Gallery, Projects and General => Gallery => Topic started by: AdeV on January 25, 2018, 10:37:57 AM

Title: My shiny knob
Post by: AdeV on January 25, 2018, 10:37:57 AM
Recently I've been doing some electronics (read: cooking transistors, mmm, tasty fried transistor on a bed of melted resistors, yum); and in a total brainwave, I decided to use a rotary encoder to handle the up/down time setting (more on this project at a later date... when it's nearer completion).

So... what does one put on a rotary encoder? Why, a knob of course! But this meant buying one. Being a bit of snob about my knobs, I wanted it to be aluminium, ideally not have an ugly set screw in the side, nor a removable top, nor must it have a pointer. With these eminently sensible criteria in mind, I plunged headfirst into google, and I found.....

....nothing. Not one single knob met my criteria. The ones that came closest, cost at least Ģ7 (US$10) each!! I'm not paying that! For a knob!

[cue the A-team music]

So I made one instead, pictures below. Other than the set-screw, I'm not actually sure how to mount it. I think I'll just use superglue...

Title: Re: My shiny knob
Post by: chipenter on January 25, 2018, 10:50:18 AM
You could mount it with a taper will only need 2 degrees ish , make a mount at the same setting would cover any screw or glue .
Title: Re: My shiny knob
Post by: Nicolas Hulme on January 25, 2018, 05:44:24 PM
I'd use an internal groove & O ring
Title: Re: My shiny knob
Post by: John Swift on January 25, 2018, 06:27:50 PM
Hi Ade

what's the rotary encoders spindle like ?

D shaped , solid metal splined or split splined

some old Bakelite knobs that fit onto D shaped spindles
had a 1/4" circular hole with a slot to take a flat spring that pressed on the flat on the spindle

Title: Re: My shiny knob
Post by: AdeV on January 26, 2018, 03:33:11 PM
Thanks for all the suggestions, most welcome!

The encoder shaft is 6mm with a "D" shape, so John, I think I'll do something based on your suggestion... I'm thinking, If I cut a shallow(ish) 2mm  slot across (2mm being the smallest cutter I have), in pretty much the exact right place, I could glue a thin piece in which gripped the "D" tight enough that it doesn't fall off when inverted, but can be pulled off if needed for maintenance reasons. My other thought was to turn a piece of ali to be a moderately tight fit in the knob's mounting hole, then mill away all but the male equivalent of the "D" cut-out, and glue that in. I may investigate that idea too...

I forgot to mention that the encoder also has a push switch in it, although that shouldn't make any difference to the way it mounts.
Title: Re: My shiny knob
Post by: John Swift on January 26, 2018, 03:57:19 PM
Hi Ade

I can't find a photo of the exact knob I am thinking of but these are other versions

the first knob is very near to what I was looking for


Title: Re: My shiny knob
Post by: Baron on January 27, 2018, 03:00:33 PM
Hi John, Guys,

A lot of this style knob just had a flat curved spring.  At one time you could buy both the "D" shaped ones and the flat ones from RS Components, Farnell used to sell them as well.
Title: Re: My shiny knob
Post by: DeanDK on January 29, 2018, 07:38:06 AM
Wow that is very cool! without a size reference you could get away with that being mistaken for the crown of watch. (the knob to set the time and wind the watch)  :clap:
Title: Re: My shiny knob
Post by: hanermo on January 30, 2018, 05:26:14 AM
Really cool shiny knob !

But itīs not polished.
Just saying ...

Grin ;)
Title: Re: My shiny knob
Post by: AdeV on January 30, 2018, 06:51:15 AM
Thanks for all the comments :)

Dean - I wish I could do work at that scale..... unfortunately, my eyes just aren't up to it these days, and IMHO my lathe doesn't spin fast enough to do really intricate tiny work, at 670rpm, by the time you get down to turning a couple of mm, it's more likely to bend than cut... One day, a smaller and much faster lathe will be on my shopping list.... unless I can get the Mazak CNC going, I think that's capable of a couple of thousand RPM.

So anyway, in lieu of references, the knob is approx 34mm OD, the mounting shaft is 6mm (+ a bit of error in the drill bit). I didn't quite get it perfectly trued when I cut off the front face, which a close inspection will reveal; and for some reason the ball-end cutter that I cut the flutes with left a fairly bumpy finish. I may try a different technique next time I make a knob (plunge cut with a straight cutter, but only removing the same sort of amount of arc.

Hanermo - you're right, it's not polished... at least, not completely. It spent a few moments under a brass wire wheel, until I got fed up of bits of brass hitting me in the face.... then it spent a few minutes under a cotton polishing mop, with whatever polish was left over from a previous job. The only polishing gear I have is a small pot of Meguiar's "Metal Polysh" and some rags (when I can find them)...

One day, I will polish a knob to the point you can see your face in it...... erm, did I say that out loud?  :doh: :lol:
Title: Re: My shiny knob
Post by: hanermo on January 30, 2018, 02:50:48 PM
If not clear at first .. my comment was a joke as You hopefully saw re: "polishing the knob".

I donīt know the right processes for polishing a one-off knob ..
Slow turning or indexing in a lathe etc. and a rotary-tool like Nsk (dremel) might work for the insides of the knob perimeter.
(Vs a vibratory setup.)