R4511 Table top alignment instructions

[DaveWoodWork]

When people started talking about aligning their table tops with the saw blade at both 90 and 45 degrees, it got me to thinking about the procedure. While I know this is old hat to many, it was not immediately intuitive to me. I had to go through the process in detail on paper until I felt I understood things. I wrote the process up and decided to share it with whoever might be interested. It seemed to have worked for me. Hopefully others may find it useful. Feel free to point out the errors I've made (I'm sure there must be some).

My instructions are attached as a PDF file. Have fun!

Dave

[Bob D.]

A very nice write up Dave complete with informative photos.

You didn't throw that together in an hour.

Washers can easily be 'tuned' to the required thickness with some wet/dry paper and a little elbow grease.

Much of what you have said in your article would apply to a contractor saw except of course that the table can not be moved, you have to shift the position of the carriage which is slung from the underside of the table. But checking for parallelism between the blade tilt axis and the miter slot is important on a contractor style saw but probably not as easy to correct as a cabinet saw.

[BadgerDave]

Very nicely done Dave. I'm sure that your hard work will help many new owners with their own setups.

[chrisexv6]

I know when someone here mentioned doing this (I think it might have been you, DaveWoodWork), it sure didnt make much sense to me. Then I went home and put the blade a 45 and stared at it for a bit, then the light bulb lit up.

My way wasnt nearly as scientific as yours, so I may re-check my measurements using your guide as a guide.

Thanks!

-Chris

[Bob D.]

Well I had nominated this thread when it first came up and then withdrew the nomination because when I went to the TOTW thread it says the poll is closed. To me this meant that no one else would be able to vote for Dave fine alignment procedure as the nominations had just closed soon after I made my nomination. I emailed Josh and explained why I had removed my nomination so that this thread could be nominated again in the following week.

But, I see that Badger Dave has now also nominated it and the nomination was placed in the same week as when I nominated it, so apparently it is not closed as it plainly states under the poll results.

So I now add my vote again to this thread not knowing how much more time there is for other people to vote for it.

Come on you lazy woodworkers, click on the button and VOTE!.

[The Grey Knight]

Good info, I still have to do this to my 4511 that I put together last weekend. I am guessing we all had to realign the top since we took them off to unload the saw.

[airChris]

Great write up -- it seems that from the results contained in the file (appendix B), it works.

But I was wondering.... It appears that you are using pythagoras theorum to derive 't'. In appendix A you write "Remember back from high school that the square of the hypotenuse is equal to the sum of the squares of the adjacent sides." As far as I remember (and it's been a while), phythagoras only applies to right triangles, not isosceles triangles. Or have I overlooked something ??

Chris

[DaveWoodWork]

Originally Posted by airChris

..., phythagoras only applies to right triangles, not isosceles triangles. Or have I overlooked something ??

Chris

You are correct. Remember, I said to angle your dial gauge down 45 degrees. That together with the 45 degree tilt on the saw blade gives you a 90 degree angle for one of the angles. The triangle is a right triangle with two equal sides. You can measure at other dial gauge tilt angles, but then you'd have to use sine values to calculate the side, something I was trying to avoid.

Good pickup. I enjoyed geometry in school, but I've had to dust away quite a few cobwebs to use it here.

Dave

[Smack]

Originally Posted by DaveWoodWork

You are correct. Remember, I said to angle your dial gauge down 45 degrees. That together with the 45 degree tilt on the saw blade gives you a 90 degree angle for one of the angles. The triangle is a right triangle with two equal sides. You can measure at other dial gauge tilt angles, but then you'd have to use sine values to calculate the side, something I was trying to avoid.

Good pickup. I enjoyed geometry in school, but I've had to dust away quite a few cobwebs to use it here.

Dave

a right triangle does not have to have equal sides, just a 90-degree angle. An isoceles triangle has 3 equal sides.

[DaveWoodWork]

Originally Posted by Smack

a right triangle does not have to have equal sides, just a 90-degree angle. An isoceles triangle has 3 equal sides.

Correct. A right triangle does not have to have equal sides, but in my setup, the resultant triangle is both a right triangle and happens to have two equal sides. An isoceles triangle has two equal sides. An equilateral triangle has three equal sides.

I specifically measured my saw blade with the blade angled to 45 degrees and the dial gauge angled down at 45 degrees. In the attached diagram taken from appendix A, angle BAF will be 90 degrees due to the blade and gauge angles. Angle ABF is the dial gauge position angle, which we set to 45 degrees. Since all the angles in a triangle must add up to 180, we know that angle AFB must also be 45 degrees. Since two of our angles are the same, we know that this is an isocelese triangle and the two corresponding sides must also be equal (both equal to d). Since this is a right triangle, we can calculate the hypotenuse (side t) using Pythagorean's theorem.

Dave