Three planes with different blade angles
Last week I wrote how having a very tight mouth on a plane prevents tear out. But a tight mouth is just one way to prevent tear-out. This week, let's take a look at a different way to avoid tear out - one that is used all the time: simply raising the angle to the wood of the plane blade.
Suppose you have a shaving and you start bending it up higher and higher. It's going to break. And a broken shaving has no strength. In the picture above, we have a typical Stanley #3 bevel down plane set at "Common Pitch," which is 45° generally considered a good blade angle for softwoods. Behind it is a Norris wooden plane from the mid-late 19th century. Its bevel down blade is set at "York Pitch," or 50° which is pretty usual for wooden planes and recommended for hardwood. Behind that is a Marples hollow from about 1900. Its blade is set slightly higher to 55° or "Middle Pitch," which is normal for molding planes on softwoods. The trickier the wood, the higher the blade angle goes. These angles are really most appropriate for single iron planes. Planes with a double iron can be at common pitch and work great. On molding planes and other planes where a double iron can't be fitted, the higher angle is important, especially since you can't always choose your grain direction when you are molding an edge.
The tradeoff is the higher the blade angle. The more drastically you are trying to turn and break a shaving, the harder the plane will be to push.
There is a very important special case of a very high-angle plane - a very common case. Supposing you angled your blade not at 45° or 50° but at 90° or even 100° Of course a regular blade would just scrap the surface and do very little, but what would happen if you burnished a little hook at the end of the blade?
Scraper plane blades are beveled and then a hook is burnished at the end to cut the shaving.
Cabinet scrapers are hand held, and the blade is sharpened square and then a hook is burnished on one or both edges to produce the cutting edge.
What you would end up with is a very, very short blade at a normal cutting angle (the hook) in which the shaving is immediately bent up and broken by the nearly vertical body of the blade. This is essentially what cabinet scrapers or scraper planes are. And they work wonderfully! Scrapers really have only one drawback. Because the hook is turned by a burnisher, it is easily turned back by use, and scraper edges are just not very long lasting. But the tool itself is the best and most popular way of finishing highly figured wood. A common cabinet scraper is typically held by hand at an acute angle and pushed or pulled through the wood. The hook prevents the blade from digging in. The method is very reliable, although if you have a lot of planing to do it can get tiring. We also stock a scraper plane that holds the scraper at the correct angle and is easier to use. In the following photo, we have two Stanley scraper planes, a No. 81 which like the one we stock, has a fixed angle for the scraper, and a Number 12 1/2, which allows you to adjust the attack angle of the blade. In all these examples, including a hand held scraper, the higher angle requires more pushing force - hence these planes are double handled so both hands can be used. These two scraper planes are meant to be pushed left to right and the blade angle is past 90°.
By the way, the magic of getting a shaving out of a handheld cabinet scraper, or a scraper plane, isn't actually magic. It's learning how to sharpen one consistently. If you are having trouble, I highly recommend a new scraper burnisher that we are stocking called the Accu-Burr. It really makes the process more consistent. The planes mentioned in this blog: (front) Stanley no. 81; (back l-r): Stanley no. 4;Norris;Marples 17 hollow;Stanley 12-1/2.
Next time: toothing irons, and then we finish this up with cap irons.
Join the conversation
05/17/2023 David Lamoureux
Joel, Appreciate this great series on the options for dealing with tear out and difficult woods. I put a 17 degree back bevel on a VMP 11 iron - I use a Veritas MKII guide - and load that iron into a Stanley 605 with a tight mouth. The plane is dedicated to that purpose so it is always ready and have had good results on various hard and soft woods.
05/17/2023 CTEngineer
Finally, the concept of standard, York and Middle pitch demystified - I did not realize that higher pitch was consistent on tools that were sans chip breaker! So, is York pitch or Middle pitch more of an affectation on planes with functional chip breakers? Would it really be needed if the chip breaker were set up and maintained properly?
And, your explanation of how (and why) a scraper works is genius - I get it now! So...are you working on a chip breaker with a hollow-ground tip - perhaps one made of carbide (or with a carbide insert). Does the same concept explain why steel saw blades with a hook tooth grind give superior finish compared to a similar blade with carbide tips where a hook is difficult or impossible to employ?
Finally, I seem to recall some writers that claim to vary the pitch by have a series of blade ground with different bevels or with different secondary bevels. This makes sense only if they are talking about a bevel-up plane as in a bevel-down plane the pitch remains the same. Any benefit would come mainly from one bevel holding its edge longer than another - yes?
Thanks!
05/17/2023 Dave Fitzgerald
Whodathunk that the most boring parts of high school physics would be the most useful.
I totally forgot about back bevels on blades. So next time I will add them in along with toothing blades. Cap irons need to get their own chapter. I also didn't mention that the main reason for an adjustable scraper blade angle - as on the Stanley 12-1/2 is so that you can optimize the cut depending on how much you turned the hook. When I started this series I thought I could cover everything in just one blog entry. Boy was I wrong about that.
05/17/2023 Michael O’Brien
Joel, thanks for another good treatise on planes and angles etc in your series. No matter how much we think we know, we can always find something new in thorough explanations like yours.
Cheers,
Michael
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And, your explanation of how (and why) a scraper works is genius - I get it now! So...are you working on a chip breaker with a hollow-ground tip - perhaps one made of carbide (or with a carbide insert). Does the same concept explain why steel saw blades with a hook tooth grind give superior finish compared to a similar blade with carbide tips where a hook is difficult or impossible to employ?
Finally, I seem to recall some writers that claim to vary the pitch by have a series of blade ground with different bevels or with different secondary bevels. This makes sense only if they are talking about a bevel-up plane as in a bevel-down plane the pitch remains the same. Any benefit would come mainly from one bevel holding its edge longer than another - yes?
Thanks!
Cheers,
Michael