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Help trueing a crosscut sled

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Forum topic by toddbg posted 12-10-2016 06:18 PM 571 views 0 times favorited 5 replies Add to Favorites Watch
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toddbg

26 posts in 1452 days


12-10-2016 06:18 PM

I recently made a crosscut sled and I am at the stage of trueing the fence 90 to the blade.
I was using the “5 cut method” and have been having a heck of a time getting this correct.

I could use some advice/double checking my math and whether I need to make additional adjustments.

For the last correction I came up with the following:
A= 1.0615”
B= 1.0440”
Length of cut= 10.6875”

A-B= .0175”
.0175”/4= .004375”
.004375”/10.6875”= .00040936”

Is this good?
If I need to adjust I get:
.00040936”x28”= .01146199 = ~.00115”

Does the adjustment move back towards me or forwards towards the rear fence?

Thanks for the advice.
Your guys help is much appreciated.

-- -- Todd, Washington


5 replies so far

View bbasiaga's profile

bbasiaga

1006 posts in 1830 days


#1 posted 12-10-2016 06:57 PM

You’re only off .004 in 10”, or .0004 per inch. Others will tell you you can make it better, and you can, but i wouldn’t bother.

Whether you have to move your fence forward or back depends on which was the thick end. Looks like you are thicker at the front (end away from the fence), so that means you’d move the left side of the fence away from the rear fence. (I think I’ve visualized that right).

When I made my first one, I chased perfection until I was ready to quit wood working all together. When I made the second one, I got results similar to yours and have been very happy with it as well as glad I didn’t waste the time messing with it.

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View ArtMann's profile

ArtMann

685 posts in 651 days


#2 posted 12-10-2016 07:24 PM

I have been down this same road so many times. I kept trying to micro adjust my sled fence many times to get it close to zero and I just never could. Finally, I tried doing the same measurement several times without changing anything and I came up with a variation between successive measurements that is larger then the total error I had calculated the first time I did it. The truth is that the kind of error you are talking about can be accounted for with the natural variation in an inherently variable mechanical system. It is hopeless to repeatedly get that kind of accuracy with wood and woodworking tools.

In practical terms, 0.0004 inches per inch is completely irrelevant in terms of building something with no cracks or defects. You are likely to make cuts that will totally dwarf this kind of error and never even notice it.

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Rich

1977 posts in 425 days


#3 posted 12-10-2016 07:29 PM

I agree with Brian that you’re close enough. For reference, if you’re following William Ng’s method exactly, then if your error is positive, move the fence back, and if it’s negative, move it forward.

-- No matter how much you push the envelope, it'll still be stationery.

View toddbg's profile

toddbg

26 posts in 1452 days


#4 posted 12-10-2016 08:18 PM

Thanks everyone!
I was just getting confused if my cutting error was .004 or .0004.

Four thousands over 10” isn’t too bad. :)

-- -- Todd, Washington

View HokieKen's profile

HokieKen

4510 posts in 974 days


#5 posted 12-11-2016 12:19 AM

Yep. You’re good :-)

-- Kenny, SW VA, Go Hokies!!!

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