Plunge bit leaves ridge in mortis... - Router Forums
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post #1 of 18 (permalink) Old 03-15-2016, 03:56 PM Thread Starter
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Default Plunge bit leaves ridge in mortis...

Hi all:

I'm trying to make some mortises with a 1/2" plunge bit and it leaves a distinct ridge in the same place every time. By this, I mean that the bottom of the mortis is noticeably smaller than the top.

I thought it was being caused by me trying to do the cut in two passes, but when I tried one, I had the same result.

More experimentation (by making a very shallow cut) suggests that the first 3/8 of the bit cuts about 1/32 less than 1/2". I can't see any obvious damage to it, though.

Am I doing something wrong here? Seems like this should be easy.

Thanks...
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post #2 of 18 (permalink) Old 03-15-2016, 04:00 PM
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Measure the bit diameter...?...top and bottom...?

Also...unplug router, grab bit by the end...any play...?

Nick

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post #3 of 18 (permalink) Old 03-15-2016, 05:10 PM
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Quote:
Originally Posted by Wyomingclimber View Post
Hi all:

I'm trying to make some mortises with a 1/2" plunge bit and it leaves a distinct ridge in the same place every time. By this, I mean that the bottom of the mortise is noticeably smaller than the top.

I thought it was being caused by me trying to do the cut in two passes, but when I tried one, I had the same result.

More experimentation (by making a very shallow cut) suggests that the first 3/8 of the bit cuts about 1/32 less than 1/2". I can't see any obvious damage to it, though.

Am I doing something wrong here? Seems like this should be easy.

Thanks...

welcome to the forums Kyle...
who made the bit???
what style is it...

This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

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Last edited by Stick486; 03-15-2016 at 05:59 PM.
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post #4 of 18 (permalink) Old 03-15-2016, 05:16 PM
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Welcome to the forum Kyle.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #5 of 18 (permalink) Old 03-15-2016, 05:36 PM
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There just has to be a common sense answer to this. I wish I had some common sense.

Kyle welcome to the forum. Knowing these guys here someone will have an answer for you.

Don in Murfreesboro,Tn.

Measure once cut twice and it's still to short.
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post #6 of 18 (permalink) Old 03-15-2016, 06:22 PM
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Welcome to the forum !



Gary
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post #7 of 18 (permalink) Old 03-15-2016, 07:20 PM Thread Starter
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Thanks for the welcomes!

This is a Witeside UD5160 1+1 1/2"x1/2" Carbide Compression Spiral Router Bit bought new off eBay.

I can't reliably get calipers on it because of the design. There's no play. I actually took out out, replaced it and cut a new hole.

It appears that the ridge is created at the transition between the first spiral and the second--as though that first spiral section is cutting 1/32 too small.

Is that feasible? I tend to not like to blame my tools, but the fact that all my mortises transition to a smaller width at exactly the same place is a bit suspicious.

Also, I tried a Freud 1/4" spiral bit (different collet, but otherwise same setup) and it worked fine.

I can clean up the problem with a chisel, but man, I don't want to...

Thanks
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post #8 of 18 (permalink) Old 03-15-2016, 07:39 PM
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All compression bits leave a transitional anomaly on the work.
Change to a straight or up-spiral if you must.
And keep those stabs (cutting increments) to <3/16"/stage.
What router are you using?
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post #9 of 18 (permalink) Old 03-15-2016, 07:45 PM Thread Starter
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Interesting! What's the point of that? Seems irritating.

I'm using a DW618...
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post #10 of 18 (permalink) Old 03-15-2016, 10:12 PM
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It's not intentional; it's the consequence of the grind.
Lots of stress on the cutter during its production (aggravates the condition); it's a miracle
they work as well as they do.
Moreover, the substrate they're used on is usually such that the anomaly is of little consequence (ply-woods).
On close inspection you'll find the transition is a stress riser (high point).
Use a cheap straight solid carbide. Exotics are full of surprises.
If you're using the fixed base you're asking for multi-depth adversity.
Use the 6182.
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