How to minimize blowout using miter lock router bit? - Woodworking Talk - Woodworkers Forum
 
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post #1 of 7 Old 09-14-2020, 08:08 AM Thread Starter
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How to minimize blowout using miter lock router bit?

I just got my miter router lock bit. I tried it 3/4" plywood and it basically tore out everything instead of a nice cut. I even tried two passes and it's better but still unusable. This happened on the vertical passes. The horizontal pass looks much better and it useable. Are there some techniques to use this miter lock bit so that it minimize this blowout? Second, does this miter lock bit can only be used with certain type of wood? I tried this with a 7 ply plywood. Should I use it with a higher ply plywood boards?
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post #2 of 7 Old 09-14-2020, 09:20 AM
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Several reviews mentioned the bits they received were dull. When it comes to cutting tools, there is what appears to be sharp and then there is SHARP.

The instructions in the ad call for backer boards, presumably to reduce tear out? "Use double-faced tape to fasten the scrap pieces to all of the ends of the workpieces at once. Make them about an inch longer at each end for good stability."

Take care,
Dave McCann
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post #3 of 7 Old 09-14-2020, 09:29 AM
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Routing plywood is never fun.

If you can, locate the exact line across the face and prior to routing scribe a line.

Robert
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post #4 of 7 Old 09-14-2020, 10:02 AM
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Quote:
Originally Posted by charlielo View Post
I just got my miter router lock bit. I tried it 3/4" plywood and it basically tore out everything instead of a nice cut. I even tried two passes and it's better but still unusable. This happened on the vertical passes. The horizontal pass looks much better and it useable. Are there some techniques to use this miter lock bit so that it minimize this blowout? Second, does this miter lock bit can only be used with certain type of wood? I tried this with a 7 ply plywood. Should I use it with a higher ply plywood boards?
I picked up a similar yonko router bit about 9 months ago for a speaker build. I had the exact same issues using it on baltic birch plywood. I found that a backer board helped but didn't eliminate all of the tear out. I had the best results routing the boards out while they were a bit long and then cutting them to final length after I finished the miter locks. I didn't grab a picture of the boards after they were routed but you can see in the picture of the glue-up that almost every corner had a significant amount of tear out. Luckily this was a project that I ended up painting so a bit of bondo and a lot of sanding took care of the rough routing work.

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The same baltic birch plywood I used routed very well for other processes, just not the miter lock corners. I had some relatively thin speaker grills that I routed out of the same baltic birch. I ended up having 5 different different passes on these grills. Two flush trim cuts, one large round-over on the exterior, a 45 degree bevel on the interior and a 3/8" rabbit on the back side. You can tell on the picture that my routing skills definitely need some work but you can see there isn't very much tear out, even where the 45 degree bevel routing path intersected with the 14 holes I counter sunk to mount magnets there is very little tear out.

I haven't tried this bit yet on anything other than plywood. I'd be interested in knowing if there are some additional tricks to making this bit work better or if it simply comes down to these cheaper bits not being as sharp and not cutting as cleanly as the expensive bits.

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post #5 of 7 Old 09-14-2020, 11:41 AM Thread Starter
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Quote:
Originally Posted by Dave McCann View Post
Several reviews mentioned the bits they received were dull. When it comes to cutting tools, there is what appears to be sharp and then there is SHARP.

The instructions in the ad call for backer boards, presumably to reduce tear out? "Use double-faced tape to fasten the scrap pieces to all of the ends of the workpieces at once. Make them about an inch longer at each end for good stability."
What are some good brands that are SHARP?
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post #6 of 7 Old 09-14-2020, 11:44 AM Thread Starter
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The issue I'm having is not the blowout at the back. It's the whole thing if I do a vertical. Face down on the router table seems to be fine. One more thing, does the speed of the router bit matter? I think I put it on the low end.
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post #7 of 7 Old 09-14-2020, 01:04 PM
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I just bought a Freud Drawer Lock bit (the straight version, not the miter version). Right out of the package using for the first time I had a lot of tear out all along the vertical cut in Baltic Birch ply. The next piece I fed very slowly and it reduced the tear out but didnít eliminate it. Very disappointed with this bit. The cut with the BB flat against the router table was fine.

The max RPM for my bit (as per the package) is 16,000 and I have my router set to it. So not a speed issue.

Last edited by Tom-G; 09-14-2020 at 01:08 PM.
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