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Post by charley1968 on Nov 5, 2015 11:52:35 GMT -5
Being of the non-patient kind, unable to wait for the delivery of books on TF i ordered, i ask the following question: could someone please be so kind as to explain the terms Square rule, Mill rule and Scribe rule? Thankee!
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Post by Red on Nov 7, 2015 3:53:30 GMT -5
These are very broad topics, Charley, so I'll have to find some time to figure out how to summarize it for you. In the meantime, I'll give you some quick thoughts...
Mill Rule is a joinery layout method based on the ideal square timber.
Square Rule, on the other hand, is based on the concept that there's an "ideal" timber within every timber -- square or not. In my experience, this is the prevailing layout method in use in the American TF revival.
Although I haven't seen it used since the barn builders I grew up around employed it, Scribe Rule layout is a method where certain tools -- i.e., plumb bobs, plummets and scribes -- are used to transfer layout from one timber to another.
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Post by charley1968 on Nov 7, 2015 5:07:08 GMT -5
Does Square rule imply that you (theoretically) reduce the dimensions of the available stock during layout?
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Post by Red on Nov 9, 2015 0:58:27 GMT -5
Does Square rule imply that you (theoretically) reduce the dimensions of the available stock during layout? I'm not exactly sure I understand your question, Charley, but I'll try to summarize some of the important aspects of how I was taught square rule layout.
To simplify things, let's assume that you've placed an 8 x 8 timber on top of two trestle ponies (heavy duty saw horses). Next, the timber is sighted from one end along each face of the timber until the face with the crown in it is facing up. At this point, the frame plan is consulted for guidance. Generally speaking, the frame designer will make a note on the plan telling the joint cutter which side of the frame to reference joinery from -- and this is generally referred to as the reference edge.
Going back to the crowned timber...the adjacent faces must be inspected until the best face -- the face with the least amount of flaws -- is identified. In general, the frame designer will place the reference edge, whenever practical, on the outside of the frame. As the outside of the frame is eventually covered with siding, it is, obviously, best to have the face with most flaws facing outward, which is to say that the reference edge chosen by the frame designer is "referenced" to the outside of the frame.
Keeping all of this in mind, the reference edge -- which the old-timers called the arris -- is identified by the joint cutter with two hand-drawn triangles. The tips/tops of both triangles [arrows] point to the arris and the triangle on the top (crown) face is filled in so that this "solid" arrow points directly to the open arrow. The edge identified by the tips of the arrows, once again, is the arris.
Why is it important to visually identify the reference edge? It's important because most timbers are not perfectly square and, therefore, one must have a point to "reference" the joinery layout from. I was originally taught to use a framing square, but I've since been shown the virtues of a metal layout jig that was specifically fabricated for timber framers -- and this tool is usually referred to as a Big Al (after its inventor). Much like a roofer's speed square, the Big Al (pictured below) has an overhanging lip/edge, and this edge of the tool is placed against the timber's reference edge first. As this placement rule is practiced each and every time joinery layout is initiated, this is an important basic principle of the Square Rule layout method. In short, all joinery measurements and layout lines begin at the reference edge, the arris. Once the timbers have been properly marked, the joint cutter is now set to begin laying out and, more to the point, cutting joinery as per the frame designer's specifications.
Big Al Layout Jig:
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Post by charley1968 on Nov 9, 2015 12:56:16 GMT -5
Thanx, Red, for your exhaustive reply. I will read, swallow and digest it in my spare time.
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Post by Red on Nov 9, 2015 13:01:14 GMT -5
Thanx, Red, for your exhaustive reply. I will read, swallow and digest it in my spare time. I believe I previously mentioned that this is a broad topic and, therefore, summarizing is tough. Regardless, please take the time required to digest the information. If you wish to learn square rule layout -- the prevailing method -- these words are a very good starting point (that I had to learn as an apprentice).
Have a good one, Red
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