Dialing In Fence, Cutter, Blade and Table Position

      Once you know your machine, you can adjust it accurately from memory. March 10, 2008

Question
An issue one can consider about the positioning of fences, spindles, and the like is that all the components imparting the movement are moving at a predictable amount. This element is designed into the equipment we use. Some are easier than others, but nonetheless, they can be anticipated and used for our benefit.

Some examples:
One complete clockwise revolution of a hand wheel on an Oliver 399D planer will raise the table 1/16". Once you know where the machine is, count the turns and divide them into whatever you need visually, and you will find you can accurately get to where you need to be by simply counting turns. Use the scale only as a rough guide, because if 3/4" is at 3:00, then 23/32" is at 9:00, and so on.

One complete turn of a Buss 4L planer moves the table .100". Buss as an option had an adjustable ring around the outside that has divisions for movement to .001". Again knowing where you are, you add or subtract and move accordingly, and if your calculation is correct, the new setting will be as well.

One complete turn on the elevating handwheel on an Oliver 2002 table saw moves the motor platform 1/4". One complete turn on a Whitney Model 91 double spindle shaper raises the spindle 1/8" - again the handwheel conveniently divided with 125 marks starting at 0 and going to 125. Oliver rack and pinion fence are easily positioned by reading the divisions on the fine adjustment wheel. One turn equals 1/4" with 16 divisions going around it. Adapting these fences as outboard fences on shapers and router tables helps in all regards for the setting depth of cut and as a guide for parts to track through. Older Martin shapers had divisions on the elevating handwheel for specified movement in mm and they are quite accurate.

I am writing these things because I use them all the time quite successfully. I can only speak for the machines I have used. I do not know what a Grizzly planer does, for example, but if I had one I would figure the per revolution movement out as an indispensable piece of information. The CNC machines are counting turns, granted faster than a human can, but that does not mean one can't count for themselves to the degree they want to, and be accurate at the same time.

Forum Responses
(Solid Wood Machining Forum)
From contributor J:
You make a very good point, and that is a useful method for closing in on a measurement, but there's one catch. Depending on how high the quality of the machine is, and how much use it's had, you'll have to deal with backlash. Since most woodworking machinery is not built to the same tolerances as, say, a nuclear submarine or such, there is always a certain amount of backlash when reversing direction. And for those of us using the slightly cheaper machines (yup, that's me - lots of Delta and Powermatic), that backlash is more pronounced, making repeat precise setups difficult between raising and lowering of the spindle or other mechanism. The machines you mention I would think are much more accurate, but for me it's setup blocks and test cuts. At least until I get one of those handy electronic positioning add-ons. :)



From contributor C:
If you adjust one turn past your target and then one turn back to the target, you solve the problem of backlash. It makes no difference how much backlash you have. The screw has so many threads per inch and will move exactly that amount per revolution, as long as you are moving in the same direction. This is what CNC controlled machines do. One turn past the target, then back to it with the final move, always in the same direction.

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