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Thread: Climb cuts in ash?

  1. #1
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    Climb cuts in ash?

    ...just don't do it.

    I was helping my nephew build his electric guitar. Today we finally got around to shaping the body, which is 1-3/4" ash. We band-sawed close to the line, then double-taped the template to the body and took it to the router table.

    The hourglass shape meant that some cuts skimmed over the tops of the leaning-away grain, but just as many needed to confront grain rising against the bit. I did all the easy cuts first, and attempted climb cuts with the rest. Small mistake, and then big mistake. I had a few little scares when the big, heavy part skipped a little, but more or less held my own...

    ...until I got to the U-curve at the cutaway part of the guitar. I went a little too far past the bottom of the U, and backed into a big problem: about an inch of borderline blew out in a dangerous instant, leaving 5/8"-long shards sticking out like Lady Liberty's crown. Hard, angry shards. Fortunately, the body and template probably weigh 8 pounds, so I was able to avoid a projectile.

    I went into damage control mode. I decided to do the rest of the trimming to the line with spokeshaves, and so far the results have been better than I expected (hooray: a silver lining here; I've been spokeshave-challenged before this). Also, I actually used a coping saw to whack back the errant shards in the blowout area. We're also going to turn to convex sanding blocks for the curves that are more acute than my curved shave. With those three adaptations we hope to finish the body's edge. And I have given up any dream of using a 1/4" rounder bit to ease the edges!

    But anyway, what is at about ash that just explodes like that against the grain? I have to confess I was using a two-flute straight bit (1/2" diameter, 2" length of cut). I might have had better luck with a compression spiral bit, but even Whiteside's $175 compression bit only cuts 1-1/8".

  2. #2
    One thing that helps ,with all woods, is after the rough band sawing ,use 1/4 inch ,or larger round over bit to climb cut
    the top- side corners and bottom -side corners. Then do the straight bit trimming . Removing the " loose threads" stops most
    tear out. You could also just use some coarse sand paper instead of the round ove bit.

  3. #3
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    I saw a video once where he advised doing the climb cut in very small increments. He placed painters tape in a couple of layers on the template edge so the bearing would ride just proud of the finished cut. He removed the tape layer by layer when doing the climb cut.

    Basically showed that climb cuts in difficult wood is fine, but you need to do it in very light passes.

  4. #4
    How much material were you trying to remove? Cutting as close to the line as possible with the bandsaw helps, but as you know hand guided climbcuts are inherently hazardous. Even 1/16" can cause trouble. A coarse rasp or spindle sander would be useful here (or spokeshave, as you found). I don't think the species is the problem. A bit more time spent on handwork is not a great price to pay compared to wasting the blank or losing a finger.

  5. #5
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    A technique that helps with this issue is to leverage a long cutter with bearings on both ends so you can flip the body blank so as to always be cutting in the best direction and not bucking the grain. It's a series of "stopped cuts" in that respect. If I were not cutting my bodies with my CNC, that's the method I'd likely adopt. And you always want to saw as close to the line as you can. As an alternative to pattern routing the edge, you can also use an OSS to bring the body to final contour.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  6. #6
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    A spiral flush trim bit bit helps too. Whiteside's two bearing compression spiral flush trim bit is sweet, but $$$.
    --Certainty is the refuge of a small mind--

  7. #7
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    The Infinity spirals (compression format I believe) are also very nice....also a big investment, but probably worth it for anyone doing a lot of pattern work.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
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    One more thought...the Robosander flush trim sander works great on tough grain. One year I was making a bunch of hand mirrors for gifts and after I ruined two blanks at the router table, I picked up the robosander. Works just like a flush trim bit using a template, but without the "excitement".
    --Certainty is the refuge of a small mind--

  9. #9
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    Never do climb cuts on the router table, simple as that, unless you have a power feeder. I regularly do climb cuts with a handheld router, however. There definitely is some technique involved when using larger diameter cutters, but it's far safer because you are holding the router and can easily adjust the depth of cut so it doesn't run away with you.

    John

  10. #10
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    Careful work with a spindle sander will get very close so that climb cutting material removal would be minimized. But it is easy to nick the template..

  11. #11
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    There are many species of ash trees. I've machined ash that is brash and brittle, and also just the opposite. I've gotten some that machines like walnut or mahogany. The key to better pattern cutting is using the largest diameter bit you can. Freud makes one that I think is 1 1/4 or 1 1/2" diameter. Machines wood exponentially better than a 1/2". I'll run the pattern work on that large diameter bit, then come back with smaller diameter if the details require it. Of course a large cutter in a shaper is even better. With an extra tall 1/2" bit, you'll get a lot some flex in the bit and that won't help with surface finish one little bit. You can also run on a shorter bit with a bearing on the top of the bit and on the pattern, then raise the bit and run the bearing on the profiled stock to complete the cut. Lots less vibration.

  12. #12
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    Quote Originally Posted by Jim Becker View Post
    A technique that helps with this issue is to leverage a long cutter with bearings on both ends so you can flip the body blank so as to always be cutting in the best direction and not bucking the grain.
    This is what I do. It pretty much removes the problem.

    template bits.JPG
    "The Danish government believes that if we train 5,000 designers, and produce
    one Hans Wegner, the money is very well spent." - Ole Gjerlov-Knudsen

  13. #13
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    Honestly, I did try to take the slimmest of passes. The one that got away from me was a climb cut around a small-radius curve.

    Quote Originally Posted by Richard Coers View Post
    The key to better pattern cutting is using the largest diameter bit you can. Freud makes one that I think is 1 1/4 or 1 1/2" diameter. Machines wood exponentially better than a 1/2". I'll run the pattern work on that large diameter bit, then come back with smaller diameter if the details require it. Of course a large cutter in a shaper is even better. With an extra tall 1/2" bit, you'll get a lot some flex in the bit and that won't help with surface finish one little bit. You can also run on a shorter bit with a bearing on the top of the bit and on the pattern, then raise the bit and run the bearing on the profiled stock to complete the cut. Lots less vibration.
    Richard, I have a 1-1/8" diameter Whiteside bearing bit that cuts 1-1/2" length, and I considered using that. I guess I balked at needing to advance the bit after the first pass, but it would have been considerably more robust than the 1/2" diameter 2" bit. As you imply, there's something to be said about the lower angle of attack with a wider bit:




    But I doubt this alone would have gotten me through the climb cuts. I'm intrigued by the tape layers! Thanks to Phil for that idea.

    As Jim and Glenn say, a single bit with top and bottom bearings can do the job with one template. I do like that idea, but only for work less than the thickness of the cutting length.

    Maybe if there's a next time with 1-3/4" wood, I'll make top and bottom templates and use the 1-1/8" diameter single-bearing bit coming and going, by flipping the work when the grain changes. But we didn't have two templates.

    Live and learn.

    We ended up redrawing the edge profile of the guitar to swallow up the blowout, and I cut the new profile on the bandsaw with a 1/8" blade. There's still lots of edge cleanup to do, but I gave that to my nephew to do. He has time on his hands, it's a labor of love, and it will help him appreciate planes and power tools.

  14. #14
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    This is the image I tried to include with my earlier post.

    cutter diameters 2.jpg
    Attached Images Attached Images
    Last edited by Bob Jones 5443; 12-03-2020 at 3:22 AM.

  15. #15
    " The one that got away from me was a climb cut around a small-radius curve."

    Yes, the one that got away- infamous in fishing and woodworking tales. In a busy shop the one that got away can bring progress to a screeching halt until everyone has recounted their memorable incidents, particularly if the latest one resulted in injury.

    One of my workmates cut his hand rather badly trimming the end of a full size door with a climb-cutting router. It can easily get away even when you think you have it nailed.

    What's the difference between a fairy tale and a fishing story? One begins "Once upon a time" and the other with "This is no s--t".

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