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Thread: Sanding before router edge profiling?

  1. #1
    Join Date
    May 2007
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    Sanding before router edge profiling?

    Greetings everyone.

    In the past I have done the router corner roundovers after assembly but before doing any sanding.

    I recently read that it may be beneficial to so some of the sanding *before* routering the corner round overs.

    Anybody have any thoughts on the matter?

    What grit do you stop at before adding the roundovers? I'm guessing 150 or 180, but wondering what others do.

    Thanks in advance!

    -T

  2. #2
    I try to do the roundovers prior to machine sanding if I can, but sometimes it works better afterwards. I know the grit is probably bad for the router bits, but I use the inexpensive Rockler brand ones for roundovers, so if I have to replace them a litter sooner, so be it.

    I almost never sand past 180, so that is where I stop I normally use film finishes, so no need to go finer. I always do the final hand sanding after routing, so the whole surface is consistently abraded, especially if using any kind of stain or dye since their absorption is affected by surface roughness.

  3. #3
    Making a round-over is sometimes spoiled by the router grabbing a “loose thread”, AKA sharp corner. A little sanding to remove the sharp
    corners can prevent tear-out by the router. But that deposits grit into the wood dulling the bit. I prefer running the router backwards
    ( climb cutting) just some of the depth to remove the sharpness of wood corner. Then run full depth profile , with standard full forward .

    That initial “safety “ cut is done with a round-over bit , regardless of what the finished profile will be.
    Last edited by Mel Fulks; 03-30-2022 at 12:05 AM.

  4. #4
    I was taught to respect your cutting tools and sand last. The reason being that any cutting tool touching a sanded surface will be dulled by the sanding grit left behind.
    Sanding grit will dull a cutting tool surprisingly quickly.

  5. #5
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    I typically only do whatever flush triming and sanding I have to before putting profiles onto a piece and typically at 120. One reason is you will often get some marks from the bearing running on the wood... especially on softer materials, not to mention you might get handling marks from doing the work....I hate to sand twice!

    That said, try it, might work for you... probably won't take long to see which you prefer.

  6. #6
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    If the edge has roughness to it, I'll sand that smooth before routing. I've had ripples transfer into the round over or chamfer otherwise.

  7. #7
    Quote Originally Posted by Frank Pratt View Post
    If the edge has roughness to it, I'll sand that smooth before routing. I've had ripples transfer into the round over or chamfer otherwise.
    Same here. Often I clean up the edge with a hand plane. But it depends on how bad the saw marks are.

  8. #8
    Quote Originally Posted by Edwin Santos View Post
    I was taught to respect your cutting tools and sand last. The reason being that any cutting tool touching a sanded surface will be dulled by the sanding grit left behind.
    Sanding grit will dull a cutting tool surprisingly quickly.
    That's a fallacy. If abrasive grit is embedded in your workpiece, something has gone wrong. S
    Sandpaper doesn't shed it's material like a brake pad. If that were true, you'd certainly see the embed abrasives in your finishes.

  9. #9
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    I almost always sand to shape with 80 grit on the 12" disk sander before routing, but that's because I'm not good enough on the bandsaw to leave a smooth edge that the guide bearing will follow nicely. If I routed first there would be a lot of chatter that would show up in the routed edge. Often I'm routing curved surfaces, so concave edges get sanded on the spindle sander first, then routed. Straight or convex on the disc.

  10. #10
    Join Date
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    I sand everything, top and edges, to P150 or P180 with the RO, then roundover / edge treatment, then last pass with P220.

    I've never heard that sanding will embed grit into the wood. Probably this is advice from before sanders hooked to dust extractors using abrasives with dust holes or mesh abrasives.
    JonathanJungDesign.com

  11. #11
    accurate on the sanding grit. Lots of people in the trade know that and any sandpaper company that has anyone working there that knows their stuff will tell you as well. Nothing new.

    Climb cut first before forward.

  12. #12
    Quote Originally Posted by johnny means View Post
    That's a fallacy. If abrasive grit is embedded in your workpiece, something has gone wrong. S
    Sandpaper doesn't shed it's material like a brake pad. If that were true, you'd certainly see the embed abrasives in your finishes.
    So then what is actually happening when sandpaper wears?
    By design the grit is harder than the wood so it's not like the wood is abrading the silicon carbide.
    The carbide grit must be breaking off with wear like the abrasive in a sharpening stone.
    Or if it IS being abraded, the abrasive is then being turned into smaller microscopic abrasive particles in the same way that abrading wood turns it into dust particles.

    In either case, where does this grit go?
    Last edited by Edwin Santos; 04-01-2022 at 3:44 PM.

  13. #13
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    The same arguments can be applied to metal too. If your saw blade becomes dull the sharp corner at the cutting edge has worn away, and where did it go? Is a smaller amount of carbide embedded in the wood better or worse for a router bit than a potentially larger (but still small) amount of aluminum oxide or ceramic?

    Also, I don't see any reason to suppose that much of the grit that comes off the sandpaper would be embedded in the wood. It seems more probable to my uneducated mind that it would fly off into the dust stream.

  14. #14
    sandpaper is engineered to break down in some fashion. Id think so it keeps opening up a new sharp surfaces. Some amount of that break down gets pushed into the wood. Id think a wide belt would leave more grit in wood as its a constant pressure compared to a stroke sander where your pressure is only what you need.

    Ask your sandpaper company, if nothing else you will see what they know. In some companies older employees are gone or retired and the new ones dont have the same knowledge or history.

  15. #15
    Quote Originally Posted by Edwin Santos View Post
    So then what is actually happening when sandpaper wears?
    By design the grit is harder than the wood so it's not like the wood is abrading the silicon carbide.
    The carbide grit must be breaking off with wear like the abrasive in a sharpening stone.
    Or if it IS being abraded, the abrasive is then being turned into smaller microscopic abrasive particles in the same way that abrading wood turns it into dust particles.

    In either case, where does this grit go?
    Your supposition that the abrasive must be continually breaking down is erroneous. I use large abrasive belts every day, creating trailer loads of sawdust every week. I've never seen an abrasive belt from a wide belt sander wear out due to mileage. With regular cleaning and a little care, the inside of the belt will fail before the abrasive wears out.

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