Greetings all...
I have been constructing a new crosscut sled, and the thought came to me, how close does this need to be to make nice joints...
Instead of using a square I cut the sides off an 8" square of birch plywood, I then ripped a strip off the first side and measured the difference with a dial caliper, and over 8" there is less than 1/128 difference, but that would be compounded over 4 cuts right?
So would you guys try to get it closer of just leave it as is?
I might try to get it closer but some times measurements can deceive or may not be done accurately. Sawing technique can often render measurements useless.
Use some scrap wood, make a frame and ask yourself, is that good enough?
Keep in mind that opposite parallel sides must be exactly the same length also or even perfect 45's will not close properly. Use a stop to insure same length "opposite" sides.
Depends on the project. What's the maximum width?
"Leon" wrote in news:dFpPj.9595$ snipped-for-privacy@nlpi070.nbdc.sbc.com:
its kinda funny....but I was able to get it almost perfect, within a needles width on the dial caliper, I would think that would be close enough, but last night I had painstakingly straightend and squared the bit that would become the main fence and after all that I managed to install it with the wrong face to the saw....after switching things around my test cuts came out much better....
So why not eliminate the 'sawing technique error from the equation when calibrating the fence?? Hmmmm.
This won't do it. 'Sawing technique error still there.
RE: Subject
Remember the old saying, "A flying Red Horse can't spot the difference from 1,000 ft."
Still works.
Lew
I couldn't agree more with everything Leon said, not the least being to try it out to see for yourself.
You are talking about making a wooden device that you think will hold tolerances to within one 0.0078125th of an inch. Think about it; a wooden jig that will hold completely true through humidity changes, temperature changes, techniques differences, movement of the sled in response to different weight, density and size of material, etc., etc. Not happenin'.
Don't cheat yourself For dead bang spot on, buy a calibrated miter gauge.
Or... just use your miter saw. I for one have never understood the folks that have to use their tablesaw for everything from precision miter work for small pieces like building picture frames to making raised panel doors.
Maybe its just me. I could see it on really large pieces I guess, but even then... how often does one need a miter on a 12" board?
Robert
When calibrating tools 'eye-balling it' is NEVER good enough in my shop - wooden or otherwise.
In lots of situations, the precision of decent eyeballs and finger tips is actually very useful for checks.
Two examples:
Thickness planer parallelism - plane a board, cut it in half, put opposite edges together, rub the fingers over the meeting point.
Table saw blade or miter gauge/sled 90 degree accuracy - Cut a board in half, flip one board, place the cut edges together and check for gaps.
If they don't work out, the calibration tools make recalibration easier and faster than more test cuts, but the cuts are good enough for in-service spot checks.
So why not eliminate the error you have control over (the original calibration)?? Why settle for a sloppy calibration because you might experience wood movement?
Error Total = Error in calibration + error from wood movement over time + ...
The 'error in calibration' can be eliminated completely w/o making a single test cut.
You don't even need to settle for the 'error from wood movement'. Just check the dam thing before you use it and fix it.
That would be my point. I am indicating that measuring will not always over come techique and when you are talking a visible or invisible joint line the technique problem may be so small that it could involve dozens of factors. Including but not restricted to, is your table flat, is your stock perfectly straight, are you working with soft or hard wood, is you blade "sharp", is the surface of your table smooth, and the list goes on.
It certainly does it for me. Because we are not machines there will always be some degree of imperfection with every cut. Measurements only get you so close and if you were able to obtain the perfect setting your technique will always add some degree of error from one cut to the next.
Perhaps one day you will learn to make eye-balling work for you. It certainly speeds up production.
Why correct error so small that it does not factor? Very often climate changes totally negate all accurate measurements. One day your loose parts to a drawer fit fine, the following day the fit is too lose or too thight. With years of experience you learn to compensate and work with mother nature. Precice measuring tools are fine to use for a start but the results are often out of phase with climate changes and your technique.
Keep in mind that neither is a constant, one element is constantly changing which pretty much over rides the results/effect of a particular setting.
Calibration is important but results with any given calibration often change with the climate and your technique. It's not a labratory invironment where you can calibrate "everything" with materials that are a constant shape and size.
Experience counts for a lot in the results you get.
LMAO.... pretty hot issue, eh? I like it when someone replies to their own posting.
You missed my point. You should always get your jigs, measuring devices, etc. as close to perfect as you can.
We were talking about a >>WOODEN
Perhaps one day you will learn that precision is better and faster when you learn the tricks.
Then eliminate the 'factors' you have control over. Like a precise calibration.
All variables that effect final result. Which of those do you have control over?
You are missing my point. See above.
See above.
Did you see any constants in my equation? That's why they are called variables NOT constants. (See equation).
True. Eliminate the error you have control over by doing a precise calibration at the beginning.
True. But this is extremely relative.
I missed it because you never made this point. Where was it posted?
You stated that you don't understand folks that like to use their table saw for precision miter work.
Check it before you use it. I do. And w/o a single test cut.
I would take that challenge.
That is not what I was talking about, I'd be willing to bet that you would find nothing wrong with my precision and or joints. It's that with years of experience you learn how to achieve that with out having to use high precision measuring tools with every adjustment.
Case in point, you bought a new Powermatic 2000 TS. If your measuring and precision set ups on your old Delta saw were good why change saws? I'm just saying that a precision measurement is not always the answer to a problem.
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