1Q22 Challenge - Knob Twiddling

WezV

I'm going to be making some guitar knobs.  More specifically, I'm going to be casting some, which is an approach I have not used before.

I've drilled and turned basic knobs before, did some just the other day, although i need to redo them as the cat has stolen one and i can't find it!



For his challenge I am going to be casting some to try and learn a new skill.

I picked up a silicone mold making kit, and some clear casting resin.

First step was to choose some knobs.  I decided to go with 4 Gibson Style bell knobs. 4 strat knobs (2 vol/2 tone) and a few basic dome knobs.  these have been glued to the takeaway tub  with a hot glue gun



I measured the required volume of silicone mold mix and the next day we have the mold 



Next job will be to tidy up the top edges and try casting some. 

After that I need to figure out the drilling of the knobs as I'm not attempting a 2 part mold here.  I also some inserts to go in the middle.   I have some brass set screw inserts from the wooden knobs which can be used for the dome knobs.   You can buy plastic ones for push fit knobs but it means importing them.  For the challenge I'm going to see if I can come up with a home grown solution 

paulnb57

Great stuff! Interesting seeing the process, especially how you come up with an insert…

TTony

Interesting! 

I've never even thought of doing something like that.

WezV

I may also try making some torty plate material as part of this challenge.   I have a flat silicone mold on the way for that.  be nice to pour some knobs and a plate from the same stuff 

WezV

I thought I would try the mold out with some wax first.  This is all leftover from the bottom of the million scented candles my girlfriend gets through ... maybe it can be a line of scented wax melts for the more discerning guitarist??

I was thinking i could then carve some of the wax knobs and recast from that to make something unique, but as it stands there is probably a few too many bubbles for it to work well. I may still have a play and see what happens.

 The molds seem great though, no loss of detail, except for that caused by bubbles and impurities in the wax.

TTony

The text on top of the knobs has come out remarkably clearly.

WezV

There is no reason it shouldn't give a perfect reproduction, except for bubbles.  bubbles are the enemy here.  The best way to solve them would be with a vacuum tank, but i'm not investing in one of those just yet.


I've mixed up my first lot of resin, going for a fairly safe brownish colour.  Its a clear epoxy resin with brown analine added.  It has a 40 minute work time on the resin. 

I mixed for 5 minutes, then let it stand for 5 minutes so most bubbles from mixing came to the surface, I blowtorched it to remove them

Then I poured into the mold as a slow drizzle from as high as I dared.  This is supposed to help minimize bubbles.

I then took a cocktail stick and very gently dragged it round the detail in the knobs to hopefully remove any bubbles.  Waited another 5 minutes and blowtorched again to remove the new surface bubbles

I made sure the mold was filled slightly proud to allow for a little shrinkage of the epoxy.  If I have too much teh bottom can always be sanded.


I now need to give that 24 hours to cure before I touch it again

I have some more resin on order with more dyes

Sesh

Do you reckon you could use the molds for chocolate? Chocolate knobs, anyone?

WezV

I was thinking the same thing... but I think  I might need a different silicone for that.  I would want to make sure I was using one that was classed as food safe

Roland

My wife would love this for making soap moulds.

WezV

Roland said:

My wife would love this for making soap moulds.

I was considering making some soap bar P-90 covers

ThePrettyDamned

This is super cool!

I fancy using some great big witch hat type knobs on my new build, but would love it if they were available in more interesting colours than "off white" and "black"... Maybe this is the answer for me. 

WezV

well i cheated slightly for these test pieces and put them in the oven on the lowest setting, checking regularly.  That sped up the cure a lot



I need a better solution for bubbles, but a promising start for my first resin cast

TTony

Reminds me of a friend I had back in schooldays - he was into model soldiers, wargaming stuff.

He used to cast his own figures, though that was using molten metal of some sort (lead perhaps?) into small moulds of something.  We used to have "fun" copying keys ....

paulnb57

Thats pretty good for a first attempt, huge potential  

ThePrettyDamned

You know, the bubbles add something of a rusted, "shipwrecked" look. With the right colours or a bit of relic treatment they might suit a driftwood type build really well. 

I suppose it also opens up the possibility of modifying knobs, or designing your own using putty. Very cool. 

WezV

Yeah, I've seen some guides where imperfect castings have been bronzed for relics.


I could probably get these most of the way to a normal black relic knob with a bit of black wax

I will make use of these, even if its just for testing other things

Andyjr1515

WezV said:

well i cheated slightly for these test pieces and put them in the oven on the lowest setting, checking regularly.  That sped up the cure a lot



I need a better solution for bubbles, but a promising start for my first resin cast

Great stuff

Ref the bubbles - a short and mild suck in a vacuum bag?

WezV

Andyjr1515 said:

WezV said:

well i cheated slightly for these test pieces and put them in the oven on the lowest setting, checking regularly.  That sped up the cure a lot



I need a better solution for bubbles, but a promising start for my first resin cast

Great stuff

Ref the bubbles - a short and mild suck in a vacuum bag?

I have a sous vide for the kitchen, so may try doing it in the vacuum bags for that

WezV

So a bit of reading has been done on the bubble issue.

A long thin stream was the right way to fill the molds, but I should pour into a corner first, not straight down into the middle 

I can try vibrating  the mold to bring bubbles to the surface.  I'm sure I can find something it the house that would do that.   Stop thinking rude thoughts, I'm considering the dremel graver as the best option.

Then the options are a vacuum or pressure pot.   

A pressure pot is recommended for hard resin, vacuum recommended for silicone molds...but  I will try the sous vide vacuum bag option first as it's easier.

I will try something fairly translucent soon to see how that goes... it will show the bubbles more, so I can see if it's worked 

davros

Pop it on top of your phone and call yourself? Dunno if that would be strong enough