If you’ve had trees removed from your yard, chances are some of that tree was run through a chipper. While one run through the chipper creates a coarse mulch, a second run will smooth it out more, and a third will bring it to a dimension akin to the bags of mulch you can purchase at any DIT big store, large retail store, or landscaping supplies store.
But, if you’re in your woodworking shop and you are using your planer or jointer, chips are not what you are hoping to get. Rather, you’re probably taking a small amount of material, a thin plane, and are doing that to create a smooth face on the board. Chipping is not what you want to have happen.
- Chipping occurs in woodworking when planing a board with dull bit edges or improper feed speed.
- To prevent chipping, planer blades should be kept sharp, and the feed speed should match the capabilities of the machine.
- Chipping can also be caused by incorrect blade depth, wood grain direction, and using improper wood for the project.
We’ve written about planer symptoms in a part article on the subject of planer snipe. This is not uncommon and is really annoying when it happens. We made a few recommendations in that article to help avoid planer snipe, so if you are curious, check it out.
First, though, let’s consider how planers work.
The Workings of Planers in the Woodworking Shop
It’s a power tool with a flat, closed bed, and boards are pulled along the bed by rollers from above and under a spinning blade that removes material. The bed height is adjusted to the amount of material you want removed from the board as it passes beneath the blade.
The bed serves as the measure of flatness to be achieved by the removal of enough material from the board to create a flatness on its face. The effect is to trim boards to create a uniform thickness from end to end.
The blade moves quickly and removes material just as quickly as the board is pulled through the planer along the bed. These are dangerous machines, and all precautions must be taken to prevent injury. Safety goggles should be worn when using it, and make sure your fingers do not extend into the chamber where the cutting takes place. Otherwise, you will lose some skin, if not a finger, as my eighth-grade shop teacher did too many years ago to acknowledge.
In the earlier article on snipe, we defined it as a too-deep cut at either end of the board, creating a slightly thinner beginning and end of the board being planed. More work will be needed to cure sniping, whether it is to run the board through the planer again, using a hand plane to level the area affected, or a lot of power sanding.
We also recently published an article on the different types of planer cutterheads – spiral and helical – and how they differ, how they work, and which is a better choice for a task. Again, if you want to learn more about how planers work and what their cutter heads are like, check it out.
In this article’s case, though, we’re discussing the actual chipping of wood as the board is pulled through the planer and beneath the spinning planer blades.
What Causes Planer Chipping?
Sharp Bit Edges.
Now that we know how a thickness planer works, we can guess what one of the causes of planer chipping. Planer blades, just like any other blade in your shop, work best when it is sharp. You want the bits on the planer blades to be sharp, of course, and with both spiral and helical cutter heads, the bits have 4 edges; when one edge has become dull, it is simply a factor of rotating the bit one-quarter to bring a sharp edge forward for cutting.
Dull bit edges run the risk of causing chipping. Sharp edges will improve your planer performance and lessen the risk of chipping the wood. Both helical heads and spiral heads have this feature – a four-edged bit that can be rotated so that each bit cutting the board will have a sharp edge. Remember – knives dull, as do bit edges, and dull knives and dull bit edges need to be avoided.
Avoid pushing your board faster into the cutting chamber than the planer wants to work. Rollers above the board as it sits on the bed will pull it beneath the cutter head at the proper speed for cutting away the wood fiber and the speed appropriate for the type of cutter head your planer is using – planer knives, spiral cutter heads, or helical cutter heads.
Be patient and don’t rush the board through, or you do run the risk of some chipping or at least an uneven material removal. If you are working with a soft wood, this can be even more problematic. You want wood dust, not wood chips, being sucked away by your dust collector.
Grain Reading, Sort of Like Grain Whispering
For this talent, we give a separate section of its own. It applies not just to planing, but also to cutting, assembly, and finish. Today, though, we’re concerned simply with planing.
The direction and depth of grain in the wood you are planing can also affect the possibility of chipping. Again, we want dust, not wood chips, being drawn away by the dust collector. You can avoid tear-out and chipping by reading the grain of your board properly before you lay it on the planer bed.
Method of Milling Affects Grain
Where a board was cut from a log will determine the grain of the board you are working with, as will the manner in which the board was cut.
Flatsawn Boards. This cut will make it easy to read the grain of the board. The growth rings on a flatsawn board run pretty much parallel to its face. They’ll be curved, and when running the board through the planer, most woodworkers who are also grain whisperers will tell you to “cut uphill” – if you view each grain as a small mountain-shaped line on the board, run the base of the mountain through the planer first, so the cut moves up the mountain. While you will be less likely to encounter chipping, it is not fully guaranteed that you won’t.
Quartersawn Boards. We wrote about quartersawn lumber in a previous article, and if you want to learn this milling technique, you should check it out. The video in that article is pretty cool and shows a milling operation as an oak log is broken down.
Quartersawn is the opposite of flatsawn: the cap is removed from the log, and then it is rotated one-quarter before the boards are cut. The growth rings will run perpendicular to the board’s face rather than parallel to it as in flatsawn boards.
For planing quartersawn boards, read the grain in the opposite way as for flatsawn boards, where we read it on the face. For quartersawn boards, read the edge, and find the lines of the grain. Run the board through the planer with the lines to minimize the chances of planer tearout or chipping.
Recognizing grain and reading it properly will help you in other aspects of a project – cutting (ripping and cross-cutting), sanding, and even using the hand planer. It’s a good skill to master and will serve you well in your woodworking. When it comes to avoiding planer chipping, it’s not always going to work for you, but you increase your chances of avoiding chipping if you take a moment to read the grain.
Soft wood, with its less dense wood fiber, is always at risk of chipping. But, keeping your blades and bit edges sharp, patiently allowing the boards to proceed through the planer at a slow and steady pace, and reading the grains to determine how to run the boards through, will minimize the chance of chipping and tear-out.