Replies

1. 
   WillGeorge | Dec 03, 2005 09:56pm | #1

   This may sound dumb but may work.. Old trick I learned in the Army for welding (Well, checking first if it was straight)..

   Tie one end of a string or fine gauge wire at one end of the fence..

   Pull it really tight at the other end.... Eyeball or clamp the ends down and measure with 'feelers'..

   Note: DO it in a sort of 'X' pattern.. As in top one end and to bottom at the other end..

   also..

   Wire works better than string.. Thinner the better.. Well, till ya pull it to tight! Wire may also cut into the edge but shoulden't bother anything..

   EDIT:: I NEVER get anything right the first pass.. Dang.. clamp on 'back' side of fence.. If you use both sides of the fence do BOTH sides!

   
   

   ---

   Edited 12/3/2005 1:59 pm by WillGeorge

1. 
   JohnH | Dec 04, 2005 12:04am | #2

   Hi WillGeorge,

   Thanks for your reply. But it appears that I was unclear in my request. I'm not concerned that the fence itself is true. I'm concerned that the tablesaw blade runs parallel to the fence.

   Here's what I came up with in the meantime. Take a piece of stock of convenient length (24" in my case). Choose one end; label it LE for leading end. Get one edge STRAIGHT. Place the straight edge against the rip fence with LE toward the blade and rip a convenient width. Flip the stock edgewise so that the sawn edge is against the fence and LE toward the blade. Move the fence and rip the stock again. Measure the width of the stock at LE and the opposite end. The difference in the widths is twice the error in parallelism.

   Basically, the method is cumulative-error just like testing squareness by sawing successive sides of a square, as shown in the last issue of FWW.

1. 
   BG | Dec 04, 2005 12:32am | #3

   JohnH,
   I answered this elsewhere so I did not want to repeat but this might help. First, square the blade to the miter slot...Second, square the fense to the miter slot. I put a verticle straight edge in the miter slot and bring the heal of the fense flush to the verticle and lock down...now run the verticle down miter slot along the face of the fense and see it its flush...make adjustments as necessary.

2. 
   JohnWW | Dec 06, 2005 03:09am | #6

   I've thought about this for quite a while and I don't believe your method works. 

   A simple way to check for parallel is to use a small, 3" square, block of wood.  Adjust the fence so that the block just touches a tooth on the saw blade at the infeed side.  Then move the block to the outfeed side of the blade and, using the same tooth on the blade, see if the tooth again just touches the wood.  A gap or binding means the blade to fence alignment is off. 

   Also before checking for parallel first check that the face of the fence is straight, on many saws, especially those with plastic faces, they are quite a bit out.

   Also any test of blade to fence alignment is only as good as the straightness of the saw's front rail. If the rail isn't straight then the parallelism will be better or worse at different positions of the rip fence.

   John W.

1. 
   John_D | Dec 06, 2005 04:02am | #7

   Here's another way to test whether your rip fence is parallel to your blade.  All it requires is one edge-jointed board and a straightedge, or two edge-jointed boards.

   One-board plus straightedge method.  Set your fence for a very thin cut, removing very little material.  Referencing the jointed edge of the board against your fence, rip half the length of the board, then stop the saw.  Flip the board end to end (keep the jointed edge against the fence), rip the other end, meeting the previous cut halfway up.

   Then use a straightedge on your newly sawn edge.  If it's convex, the far end of your fence needs to be adjusted closer to the blade.  If it's concave, move the end of your fence away from the blade.  If it's straight, your fence is parallel.

   Two-board method.  Saw two boards as described above, for a total of four cuts.  Then put them sawn side together.  If there's space in the middle, that's concave (move end of fence away from blade).  If the ends rock, that's convex (move end of fence toward the blade).

2. 
   JohnH | Dec 06, 2005 06:42pm | #8

   I think I understand your objection to my proposed method. In an ideal world with perfectly straight fence, rigid blade, ample set to the saw teeth, and zero gap between the workpiece and the fence, then both the front and rear ends of the blade cut the workpiece. Then the saw will rip a parallel edge on the workpiece with its width equal to that end of the blade that is closer to the fence. Non-parallelism just makes a wider kerf, similar to the way cove molding is made on a tablesaw.

   The trouble is in a real world, non-parallelism means the blade is trying to pull the workpiece away from or push it toward the fence. As the workpiece passes along the blade, the sawn edge is not parallel to the fence. In extreme cases, a gap appears at the fence or the blade binds in the cut and the sawn edge is not straight.

   FatherJohn's methods, especially the two-board method are cumulative-error techniques and give a more accurate test than simple measurement.

   Thanks to all who responded!

2. 
   HowardAcheson | Dec 04, 2005 06:22pm | #4

   Here is the low tech, low cost way to align a tablesaw that I learned maybe forty years ago and teach to my students now.

   Make 3/4 x 3/4 x 12" hardwood stick. Drill a hole somewhat centered in one end and insert a brass #8 x 1" round head wood screw about half way. UNPLUG THE SAW.  Raise the blade completely up. Clamp this board in your miter gauge (if you determine that there is some slop in your slot to miter gauge, use a playing card to take up the slop) so the screw head just about touches the blade at the front. Now rotate the blade by hand and determine which tooth is the closest. Adjust the screw in or out until it just touches this tooth. Mark this tooth. Rotate the blade so the tooth is now at the back of the table and move the miter gauge/stick assembly to the back and see if it touches the marked tooth to the same extent. If it doesn't, adjust the trunnion (if a contractor saw) or the tabletop (if a cabinet saw) until it does.

   For a contractor saw, first use a small c-clamp on the rear trunnion and cradle to keep the assembly from moving.  Then loosen the two rear trunnion bolts and one front trunnion bolt.  Slightly loosen the other front trunnion bolt and use a stick to tap the trunnion until the blade and screw lightly touch.  The blade does not move directly around the center so you will need to repeatedly go back to the front of the blade, readjust the screw, and then again measure the back. Be sure to check after tightening the trunnion as the trunnion frequently moves when being tightened.

   For cabinet saws, loosen the bolts that hold the tabletop and tap one corner until things come into alignment.

   The same adjustment gauge can be used to set the fence parallel to the miter slot.  Slide the miter gauge to the front of the table and move the fence over to the screw head and insert a playing card between the screw head and the fence just so you can move the card as it touches both the fence and the screw head.  Now move the miter gauge to the back of the table and see if you have the same feel when you insert the card.  I like my fence absolutely parallel--if you want to have a slight opening to the fence, you can easily estimate the opening by adding a thickness of paper to the card.

   I always show my students with a dial gauge that their adjustments are within .001 - .002.

   You can also use the same gauge to measure blade runout by using a $5.00 feeler gauge.

   Finally, after you are satisfied with the above adjustments, check the position of the splitter to make sure it is exactly in line with the blade.

   Bottom line, there is no need to spend more than the $0.05 for the brass screw.

   Howie.........
1. 
   JohnH | Dec 05, 2005 03:36am | #5

   Hello Howie,

   Thanks for the comprehensive method!