1Q22 Challenge - Knob Twiddling

blobb

https://www.thespruce.com/how-to-vibrate-concrete-844451

WezV

So according to that it would be best to vibrate from inside the resin.

I can probably fashion a probe to go in the graver that will do the trick.     

Roland

How about sitting it on a speaker cab while you practice some low end riffs?

WezV

i'm surprised the suggestions have been this clean

WezV

vibrating definitely got it so there was only small bubbles in the mix

I should have done a dry run with the vacuum sealer... would have been better with a lid on the tub and a hole drilled in to it so as it didn't get squashed. I don't think the bubbles have got anywhere to go now, but lets see how these turn out

i also worked out that 60g of resin fills the molds nicely

WezV

I ditched this test quite quickly thanks to the squashed bag affecting the casting and pushign epoxy out of the mold.  we can see bubbles are reduced, and there are a lot less on the surface.  This would probably work fine with a coloured knob,  but can still probably be improved by changing the way I used the vaccum set-up


you can see here the bubbles were definitely on their way to the surface/bottom of the knob


The dome knobs were not far off at all


Strat knobs continue to be a challenge, but the detail on theses isn't actually that bad... might spray a coat of paint on them to see

WezV

Attempt 3

I have to remember I have a really long working time on this.

I mixed for 5 minutes. 

I then did a long pour into a small plastic bottle.  The long thin drizzle gets rid of some bubbles so we only have small ones in the bottle from big ones in the mixing cup 

I could attach the bottle ttothe vacuum sealer with a hose.  This reduced the bubbles even more.  The remaining ones were tiny

I then did a long slow pour into the mold.

Finally, that was placed carefully into the tupperware with drilled lid, and sealed in a vacuum bag.  It's enough pressure to start crushing the lid in, but the mold and resin is safely untouched inside 



I'm not going to cheat and heat this time.  It was likely a mistake to do so.

The heat will be expanding any air bubbles that are in there, as will as speeding up the cure so they have less time to escape.


Will need to be patient now.

WezV

I sanded the base of one of yesterdays efforts. Buffing compound got in the bubbles, I'm not unhappy with how it looks.  Doing that purposefully with paint could be a good look



In a few days i will show the plan for drilling these, and ensuring I get nicely centered holes each time

davros

Gold or silver paint rubbed in the holes to fill them up would look pretty cool.

TTony

WezV said:

I'm not unhappy with how it looks.  

That's exactly what I thought when I looked at the pic (before reading the text).

Roland

It looks like woodworm. There must be a relic market for that

WezV

same with the dome knobs,  these are pretty much a usable set.  Black wax would have hid all the bubbles pretty well. This pic is to highlight them but you don't actually notice them in the hand

ThePrettyDamned

Can't wait to see what results you can get.

Any interest in selling them? Not that I'm after any (maybe) but just in general. I like the idea of clear witch hat knobs with a white or silver top...

WezV

I'm not sure yet, I need to see what sort of results I can consistently get first

I'm starting to consider things I could put in the resin too

WezV

Round 3 is much better, really happy with these.  Just some tiny bubbles in the middle of them.  The strat ones are nearly bubble free






Still have some bubbles on the top edge of these so need to pay attention to that area shortly after pouring in.

Mattharrier

Looking nice! Really cool to see the evolution of the process.

WezV

i'm still trying to figure out inserts for push fit knobs, but i do have some brass set screw ones that I can use with the dome knobs.

So I have drilled out the clear ones from yesterday and  we have our first working set of cast resin knobs



Issues.
They were only cast yesterday, so still a little soft and have gone cloudy from working on them too soon.  I will wait a few days before polishing them up again

The insert is bang on center, but the recess so they sit over a washer isn't.  Wouldn't matter on a solid coloured knob.

TTony

How did you hold them steady when drilling out the centre?

WezV

TTony said:

How did you hold them steady when drilling out the centre?

I use a very simple jig with a few holes in it.

1st drill 2 holes going halfway through the jig, full diameter of the knob
In one of those holes drill a centre hole to the diameter of your pot shaft/insert
In the other drill the base recess diameter close to the full width of the knob

the first drill hole gives you a handy center point for the next 2

Pop knob in hole, flip over jig, drill.

works well for 1" knobs like the gibson and fender ones, but the dome knobs are 18mm and I don't have a drill for that. I used a 19mm spade bit and taped the knobs up to size..., but that is why the recess ended up off center

WezV

Now the fun can begin.



For this torty set I  mixed up an Amber,  red/brown and brown mix.  I degassed it all in the vacuum bag and let it sit for about 40 mins, to the point its just starting to get thicker.

I initially mixed the 3 colours in the mixing tub, getting a nice tortoishell pattern.  When I poured that into the mold, the pattern disappeared.  So I added some more  black brown at this point and gently swirled it through the molds with a toothpick.

Slightly worried this could add a lot more bubbles, but let's see what happens.  Back into the vacuum bag it goes

If this works I may be able to cast my own tortoishel plate material.