Not sure where the best forum for this post is.
LIke many others here, I'm in the process of making my own version of an MFT top with 20 mm holes so I can use the clamping elements. Mine are just narrow box beams that I'm using on a couple saw horses, a configuration I've decided I really like. They're not as wide as those designed by Ron Paulk, but I like the "split" ability of them, and they are easier to move around.
So, I searched the forum and while I certainly found several threads discussing which bit is bets to use for making the 20 mm holes, I was surprised that I couldn't find any strong opinions which to use (a rarity here!). So I ordered both the Festool 20mm bit as well as the CMT 20mm bit a did a test. Here are the results:
Setup: I used the OF 1400 with the LR 32 setup on a guide rail. I made two holes with each bit in 3/4" baltic birch ply:
Here are the two bits (after use, of course!)
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Here are the holes cut by the Festool bit:
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And here is the underside of those holes. Note that the ply was backed by rigid foam insulation
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Here are the holes cut by the CMT bit:
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And here is the underside of the CMT holes, once again backed by rigid foam
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So the results are pretty clear to me. The CMT bit burned the sides of both holes, was harder to plunge, and caused more tearout on the underside (it's not clear how much tearout there would be if backed by plywood or MDF rather than rigid foam).
I'll be using the Festool bit for worktop holes.
LIke many others here, I'm in the process of making my own version of an MFT top with 20 mm holes so I can use the clamping elements. Mine are just narrow box beams that I'm using on a couple saw horses, a configuration I've decided I really like. They're not as wide as those designed by Ron Paulk, but I like the "split" ability of them, and they are easier to move around.
So, I searched the forum and while I certainly found several threads discussing which bit is bets to use for making the 20 mm holes, I was surprised that I couldn't find any strong opinions which to use (a rarity here!). So I ordered both the Festool 20mm bit as well as the CMT 20mm bit a did a test. Here are the results:
Setup: I used the OF 1400 with the LR 32 setup on a guide rail. I made two holes with each bit in 3/4" baltic birch ply:
Here are the two bits (after use, of course!)
[attachthumb=#]
Here are the holes cut by the Festool bit:
[attachthumb=#]
And here is the underside of those holes. Note that the ply was backed by rigid foam insulation
[attachthumb=#]
Here are the holes cut by the CMT bit:
[attachthumb=#]
And here is the underside of the CMT holes, once again backed by rigid foam
[attachthumb=#]
So the results are pretty clear to me. The CMT bit burned the sides of both holes, was harder to plunge, and caused more tearout on the underside (it's not clear how much tearout there would be if backed by plywood or MDF rather than rigid foam).
I'll be using the Festool bit for worktop holes.