I’m fairly new to using rivets and the 1/16th inch solid rivets are taking me some time to master. Therefore, I thought it would be important to share some of my learning. My use for the rivets is on the 1/20th scale Burrell traction engine where they are required for a number of fixings and for a number of materials. Hence I’m using a mix of steel, copper and brass solid rivets.
Rivet is defined as a permanent fixing used to join plates. The unheaded end is forged or flattened to upset or close it.
One of the first things I made was a silver steel rivet head punch. Heat treated for hardness and then tempered to ensure it did not fracture under the impacts it would see.
This is known as a “rivet snap” and has a concave dome in one end to form the head on the tail of a rivet.
This concave dome needs to be 1.75D in diameter and 0.75D in depth. D being the diameter of the unheaded or straight section.
The domed rivet, perhaps the most common type of rivet used in model engineering.
When you buy rivets you will be buying them based on the dimension D (eg 1/16 inch) and the length of the unheaded section L (eg 1/4 inch or 1/2 inch).
It is important to note that the height of the domed section is not half the width of the dome as would be expected if it was half a sphere. We will look at that again later.
The tail of the rivet is the plain straight section of material. The diameter of this straight section is what determines the size of the rivet.
The setting allowance is the amount of rivet that should protrude through the parts being fixed to allow a head to be formed.
Whatever the size of the rivet this setting allowance means that the same volume of material is contained in this length as is contained in the domed head of the rivet. Sapphire Products Ltd have tables for most of the rivets available.
Here is some simple mathematics to show that 1.43D is the correct number.
As mentioned earlier the dome of a rivet is not half a sphere. Hence the volume of this section needed to be expressed independently of the radius R of the sphere. This is because we don’t have the radius of the dome, R. We have the diameter of the dome, D which is equal to 2x r
This equation allows us to define the volume of the dome in terms of D.
Below I have written the volume of unheaded rivet that protrudes through the metal plates that are being joined. I have also written the volume of the dome in terms of D and then simplified this.
I then set the volumes to equal each other and then expressed the result by keeping SA as the unknown.
Hence the setting allowance, SA = 1.43D
Rivet Setting Allowance Jig
As this setting allowance is important I machine a jig so that it’s thickness equals the required overall length of the rivet. I then push the rivets into the jig and cut then off clean to the surface of the jig with a cold chisel (I have to thank SGSengineering on instagram for this hint – allchinmodel.weebly.com).
I’m sharing this example of my riveting. Not perfect, lots of practise required. However, this has moved a long way on with careful setting of the rivet length.
There are lots more opportunities to improve my riveting abilities on this 1/20th scale Burrell.
When you’re hammering a rivet head you need to react the force against an anvil.
This is a 1/4 inch mild steel plate with a 4mm blind hole drilled in the end to accept a silver steel punch.
The bracket allows me to support the other side of the rivet inside a structure.
The punch is not fixed in the bracket just in case it needs changing. The punch is hardened silver steel and has a domed concave feature to fully support the head of the rivet.
Also, I sandwich the mild steel bracket with a sheet of aluminium in the vice as this then adds some compliance and so more easily maintains the clamp load.