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Cutting Holes in Plastic Enclosure - How to do it quickly?

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  • Cutting Holes in Plastic Enclosure - How to do it quickly?

    So I have to cut out holes for some 9V battery trays in the side of a plastic box. I need two 9V battery trays per box and I have about 100 boxes to do. The box is pretty rectangular and made from a thin ABS plastic. I'm thinking about coming up with some kind of jig and using something like a rotozip or dremel to plunge in and trace out the pattern. What I really need is a very small router bit with a guide bearing that can plunge cut and then use a jig/template.

    What do you guys think? Any ideas?

    Battery tray, Page 9 BX0023:
    http://www.hammondmfg.com/pdf/1591D.pdf

    Box:
    http://www.hammondmfg.com/pdf/1591D.pdf
    Last edited by Fasttrack; 02-16-2015, 02:37 PM.

  • #2
    "Any ideas?"

    What fer hole size? Most sparkys I know swear by uni-bits.
    I like drill bushings, if the pattern is all the same, easy work, and you can use a plunge router without interpolating. For your run quantity lathe cut bushings would be fine, with a little care. Or make 'em bigger and use a collar.
    Upshear might eliminate burrs. Think about support inside the box or clamp your pattern plate if the tool has any thrust. ABS cracks pretty easily.

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    • #3
      The holes are rectangular, roughly 1" by 1.34" with two screw holes on either side. It doesn't have to be super neat because the battery tray has a flange that will cover the cutout. See the posted data sheet, page 9.


      Heat is an interesting idea but not sure how I feel about the smell. I was hoping to come up with something that could be done at a workbench in a lab instead of in a shop with ventilation.

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      • #4
        What I really need is a very small router bit with a guide bearing that can plunge cut and then use a jig/template.
        Or if you make the template thick enough maybe you could use part of the body of the Rotozip as a guide.
        Last edited by RichR; 02-16-2015, 10:15 PM.
        Location: Long Island, N.Y.

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        • #5
          "What I really need is a very small router bit with a guide bearing that can plunge cut and then use a jig/template."

          Dead simple, find a ball bearing with an I.D. that fit's your shank, what 1/4". Loctite below the collet grip. I have a can of quarter and half inch bearings for this, bought surplus.
          Or turn a bit of UHMW or brass to do the same thing.
          If your pattern is steel, you don't need the bearing, just a deft touch. But I was thinking a reasonable grade of ply, like Baltic birch.

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          • #6
            make a steel band mounted on a block of wood like a cookie cutter. heat it with your propane torch, set the plastic on a backing board and press the hot cookie cutter thru it. . . a little stink and its done. . . quietly too. . .

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            • #7
              does your mill have stops on it ? I assume you are cutting rectangles
              just set the stops to confine the work envelope of the machine, then make a jig to hold the part and cut the biggest rectangle possible within the stops
              My neighbours diary says I have boundary issues

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              • #8
                I don't work for OSHA and I'm not a safety Nazi, but if you're gonna melt plastics read up and form your own opinion about toxicity.
                Ya got yer health, ya got everything.

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                • #9
                  I'd make 2 jigs.

                  1/ Outside 'template jig' for hole drilling - drill x6 (4 battery tray mounting holes and 2 for rotozip start points.)

                  2/ An internal wood block with suitable sized/positioned wells cut into it.
                  - Clamp block in box.
                  - Start rotozip in hole and go around the 'wells'. Go the right way, the other way will be too exciting. Make sure rotozip follower tip touches wood but not cutting edges.

                  Maybe have a vacuum cleaner set up to collect chips as you go.
                  Last edited by MotorradMike; 02-16-2015, 05:06 PM.
                  Mike

                  My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."

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                  • #10
                    I have made many electronic enclosures and control panels. When I want a square or rectangular hole, I usually use chassis punches.

                    https://images.search.yahoo.com/yhs/...&hsimp=yhs-001

                    In this case, I would use a 1" square punch twice to get the 1.34" width. Drill two (1/2") holes, 0.34 inch apart. Punch one side. Keep the slug from the first punch in place and punch the second side. Done.

                    For plastic, you can use a reversible electric drill to power the operation. Fast punch and fast release of the slug. With the punch part on the inside and the die part on the outside you can punch right up to an adjacent wall. And there is little or no cleanup.

                    I have a larger collection of chassis punches for things like this, but they can be purchased from a number of sources like McMaster and WW Grainger and electronic supply houses like Mouser, Newark, and Digi-Key. For punching plastic, you do not need the ball bearing models, just a bit of lube on the bearing surfaces of the punch.
                    Paul A.
                    SE Texas

                    Make it fit.
                    You can't win and there IS a penalty for trying!

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                    • #11
                      Seriously? If I had 100 to do I'd call Hammond and ask how much they charge you to do it, or check if Polycase has an equivalent enclosure. I know Polycase's prices for enclosure modification are well below any reasonable value of my time.

                      If that was not an option, I like the template option but there would have to be a way to keep the tool perfectly vertical. I know from experience I'm not good enough to hold the dremel perfectly correct without a good guide, so I just use my mill. It's slower, but I've never had to do more than about a dozen at once.

                      I've tried punches, but you still have the problem of keeping the punch aligned properly as you screw it in if it only has one guide hole.

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                      • #12
                        Originally posted by lwalker View Post
                        Seriously? If I had 100 to do I'd call Hammond and ask how much they charge you to do it, or check if Polycase has an equivalent enclosure. I know Polycase's prices for enclosure modification are well below any reasonable value of my time.
                        I would check this out as both of your parts are from Hammond, they might be very reasonable as they have a lot of fast CNC equipment.

                        R
                        Robin

                        Happily working on my second million Gave up on the first

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                        • #13
                          Originally posted by lwalker View Post
                          Seriously? If I had 100 to do I'd call Hammond and ask how much they charge you to do it, or check if Polycase has an equivalent enclosure. I know Polycase's prices for enclosure modification are well below any reasonable value of my time.

                          If that was not an option, I like the template option but there would have to be a way to keep the tool perfectly vertical. I know from experience I'm not good enough to hold the dremel perfectly correct without a good guide, so I just use my mill. It's slower, but I've never had to do more than about a dozen at once.

                          I've tried punches, but you still have the problem of keeping the punch aligned properly as you screw it in if it only has one guide hole.
                          That's interesting - I thought about this and discounted it, assuming the cost to have them tool up for a run of only 100 would be too high. I will contact Hammond and see what they say.

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                          • #14
                            I took a quick look at Polycase's calculator. For the enclosure I most commonly buy from them, it would be a one-time setup fee of $100 + $1.04 per enclosure to machine a single feature @ qty 100. Their prices went up a bit since I last did this, but still much cheaper and faster than I could do it by hand.

                            Happy to plug Polycase. Been doing business off and on with them for almost 20 years.

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                            • #15
                              Personally, I'd use a router bit with a guide bearing up on the shank, and use a real router also. A trim router would be perfect for this. The guide hole jig would have a 'nest' made on it to hold the boxes in the right position. I would set the box down, position the jig over it and hold with one hand, then plunge cut and guide the router around the guide hole with the other hand.
                              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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