little too small, you can usually force it through
> anyway, especially if you are using a plastic faceplate, that ensures
> that you get a nice tight fit.
> 
> As far as grounding the pots goes, Laurie's suggestion of eyelet
> washers is the best approach. IF you are desperate and you NEED to
> ground the pot and you don't have any eyelets, you can solder a
> ground wire to the body of the pot. But be aware that the pot will
> get very hot! This could damage the plastic elements of certain pots,
> like the back cover or the shuttle which holds the center lug wiper.
> You will need to abrade a small area on the side of the pot where you
> will be soldering your ground wire. I use a dremel with a cutting
> wheel to do this. Don't cut into the pot! you just want to rough up
> the surface. Then you will probably need some flux to help solder to
> the surface. Flux is a toxic pasty material that helps prepare the
> surface of dirty metals for soldering. Just put a little dab on the
> area you are going to solder to. Another thing to be aware of is that
> soldering to large metal surfaces is much more difficult than
> soldering to the little lugs on a pot or leads on a circuit board.
> Metal dissipates heat very quickly through it's mass... so as you are
> heating up the areas to solder to, the heat is being pulled away..
> you will need to turn your iron up higher than usual or if you have a
> set temperature iron, you will need to hold it there longer than
> usual. Melt a big blob of solder onto the tip of your iron as you are
> heating the ground spot. This will help spread the point of contact
> between the iron and pot surface which will allow for a quicker
> transfer of heat.
> Despite my little rant above about the importance of reliable pot
> behavior, I have used this grounding technique more than once.
> Luckily I have not had any problems with melting parts or
> malfunctioning pots. If anyone thinks this a totally wacko
> suggestion, don't hesitate to say so!
> -pete
> 
> On Mar 9, 2009, at 7:23 PM, Elby Designs - Laurie Biddulph wrote:
> > I am happy to try and answer any questions you may have.
> >
> > With regards the pots.
> > the tab is an anti-rotation device. It fits in to a mating hole or
> > recess on the
> > panel and stops the pot from trying to spin in the hole should you
> > try and ram
> > the control past its end stops. If youu have a sufficiently large
> > knob that will
> > cover the hole, then I would include this. It is, however, a lot of
> > extra work
> > and if you intend to treat your controls with some respect then you
> > can forget
> > them. On pots that have the tab phsyiclly aprt of the pot body,
> > simply get a pair
> > of heavy-duty pliers and snap it off (this is usually just a matter
> > of wiggling
> > it back and forth a few times) - it is unlikely that you will do
> > any damage to
> > the pot unless you are ridiculously clumsy. Some pots have a tab on
> > a separate
> > washer (much like many switches have) and you can discard the
> > washer or sometimes
> > just flip it over so the tab points towards the pot body.
> >
> > If you are using plastic/rubber/wooden or other similar non-
> > conductive knobs then
> > there is no real need to ground the pots. Once the panel has a
> > ground connection,
> > you can usually rely on the metal bush of the pot making the
> > electrical
> > connection to do this for you. If you WANT to ground the pots then
> > you need what
> > are commonly called eyelets or lugs. These are like a washer with a
> > tag sticking
> > out one side. Fit the washer over the bush before mounting the pot
> > to the panel.
> > You can then attach a ground wire to the tab.
> >
> > Hole size is dictated by the pot. You should have a datasheet for
> > the pot or the
> > catalogue where you got them from should at least mention the panel
> > hole size
> > needed. if you can't find that then just grab one of the pot
> > washers and measure
> > the inside gap at the widest point or just get a box of drill bits
> > and find the
> > bit that just fits in the washer.
> >
> > Best regards
> > Laurie Biddulph
> > www.elby-designs.com
> >
> > On Tue Mar 10  9:15 , Horton  sent:
> >
> >> There are so many basic knowledge things out there that are just
> >> taken
> >> for granted by the computer-brain electronics wizards, so for a new
> >> hobbyist there are no real guides or 101-style information.
> >>
> >> I'm in the middle of a project and suddenly I need to mount a
> >> punch of
> >> pots and switches into a typical plastic project enclosure. I have no
> >> idea where to begin! What's up with the nuts, and that little tab
> >> sticking out of the pot body? Should I ground each pot to the
> >> metal in
> >> the case in addition to the ground bus on the PCB? How? What size
> >> drill bit do I use to make the holes, and how do I secure the pot
> >> body
> >> against the frame of the enclosure anyway? I need all this basic
> >> info.
> >>
> >> Ideas? Tutorials? Instructables?
> >>
> >> AH
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> >> )
> >
> >
> >
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