A little math help please

[db5]

I’m leveling my table per Nick Engler’s instructions, Sawdust Sessions #22. Fore and aft are at 0.01. There is a delta of 0.28 between port and starboard. I have the following shims:
6-0.10
2-0.25
1-0.35

I couldn’t understand his explanation on how you do the math to determine what shims to put on the low side. There are some math whizzes and engineers here who can do that in their heads. Would you put it in writing so that lesser gifted can understand.

[garys]

Why bother to calculate it? Put in one size shim, tighten things down and measure again. If it still isn't correct, you know the thickness of the shims used and can easily get it right the second time.

[JPG]

No amount of wizardry will provide a solution with only those size shims. Are you sure of thy decimal points? Them be pretty thick 'shims'. 0.28 is also huge.

[thunderbirdbat]

No amount of wizardry will provide a solution with only those size shims. Are you sure of thy decimal points? Them be pretty thick 'shims'. 0.28 is also huge.

Not if the measurement is in millimeters. Some of us in the U.S. often forget that not everyone measures in inches and sometimes we forget to check what measurement scale the digital micrometer is reading in.

[dusty]

If I read you correctly, you need to raise the low side of the table .28 so ideally you need two .28 shims. I doubt that number but let's run with it for now.

You don't have .28 so the closest you get with what you have is .25 which leaves your table .02 low on the same side. No way you can get closer with what you have.

No math involved really.

Is it possible that .02 is really .025 (25 thousands) rather than .25 hundreds, etc.

Rather than rotating arm that Nick used, I would consider something much more rigid and known to be at 90 degrees to the axis of rotation. An old saw blade on an arbor would be more accurate

You might want to consider something on this order rather than the stick that Nick used.

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[DLB]

I don't really want to watch the video again because I don't use that method. But from my understanding, also the way I do it, I only shim what you'd call fore and aft. I think your port : starboard error is table tilt angle, and if this is different in DP mode with a Drill chuck than it was in horizontal mode with a saw blade (or whatever) then I'd have a whole new set of concerns. I true my table, both directions, in horizontal mode to a blade or sanding disc with the table (only) tilted 90 degrees. I'd prefer horizontal mode even if I did it with a drill chuck, because that's how I use my ShopSmith if possible.

There may be some math to the correction depending on how far you measure from the spindle Vs. how far you shim. Using my example, if I use a saw blade my measurement points are a bit less than 5" from the spindle, but the shims are installed ~8" (510/520) from the spindle. One thing Nick did in the video, IIRC, that I really liked was to note that he could use two different shim thicknesses on the two bolts and the change would be the average of the two. For even better results, there are peelable shim products where you peel off laminated layers to get the shim thickness you want. IIRC those layers are 0.002". I know, probably ridiculous for woodworking. In the dark ages there were some applications in military aircraft, I don't know if they are still commonly used for that but they are available so there are applications.

- David

[JPG]

No amount of wizardry will provide a solution with only those size shims. Are you sure of thy decimal points? Them be pretty thick 'shims'. 0.28 is also huge.

Not if the measurement is in millimeters. Some of us in the U.S. often forget that not everyone measures in inches and sometimes we forget to check what measurement scale the digital micrometer is reading in.

Until the "US" fully moves into the metric system, I will continue to assume inch unless there is something to dispute that. I went through a difficult period a couple decades ago where My employer insisted on metric dimensions regardless of whether the design was originally in inches. Thus circuit boards with a 1/10" hole pattern became a 2.54mm hole pattern. All our vendors had to convert those 'metric' numbers into inch equivalent to match the inch graduations on their machinery. Needless to say this increased costs and introduced conversion errors. Grumble grumble.

OK .28mm is .011 ".

Now for the redefined initial question. If the difference of the distance between measurement point and the shim location is not = 0 then the shim dimension needs to be multiplied by the ratio of the distances. If the measurement is at 5" and the shims are at 8" then the shim needs to be 8/5 times the amount needed at the measurement point.

[db5]

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[attachment=0]Thanks for the suggestions. The shims are thicker than you'd expect; they came from an extension table I bought used. It was from the earlier 510 and the p.o. had used shims to level it. I put two 0.10 shims on one side and it reduced the delta to .18. So I added two more. Now it's within .02; close enough. I like Dusty's set up and actually had some milled aluminum I could have used but I made one similar to the one on the video using steel. Here's a pic of my dial indicator gauge mount. Made from stuff collected over the years.

[DLB]

I re-watched the first part of SS-22. What I earlier called Left/Right (or port/starboard) error Nick calls front to back in the video. Both of us correct it with table tilt. So confusing, I have no idea which version the OP might have meant. For me, the infeed side of the main table in table saw mode, the one with a front rail for the fence, is always the front of the table regardless of how the SS is setup or where I may be standing or what might be my current feed direction. Nick, perhaps, switches references with modes, so for him table tilt became front to back in DP (or at least in SS-22). Standardization, anyone?

I would correct my earlier post, except that for me it was correct. In either case, one direction is corrected with shims and one with tilt (including tilt stops) and its pretty obvious which is which. If one measured .01mm, it is essentially perfect, 0.0004". But it looks to me like the OP's dial indicator is of the 0 to 1" variety. So

- David

[dusty]

I re-watched the first part of SS-22. What I earlier called Left/Right (or port/starboard) error Nick calls front to back in the video. Both of us correct it with table tilt. So confusing, I have no idea which version the OP might have meant. For me, the infeed side of the main table in table saw mode, the one with a front rail for the fence, is always the front of the table regardless of how the SS is setup or where I may be standing or what might be my current feed direction. Nick, perhaps, switches references with modes, so for him table tilt became front to back in DP (or at least in SS-22). Standardization, anyone?

I would correct my earlier post, except that for me it was correct. In either case, one direction is corrected with shims and one with tilt (including tilt stops) and its pretty obvious which is which. If one measured .01mm, it is essentially perfect, 0.0004". But it looks to me like the OP's dial indicator is of the 0 to 1" variety. So

- David

Are you sure? Maybe just a little tweak.