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4" Byrnes Thickness Sander
By: Phil Krol
Wheaton, Illinois

Jim Byrnes now offers a thickness sander in addition to his 4 inch table saw and draw plate. As with the saw, I have been given the opportunity to review the sander and put it through its paces.

The sander is constructed of heavy aluminum plate fastened with socket head screws and weighs in at 24 pounds. This hefty weight is contained in a compact foot print of 9" x 9" at the base and is 12" tall. The drum is made from solid aluminum rod 2 1/2" in diameter by 6" long and bored for a 1/2" precision machined steel shaft for a tight fit and is pinned to the drum for added security. This rotates in heavy duty sealed bearings designed to take the lateral pressures from sanding and are fitted to 1/2" thick aluminum supports. These are fixed and not adjustable to assure absolute flat sanding results. A 1/4" thick plate across the front of the drum supports braces the assembly for extreme rigidity which is a welcome attribute on a sander. A milled recess on the supports and across the brace plate top accommodates an aluminum dust cover. This is fitted with a receptacle for a standard 1 1/2" vacuum nozzle and is fastened to the sander with 4 thumb screws. In operation this provided virtually dust free collection.

The table is 6" wide by 8" long by 3/8" thick and pivots in the front on 2 heavy tabs fastened to a 1/2" thick base. The table tension is controlled with 2 springs and is adjusted with a knurled and calibrated 2" wheel mounted on a Ĺ -20 screw that raises and lowers the table. Raising the table with Ĺ a turn of the wheel will remove .020" from the wood. The opening between the table and drum at the widest setting can accommodate material up to 1 1/8" thick. The sander is powered with a 1/3 HP continuous duty motor with sealed ball bearings. Machined pulleys on both the motor and drum shafts have flanges that fit matching grooves on the belt.

Much thought has been given to the methodology for mounting the abrasive. No dismantling of the drum from its bearings is required and economical sheet or roll stock is used in lieu of more expensive sleeves. A wedge shaped groove is machined across the length of the drum. A strip of abrasive is wrapped around the drum and the ends are secured in the groove with two 3" aluminum wedges fastened with socket head screws. These draw the abrasive cloth down on the drum for a very tight and secure fit with very smooth operation. The abrasive selected for this machine is 3" wide industrial grade cloth backed aluminum oxide in 2 grits, 80 and 180 with both grits mounted on the drum. If a single grit is desired, then either two 3" strips or a single 6" strip of the same grit could be mounted. The 80 grit is very efficient for removing material but it does leave scratches which are then removed with a couple of passes under the 180 grit, leaving a nice smooth scratch free surface.

Now letís make some sanding dust. For test purposes I started out with a 3/4" x 1 1/2" x 18" long piece of beech and started pushing it through under the 80 grit abrasive. The wood is hand fed by pushing against the rotation of the drum. Large thickness sanders with power feed cost many hundreds of dollars more and are not as well suited to precision dimensioning of model lumber. Pass after pass was made with the beech strip trying to bog down the motor or make something else fail. The motor is up to the task and the over engineered ruggedness of this high quality machine is built to take heavy use. When my test strip got down to approximately 1/32" I wanted to see just how thin I could make it. When further sanding this close to the table, it is a good idea to mount the strip you are processing to a backing board. This will protect the table from unwanted marring should the rotating drum get to close. I mounted the 1/32" x 1" wide wood strip on a backer board with a cross strip glued across acting as a stopper block. Taking several light cuts under the 180 grit abrasive, I was able to get the strip down to .008" thick. It is possible to go even thinner, however, some experimentation would be needed as not all wood species will hold up to this and will begin to disintegrate. Other methods can be employed to hold the wood to a backer. Two sided tape or rubber cement applied to both surfaces and allowed to dry before sticking is effective. Solvent such as acetone or naphtha is generally needed to free the very thin strip from the 2 sided tape as the bond is stronger than the wood when this thin.

For those unfamiliar with operating thickness sanders of this type it is good practice to stand to one side of the sander as the wood is being pushed against the drum rotation. This will avoid being struck by the wood piece should a kickback occur. To assure an even flat surface, it is important to push the wood through at an even rate with no pauses. Otherwise a dip or depression will be evident. This can be removed with additional passes, but you may over process missing the desired measurement. A pusher stick is useful in pushing the wood through. You can also reach around the drum and with your other hand in a seamless motion pull the wood through to finish the last couple of inches. A digital or dial caliper is a useful measuring tool to check your progress. If a batch of the same size is being processed, all the strips should be run through with each table setting. This will assure all the pieces will be exactly the same. I have found that running everything through on a final pass without any table adjustment assures end to end evenness.

In summary, the high quality of materials and build make this sander a pleasure to use and is capable of dimensioning model lumber with uniform precision. The ease and economy of changing abrasive was a welcome change. The pictures show the machine in natural aluminum. The production machines will be anodized black.

The cost of this sander will be in the range of $320 - $340. Pre-cut abrasive strips as described in the foregoing will be available at nominal cost.