[sdiy] Pot mounting holes?

[Jim Johnson]

That's what I love about this list. Thanks x 10^6, Theo!

Jim

*********** REPLY SEPARATOR  ***********

On 2/15/02 at 2:33 PM Theo wrote:

>Ok here is a basic nuts & bolds lesson.
>Probably more than you asked for,
>but maybe some of it is useful for others.
>
>M7 x0,75
>M indicates metric tread.
>7 means the outside diameter of the tread is 7 mm.
>Depending on the tolerance you need your mounting hole should
>be larger than 7 mm diameter.
>7,50 mm is often used, if the pots are panel mount OR
>if the pots are PCB mount with sufficient precision.
>If your pots are on a home brew PCB a tolerance of 1,5 mm
>may be more realistic.
>In this case the hole size would be 7 + 1,5 = 8,5 mm
>
>The 0.75 indicate the 'speed' of the tread,
>every rotation the tread advances 0,75 mm.
>So this number has nothing to-do with the hole size,
>but indicate the nut type/counter tread  you need.
>
>The height of nuts is also measured in M.
>For M tread the standard nut type is 0,8M
>so for M7 tread the standard nut is 0,8 * 7 = 5,6 mm high.
>However nuts to mount pots are usually much flatter,
>often only one speed high , in this case 0,75 mm.
>Needless to say a one speed nut can easily be turned too
>tight and damage the tread.
>
>PP sometimes ask on this list for methods to avoid damaging the
>front panel when mounting the pot nuts.
>Well washers where invented for exactly that purpose.
>The washer should be on the side where the bold / nut rotates
>during mounting.
>So when mounting a pot the washer should be under the nut,
>and not on the side of the pot.
>
>The washers protect the mounting surface (font panel) in two ways.
>First off the washer prevents that the nut "eats" itself into the mounting
>surface.
>
>Second the spanner lays on top of the nut.
>This creates a distance between the spanner and the mounting surface,
>so scratches are avoided.
>Some "socked" and "ring" type spanners fall over the washer,
>making scratches after all. (note _some_ most are ok)
>"Open" spanners don't have that problem.
>But when you don't use them right the "open" may spring or the nut
>and damage your front panel.
>
>
>Class dismissed.
>
>Cheers,
>Theo
>
>
>
>From: Jim Johnson <jamos at technotoys.com>
>
>> Argh.. drivin' me crazy..
>>
>> Trying to lay out a front panel using the Schaeffer software.. What size
>> hole does a pot with an  M7- 0.75 shaft need?
>>
>> Maybe I should just go to bed -
>>
>>
>> Jim Johnson
>> Metaphoric Software
>> -------------------
>> Makers of Techno Toys
>> Software for Electronic Music
>> http://www.technotoys.com
>> info at technotoys.com
>>
>>
>>