Cutting dowels using a rounder plane
Details on how to make your own
I use a 20 degree blade bed, to save wood I rotate the bed 20 degree so it's parallel to the top.
Blade used is extra blade for cheap mini plane 40 mm wide, I use it bevel up.
1. Based on the dowel diameter wanted - here 10 mm you need a square of 12x12 mm with the length of the dowel rod.
2. Calculate the entry hole size, length of the diagonal sqrt(12*12+12*12) = 12 * sqrt(2) = 16,97 mm
3. Pick a entry hole size close to the size of one of your forstner drills - here 20 mm is used for the entry hole.
4. Make a block with a height at least 2*10mm larger than the diameter of the entry hole, 2*10mm + 20 mm = 40 mm, about 40 mm wide to accommodate blade width, and 100 mm long. I use birch ply.
5. Mark center of entry and exit hole from the top of the block, this way you leave more wood for the blade holding bolt. 10 mm + radius of entry hole. Entry hole must be to the left of the plane bed.
6. Calculate the height from center line to the tilted plane bed, by using this formula radius * cos(20) - here the entry hole give 10 * cos(20) = 9,387 mm, the exit hole 5 * cos(20) = 4,698
7. Mark the plane bed on both sides of the block and connect the lines on the back. This will tilt the plane bed so blade follows the cone shaped guide hole.
8. Using forstner drill of 20 mm to mark the entry hole to a depth of 1 mm, this help guiding you in the reaming process.
9. Split the difference between entry and exit hole - here 20 mm - 10 mm = 10 mm divide by 2 giving 5 mm subtract from entry hole, 20 mm - 5 mm = 15 mm is the next forstner dill to be used.
10. Drill to half the width (40 mm / 2 = 20 mm) using the 15 mm
11. Drill through using a 10 mm wood drill.
12. Use a round file to remove most of material and a reamer to smooth to a near perfect cone shaped hole.
13. Make a cut from the top of the block to the center of the hole.
14. Using a bandsaw or japan saw cut the bed just below the bed line marked, this will leave room for some shims (small piece of paper)
15. Use the cutoff to block up the block on a drillpress to drill a hole at an right angle to the tilted plane bed.
16. Mark position of blade holding screw so the blade can be moved forward and back.
17. Drill hole for blade holding screw, i you a M8 bolt, and want to tap some threads into the hole, so I use 6,5 mm drill and the 8 mm tap.
18. Tap the hole.
19. Mount the mini plane blade with a M8 bolt and some wachers.
20. Tighten bolt and have a go, first shavings may be coarse.
21. A super sharp blade and adjustment makes it perfect. (Mark the blade block, if you have to remove/resharpen blade to ease readjusting)
Avoid wobble by adding guide blocks to exit - meaning more straight dowels - let gravity help removing shavings.
22. Make 2 guide blocks with the exit hole diameter.
23. With some dowel exiting the exit hole 150 mm, glue one block to the plane aligned with the exit hole.
24. make a spacer board 100 mm wide
25. Put the other block on the dowel, with the spacer board between the blocks and glue board to first and second guide block, make sure the dowel still can be turned.
26. Placing the spacer board above the dowel, will enable you to turn the rounder plane/cutter - letting gravity help remove the shavings.