Fence alignment question

rlkeeney · Post by **rlkeeney** » Sat May 10, 2014 9:14 am

I'm with Dusty on this. I try to set the fence as close to parallel to the blade as I can get.

From the very beginning having the fence adjusted with the rear offset on a system that lets you use the fence on both sides of the blade seemed like a bad idea.

Then what effect does the fence offset have when it is used for all those other things you do with your Shopsmith that use the fence?

keakap · Post by **keakap** » Sat May 10, 2014 2:42 pm

zooman65 wrote:I have heard numerous people say when aligning the fence to make the outfeed side slightly off about 1/16 from the infeed side. I cannot remember which direction if it is less or more, but my questions is can anyone explain why I would offset the fence rather than keep it perpendicular to the blade?

Instead of trying to remember the specific details understand the basic reasoning. When a piece is pushed into the blade it is cut by (this is an example) teeth that are 1/8" wide. The blade plate is half that, 1/16". So the wpiece has 1/32 of air on each side as the cut moves past the blade. If the fence is perfectly parallel, when the lead of the cut reaches the teeth again, at the rear of the table, it will slide right past with very little contact- not enough to cause a problem.

But if parallelism is off, one side of the cut OR THE OTHER will encounter teeth that are not pushing the wp down "into" the table, but rather up up and away from the surface and "into" the operator.

Mis-aligning the fence 1/16 (a huge amount) "blindly" away from the blade assUMES the parallelism is off in ONE direction, or not at all. But consider: what if the pllsm is off the other way? Guaranteed kickback. What if it's perfect? You'll skate, as long as everything else about the cut operation remains perfect.

And what about the "waste" side? If parallelism is properly adjusted and all else is normal, the cut surface of the waste piece will be as clean as the WP, not trashed with sawmarks and burning. Ready for the next rip, if you're even a little bit lucky.

Having had bad things happen due to wood reaction to being cut I am aware also that the nice clean 1/8 cut that leaves the (front) teeth may not be the same as when it reaches the rear. Reset the smoke detector!

Jmho.

keakap · Post by **keakap** » Sat May 10, 2014 2:47 pm

[quote="JPG40504"]Parallel to the sides of the blade is the ]

I have to disagree. If you have the fence perpendicular to the blade you will never have kickback.

Of course you'll never have a cut, either, but what price safety?

;-)

keakap · Post by **keakap** » Sat May 10, 2014 2:56 pm

rlkeeney wrote:I'm with Dusty on this. I try to set the fence as close to parallel to the blade as I can get.

From the very beginning having the fence adjusted with the rear offset on a system that lets you use the fence on both sides of the blade seemed like a bad idea.

Then what effect does the fence offset have when it is used for all those other things you do with your Shopsmith that use the fence?

Another plus to push for perfect parallelism, perchance, is the idea that if perfect you have half the difference (1/32) between the teeth width and the plate thickness (1/16) to 'play' with per side, so in a perfect world with no wood movement from internal forces you'll have no contact with the teeth at the rear whether fence Left or fence Right. No saw marks from misalignment.

rpd · Post by **rpd** » Sat May 10, 2014 5:12 pm

Matthias Wandel did a YouTube video last fall showing how a misaligned fence affects kickback. Effects of table saw misalignment, and kickback

I like the way he checks the alignement.

dusty · Post by **dusty** » Sat May 10, 2014 5:55 pm

A quick check to verify that the blade is parallel to the fence.

Reference the second and third photos in the link.

edflorence · Post by **edflorence** » Sat May 10, 2014 9:46 pm

JPG40504 wrote:I would think a splitter closer to the fence than the blade would help prevent the workpiece getting caught between the fence and the blade, however, it would tend to bind the workpiece between the splitter and the fence.

Again dead on is the goal!

Agreed...fence parallel to blade is what is needed...I mentioned the 500 splitter because I had to shim mine to get it lined up with the blade...it wasn't that the entire splitter was closer to the fence ...sorry if I gave that impression...what was happening was that when locked down the plane of the splitter would wind up skewed to the plane of the blade, and thus also skewed to the face of the fence, making the infeed and out feed ends of the splitter at different distances from the fence. This caused pinching and burning but thankfully no kickbacks.

I used a couple of washers as shims to keep the splitter in line with the blade.

JPG · Post by **JPG** » Sat May 10, 2014 10:02 pm

edflorence wrote:Agreed...fence parallel to blade is what is needed...I mentioned the 500 splitter because I had to shim mine to get it lined up with the blade...it wasn't that the entire splitter was closer to the fence ...sorry if I gave that impression...what was happening was that when locked down the plane of the splitter would wind up skewed to the plane of the blade, and thus also skewed to the face of the fence, making the infeed and out feed ends of the splitter at different distances from the fence. This caused pinching and burning but thankfully no kickbacks.

I used a couple of washers as shims to keep the splitter in line with the blade.

That makes much more sense. Details('UNCOMMON PLANE') will do that!;)

reible · Post by **reible** » Sun May 11, 2014 1:11 am

I try to keep the fence with in .005" and so far that seems to work out well with using the fence to either side of the blade. Often the adjustments allow for .003" but I don't think I have ever managed a perfect .000" and I doubt that is required.

Ed

JPG · Post by **JPG** » Sun May 11, 2014 9:47 am

reible wrote:I try to keep the fence with in .005" and so far that seems to work out well with using the fence to either side of the blade. Often the adjustments allow for .003" but I don't think I have ever managed a perfect .000" and I doubt that is required.

Ed

I question whether the sides of the fence are any closer to parallel with each other.