jointer table flatness

[Michael Handrinos]

I was wondering what you call acceptable flatness on jointer, table saw and router table surfaces. I know that the manufacturer has theirs, but how much would you accept? Say If you're dimensioning stock by going from one to another, would they accumilate and how would that affect the project? Or you really don't worry as long as they are tune to the best of your ability. Trying not to over think this being new to this.


Thanks

Mike

[Kent Fitzgerald]

Mike, I think the answer is a big "it depends." On a table saw, for example, the area in front of the blade, between the miter slots, is the important part. The rest of the table is much less critical. For quality of cut, the alignment of the miter slot, blade, and fence is what really matters.

Generally, I let the results be my guide. On a jointer, if I can create two edges that match up without a gap, I see no reason to go over the table with a straightedge and magnifier. If the edges are coming out convex or concave, it's most likely a problem with the height of the outfeed or the coplanarity of the tables, not the flatness.

Sorry, that's kind of a non-answer to your question, but if you're not having any problems with the results from your tools, I see no need to worry over 0.002" here vs. 0.05" there.

One other thing - a fairly common response to this kind of question is "wood moves, so a few thousandths don't matter." That's not what I'm saying. That response confuses the tolerances of the final product with the tolerances required for machines to perform well. There are cases where a few 0.001"s do matter, notably TS alignment and jointer / planer knife setting. Overall flatness of machine tables isn't one of them.

[Derek Arita]

I have a 12" jointer that I've been struggling with for years. Both tables are about .009 pooled in the middle. For the life of me, I can't get a straight edge from it. When I joint two boards and put them together, the problem doubles. I have two 8" jointers that are within .003 flat and have no problems. Hope that helps.

[Michael Handrinos]

Thanks for the replies. I'm feeling better now I guess I get caught up in the tolerance issues too much!


Mike