How to - The Measure of Things

A few essential Measuring Tools
"Measure twice, cut once", is an oft repeated adage that I have tended to acknowledge but not always practice. And sure enough, most of my mistakes have been due to poor or inaccurate measurement. Every time I bungle I curse myself and promise to measure twice if not thrice but every once in a while neglect to double check and end up with yet another cockup. So take the old adage seriously no matter how clich├ęd it might sound.

Measuring accurately is at the heart of woodworking and I have been surprised to learn that even this apparently elementary procedure takes practice as well as patience. My accuracy in measuring has actually improved dramatically over time, perhaps because the more I do woodworking the more I realise how critical measurements are.

There are in my view three aspects to measurement:
  • The length or distance of a cut
  • The straightness and alignment of a cut
  • The square-ness of a cut
All three have to be spot on for a proper cut. A cut may be of the right length but could be way off if the line is not aligned the way it should be; or a side might be cut perfectly as with a table saw but could still be imperfect if it is not square to the other edge.

Always check your cuts for square and be prepared to fine tune
Often ripping stock with a circular saw and guide seems easy; measurements have been made, alignments checked and yet when it comes to fitting, the parts don't match perfectly. What could have gone wrong? Any one of the three aspects of measurement might be off. Check and re-check before cutting and even then be prepared to fine tune your cuts.

Some measuring tools are essential equipment.

For size:
  • Measuring Tape
  • Folding rule
  • Ruler

For straightness:

  • Straightedge
  • Combination square

For square:
  • Try Square
  • Combination square
  • Carpenter's (or steel) square

Measuring Tape
Measuring Tape

Def. A steel ribbon used for the measurement of distances.

Measuring tapes are easily and widely available but as with every tool it is better to find an accurate one. When buying a measuring tape make sure that its measurements are accurate when the steel tip is hooked against an edge and also when it is butted against something to get an inside measurement. This can easily be done by matching the tape readings against a ruler.

Folding Rule
Folding Rule

Def. A rule which is jointed at fixed intervals for convenience in carrying.

The folding rule is a little more difficult to get hold of these days but at one time they were very common with Indian carpenters. I had a hard time getting hold of a decent one locally but finally got one. In many occasions it is possible to get more accurate readings with a folding rule because it does not bend like a tape. Also, some folding rules come with a brass tip that slides out making it easy to take accurate inside measurements.

Ruler
Steel Ruler

Def. A strip of wood, metal, or other material, having straight edges graduated usually in millimetres or inches, used for measuring and drawing straight lines.

The good old ruler is something we have been using since we were kids in school but even here there are issues of accuracy, so be warned and choose a good one. Get an accurately ground steel one which could also serve as a straightedge. The most useful length is 12 inches but if you have the money get a 6 inch and a 24 inch ruler as well.

Straightedge
A 36 inch straightedge

Def. A rigid flat rectangular bar, as of wood or metal, with a straight edge for testing or drawing straight lines.

A straightedge could be a good quality ruler or an accurately ground machinists edge. Some amount of accuracy is required here as well but it does not have to be to engineering tolerances. A decent straightedge or ruler checked against a piece of flat plate glass or granite would be good enough.

Combination Square
Combination Square

Def. A combination square is a tool used for multiple purposes in woodworking, stonemasonry and metalworking. It is composed of a ruled blade and one or more interchangeable heads that may be affixed to it. The most common head is the standard or square head which is used to lay out or check right and 45° angles.

A combination square, on the other hand, is altogether a different matter and given its importance at every stage of woodworking nothing but a very accurate one will suffice. I have one made by Stanley (available locally for about Rs 1,400) and an expensive one by the famous American company Starrett. A combination square is useful for checking square-ness, mitres and much more, and is easily the most versatile measuring tool available.

Try Square
Try Square

Def. A carpenter's tool consisting of a ruled metal straightedge set at right angles to a straight piece, used for measuring and marking square work.

Try squares and engineers squares are relatively cheap in India but their accuracy varies widely and I might add, somewhat wildly. I have generally been extremely disappointed at the variable quality of India made squares and spent much time tuning some of them; others I have been compelled to discard.

Fortunately square-ness can be checked easily by holding one edge of the square tightly against the edge of something straight such as a piece of A4 size art paper and drawing a perpendicular line with the other edge; then flip the square and draw another perpendicular line next to or over the first one and if the two match the square is accurate.
Checking for Square: Draw a Perpendicular line with the bottom edge of the square flush against the edge of the paper

Checking for Square:Now flip the square and draw a line over the previous one

Checking for Square: Voila! The lines meet. The square is square.

Engineer's Square
Engineer's Square

Def. A machinist square or engineer's square is the metalworkers' equivalent of a try square. It consists of a steel blade inserted and either welded or pinned into a heavier body at an angle of 90 degrees.

These are usually more accurate squares made of steel, and are useful when greater accuracy is required. I have a small one for checking square-ness which I use very often because of its convenient size. I have a couple of bigger ones which I use as reference squares to check the accuracy of my other squares.

Carpenter's Square
Carpenter's Squares

Def. The carpenter's square more commonly referred to as the framing square, consists of a long arm and a shorter one, which meet at a right angle.

These are large steel squares (2 feet plus by 1 feet plus) also sometimes called framing squares as they are used in house construction. These large squares are very useful in larger projects and crucial for accurately measuring sheet goods.

Other Measuring Tools

There are a whole bunch of other measuring tools, some cheap and other expensive, which make life easier but are not entirely essential. These would include a feeler gauge (used for measuring fine gaps), depth gauge, angle gauge and so on.

The need for more specific measuring tools arises as one goes along. For instance, I soon found myself searching for an easy to use depth gauge and came across a pretty nifty one in Chawri bazar for just about a hundred rupees. Good measuring tools are well spent, don't stint and always double check for accuracy.

Indranil Banerjie
23 Nov 2013

Comments

  1. Hi Indranil, I was too behind all these measuring tools but now, I haven't touched any of these tools, barring the measuring tape, after I brought Incra Rules.
    http://www.incrementaltools.com/category_s/271.htm
    The are bit expensive, but very accurate and save you a lot from mistakes!
    --regards, Praveen

    ReplyDelete
  2. Praveen: Incra makes super accurate measuring tools. Once you have a set of tools like that you will never look back. I have some of them but as you said they are very pricey

    ReplyDelete

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