Popular Woodworking 2008-10 № 171, страница 42
Trammel point*. A pair of trammel points mourned on a wooden bar are used to lay out large circles. One point is pushed into the work-piece surface and remains stationary whHe the other swings on the bar and scribes a circle.
Large circles arc easily laid out with a pair of trammel points. They differ from a pair of dividers in that you mount trammel points on a wooden bar. One point is pushed into the wood surface and rcmainsstationary. The othcrswingson the bar.and it isuscd toscorc a circle. How big a circle you can make is a function ofthebar'skngth. Ifyouusctrammcl points a lot I would recommend keeping several barsofvaryinglcngths. It is awkward to use a bar a lot longer than the circle's radius.
Dividers and trammel points will lay out circles. However, the ellipse is another common shape used in woodworking, especially forsmall tabktops. Layingoul an ellipse requires another device. My ellipse maker is plastic and was purchased from a tool catalog It isonly one of numcrousellipse makers available to woodworkers.
An ellipse has two axes. So. when crcat ing an ellipse it isnccessary tocstablish both these kngths. By altering either axis you change the shape of the ellipse. On one extreme, you can make an oval that is almost a circle. On the other extreme, you can make long, narrow ellipses.
If you only need to make an ellipse once and don't want to invest in an ellipse maker, youcandoit with nothingmore complicated than two push pins, a string, and a pencil. Tie the string into a loop. You have to work out
lllipse maker. This handy tool is available from a number of woodworking tool catalogs.
Shop-made ellipse maker. If you don "r mark a lot of ellipses, consider making yxxrr o«n ellipse maker when needed with twv push /wis, a/veer of string and a pencil.
the length of the loop and the pin locations through t rial and error based on the major and minor axes. Loop the stringaround the two pins and pull it taut with the pencil. As you draw with the pencil, the loop of string will hold it in a path that forms an ellipse.
There arc. of course, many other layout tods. Some arc available in caialogsand some arc shop-made. There arc far too many for me to list. So. here is an example of several others that I use.
Dovetail marking gauge. This gauge has a 1:8 ratio on one edge, and a J:6 ratio on the other. Others angles an- available.
While a bevel square will lay out dov etails, a lot of woodworkers like to use a dovetail gauge. These usually look like a small square, only the edge of the blade is not set at a right angle. One edge isat an 1:8 nuio for softwood and the other at a 1:6 ratio for hardwoods. Once the baseline is made with a marking gauge of with a try square, the tails and pins arc marked off with the dovetail gauge.
My other dovetail gauge isa bit different. It is two brass blades hinged in the middle. The edge on one blade is at the 1:6 ratio and on the other the 1:8. To use the gauge, I bend it to a right angle and lay the desired ratio on either the face or the end of the board, with the other blade over the other face or end.
I make my own layout tools for some special projects. 1 have adcvke I use for dividing a turned surface into horizontal segments: for example, rcedsand (lutes. It is nothing more complicated than a pencil held in a dowel, whik the dowel is held in a flat base. The distance between the bottom of the bascand the pencil is the same as the height of my lathe centers above the lathe bed.
I use the index head on my lathe todividc the turning into segments. Then, I slide the base a long the ways with the pencil in contact with the turning. The pcncildrawslinesthat lay out the segments. No matter the turning's shape, the pencil tracesa line at the height of the lathe ccntcrs. PW
A chtirmaier since 1971. Michael is the founder of The WmtfyM ImtiMc in Htmpkm. .V, H. vvfxvi' he (r* hes hundreds <x'irurfow< each v«su *> bu&i Windsor chairs. YnM thcwsndiOtinsUine.com for more information and tonudhbbkjg.
Dividing a turned surface. I use this shop-made jig for laying out reeds and flutes on a turning. It's simply a pencil hekl in a dowel, with the dossel in a Hat base.
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