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This thread has me intrigued. Using just an engineer's square, when aligning the table to the blade, wouldn't this take care of most of the issue of table alignment?
BPR

This thread has me intrigued. Using just an engineer's square, when aligning the table to the blade, wouldn't this take care of most of the issue of table alignment?
BPR

ryanbp01 wrote:This thread has me intrigued. Using just an engineer's square, when aligning the table to the blade, wouldn't this take care of most of the issue of table alignment?
BPR

Well, last weekend I gained a new appreciation for accurate alignment. I had aligned my table with the rod-in-the-miter-gauge technique, per the SS manual, and assumed that I was good. A few weeks ago, I bought an inexpensive dial indicator, but had not rechecked the alignment with it. This thread motivated me to do so, and I measured the blade-to-table misalignment at about 0.007". Gotta be good enough for woodworking, I figured.

As for the rip fence, I clamped it on so that it's edge was directly over the edge of the miter slot, and confirmed by sight and feel that there was no discernable misalignment. I figured that should be accurate to better than 0.005". Good to go, right?

Later, I was ripping a fairly short length of 2x4, with poor results. The motor was loading down when the workpiece passed the backside of the blade. Worse, I got a bit of "chatter", along with some very noticable score marks (several per inch), that were obviously made by the backside of the blade on the upcut.

So I decided to check the blade-to-rip fence alignment directly, using dial calipers in depth-gauge mode, and found that the fence was 0.010" closer to the back of the blade than it was to the front. That still didn't seem excessive to me (for wood), but as a test I realigned the rip fence parallel with the blade.

After realigning, the cuts were perfect. No motor loading, no chatter, and a nice smooth finish on the workpiece. Now I'm a believer.

I do believe that it would be difficult to align the table and fence that accurately without an indicator.

BuckeyeDennis wrote:...
Later, I was ripping a fairly short length of 2x4, with poor results. The motor was loading down when the workpiece passed the backside of the blade. Worse, I got a bit of "chatter", along with some very noticable score marks (several per inch), that were obviously made by the backside of the blade on the upcut.

So I decided to check the blade-to-rip fence alignment directly, using dial calipers in depth-gauge mode, and found that the fence was 0.010" closer to the back of the blade than it was to the front. That still didn't seem excessive to me (for wood), but as a test I realigned the rip fence parallel with the blade.

After realigning, the cuts were perfect. No motor loading, no chatter, and a nice smooth finish on the workpiece. Now I'm a believer.

I do believe that it would be difficult to align the table and fence that accurately without an indicator.

And then there's the school of thot whut says to use results to get results. When I get tired of the micrometer I revert to 'results' mode. Turns out it's faster 'cause I worry about blade runout and all that jazz.

Loosen & snug three of four table bolts so to move it requires a 16-32oz Fine Alignment Device (FAD). Eyeball it parallel, whack where necessary with FAD. Run a test piece as above. Whack where necessary.

Opinion: If your test piece is, say, 3/4" x 4" x 20" and you rip off a 1/8"strip {(for half length- safer), and then flip it end-end, set to cut only 1/16} and run it through again, if you hear the same contact noise as it passes the blade "front" as you hear when it passes the "rear" teeth, your blade is perfectly parallel, no?

Then you've got half the difference between blade teeth and blade plate to play with "perfect" vs clearing the "rear" teeth. This removes wobble, miter slot variations, micrometer mounting imperfections, phase of the moon and last night's supper as potential error sources.

Repeat until whacking not necessary, tighten, a bit at a time, three bolts in sequence. One minor grunt at a time should do it. Test after each grunt.
If still no whacking needed apply major groan to all bolts, last test.

[the usual obvious "assumptions" are assumed]

dusty wrote:Are we really becoming addicted to the computer that bad? I don't think so. I certainly hope not.

There is a thing called long division. It is done with a piece of paper and pencil.

The answer (provided by my computer) to your question , however, is 1/64th = .015625.

Howabout "short" division(s)?

by halfs--

half = .500
(500 thousandths)
quarter = half that or .250
{250 thou}
eighth, half 25 or 12-1/2 (.125)
{125 thou}
1/16, about half twelve or 6 (.06)
{60 thou}
one thirty-second just happens to be about 32 (!) (.03125)
{31 thou}
and half that is about 15-1/2 or .015625
{15 th}

keakap wrote:Howabout "short" division(s)?

by halfs--

half = .500
(500 thousandths)
quarter = half that or .250
{250 thou}
eighth, half 25 or 12-1/2 (.125)
{125 thou}
1/16, about half twelve or 6 (.06)
{60 thou}
one thirty-second just happens to be about 32 (!) (.03125)
{31 thou}
and half that is about 15-1/2 or .015625
{15 th}

Yeah, that works real well. What hurts my ego is that back when I was doing this every day, those numbers came to me without thinking. Now, I gotta double check and I write a lot of notes so that I can see what I am thinking.

[quote="JPG40504"]...As for degree of accuracy needed, we be cutting wood fer crying out loud!(Unless refurbing a Chris Craft:D)* Not a stable absolutely straight, flat workpiece anyway.

Still perfection is a lofty goal(prone to oft repeated frustration:eek: when taken to extreme IMHO]

Browsing, came across an interesting article on this subject in an old Fine Woodworking, Issue 24 of Nov/Dec 1980, P. 68-71.
The author, Allan J. Boardman ("an aerospace systems engineer and lifelong amateur woodworker"), makes good points on both sides. Many or most of them have been raised here at one time or nuther, but he adds some eye-opening numbers, measurements and statistics (of sorts) that refocus the issues. The article is "On Precision in Joinery, How close is close enough?"

Consider the miter joint. He constructs one of 3" material that is tight at one end and open 1/64 (.016) at the other. Aint no beeg ting, bro. Sure one can clamp it a little tighter and make a closed joint. But internal stresses aren't happy. Long and short of it is, some months or years later this could blow apart, and be incorrectly blamed on any number of possible causes.
1/64".

Et cetera.

dusty wrote:Yeah, that works real well. What hurts my ego is that back when I was doing this every day, those numbers came to me without thinking. Now, I gotta double check and I write a lot of notes so that I can see what I am thinking.

Ah, ya got me!
On the beam of my caliper is written the decimal equiv. of 1/16, 1/32, 1nd 1/64.
:-(

One more observation on blade to table:
quick check, using the micrometer, blade parallelism .002. Happy.

Blade runout .010. Not so Happy.

At first. Then I remembered-

turn on, up to nominal speed of 3450 rpm, visual runout at speed observed at approximately 10 to 15% of static, or, in other words, Happy once more.

Also, I did have the manufacturer's 'stabilizer' disc attached originally, and my guess is that it handled about half of the runout, -- static that is, I didn't check running. Runout w/ stabilizer at speed is likely negligible.

["static" is either stopped or rotating at 250rpm, for visual.]

As I read this, I wonder if the table loses it's relative "reference to square" with the blade not only because of the base is moved and there by it sets on a different (and possibly varied) section of the floor, but also

could the bolts that hold the table become stretched and lead to premature loosening and or deflection?

Too cold to be in the garage so I am lazing around in bed in the mornings which allow my thoughts to wonder more than usual. Yes that IS scary!

Anyway, decades ago when building race engines we would reinstall everything with a thread, every time that threaded piece was removed. A company called ARP had an interesting article regarding torquing and stretching the bolt (rod) which distorted the threads. I remember being amazed at just now much distortion and deformation would occur at low torques (40 foot pounds)

Therefore, could repeated loosening tightening of the bolts that hold the table increase the possibility (and probability) of the table losing it's setting? There might be some thought about the deflection of the table adding to that, but that was way too much for this old fart mind to deal with so early in the morning!

Just curious.

Be well,
Ben