This unusual jig is designed for chainsaw-milling “tree cookies”, aka “tree slices” or “tree rounds”. Even if you never need to make tree cookies yourself, some of the jig’s unique design details may provide inspiration for other fixturing challenges. This WoodAnchor™ application amazed even us!
So what possessed ToolQuest to create this thing, you ask? Well, our founder’s youngest daughter was soon to be wed, and he was enlisted to produce tree cookies for wedding-reception table decorations. Cutting tree cookies is just a matter of making some nice flat parallel crosscuts through a log, bark and all. The cookie thickness isn’t particularly critical. So it should be pretty simple, right?
Well, after thinking through the details, it turned out to be not so simple after all. At about 12” in diameter, the logs were too big for most home-shop woodworking machinery. And worse, we couldn’t mill a flat reference surface on them without messing up the tree cookies. On the plus side, we already had a simple Granberg G555B chainsaw mill, and a chainsaw with a 20” bar. But the mill had to somehow be fixtured for making repeated square crosscuts.
Fortunately, we didn’t have to build a jig from scratch. It was a piece of cake to mount a guide board for the chainsaw mill atop our portable WoodAnchor™ fixturing grid worktop, and the worktop itself made a fine platform for holding the logs.
Pairs of 45° wedges, mounted to WoodAnchor fixturing slots in a simple sacrificial sled, solved the irregular-log fixturing problem. They create split-Vee blocks that can be adjusted fit to almost any log, and a hole near the top of each wedge makes a dandy attachment point for tie-down strap hooks. Finally, the sled assembly provides a way to feed the logs for repetitive cuts.
Below, you can see one of the finished tree cookies, arranged with the other table decorations at the wedding reception.
How it works
To mount a log, we first slide all the inner wedges to the outside of the sled, so that they completely clear the log. Then we place the log on the front and back wedge pairs, adjust them to eliminate any rocking, and lock them down. Finally, we slide each inner wedge into firm contact with the log, and lock them down as well. As the log and the sacrificial sled are advanced and consumed, the forward-most wedges are removed. Thus we attach the tie-down straps to wedge pairs near the rear of the log.
The logs used for this project were from a black cherry tree that had blown over a couple of weeks before the wedding. The nice straight 12” diameter section of trunk was destined to be milled into a mantel, so the tree cookies had to be cut from what were basically firewood pieces. No problem -- the picture below shows how the adjustable half-Vee’s can conform to pretty much anything.
The first cut squares the front end of the log. We move the sled forward until the end of the log is fully in the chainsaw’s cutting plane, and immobilize the sled with a couple of worktop clamps. Then it’s simply a matter of sliding the chainsaw along its guide to make the cut – it’s basically like using a track saw on steroids.
To make each tree cookie, we advance the sled by a fixed amount, re-clamp it, and made another cut. As the sled advances, we remove the forward wedge pair just before it reaches the sawing plane. When we come to the last two pairs of wedges, that particular log is finished.
If designing a jig for serious tree-cookie production, a segmented sled could be used, with the individual segments removed before they reach the cutting plane. But a sacrificial sled is just fine for limited use. The one pictured here yielded twenty-three 1-1/2” thick “cookies”, while consuming less than $5 worth of MDF.
The rear ends of the logs didn’t go to waste either. After reversing them to make a squaring cut on their back ends, they made lovely flower and candle stands.
Summary build notes
As you can see in the pictures, the chainsaw-mill guide board is mounted to the worktop on two riser posts. What you can’t see is that the whole guide assembly is attached to two of the worktop’s fixturing slots, using a single ¼”-20 threaded tie rod through the center of each riser post. We constructed each post from two pieces of 2x4 construction lumber. We milled each board square, and then routed a 5/16” wide x 5/32” deep groove along their centerlines. Once the halves were glued up, the grooves formed a clearance hole for the ¼”-20 threaded rod. After glue-up, we cut the risers to final length.
The guide-board assembly goes together quick & easy, and is absolutely rock-solid. WoodAnchor sliding nuts attach to the bottom ends of the threaded rod, and simply slip into fixturing slots in the worktop. The guide board has ¼” clearance holes for the threaded rod, with countersinks on top for washers and hex nuts. The jig breaks down just as easily for storage, so that we can use the worktop for other projects.
A WoodAnchor router slotting guide made very short work of milling the sacrificial sled. MDF mills very easily, so we skipped the pre-slotting step, and the Whiteside router bit still cut the MDF like butter.
By pure coincidence, our half-Vee wedges were also made from black cherry, using ¾” thick cutoffs from another project. We used a tongue bit (from a tongue & groove router bit set) to mill 31/64” thick tongues on the bottoms the wedges. The tongues align the wedges to the WoodAnchor fixturing slots, slide smoothly, and leave plenty of shoulder for vertical registration and load bearing.
The chamfers on the tie-down strap holes aren’t for aesthetics; they’re necessary for the S-hooks on the ratchet straps. A zero-flute countersink bit did a very nice job of forming the chamfers.
The wedges mount to WoodAnchor fixturing slot with a long button-head screw and a sliding nut. In the picture below, you can see the alignment pins that keep the sliding nut properly positioned. We cut the nut-clearance slot into the tongue with a few passes over a 3/8” dado stack. A sacrificial auxiliary fence on the miter gauge, with a stop block clamped on each side to limit the cutting width, enabled us to cut all ten of these slots in just a couple of minutes.
Best of all, there’s absolutely no fumbling around when installing these wedges in a fixturing slot. Just drop the front of the tongue into the slot at the edge of the table, slide the wedge forward, and the sliding nut is guaranteed to engage the slot perfectly.
The WoodAnchor™ advantage
- The WoodAnchor fixturing slots in the Baltic Birch plywood worktop have outstanding load capacity. We tested side loads on the chainsaw guide board that would undoubtedly have pulled T-track mounting screws out of the worktop. The worktop emerged unscathed, the only significant flex we detected during those tests was in the metal stand.
- The fixturing slots in the sacrificial sled were also plenty strong for this application, even though the sled was made of inexpensive MDF. Eliminating metal T-track from jigs frees you to create whatever sacrificial component your fixturing application may require.
- The unique design of the WoodAnchor fixturing slot and sliding nuts enabled a very simple and user-friendly sliding Vee-block design for securing irregularly shaped objects. This fixturing method is directly applicable to virtually any turned part.