Primary bevel not parallel with factory grind

[Thomas Kila]

I'm using Shapton Glass Stones and a Veritas Mark II jig to sharpen my plane blades. When sharpening my primary bevel, I notice that it (the bevel) is not parallel to the factory grind. It seems as if the blade is not set at 90 degrees to the jig, but I am using the jig as per instructions and even double check it with an accurate square. I'm not sure what I'm doing wrong. How important is it for the primary (or secondary) bevels to be totally parallel to the factory (25 degree) grind?

[Rob Luter]

I've found the same thing. One of the problems with a high degree of precision and mirror finishes is that any error at all is magnified. In the end it doesn't matter. When I noticed the same thing I just made sure I worked the "new" primary bevel (I use 30 degrees on bevel down planes) back into the 25 degree factory bevel a bit, then created a 31 degree secondary bevel that was parallel with the primary I just ground. The wood never knew the difference.

[Alan Turner]

On a bench plane, and many block planes, it is probably not critical that the cutting edge be exactly 90 deg. But on a shoulder plane, this is quite important as there is little room for adjustment. I don't have a comment on why yours might be off, but I would be less concerned about where the factory grind is and more concerned about whether the cutting edge is at 90 deg. to the sides. Perhaps the factory grind was off a bit?

[Rob Luter]

Good point Alan.

I use a LV medium shoulder plane, and the blade adjustments can take care of minor deviations in perpendicularity.

[Derek Cohen]

Check that you are applying equal pressure on each side of the blade via the screws. It is a common error to apply more to one side than another - this causes the blade to tilt slightly, and grind off square.

Regards from Perth

Derek

[Dave Anderson NH]

In addition to the excellent suggestions from Alan and Derek you might want to check one more thing. Not all plane irons are parallel along their long sides. Some taper slightly and even a .032" to .062" difference in width between the top and bottom of the blade will cause the difficulty you are describing. This lack of parallelism is most common on older planes but I've also seen it on some of the current offerings. You can check this out two ways. First is to use dial or digital caliper to measure the blade width at the top and again at the bottom. The second is to put a combo or engineers square across the bottom and up one side and then reverse and do the other side.

[Thomas Kila]

Guys,
All great points. Thanks again. I'll try the suggestions offered and let you all know how it turned out.

[John Guarino]

Yes, you are likely to find non-parallel sides.

In many cases, you don't need parallel even if you want to sharpen perpendicular. For bench planes, no matter whether the sides are parallel, just sharpen your blade perpendicular to one of the sides. Scribe a mark into that side as it will be your reference. You need not make the sides parallel. Just work from your reference side every time you sharpen. Deviation in the other side does no harm. You have the geometry you need.
If you do need the sides parallel (shoulder plane is an example), a quick way to check is to use an engineer's parallel. Run it along one side to see if the blade is uniform width along its length. If yes, then the sides must be parallel. If the width varies, scribe or mark the uneven areas with felt tip marker. Stone away the ink and you've got parallel.

[Thomas Kila]

Using my Veritas Mark II jig, I've found it somewhat difficult to tighten both screws using equal pressure. On top of that, I noticed obvious differences when engaging the micro-bevel feature. I've since switched back to the Eclipse (?) jig used by David Charlesworth and have had no more problems with the edge not being parallel.

However, I do appreciate all of the above suggestions. It's good to know that it is not at all uncommon for plane irons not to be parallel along their sides. Thanks again, Creekers!