14 Set Up and Maintenance
Compared to other machinery, the planer does not generally require a lot of set up, unless the factory adjustments are out of alignment. Once properly set, these tend to stay in alignment. Changing the knives is the most common maintenance task the planer requires.
Changing the knives
Planer knives are either straight knife, indexing, or carbide insert. For changing indexing and carbide insert, the procedure is the same for jointer knives of the same style.
There are several methods of securing and adjusting straight planer knives, if possible refer to the machine manual for specific instructions. In general, straight knives are secured using gibs and gib screws in a fashion similar to jointer knives. The cutterhead in a planer may use springs or jack screws to assist in locating the knives at the correct height in the cutterhead. In contrast to the jointer, the planer lacks a reference surface (such as the outfeed table) to use to set the knives. Most planers come with a knife setting jig that is used to properly locate the knives, particularly if they use a spring. The jig rests on the cutterhead, and has a stop at a set distance that that knife references. Some jigs are magnetic, the knife is held by the magnet at the correct height while the gib screws are tightened.
The procedure for removing planer knives is the same as removing jointer knives. Remove one knife at a time and install the new one before continuing on to the next. Ensure the new knives are free of burrs, use a fine waterstone to remove them if required. The knife should be wiped clean of oil or grit before installing. When tightening the gib screws, snug up the end screws first, then the centre, then the intermediate screws while alternating left and right sides. Once they are snug, tighten them in two or three steps in the same order. This method helps keep the blade from shifting during tightening.
Once the new tooling is installed, run a test piece to ensure the machine is operating correctly.
Checking the alignment of the table to cutterhead
There are some adjustments that should be checked with a new machine. The cutterhead should be exactly parallel to the machine table so that the material being planed comes out the same thickness regardless of where it is run along the cutterhead. To check this, run 2 narrow pieces of stock, about 25 mm wide, on the far left and far right side of the table. Measure each with vernier or digital calipers, the thickness should be exactly the same. If it is not, the table needs to be aligned with the cutterhead. You can also use a dial indicator mounted to the machine table and measure the distance to the cutterhead on each end. Ensure that the indicator contacts a smooth portion of the head, partway between 2 of the knives. Adjust the height of the table so the tip of the indicator engages the roller and the dial rotates a few times. Zero the indicator, then measure at both ends of the cutterhead. The dial should read zero on both ends.
Adjustments to correct any discrepancies will vary depending on the exact planer. In general, the adjustment is made by raising or lowering one side of the table. Whenever possible, refer to the machine manual for detailed instructions. Most tables are adjusted by turning the jackscrews (or bushings they are housed in) that the table moves up and down on.
Infeed and outfeed roller adjustments
On most planers the pressure the rollers exert on the workpiece is maintained by springs at each end. On some planers, this can be adjusted. If the material is difficult to feed into the machine, the spring tension on the infeed roller may be too high. Before adjusting the tension to correct for feed problems, ensure other causes have been eliminated, such as a dirty table causing excess friction, dull tooling, or the material binding on the chip breaker or pressure bar.
Locate the adjustment for the infeed roller tension. It will be at the end of and directly above the roller. If the stock is jamming, back off the tension. If a serrated infeed roller is leaving imprints on softer woods, back off the tension. If the stock is not being carried through the cutterhead the rollers may be slipping from inadequate tension, and should be tightened.
Bed roller adjustments
On stationary and industrial planers, bed rollers reduce the friction and allow the stock to feed easily though the machine. They should be set a few thousandths of an inch above the main table. If the planer is sniping excessively, the most likely cause is the bed rollers are set too high. The rollers should be set to the same height at both ends of the table.
Alignment and height can be check by using a dial indicator.
- Set the dial indicator so the tip is pointing down and can touch the machine table.
- Zero the dial indicator on one end of the machine table near a bed roller.
- Move the dial indicator to measure the height of the bed roller at the top if its rotation. Rotate the roller and observe the needle. It should deviate not more than a few thousandths of an inch. If it does, it is out of round, has a bad bearing or is bent. Note the height of the roller above the table.
- Measure the other ends of the rollers using the same procedure.
The rollers should be at the same height, and no more than a few thousands of an inch above the table. If required, adjust the rollers. They should be set at the lowest possible height while still projecting above the table. On most planers, the rollers are adjusted by loosening a screw and locknut underneath the table. Adjust and re-check the roller heights.
Checking the extension tables
The extension tables should be in alignment with the main table that supports the work under the cutterhead. If they are high, they can cause sniping, if they are low, they are not adequately supporting the work as they are designed to. The extensions tables can be easily adjusted if needed. On stationary planers, the wings are usually bolted to the main machine table. To check for alignment, lock out the machine and lower the table. Place a reliable straight edge across the table surfaces (main and extension) and look for any voids under the straight edge.
To adjust, loosen the bolts just enough that the table will move with a light tap with a soft face dead blow mallet. If the bolts are too loose, it will be difficult to tighten them without the extension table shifting. Use the mallet to move the table into alignment and re-tighten the bolts. If just one side of the table needs to move, it is often easier to loosen just one side and adjust.
Cleaning and lubricating the tables
The most common reason for feed problems in a planer is excessive friction, usually caused by a dirty table and bed rollers that may be contaminated with pitch. If wood with pitch is being planed, small wood chips can get stuck to the bed rollers and cause marking of the surface of the wood as well as causing the workpieces to stall in the machine.
Use mineral spirits and fine (400x) wet dry sandpaper or an abrasive rubbing pad such as a green Scothchbrite™ to remove the contaminants. Wipe with a clean rag, and apply a generous coat of paste wax to the entire machine bed. When wet wood is planed, there is a tendency for it to get stuck in the machine due to higher friction. Rub a block of paraffin wax on the table after every few passes to help keep the material feeding smoothly.