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I am just posting this to pass along the info. On the plans it says that the form needs a 3/32 radius relief hole near the flanges and leading edge. I looked online and couldn't find whether drill bits are in radius or diameter so I assumed that drill bits are in radius. I basically used a 3-32 drill bit as a file in the drill press and ended up making it perfect like the picture on the plans. I then started making my other block using that one as a template and noticed that the hole is too small for the router bit.
I then called Bob and he said that the radius is equivalent to a 3/16th drill bit and use a 3/16 chainsaw file (in the chainsaw section at Lowes) which worked perfectly. I might do a little more filing and then rerun all the blanks that I have already made. These rib blanks turned out really nice and are all identical.
I ended up making 7 form blocks before I was happy. Some of the problems that I had were:
Took too much MDF off of the trailing edge.
Bumped the form with the router.
Didn't have the router bit low enough and chewed up the form blank.
When I finally made the perfect form blank, I put the mylar over it and the holes were off center.
On the last one where the holes were off center I noticed on the Northern Tools drill press the drill stop shaft was rubbing up against the spring causing the chuck to move, thus off centering the holes.
Took keep the information flowing I will continue to post stuff that doesn't make any sense to help others.
Lessons Learned:
Drill bits are in Diameter
Use a 3/16ths chainsaw file for the relieve holes (didn't see this in any builders manuals or anywhere online)
Bob uses Tin Snips to cut all of his blanks so this thing, so if you are worried about 1/32ths of an inch precision on the ribs, don't worry about it. This plane is built to fit.
I then called Bob and he said that the radius is equivalent to a 3/16th drill bit and use a 3/16 chainsaw file (in the chainsaw section at Lowes) which worked perfectly. I might do a little more filing and then rerun all the blanks that I have already made. These rib blanks turned out really nice and are all identical.
I ended up making 7 form blocks before I was happy. Some of the problems that I had were:
Took too much MDF off of the trailing edge.
Bumped the form with the router.
Didn't have the router bit low enough and chewed up the form blank.
When I finally made the perfect form blank, I put the mylar over it and the holes were off center.
On the last one where the holes were off center I noticed on the Northern Tools drill press the drill stop shaft was rubbing up against the spring causing the chuck to move, thus off centering the holes.
Took keep the information flowing I will continue to post stuff that doesn't make any sense to help others.
Lessons Learned:
Drill bits are in Diameter
Use a 3/16ths chainsaw file for the relieve holes (didn't see this in any builders manuals or anywhere online)
Bob uses Tin Snips to cut all of his blanks so this thing, so if you are worried about 1/32ths of an inch precision on the ribs, don't worry about it. This plane is built to fit.