The Saw Blade Truing Disc is made by Veritas Tools Inc, model number 05T0101. Its function is to reduce saw blade wobble caused by an untrue arbor, but it will also correct for wobble caused by an untrue flange or a warped blade.
I purchased this device to see if it could correct the blade wobble in my early 1960ís Rockwell tablesaw, which is fitted with a 10" Freud 50 tooth, carbide combo blade. The amount of wobble near the perimeter of the blade measures about 0.030" to 0.040", which I consider excessive. In my case the wobble is not caused by run out in the arbor, or a warped blade, but by a tilted flange. The blade itself is close to perfectly flat, but wobbles since it does not sit perpendicular to the arbor centerline.
The truing disc arrived in a plastic pouch with a small instruction sheet and hex key. It is an aluminum plate, 3/8" thick and 4 ĺ" in diameter, with 8 setscrews located every 45 deg near the perimeter, and a center hole for a 5/8" arbor. It is well machined, with a black finish, and one relieved face. You install it on the saw arbor with the relieved face against the outboard face of the blade. The device is made to provide adjustable pressure against the blade via the setscrews, thereby tensioning the blade so the teeth all rotate in the same plane (no wobble). Alignment involves adjusting each of the setscrews while observing a dial indicator (not included) and seeking uniform indication throughout the bladeís rotation.
The alignment procedure probably took about 5 minutes. The instruction sheet was well written. I was quickly able to tension the blade to about 0.001" uniformity.
While I was waiting for delivery I speculated on how it might work. At first I thought the device might work as an "adjustable wedge", installed on the inboard side of the blade, between the flange and blade. Instead the disc installs on the outboard side (on the side of the blade where the nut is), and works by slightly bending the blade to correct the wobble. I had some questions so I emailed Veritas customer service. The following paraphrases our "conversation".
Improved cut quality - The wobble-free blade produces very smooth cuts. This should be no surprise to those already with a true running blade, but in my case I was elated to suddenly see cuts with jointer-like surfaces. A small part of this increase in performance may be due to the disc serving double duty as a large blade stabilizer.
More accurate cuts - More accuracy now possible in setting rip fence distance. Since my fence did not have a direct reading scale, I had to measure from the blade teeth to the fence to set the fence location. The wobble either affected the accuracy of my measurement (as the distance depended on where the blade happened to rest), or it forced me to take the time to rotate the blade to find the nearest point to the fence before measuring. Similar situation on cross cuts.
Kerf is minimized - Blade no longer "dados" itís way through the cut.
Veritas claims - that the blade is dynamically true because it is tensioned into a flat plane while on the saw arbor.Cons
Loss of cutting depth - With the truing disc installed, a 10" blade is left with ~2 5/8" of cutting depth at 90 degrees.
You really need a dial indicator - This is an extra expense. Not a con if you already have one.
Increased setup time - I use a combo blade and so I donít change blades very often. If you do change blades you have to allow a few minutes time to tune the blade each time you change them.
Loss of a true reference surface - This is perhaps the most subtle result of "tensioning", or warping an already flat blade to eliminate wobble. It has a very slight effect on the geometry of the tablesaw. Like the plane of the table and the line of the miter gauge slot, the plane of the blade is a reference surface, as it establishes the blade alignment with the slot and the angle the blade makes with the table. Once you warp a flat blade you no longer have a true physical reference for how the blade is aligned with the table. In my case the blade body now has a slight bow, making the setting of blade angle less determinate. I donít mean to make this a major issue, and it probably has no serious impact for most situations. Correcting less wobble than my 30 or 40 thousandths might result in a barely detectable blade reference surface distortion.Summary
The Veritas Truing Disc is a relatively inexpensive device for virtually eliminating wobble in a tablesaw blade. Itís possible that circular saws, miter saws, radial arm saws, etc would also benefit from this application but a careful checking of clearances would be in order. I am very happy with it as it certainly improved the performance of my tablesaw. Should you get one? Iíll offer this judgement: If your wobble is much beyond mine then perhaps the root cause should be addressed instead. If the wobble is between 10 and 40 thousandths then using the Truing Disc may be a good idea if your normal workload does not require cuts in excess of 2 5/8". Correcting wobble less than 10 thousandths probably becomes a function of how well tuned an operator desires to have his/her machinery. I would not expect a great deal of performance improvement by correcting wobble that is already less than 2 to 4 thousandths.
I purchased the tool from Lee Valley, price was $26.96 including shipping.