Am I being obsessive

[Bruce Cohen]

Just did my annual "tune up" to my 3100. I'm getting a varience of .001 (one one thousandth of an inch) over a 10" rip on 3/4 baltic birch ply. I used a caliper for the measure, and the thinner side was the leading edge of the piece.

Being a closet obsessive/compulsive, should I strive for a perfectly parallel rip, or is this "good enough for Government work".

Bruce

[bmyers]

I wouldn't chuck your saw in the garbage just yet. You may be able to sleep at night with that amount of error. If it was at the end of the board that last touched the blade, it may have just slipped a little.

What method do you use to set the rip fence?

Bill

[Hellrazor]

Bruce, that was from the dust on the caliper from the first measurement

[Stytooner]

When I get close measurement's like that, I just mash the thumbscrew on the caliper a little harder and then it's perfect.

[Bruce Cohen]

Hey Lee,

How'd you know I did that.


Bill,

All I did was follow the Ryobi instruction book, that was the hard part. I been reading the skinking thing for about two years now, and I'm still not sure if I'm doing it right.

Bruce

[just4funsies]

"CLOSET obsessive"??? I'd say your secret's out now...

[jabe]

Bruce, do you check the measurement from the fence to the tooth of the blade facing the fence on the back side of the blade as well as the front side to make sure your fence is parallel to the blade? I always do this b4 & after locking down the fence just to be sure. I had that same problem and had found that the fence did not lock down tight on the back rail, it moved a little as I fed the material into the blade with pressure against the fence. .001" isn't much but, I'm like you, I would have a rough time sleeping at nite, Hope this helps.

[bmyers]

Yeah, sounds like you're fine.

I use the no--measure thing with the two magnets and the nail?? Anyone have a link to that for Bruce? I can't find, I think it was on the Ryobi forum. But it doubles the amount of error you could measure so it's easier to deal with I think.. Try it..


Bill

[Lonnie in Orlando]

No-Measure Alignment

My computer crashed. My "No-Measure Alignment" file is on the crashed hard-drive. I'm trying to recover. I'll post it again when I can.

By the way --- As long as the rip fence is not out of alignment more than half of the difference in the thickness of the teeth minus the thickness of the plate of the saw blade in 10", the rip cut will be staight and parallel. The cut may be scored from the teeth scraping against it.

- Lonnie

[Bruce Cohen]

Lonnie,

Sorry to hear of your computer problems, I usually kick my Mac and it behaves itself.

Thanks for the comeback, now if you can only explain it in English, I'd be right greatful.

Failled math more times than I took it.

Bruce

[Knottscott]

Most wood will move that much over a period of time.....I wouldn't worry about it at all.

[Lonnie in Orlando]

"Lonnie's Theory of Rip Fence Relativity"

Bruce -

You Mac users always have to poke us PC'ers in the ribs when we cry about our crashes!

Here is my rip fence theory. Disclaimer - It's my opinion only, I haven't read a confirmation anywhere.


I feel that a lot of woodworkers spend too much time looking for perfect ripfence alignment. The kerf of the sawblade produces a built-in allowance for small errors in alignment. The sound of the saw, the feel as the workpiece goes through the blade, and the quality of the cut will tell you when the fence is out of alignment. Having to duck because of kickbacks is another pretty good indicator that the fence is out of alignment.


>> "LONNIE'S THEORY OF RIP FENCE RELATIVITY"
> The rip fence doesn't need to be 100% parallel to the saw blade to cut straight and parallel.
> Your saw blade cuts at the point where the teeth enter the wood (teeth rotating down).
> The entry point of the teeth is always the same distance from the fence.
> If the rip fence is slightly out of alignment, the teeth cut the wood again where they exit the wood. (teeth rotating up)
> The exit point of the teeth is always the same distance from the fence.
> The teeth cut a kerf wider that the plate of the saw blade, so the workpiece does not contact the plate of the blade.


==>> MINOR OUT-OF-ALIGNMENT
> Assuming that the rip fence is not out of alignnment so much that the workpiece contacts the plate of the saw blade before it contacts the exit (up) teeth of the blade:
> MINOR #1 - The entry point of the (down) teeth is closer to the fence than the exit point of the (up) teeth. The width of the cut piece will be the same as the distance from the entry teeth to the fence. All points along the cut piece will be the same width. Therefore, the cut will be parallel to the fence.
> MINOR #2 - Same results when the exit point is closer to the fence.
> #1 AND #2 - Since the teeth are scraping against the workpiece, similar to cutting coves on the table saw, the edges of the cut pieces will be scored by the saw teeth.


==> MAJOR OUT-OF-ALIGNMENT
> I call out-of-alignment "major" the workpiece is cut by the entry (down) teeth, but contacts the plate of the saw before being cut by the exit (up) teeth.
> Math: The fence is out of alignment by an amount greater than [(thickness of teeth minus thickness of plate) (divided by 2)], over a distance of a little less than 10". The distance from the entry teeth to the exit teeth. The distance will vary depending on how high the blade is raised.

>> MAJOR #1 - INFEED END OF RIP FENCE MAJOR CLOSER TO ENTRY (DOWN) TEETH:
> The entry (down) teeth start cutting the workpiece, but the workpiece contacts the plate of the saw blade on the side away from the fence before it reaches the exit (up) teeth. The plate of the sawblade will push workpiece away from the fence.
> The resulting cutpiece may be curved. The exit (up) teeth may kick the workpiece up, and possibly kick back.

>> MAJOR #2 - OUTFEED END OF RIP FENCE MAJOR CLOSER TO THE EXIT (UP) TEETH:
> The entry (down) teeth start cutting the workpiece, but the workpiece contacts the plate of the saw blade on the side nearer the fence before it reaches the exit (up) teeth. The plate of the sawblade will push the workpiece against the fence and pinch it between the plate and the fence.
> The workpiece will either be stuck at that point, compress and continue thru the blade, burn, kick up, or kick back. All are "not good" The resulting cut piece may be parallel, but will probably be damaged by saw teeth marks, or by operater teeth marks where the kickback hit him in the mouth.


Sorry for the long, boring dissertation.

- Lonnie

[Bruce Cohen]

Lonnie,

Thanks for the english translation of your previous post. I believe I got it!!

So I guess that .001 "out of alignment" is OK?

Bruce

BTW, I believe Macs crash way more than Wintel boxes.

[Wood_workur]

Can I switch saws with you?


and yes, Macs do crash a lot... Just look at Kansas

actually, my PC doesn't crash when I reformat it every 6 months...

[Bruce Cohen]

Hey Alex,

NO!!

But could explain the "Kansas" bit.

Bruce