R5 Marking out techniques

Posted: October 10, 2010 in Resistant Materials

Initial knowledge – 1

Current working knowledge – 2.5

I have used marking techniques in woodwork before in school and I don’t think much has changed in technology since then, although it does seem like a long time ago!

When marking out my dovetail joints I used a pencil and carpenter’s square to mark out the shoulder lines of the joint at the correct width of the wood.  I know you can get dovetail templates but I chose to just find the center of the wood and calculate how many dovetails I can fit that are 10 mm at the shoulder 20mm at the end with a 5mm gap in between.  Once I had marked out the dovetails and crossed of the waste I used a marking knife to go down the shoulder line where the waste will be taken away which helped with my chiseling, you can also use a marking gauge for this

Tom also reminded me about marking out face sides, face edges and the datum faces although on my first attempt I still managed to try and glue the wrong 2 faces together in a panic.  Still, lesson learned have everything to hand, glue, cloth and plenty of clamps!

For marking out the aluminium for my plate rack I used a similar process except I used a meter steel rule and an engineers square.  I simply used a graphic fine liner on the protective plastic although a scribe is usually the tool used for marking out metal.

Similarly with the acrylic I used the engineers square and meter steel rule (steel rule for the smaller pieces) and a felt tip pen on the protective plastic .

For accuracy when marking out the holes  for my rivets I used a center punch.

Other marking out tools are odd leg calipers.  These are for marking out parallel lines to an edge on metal, the piece of aluminium I used was too large to use these.  For marking out circles or arcs on metal you would use divider calipers which are sharpened like scribes to mark the metal and are used in a similar way to as you would use a compass for marking circles on anything else.

A slightly different caliper is one that has a vernier scale which allows for a more precise measurement.  Vernier calipers can be used to measure internal dimensions using the upper jaws or external dimensions using the lower jaws.  On some vernier calipers depth  measurements can be taken if the caliper accommodates a probe that is attached to the movable head and slides along the center of the body.  This can be a useful instrument because the probe is thin and can get into deep grooves that other measuring tools can’t access.  They can measure to 100th of a millimeter or 10 micrometers and in fact there is a similar precise instrument also known as a micrometer .

micrometer

When marking out the Tenons for my space saving unit I used a mortise gauge.  This was a really useful instrument as not only could I mark the mortises at the exact width of the bit on the mortiser but I could ensure that all my joints were exactly the same on each piece of wood which was vital for creating a square frame.

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