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Mini 8-Way Rotary Selector Switch - SP8T (ADA2925)

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When you need a lot of options, you need a Mini 8-Way Rotary Selector Switch. This is basically a single-pole to 8-throw switch. As you rotate the knob around, the … read more

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re Mini 8-Way Rotary Selector Switch - SP8T

What diameter is the threaded shaft? And also the shaft which holds the knob?



Hi Bob
If you click on the link to Core web page there is a drawing. The threaded bush is 9.3mm and the splined shaft is described as T18 size. Now I have no idea what that means. Maybe Adafruit’s sizing system but the only place I have heard of that terminology is Torx driver sizing. It may have 18 teeth, I haven’t counted them. The drawing shows this shaft as 4.5mm which I think is a pretty odd size and I would question that. I have quite a few pots etc with splined shafts and they are all 6mm (5.96). I have only heard of this type described as “Metric splined” implying 6mm as against 1/4 inch for round or “D” shafts.

I could be wrong here and this T18 is a size which has sneaked in under my radar and if the drawing is true you might find yourself having to purchase knobs to fit from Adafruit or Core. I might check Element 14 later and see if this size exists in the commercial world.
Cheers Bob

EDIT: Just had a look at Element 14 for that shaft diameter.
8 pos switch only 1 listed. seems to be an odd size.
Plenty of different shaft sizes, too many to go through but of the ones I did look at 4.5mm was not listed.
I did look at pots. There was a filter for shaft diameters and I found the following.
4.5mm Qty listed 1 “D” shaft
6.35mm Qty listed 342 mostly D shaft
6mm Qty listed 389 spline and D

I think it would be best if Core staff were able to measure this for you.
Cheers Bob

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Hi Bob,

Unfortunately, the only info we have from our supplier is this fuzzy image:

However, it does reveal that the threaded section is M9x0.75, and that the splined section is 6mm with T18 splines.

Mouser have a category for these knobs, so they do exist elsewhere, and from the look of things, it just refers to the tooth count: Knobs T18 Knobs & Dials – Mouser Australia

We’ve also got a range of knobs available if you’re looking to get one from us:

All the best with your projects!

Thank you. I think the threaded bit is too short to go through a guitar body.

Appreciate your reply!



Tuesday, September 14, 2021, 1:47:06 PM, you wrote:

Hi James

Pretty disgusting actually.
So disgusting I missed the splined shaft dimension in the top left image. It does say 6mm.

BUT. The dimension I did see is on the centre image plainly says 4.5mm.

So for the sake of compatibility if we assume 6mm it is possible any “standard” “metric” knob would fit.

Not difficult for Core to measure though surely.
Cheers Bob

Hi Bob,

Looking over that diagram it looks like the switch is drawn with a D-shaft instead of a T18 splined shaft. I’ve made a note to have that product page reviewed and updated to see if we can get a more accurate drawing from the manufacturer. Failing that we may need to remove the diagram and just list our own measurements and descriptions from the warehouse stock.

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Hi Trent.
You are right. I missed that. Must be getting sloppy in my old age, more likely a bit slow. That’s my excuse anyway. I think we might blame whoever produced that drawing and more to the point who checked it. Sloppy QA, but that sometimes seems to be the norm these days. Not always thank goodness.
Cheers Bob

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Hi Robert,

Thankfully, I’ve been able to measure a unit from stock, and confirmed the dimensions. The discrepancy between the shaft measurements is likely due to the D-shaft seeming smaller from the side, and the correct measurements are at the bottom now.

We’ll see if we can find a better diagram, but that should tide you over until then!

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