When to be concerned about tear-out?

[Randy Klein]

I'm still new to planing and have a question. I've seen several videos (Schwarz, Charlesworth, Cosman) read books and threads here. Here's what I learned:

The process for flattening/smoothing (after the powered jointer and planers) is to flatten with the longer plane (jointer/jack) and then smooth with the shorter plane. I have the LV BU Jack and Smoother.

I've also read that the lower the angle, the easier it is to plane but the chances of tear out are greater. So you increase the bevel angle to reduce tear out.

But do you need to be concerned about tear out when flattening/edge jointing? Or is it really only when smoothing?

It seems ideal to use the smallest bevel angle while flattening/edge jointing, to make the process easier, and accept the tear out that occurs. And then switch to the appropriate bevel angle for the smoother to reduce additional tear out and in the process of smoothing, remove the previous tear out.

[Narayan Nayar]

Since your stock dimensioning is done with power tools by the time you're breaking out your jack, you're moving towards getting the surface finish-ready w/ the smoother. So if you tearout with your jack, you're going to have to take more passes with your smoother to get rid of the typical divots left from tearout. Depending on how bad the tearout is, you may have to take many more passes with the smoother.

As a general rule, as you move towards your smoothers and scrapers, tearout is more and more of a concern. On a lot of hard/figured woods I've worked with, tearout is not just a surface problem, and it can be a long time before a smoother, which takes .001" shavings or so, planes off enough surface to get underneath the tearout.

[Randy Klein]

Depending on how bad the tearout is, you may have to take many more passes with the smoother.

I guess I was under the impression that most tearout is on the order of a few thou. It sounds like what you're saying, that I have the wrong impression. This may be difficult to answer, but is there an average depth of tear-out?

[Wiley Horne]

In my experience, tearout is almost always a problem, even in initial stock preparation with cambered-blade planes, let alone in final flattening and smoothing. Tearout shows that the process is a bit out of control, and tearout usually results in setting a new low datum point, that you then have to plane down to. This is not good when you are trying to maintain a final stock thickness, especially if you started with 4/4 lumber.

In edge-jointing, I have seen it said that tearout does't matter. This is only true if if the flaw lands in the middle of the edge. But if a bit of tearout occurs at the board edge during edge-jointing, one can only hope it lands on the bottom, because such a flaw can only be fixed by filling the resulting hole if it's on your table top. It will make a very prominent flaw when the finish hits it.

The main keys to avoiding tearout are sharp blade, sharp blade, sharp blade, slight relief on the blade edge, and higher angle of attack--in that order. Not pretty sharp--really sharp.

Wiley

[Randy Klein]

In my experience, tearout is almost always a problem,

Given a strong desire to minimize tearout then, should you automatically reach for the higher angle bevel then for everything?

I've read some places that a lower angle produces a better finish than a higher angle. Do you find this to be true? If so, it would negate the automatic reach for the higher angle.

[Wiley Horne]

Randy,

99% of the planing I do is on figured temperate-zone hardwoods. Hard and soft maple, cherry, walnut, birch, often with curly, quilted, or flame figure. Sometimes quartered white oak. The other 1% would be a dense tropical, like a rosewood species, Dalbergia.

For temperate zone hardwoods, I've not seen a case where more than 50 degrees cutting angle was needed. I start with roughsawn mostly, and a typical planing sequence would be,

50 degree woodie jack plane, 6-inch radius camber (approx. 1/16" projection)
50 degree woodie fore plane, 1/64" camber
50 degree woodie jointer or 47.5 degree infill panel plane
47.5 or 50 degree infill smoother, or sometimes 55-degree Clark&Williams smoother, all with tight mouths. I like to use woodie smoothers (Japanese or C&W) for drawer trimming. Also used to use an LN4 at 45 degrees, w/tight mouth, and never had an issue with tearout.

To me, 50 degrees is sort of a mainstream attack angle for cabinetry. Note that in the sequence of 50-degree planing, the deepest cuts are the jack and fore planes, which are substantially cambered and lightweight woodies--so pushing is not an issue. Then you switch to light cuts with the jointer, panel plane, or smoother, and there again, pushing is not an issue because of the light cut.

Might mention that 50 degrees is usually overkill for temperate zone woods, because a 45-degree LN5.5 usually works perfectly well.

As for the look of the surface...never attempted a controlled study of it, but an anecdotal observation is that the depth and gloss that is imparted to the surface seems more affected by the absolute blade sharpness than by any other factor. Having said that, I wouldn't argue with anyone who said that a Japanese plane is capable of the deepest finish, though that may be due in part to attack angle less than 45 degrees.

Getting back to tearout, one other really important factor is the plane having the leading edge of the mouth sitting down on the work, and not in the air. Didn't mention this before because your LV planes will be dead flat, due to LV's recent sole-flattening technology.

Need I say...all the above is just my personal experience and opinion.

Wiley

[Randy Klein]

Wiley,

You answered my question perfectly. Thank you very much.

Those are the same woods I work with, so I hope to have similar experiences...

[Robert Rozaieski]

I'm a little late on this but my experience has been the same as Wiley's. The most important thing to avoid tearout is a surgical sharp iron. Bedding angle is secondary. Before I do my final planing, I do a final honing and stropping, even if I just did the iron yesterday. Oxidation alone from a tool just sitting in a room will begin to dull the edge. Touch the edge up before starting your smoothing and then again immediately before the final few passes so that the final surface is right off the razor sharp edge. Tearout should be very minimal. A little is ok, it shows that the piece was hand crafted. If you want zero tearout and a surface that looks flawless and machined, use a ROS :D .