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How to square up speaker boxes without a router/belt sander

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  • How to square up speaker boxes without a router/belt sander

    Hi all I have a couple of questions I am interested in getting some tips on.


    How do you guys square up/true speaker boxes without a router or belt sander?

    I have a very slight 1/32" overhang from my baffle that I have been trying to sand out by hand, but it's quite laborious.

    I first sanded it out, then sealed the mdf. I thought at this point everything was nice and square. However after priming and spray painting, the edges peaked through and it's clear that the box is not perfectly square after carefully measuring things with a wood-working square.


    Any tips? I was thinking about purchasing a finish sander to help with this (a random orbital sander is too aggressive and almost impossible to control near the edges).


    Also how do you guys do full spray paint job. I'm having a hard time figuring out from where to hold the speaker without blocking a spray paint path. If prop the speaker from the bottom, I wouldn't be able to spray paint the bottom correctly. Using strings also presents a similar problem and also how to hang heavy speakers is another issue in this case.


  • #2
    I use my cheap little Black and Decker random orbital sander on edges all the time. 80 or 120 grit. You do need to keep a firm grip and orientation. Generally particle board or plywood. I haven't used mdf since I started working in my garage. I do have a flush trim bit for really bad joggles.

    Putting a fine spray finish on an mdf buttjoint cabinet is beyond my patience level. I use a lot of stone texture paint, and shellac or varnish on solid wood cabs, highlighting the seams instead of trying to hide them. PSA veneer also works good if your cab is square. In my experience.

    A color break or intentional disjoint at a seam works too.

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    • #3
      Originally posted by mmu7 View Post
      Also how do you guys do full spray paint job. I'm having a hard time figuring out from where to hold the speaker without blocking a spray paint path. If prop the speaker from the bottom, I wouldn't be able to spray paint the bottom correctly. Using strings also presents a similar problem and also how to hang heavy speakers is another issue in this case.
      Can you "meat hook" through a driver hole or port opening? Taking care to pad the hook to avoid denting the material?

      Comment


      • #4
        MMU7,

        Regarding sanding to get a smooth flat surface,
        I've purchased a few coarse 80 grit or so 6" wide by 48" belt sanding belts. I cut them in thirds and adhere this to a board with permanent contact adhesive, bending it over tightly, and stapling it to the ends just to be sure. It ends up being three strips of sandpaper right next to each other on a 3/4" scrap piece of particle board or whatever flat piece of material you have handy. Clamp that to a sturdy work table and take your piece to be sanded and move the piece on the sanding block. It makes a sanding block big enough to sand even larger things, maybe 16" by 16"... that big if you arrange it correctly.

        I use mine all the time for projects where the seams don't quite line up perfectly for example... or for re-re-re-sanding end grain on speaker cabinets to make sure they don't start showing through veneer. It's a handy tool to have. If you made one, you could just lay the speaker flat, grab it as low as you comfortably can, and move it back and forth, around and around..... it doesn't take long to remove a fair amount of material, and you'll soon get a feel for how to move it to avoid 'chattering' the box as it moves.

        I use belt sandpaper because it's super-tough. Sheet sandpaper would scrape and tear off easily, the belt stuff has fibers in the construction of it which makes it super strong. I've had mine for a few years and it's still going strong! Whack it with a scrap stick of wood and the sawdust comes out pretty quickly. You can also lightly tap it with a wire brush for more stubbornly bedded sawdust.

        As far as propping up cabinets to paint... here is what I've done in the past:

        Click image for larger version

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        Basically, you're making little stands with a broad base of scrap wood. Screw in a little piece of wood on the end of the 2x4 or whatever you use to make that inside part stable, and have at it. This may not work well if you're also painting the baffle because it will be upside down, but if you use a smaller piece of wood like a 2x2 it may fit in the port or rear terminal cup hole. Also, the riser board can be as long as you need to get more clearance. I have these little 'stand' things in several sizes ready to go to paint or finish my projects, but I tend to make a lot of stuff, so it's easier that way.

        You may just need to paint in stages, saving the most critical part for last, likely the front.

        Hope this helps,
        TomZ
        *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
        *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

        *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

        Comment


        • #5
          I use my cheap little Black and Decker random orbital sander on edges all the time. 80 or 120 grit. You do need to keep a firm grip and orientation. Generally particle board or plywood. I haven't used mdf since I started working in my garage. I do have a flush trim bit for really bad joggles.
          I tried this on the first cabinet I made, and the orbital sander basically applied to much pressure near the edges creating a slight concave shape. I understand that this could be due to my uneven pressure of the sander, but it is hard to control regardless. By the way these are for small MDF cabinets, so I do not have a lot of surface area to stabilize the sander with.



          I've purchased a few coarse 80 grit or so 6" wide by 48" belt sanding belts. I cut them in thirds and adhere this to a board with permanent contact adhesive, bending it over tightly, and stapling it to the ends just to be sure. It ends up being three strips of sandpaper right next to each other on a 3/4" scrap piece of particle board or whatever flat piece of material you have handy. Clamp that to a sturdy work table and take your piece to be sanded and move the piece on the sanding block. It makes a sanding block big enough to sand even larger things, maybe 16" by 16"... that big if you arrange it correctly.
          Good idea. I think I will try to glue up several sanding strips side by side and try this.



          Regarding propping up the speakers; yes I was thinking of painting in stages. However, I am using a lacquer spray paint. It seems that for these types of paint, there is a time `window' so it's best to try and finish the paint job and coats before the paints cure. Painting in stages seems problematic in this regard. I could basically paint all the sides except the bottom, which I could prop up via a slender rod. Maybe better would be a slender rod supporting the bottom, propped up on a lazy susan.


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          • #6
            Good tip Tom. I'm gonna try the belt sanding belt. ;)

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            • #7
              This is what planes are for. Using a large plane, take shallow cuts coming from low to high at an angle so there's no tear-out. MDF is paper; it cuts easily.
              Frank

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              • #8
                Originally posted by Jake View Post
                Good tip Tom. I'm gonna try the belt sanding belt. ;)
                Glad my many screw-ups -- and their related fixes -- can help others!

                I swear, if you took away all my posts about how I managed to goof-up... then needed to find a work-around on a project, I'd have a LOT less posts.

                Could I offer a tip regarding this? If possible, do a little round-over on the board (at least 1/4 to 3/8" where the sandpaper curves around to the side and gets stapled. I didn't, and the stiff-backed paper tends to want to lift up at that point, although I did use spray adhesive in addition to the staples.

                I've placed 8 x 16" cabinets on it and got it nice and flat. With coarse grit, it doesn't take long at all to do. If you make the board oversized on the sides where the paper doesn't attach to, you can clamp it to a table and really get going on it.

                TomZ
                *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                Comment


                • #9
                  I use a sharp block plane on MDF, 1/3 sheet sanding pad, sandpaper glued to MDF blocks. The electric sanders don't get much use.
                  John H

                  Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                  Comment


                  • #10
                    Originally posted by jhollander View Post
                    I use a sharp block plane on MDF, 1/3 sheet sanding pad, sandpaper glued to MDF blocks. The electric sanders don't get much use.
                    I kind of agree on the electric sander issue.
                    I've been known to use the belt sander for some stuff, but you gotta be REAL careful with aggressive grits or else you've got a gumby-looking cabinet going on. There's a real technique with using power sanders without messing things up a LOT more than when you started. Some of my curvy stuff needs bulk removal of material where a router/bit situation won't work well... that's when I go to the power sanders, not for finish, or near finish stuff usually.

                    John only needs 1/3 sheet size sandpaper blocks because he only makes 1/3 sheet-size boo-boos if any. I measure my boo-boos with a yardstick sometimes it seems like.

                    TomZ
                    *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                    *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                    *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

                    Comment


                    • #11
                      Tom you don't get to see the size of my mistakes because I don't tell you.

                      Veneer and electric sanders are mutually exclusive. However, the last time I used my 1/4 palm sander was for wet sanding...
                      John H

                      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                      Comment


                      • #12
                        Thanks Tom, since buying a router this past year i've used a trim bit then a light sand, but this board technique will definitely yield more even results.

                        Comment


                        • #13
                          Originally posted by jhollander View Post
                          I use a sharp block plane on MDF, 1/3 sheet sanding pad, sandpaper glued to MDF blocks. The electric sanders don't get much use.

                          Wait you block plane mdf....how's that even possible? I think I tried that once on a scrap and it just removed a layer of the mdf sheet, needless to say I thought it was a failed experiment. What kind of plane do you use (links if possible)?


                          I spent all of last week sanding and filling holes and sanding again and again.

                          I sprayed the boxes yesterday and they look pretty decent. There are some bumps here and there and minor splatters that I think can be fixed with another color coat.

                          I'm using a lacquer based spray paint (duplicolor wheel).

                          I'm not 100% sure on how I will clear coat them. I have this duplicolor matte clear coat, but I believe I need to spray a couple more coats of color and then apply the clear coat within 1-2 hours of a color coat of paint, so that it chemically melts into the color coat. However, I have heard of people spraying the clear after the paint cures, so that it doesn't chemically bond.
                          Another option is to try a 2k clear. I think if I go with that route, the color coat needs to be fully cured before spraying the 2k clear: in other words, the 2k clear coat is urethane based and requires that the color coat if fully cured. I'm a bit afraid of using the 2k due since it's a very strong chemical properties (I always use a mask, but nonetheless, I'm painting indoors with a vent duct).

                          So I think I'd like to use the duplicolor clear coat, but I heard it's a little trickier to sand after curing. I would like to give the clear coat a like 1000-2000 grit sand and perhaps a light polish to remove any orange peel. I'm not looking for a gloss finish, but rather a matte/satin finish.


                          Any tips/suggestions/comments are welcome.

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                          • #14
                            I use Stanley 12-920 6-1/4-Inch Contractor Grade Block Plane, sharpened of course. I avoid any perpendicular to the face where I might break out the face layer, focus on the end grain edges then finish with sandpaper. You can take the nice smooth top layer of MDF off, but I'm priming so that's not an issue. If I have some time I'll post a few pictures.
                            John H

                            Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                            Comment

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