Therefore I had two options
1) Buy replacement knobs
2) Make replacement knobs
1) I had a look replacement knobs were going to be £13 EACH plus postage. No surprise there; replacement parts for household appliances are always extortionate, especially when the appliance is an old one.
2) I did make a replacement knob out of FIMO but it didn't last. FIMO is just not strong enough to handle the torque. Also the cooker control shaft is D shaped. Therefore i needed to find a way of attaching any knob i made to the shaft of the cooker controls.
The methodology here is for knobs made of Lego being permanently attached to the cooker control shaft (?) Obviously you don't need to use LEGO or use this for a cooker. Other uses - Guitar knobs? Amplifier Knobs? Door Knobs?
Other materials - carved wood, metal, cast acrylic.
So what will you need? Here is the ingredients list-
Lego - Enough to make the size shape and colour of knobs you require. I bought a bag of used mixed lego off of eBay for a few quid.
Metal Tubing - I bought a piece of 8mm od (outside diameter) 6mm id (internal diameter) stainless steel rod again from eBay but it is also possible to get this from DIY and Model/Craft shops. The tubing should have an internal diameter that is just big enough to fit over the shaft of the controls on the cooker
You will need the following tools and equipment:
2 part epoxy
Fine tipped overhead projector pen- for marking the tubing for cutting
Scalpel/ Stanley knife
Clamp or vice
Round needle file, Emery paper
Step 1: 1) Make Your Knobs
Do the next step one knob at a time to avoid mixing pieces of lego up
Take the knobs apart then using the superglue carefully reassemble the knobs gluing them up as you go. take care to ensure that the glue is in the inside of the bricks and isn't going to be visible when the knob is finished.
On my knobs i ran glue (superglue and capilliary action) into the gap between the bricks from the back to add more strength.
Leave them for an hour or so to set.
Step 2: Hollow Out the LEGO
Clamp the LEGO knobs into a vice or similar for this operation.
Using the pliers and scalpel/ stanley knife remove any part of the Lego brick from the centre point of the back of your knob this shold be to at least the depth of one brick.
The easiest method for doing this would undoubtably be a Dremel. I don't have one yet.
Step 3: Cut Tubing to Size
This step is where you have to customise this to suit your application.
For my cooker I had to consider that I have a gas cooker and as such I need to push the knob in before it will turn to allow the gas to flow.
I had a look at the old knobs and could see
1) how far the control shaft inserts into the existing knob
2) the distance between the deepest part the shaft can penetrate the knob and the flat back of the knob.
Measure these, add them together and then add on the depth the tube will insert into the new lego knob.
Now mark up and cut a length of tubing using the hacksaw for each knob you are making.
It is important to now clean up the ends of the tubing using the needle file, or emery paper. This will remove burrs and ensure the internal diameter is as it should be.
Step 4: Glue Tubing Pieces Into the LEGO Knobs
It is important to make sure the tubing is perfectly at right angles to the new knob otherwise your knob will not look right when it is installed onto the cooker.
Leave to set for at least 6 hours or as instructed by the epoxy manufacturer
Step 5: Install the Knobs Onto the Cooker
I attached my knobs to the control shafts using 2 part epoxy. Mix some up and put some inside the tubing (not too much that excess will be forced out of the tubing when you push it onto the shaft) then slip the knob onto the control shaft. Make sure it is straight and that if it needs to be pushed in to allow it to turn (eg gas cooker knobs) that it is not pushed onto the control shaft too far.
It may be possible to use other types of adhesive which are less permanent such as hot glue or loctite thread lock, but there is no guarantee that these would stand up to day to day use. Worth considering though.