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Reducing blowout while routing end grain

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  • Reducing blowout while routing end grain

    I've been having problems with blowout while doing some flush trimming on hard maple end grain:



    To prevent it, i've tried:
    • Switching between a 3/4" template bit and a 3/4" shear angle flush cut bit based on grain direction (when not perfectly 90 degrees to grain) and proximity to corner
    • reduce router speed a notch or two
    • trim as close as possible with jig saw first
    • use multiple light passes
    • use climb cuts

    but i still hit it. I have a lot of flush trimming to do on this project and i'm getting tired of fixing blowouts and short on time. Any other suggestions for reducing blowouts? I think i may try picking up a spiral flush trim bit next. Do these eliminate blowouts completely, just reduce the chance of them, or not do a whole lot for the situation?

    Thanks!
    Eric

  • #2
    I would cut with a spiral bit. I have a spiral upcut (not flush trim) that I use for timming endgrain and it helps. I also use a backer board.
    David

    The chief cause of failure in this life is giving up what you want most for what you want at the moment.

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    • #3
      I used to do it with an over-head bearing template bit. I would cut to within 1mm of the line and take the final mm with the bit and backer boards as Crockett mentioned. I never had a problem as long as the bit was sharp?

      I still cut to within 1 mm... but I use a low angle block plane to make the final two passes at this point. From the sounds of it you need them pronto and probably don't have time to develope skill with that method. If you are in a major hurry, you might consider purchasing a 90 tooth blade to get a slick cut and then a little light sanding at that point would get you to the finish line.

      Just curious if you had this happen on other species also for future reference?

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      • #4
        Originally posted by SARGE..g-47 View Post
        I used to do it with an over-head bearing template bit. I would cut to within 1mm of the line and take the final mm with the bit and backer boards as Crockett mentioned. I never had a problem as long as the bit was sharp?

        I still cut to within 1 mm... but I use a low angle block plane to make the final two passes at this point. From the sounds of it you need them pronto and probably don't have time to develope skill with that method. If you are in a major hurry, you might consider purchasing a 90 tooth blade to get a slick cut and then a little light sanding at that point would get you to the finish line.

        Just curious if you had this happen on other species also for future reference?
        Thanks.

        I think instead of the backer board i can alternate between the router and the jigsaw - cut one side of the corner with the jigsaw leaving a large overhang, flush trim it, cut the other side, cut the other side with the jigsaw, then flush trim it.

        The block plane and 90 tooth blade won't work for most of the cases. This particular cut was straight, but the majority of the project is curved.
        Eric

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        • #5
          Originally posted by SARGE..g-47 View Post
          Just curious if you had this happen on other species also for future reference?
          I had problems with walnut too on the same project.
          Eric

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          • #6
            Did you try flipping the piece over to get the grain going in the opposite direction?

            Other than that, I got nuthin'.

            JR
            JR

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            • #7
              Are you routing hand-held, or on a table? Bit choice and grain characteristics aside, I get better results with better control feeding the relatively lightweight workpiece into the spinning bit on a table than trying to finesse a heavier and bulkier hand-held router into the correct position when making a delicate cut like this.
              Larry

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              • #8
                Originally posted by JR View Post
                Did you try flipping the piece over to get the grain going in the opposite direction?
                Yes, that was why i was using both a template bit and a flush trim, so i could flip it over and change directions. I finally figured out the purpose of top and bottom bearings on the same bit!
                Eric

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                • #9
                  Originally posted by LarryG View Post
                  Are you routing hand-held, or on a table? Bit choice and grain characteristics aside, I get better results with better control feeding the relatively lightweight workpiece into the spinning bit on a table than trying to finesse a heavier and bulkier hand-held router into the correct position when making a delicate cut like this.
                  I'm routing on a table, though some of the pieces would be big enough that they could be clamped down and route hand-held.
                  Eric

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                  • #10
                    You might try changing the feed direction. IOW run it backwards on the bit before your final pass.
                    .

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                    • #11
                      What project are you working on? Are you doing the across the grain cuts first? I always cut across grain, with grain, across , then finally with the grain. If this is not possible or if you are only doing the end grain use a backer board.
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                      • #12
                        Originally posted by Black wallnut View Post
                        What project are you working on? Are you doing the across the grain cuts first? I always cut across grain, with grain, across , then finally with the grain. If this is not possible or if you are only doing the end grain use a backer board.
                        I'm working on a rocking horse. The order is somewhat forced - i have to do the joints first, then the perimeter which is all curves. About 95% of the project is flush trimming I have a spiral bit in the mail, and where possible i'm going to cut the pieces a fair bit over-sized and only cut close right before flush trimming that section to provide a little more backer material.
                        Eric

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                        • #13
                          Eric, I do a TON of flush trim work in my wood working, and I used to get blow out and such until I bought a solid carbide 1/2" spiral flush trim router bit, and Haven't had any troubles since. Ease into the cut while supporting with a starting pin, and once bearing contact is made, you'll be golden. Spiral flush trim is definitely the way to go....

                          here's an example...

                          Keith Z. Leonard
                          Go Steelers!

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                          • #14
                            Thanks everyone!

                            I've been using a spiral flush trim bit for the last couple of days, thanks to Holbren for the fast delivery. I discovered with the spiral bit:
                            • It does reduce blowout but doesn't eliminate it. I had one blowout in ten pieces.
                            • It burns less than a normal bit. I went pretty slowly and didn't get a single burn on maple. I did get a little burning on walnut.
                            • The cut wasn't as smooth as using a shear bit, and was no better if not worse than a straight bit. I was expecting to see the opposite.
                            • Under table dust collection is necessary for an upcut spiral.

                            I still have the body to trim and several smaller pieces to go, but things are going better now.

                            Eric

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                            • #15
                              I usually find that if I'm getting burning, it's due to a feed rate that's too slow no matter which bit I'm using.

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