What's this sticky tape called?

[Adrian Caspersz]

The sort that looks a bit like decorators masking tape, but used in engineering to establish what clearances lie between mating surfaces by looking at indentations when parts are assembled?

[Harry Bloomfield]

Adrian Caspersz explained :

I know just what you mean, but sorry I cannot think of the name..

[harry]

Replica tape.

[Harry Bloomfield]

harry presented the following explanation :

I had in mind the material which compresses, so that measuring its thickness once the two surfaces are disassembled = you know what the clearance is between the faces.

[Kevin]

Plastigauge?

[Harry Bloomfield]

Kevin explained on 10/07/2019 :

That is the one I had in mind..

[Chris Bartram]

Isn't that plastiguage ?

[Graham.]

But it looks nothing like decorators masking tape

[Marland]

Lead wire was an older method I have seen used to check the bearing clearance on a ships triple expansion engine. The engineer , the engine and probably the reel of the wire all dated from before the plastic age.

GH

[newshound]

Never heard of that (although I spent years measuring rough surfaces, including taking replicas).

Our replica material of choice was Acrulite, this is just methyl methacrylate monomer which you mix with powdered polymer. It sets in a couple of minutes.

You can also get replicas using RTV silicone, either two pack putty as used by dentists for replication, or creamy liquids dispensed from a double tube syringe through a mixing nozzle.

Metallurgists have a clever technique for large, immovable plant. They grind and polish the surface finishing with micron diamond paste, then etch, then apply a drop of acetone and press a thin piece of acetate sheet on to the surface, and allow it to dry. Done well, the resulting replica, examined in a metallurgical microscope, gives almost as good an image as could be obtained from the original metal.