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  • Round overs, chamfers and router bits

    I am pretty new to wood working and have some basic router bit questions.

    I typically use baltic birch but I have not been doing any sort of edge treatment so I want to incorporate this.

    Depending on what I am building I may use 3/8, 1/2 or 3/4 material and I am unsure of which size of chamfer and or round over bits are correct for each thickness of wood.

    Is there a rule of thumb on this?

  • #2
    I don't know that there are any "correct" sized bits other than the chamfer or roundover can't exceed the thickness of the material and result in unintended cutting into it. I usually round over or chamfer just a bit less than the thickness of the wood, based mostly on the "look" I'm after.
    Paul

    Originally posted by stephenmarklay View Post
    I am pretty new to wood working and have some basic router bit questions.

    I typically use baltic birch but I have not been doing any sort of edge treatment so I want to incorporate this.

    Depending on what I am building I may use 3/8, 1/2 or 3/4 material and I am unsure of which size of chamfer and or round over bits are correct for each thickness of wood.

    Is there a rule of thumb on this?

    Comment


    • #3
      I agree with Paul, and also that it's correct only if you say it's correct. While it's true that there are some rules and guidelines for safely and efficiently using router bit it basically comes down to whether or not you like the results you're getting. If you ask 50 Woodworkers what's the correct way to use a router bit you'll get 50 different answers. If you're new to Woodworking and want to help visualize the variety Edge treatments that your router is capable of I would make a bunch of small samples on scrap wood of different size thickness Woods with different size and depth round overs and chamfers.

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      • #4
        Thank you both! That is a big help.

        Comment


        • #5
          You can go for a little bigger roundover than the thickness of the wood - just means you'll be removing material from two panels instead of just one. E.g. if you round over a 1/2" baffle with a 3/4" bit, the roundover will extend into the side panels, but if the side panels are 1/2" as well, they will be thinned out to <1/2" where they meet the baffle.
          Obviously if you over do it you'll thin out the panels of the box too much and make too weak. You could however add some wooden beading inside to strengthen the joints and allow you to thin the external panels to almost nothing.

          Roundover bits larger than about 3/4" can become sketchy on a handheld router - kickback becomes a major safety concern. Larger than that you'll want a router table setup.

          Comment


          • #6
            Click image for larger version  Name:	diy htib.jpg Views:	0 Size:	57.9 KB ID:	1427748 In my opinion, Baltic Birch looks better on the exposed grain edges with a chamfer than a roundover. The way the thin layers look with a roundover doesn't appeal to me. If you're painting them, disregard.

            I made some Overnight Sensations with 1/2" BB sides. I put a 1/4" chamfer on them and liked the results.

            Crappy pic, sorry.

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            • #7
              Thank you everyone. Tomorrow I am going use some scrap and try some different edge profiles with this information.

              Thank you all so much

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              • #8
                Just becareful with the ply and the ends, i was doing something funky and making a panel out of end grain but noticed it will chip the edges easier with the 45deg bevel edge. maybe a way around it is using tape or sacrifical timber, generally it has been smooth sailing.

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                • #9
                  Originally posted by TMM View Post
                  You can go for a little bigger roundover than the thickness of the wood - just means you'll be removing material from two panels instead of just one. E.g. if you round over a 1/2" baffle with a 3/4" bit, the roundover will extend into the side panels, but if the side panels are 1/2" as well, they will be thinned out to <1/2" where they meet the baffle.
                  Obviously if you over do it you'll thin out the panels of the box too much and make too weak. You could however add some wooden beading inside to strengthen the joints and allow you to thin the external panels to almost nothing.

                  Roundover bits larger than about 3/4" can become sketchy on a handheld router - kickback becomes a major safety concern. Larger than that you'll want a router table setup.
                  Hey mate, you talking a hand held laminate trimmer or a proper plunge router? I wanting to try a 1inch bit, but wasnt sure how it would actually go.

                  Comment


                  • #10
                    A proper plunge router, 1200Watts+ with a 1/2" collet.

                    A 1" radius roundover bit is 2.5" overall diameter (1" on each 'wing' plus the 1/2" shank) and IMO it produces too much rotational inertia and gyroscopic effects to safely use handheld.

                    As a general rule of thumb, twice the diameter is four times as dangerous, so a 3/4" roundover bit while being just a little smaller is a fair bit safer (bit still dangerous if incorrectly operated). Start with smaller bits first (3/8" or 1/2" roundover) before moving up to larger ones so you know what you're getting in to and work your way up to a full depth cut in many passes - set a small depth (only removing a couple mm of material), lock the plunge, do a pass, unlock and adjust it a couple mm deeper, lock the plunge, do a pass etc until you are at final depth.

                    The cast aluminium base on many plunge routers won't allow a bit larger than about 1.5-2" overall diameter to pass through, so you'll either need to modify the base or lock the router in the plunged position and have the entire bit stick out below the base. Then make your own additional base to bolt on so the bit is flush with it. Also a good opportunity to make the base a lot larger which gives you more support and control. Obviously the latter is sketchy because if the plunge mechanism becomes unlocked the bit will retract into the aluminium base which would be bad. Do that at your own risk...

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                    • #11
                      Model all of your builds with Sketchup, then you can see exactly how much round over/chamfer you can use without weakening the stability of the joint. IME the best way to do a roundover of more than 1/2" radius is to cut away a 45 degree chamfer first, which greatly reduces the amount of material the router has to deal with. Sketchup will show you how deep that chamfer should be.
                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

                      Comment


                      • #12
                        Lots of good advice here. A couple suggestions would be to use a router table and fence (can even make your own), this adds a lot of control and safety to your routering. Also, don't disregard the speed of the bit, especially if you are getting any burning. Take small passes whenever possible and work your way up to the final cut. Finally, clean and sharpen your bits.
                        Carbon13

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