How to compensate for thousandths/inch on tablesaw
Good evening!
Pretty much a newbie here. I’m been in a slump for many years with woodworking as nothing ever seemed to come out right – ever! So I decided recently to dig my heels in deep and figure out why. Well, I have a Rigid 4511 tablesaw (the one with the granite top) and found it was off – WAY OFF – from the moment I bought it 6-7 years ago.
I scoured the internet and found videos and forums on it and the BEST I can adjust it to is within 0.008″ from front to back of blade, exact spot on blade too. No wobble from arbor, blade not warped,etc. The closest I can get, like I said, is 0.008″. I have two options at this point, remove the top entirely and drill out my mounting holes to give me some more wiggle room or compensate, which brings me to my question…………
Is there an equation out there that calculates the amount of angle required to compensate for such a small amount so I can adjust my Incra Miter Gauge (yes, it’s accurate and squared) to get a perfect 22.5* cut? (I’m cutting 8 pieces for an octagon, so that tiny amount of deviance at 3/4″ thickness is multiplied by 16 (two ~22.5* cuts each piece times 8 pcs) so when the pieces are put together to form the octagon, there’s a gap left. (Yes, this 0.008* deviance is evident on ALL squares and jigs, not just the Incra.)
Yes, I could just trim a hair off each piece “guestimating” and ‘sneaking up to it’ to get a ‘good enough’ fit, but I plan on mass producing these items and don’t want to spend all the extra time “sneaking up to it” on each finished product. If I can plug in my 0.008″ deviance on angle over x.xx” distance to give me the final angle computation(for example, +.379* to 22.5 thus equaling 22.879*), that’d be great!
I’ve been scouring the internet to no real avail, probably not using the correct search terms… so I figured I’d post here, please no armchair warriors/haters, we’ve ALL been novices and amateurs before!
Thanks so much in advance!
ScottishWoody
PS.
I HATE MATH! lol (not a good thing since I’ve been making furniture and oddball items for years!)
Replies
You know what?!? Nevermind! I took the 200lb granite top off, and using a titanium step drill bit I expanded three mounting holes and was able to adjust the table top down to less than 0.001" front to back on the blade! All's well in my woodshop again!
I assume you are trying to get your blade parallel to the miter groove. 008 is only a whisker more than 1/164". Not very much. Yes. You want to get it better than that and I'm not familiar enough with your saw to advise you on that. I understand there are some add on devices that makes this adjustment easier. Others may be able to advise you better.
However. the angle you are trying to cut with your miter gauge is not really dependent on the blade being perfectly parallel with the groove. Any cut you make using the miter gauge will be parallel with the miter groove because that is the direction of travel as you push your work piece through the blade. Consequently, your miter gauge needs to be set up with 90 deg perpendicular to the groove not the blade. Ideally, your blade should also be parallel to the groove so that the trailing edge of the blade, as it comes up out of the table. will follow the kerf cut by the leading edge. If the trailing edge is farther away from the miter groove than the leading edge (in your case by .008") then the off-cut side of the kerf will get some scoring by the trailing edge. This should not be too much of a problem. Your problem comes if the reverse is the case and the scoring occurs on the work piece side of the kerf. But, if the work piece is narrow enough so that the cut is completed before the trailing edge of the blade comes in contact, then you can minimize the problem by stopping your push just as the cut is completed.
So. Yes. you need to figure out how to get your table adjusted so that the blade is parallel. But, in the mean time, adjust your miter gauge perpendicular with the miter groove and see if that solves your angle cut problem.
Also, sometimes as you are making a cut, the cutting action will tend to pull the work piece a tiny bit along the miter gauge fence giving you and inaccurate cut. Glue some 150 grit sandpaper onto your miter gauge face and it will help eliminate that problem.
Follow up:
I just read your second post. I guess we were writing at the same time. I'm glad that you got the table alignment fixed. Good job. However, my comments regarding the miter gauge still apply. Only now that you have your blade parallel, it won't make too much difference which you reference for your miter gauge.
Your miter Gage also has to be parallel wit the blade set to 45°. and 90°.
Also I would not enlarged the table holes. The top could break out. You could have thinned the bolts in the area of the table holes. To set the Gage perpendicular with the miter groove has nothing to do with setting the Top to the Blade.
Hilmar
Glad you got it fixed!
I found this video a while ago that would have solved the problem by creating a perfectly square crosscut sled instead, then you could just add the appropriate wedge for the angle, though he has a video on how to create a miter sled too.
Sadly, some math is involved!
https://www.youtube.com/watch?v=UbG-n--LFgQ
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