Woodworker's Journal summer-2009, страница 19

QI have recently read that when a router is mounted under a router table (bit spinning counterclockwise) that you have to feed the piece clockwise and around the fence. Why is that?

Andy Pozorski Sauk Rapids, Minnesota

A Your question is best answered with a drawing. The view is looking down on the fence and bit. Notice that the bit is only partially exposed by the fence. As you push wood along the fence from your right to your left (called the feed direction in the Drawing at left below), the rotation of the bit is against the direction you are pushing the wood. This allows the bit to safely cut the wood and you to safely push the wood along and finish the cut.

Now imagine pushing the wood from your left to your right. Notice that the rotation of the bit is now the same direction that you are pushing the wood. The bit now acts as a fast spinning wheel that grabs the wood out of your hands and quickly propels the wood across your shop, often pulling your hands into the bit. This is a very dangerous practice and is to be avoided at all times.

Feed direction Climb cut

When the feed direction is OPPOSITE the rotation of the bit, it is called a conventional cut. It is easy to control and yields great results. When the feed direction is the SAME as the rotation of the bit, it is called a climb cut. Climb cuts have their place in routing, but generally speaking they are to be avoided on a router table. Save climb cuts for handheld router use only when the amount of wood you are removing is very little per pass and when you are intentionally doing it and are aware of the danger.

Carol Reed

QI want to mix a IV. pound cut of shellac using dry flakes and alcohol. My question is, do I need a conversion factor since I am mixing ounces by weight (flakes) with ounces by volume (alcohol)?

Paul L. Stotler Leonardtown, Maryland

A Good question. No, you don't need a conversion factor since the formulas for shellac are already "converted."

If you were trying to mix to a percentage, such as a 25 percent solution, you'd need to stick to either weight or volume, but "pound cut" is already a mixed measure.

Bit rotation

Feed direction Climb cut

When it comes to shellac, "pound cut" is a mixed measure — a weight (shellac) combined with a volume (alcohol).

V

Right to left feeding of your workpiece on a router table, also known as a conventional cut, is much safer than a left to right climb cut.

It calls for a certain weight of shellac flakes to a certain volume of liquid alcohol. A V£ pound cut means you add l¹/ pounds of flakes to one gallon of alcohol.

Obviously, that means you end up with more than a gallon of shellac. For smaller amounts, convert to ounces versus pints. Three ounces of flakes in one pint of alcohol also gives you a Vk pound cut.

Michael Dresdner

22 reader questions, answered