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Ways to Make Slots in Sheet Metal or Plastic

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  • Ways to Make Slots in Sheet Metal or Plastic

    I've searched for ways to make slots in sheet metal or plastic and haven't come up with anything new. I currently use a drill press to drill the end holes, and a rotary cutoff tool (much like a Dremel) to cut out the space between them. It's not a very precise method. I've also tried an air-powered nibbler, but it isn't very precise, either.

    I know slots can be milled or laser-cut (but I don't have a mill or a laser cutter), or even done in a drill press using a milling vise.

    I've searched the fabrication forum, and I come up with references to DIN slots and CF slots and slot-load, but nothing new on making slots in sheet metal or plastic.

    Does anyone know a slick, low-budget way to make slots?

    (I've asked this same question in my worklog, and I'll crosspost any answers I get.)
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    If just enough is really good, then too much ought to be perfect.

    2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
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  • #2
    I just do what you do but I make the openings a tiny bit smaller than actually needed. Then I get a smooth file and carefully remove material until I get it to the size/shape I want. Haven't come up with a better way to do it without the big tools, yet. :-(
    Kids, don't play with too many knives! -Crack Stuntman

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    • #3
      is there no way of getting a punch style tool put ur work in a vise, place the punch where you want it then either press it or the prefered methof bang it with a hammer

      not go to this stage yet, just an idea

      Comment


      • #4
        Originally posted by kibble View Post
        I just do what you do but I make the openings a tiny bit smaller than actually needed. Then I get a smooth file and carefully remove material until I get it to the size/shape I want. Haven't come up with a better way to do it without the big tools, yet. :-(
        I agree. My standard technique in metalworking is to go a bit oversize, and file to the dimension I want. On holes, I go undersize, like you, and file to the size I want. A set of miniature files makes the fine work a lot easier.

        Originally posted by Bazza_84 View Post
        is there no way of getting a punch style tool put ur work in a vise, place the punch where you want it then either press it or the prefered meth of bang it with a hammer

        not got to this stage yet, just an idea
        The problem with most of those manual techniques is aligning the punch and the die well enough that we don't destroy one or the other when we tighten the vise or whack them with the hammer.

        I did search for "sheet metal punch", and I ran into some light duty portable punches, like this $24 hand-held punch from JC Whitney. It looks very similar to this punch from BrandsOnSale.com. Neither company lists the source, but they appear to be like units from Roper Whitney, which has a webpage here showing punches and tooling, including slot-forming tooling, plus a low-cost bench-mounting base for the portable punch. This could be a pretty good alternative to hand-forming. Roper Whitney lists the price on the punch as $55, the kit with tooling and a case at $80, and the base at $28. I couldn't find a price on slot tooling, but their price for a 3/16" round punch and die set is $11.

        **EDIT:
        I modified the text to show that the punches from JC Whitney and BrandsOnSale.com are NOT from Roper Whitney, but are apparently copies. There's no way to know if Roper Whitney's slot tooling will work in the knockoff tools, so it's probably best to just buy the Roper Whitney tool if we buy this to make slots. The slot tools are available from Roper Whitney distributors.**
        .
        If just enough is really good, then too much ought to be perfect.

        2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
        .

        Comment


        • #5
          More on Punching Tools

          The sheet metal punches seem like an interesting approach for making slots, especially if slotting dies are available. The Roper Whitney tool can definitely punch slots, but it's not a low-cost solution. I don't know if the tools from JC Whitney and BrandsOnSale.com can use the same die sets as the Roper Whitney tool. Until I discover otherwise, I'll have to assume they're just good for punching round holes.

          But, even if the punch only produces round holes, it has advantages of over the drill for making the end holes; it's quieter, produces a cleaner hole, and leaves just a slug for waste. I could still use the cutoff wheel, or perhaps a series of overlapping holes could be filed down to make a slot.

          I did some more research on the WWWeb, and we can add to the list of similar tools the larger 3-1/4" throat depth Deep Throat Metal Hand Punch from Harbor Freight, which costs $25. The base for it is $10. That looked like it could be a $35 solution, plus the cost of shipping.

          It's interesting how things work out. I happened to be close to our local Harbor Freight this afternoon, and went in to see what they had in stock. Their Deep Throat Metal Hand Punch was on sale for $18, and the base for it was on sale for $5. I just couldn't pass it up.

          I'll test it this weekend.
          .
          If just enough is really good, then too much ought to be perfect.

          2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
          .

          Comment


          • #6
            Posts some pics after you try it out! I'm curious to know how it works out for you.
            Kids, don't play with too many knives! -Crack Stuntman

            Comment


            • #7
              For metal, I'd try another piece of metal with a straight edge as a guide and clamp it on, cut along the edge with a dremel. Thin aluminum might work as a guide for plastic that's curved, but molding a faceplate in might work better for small things like memory cards, and you can mess it up more.

              Comment


              • #8
                Originally posted by Curiosity View Post
                For metal, I'd try another piece of metal with a straight edge as a guide and clamp it on, cut along the edge with a dremel. Thin aluminum might work as a guide for plastic that's curved, but molding a faceplate in might work better for small things like memory cards, and you can mess it up more.
                Actually, I was referring to slots in sheet metal parts, where I think you're talking about slots in bezels and the like. But you bring up an interesting point: it may be possible to simply build a bezel without worrying about slots, and machine the slots and edges of the openings we need. I hadn't thought of that, and I think I'll try machining edges and slots in my bezel plastic to see if that's a possible production path.

                I suspect the high speed of the Dremel-type tool might simply melt the material. A lower speed, as with a mill, might do well. Because the material is soft, a drill press could probably be used to mill plastic without tearing up the drill press bearings, but I think it would add a lot of side load on bearings not designed for side loads.

                The "Dremel" that I have is actually a Ryobi 18V system. It works well, but isn't mountable like a true Dremel, and there's not a flat surface to run along a guide. An inverted Dremel in a work table might be a good idea. The way those little whizzers throw chips, though, I think I'd like to build a clear shield into the system somehow, or wear some really good goggles.

                I've also wondered if I could run a milling tool in my router -- mounted upside down under a work table -- to make slots. My router operates at a single high rpm; I'd have to bring it down to the proper rpm for plastic or metal milling. Also, I don't know that its bearings -- which handle sawdust just fine -- are set up to handle hot metal fragments. When I was only thinking of sheet metal work, I couldn't easily resolve either issue, so I abandoned the idea. I might have to revive it for machining plastic, if I could control the speed.

                I want a better way to form slots because I want to take less time and less effort, and I want better slot quality and consistency.

                But one of the secondary reasons is that the current method involves lots of metal chips. I was wondering if there's a way to do "instant" slot forming -- like punching -- that only produces a slug, or a few slugs. I end up having to take off my shop shoes every time I walk into the house, because I don't have a housekeeper (except me), and I'd rather work in the shop than run the Roomba or a mop. If I can make less mess, I'll get more done because it'll be easier to clean up after myself.
                .
                If just enough is really good, then too much ought to be perfect.

                2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
                .

                Comment


                • #9
                  Originally posted by rdholtz View Post
                  I suspect the high speed of the Dremel-type tool might simply melt the material.
                  They actually have some wheels that are made to cut through plastic. They look like the big metal cut-off wheels. I use them myself and they work pretty well, but you have to make sure to not stay in one area too long or it will start melting the plastic.
                  Kids, don't play with too many knives! -Crack Stuntman

                  Comment


                  • #10
                    Originally posted by kibble View Post
                    They actually have some wheels that are made to cut through plastic. They look like the big metal cut-off wheels. I use them myself and they work pretty well, but you have to make sure to not stay in one area too long or it will start melting the plastic.
                    I'd bought a kit of Dremel tools, and there's a mini-sawblade in there. But I was thinking of something more akin to a milling head, where we could simply machine a slot in the face of a plastic bezel. That would save a huge amount of finishing time. I believe the primary issue will be matching tool speed to the material; the softer the material, the slower we'll want to run the tool. Controlling the tool speed is probably easier in a 110V machine than a battery-powered one like mine, so I may have to invest in another Dremel-type tool (for research purposes, of course).

                    Unfortunately, I'm going to have to delay experimenting with plastic machining, because I'm leaving in the morning for an unexpected week or more on the road.

                    The good news is that today I got pictures of the punch and its results, and I'll get them posted as soon as I can write it up. I use GMail and Google Docs, so everything travels with me. Shouldn't be more than a day or so . . .
                    .
                    If just enough is really good, then too much ought to be perfect.

                    2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
                    .

                    Comment


                    • #11
                      Having a variable speed rotary tool doesn't compare to a fixed speed one. Get yourself one, you'll be glad you did!
                      Kids, don't play with too many knives! -Crack Stuntman

                      Comment


                      • #12
                        Originally posted by kibble View Post
                        Having a variable speed rotary tool doesn't compare to a fixed speed one. Get yourself one, you'll be glad you did!
                        The Ryobi seemed like a great compromise when I found it. I've had excellent service from all my Ryobi tools. But this rotary tool is struggling to find its place. I think you've highlighted a major weakness in its lack of variable speed, and it may force me to get a Dremel-branded tool.

                        There are a couple of other reason to get the Dremel brand. At Home Depot, I saw the #220-01 WorkStation mount for Dremel tools that looks really slick. There's also the Dremel #231 Shaper/Router Table, which might be a nifty slotting device.

                        There may be a Dremel in my future.
                        .
                        If just enough is really good, then too much ought to be perfect.

                        2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
                        .

                        Comment


                        • #13
                          Originally posted by kibble View Post
                          Post some pics after you try it out! I'm curious to know how it works out for you.
                          Punch Testing

                          I've been playing with the Deep Throat Metal Hand Punch from Harbor Freight. It appears to be a knockoff of the Roper Whitney No. XX seen on this page. If the tooling for the Roper Whitney model fits this tool -- and pictures suggest that it might, then this tool may be able to punch slots. So far, though, I've only punched round holes.

                          I'm glad I bought the base; it makes it easier to use, but it needs to be mounted to a board; without it, the tool just tips over onto its nose. I attached the tool to the base, and the base to a piece of 5/8" plywood 5" x 8" with some 1" screws and fender washers. I didn't do any finishing to the base board other than file the edges to knock off the splinters. Here's how it looks mounted:

                          Click images to enlarge.

                          For size reference, the slot on the depth gauge is 3" long.

                          The manual assures us that everything we need is included, but there's a 2.5mm Allen wrench needed to tighten the set screws; it's not in the box, nor is it on the parts list. If you go to Harbor Freight to get this, buy a set of metric Allen wrenches at the same time.

                          I installed the 3/16" die set. I tried the punch on scraps of the types of steel I've been using for parts -- some .022" galvanized steel, an old computer case (.028" steel powder-coated on both sides), and some .031" stainless steel. The punch went through all of them. The force required depended on the material. The painted steel was easiest, probably because of the paint acting as a lubricant. The galvanized was almost as easy. The stainless steel was tougher, and I don't think I'll want to use this punch on that material. The stainless steel may have dulled the punch in a single use, because holes were just a little tougher after that. I confess that the instructions say "mild steel", and stainless isn't mild steel. Any damage done to the die set is clearly my fault for pushing it beyond its specified use. But that's just what research does.

                          There's a locator point on the tip of the punch, so I can locate holes precisely; once the punch is positioned, I just a push on the lever arm, and I have a hole. "Push" means "apply some pretty healthy pressure".

                          Here's a picture of the resulting holes in the test pieces:


                          The material on the left is .031" stainless steel; in the center is .028" powder-coated steel; on the right is .022" galvanized steel

                          I also tried punching 1/8" polyethylene, and it did just fine. The hole was smooth and very clean.

                          The dies come grease-coated and packed in clear wrap, which makes me suspect they need corrosion protection in the humidity of south Florida. I made a small container for them in my tool chest and I'll keep a grease rag over them so the atmosphere in the box is oily air.

                          The punch takes more initial setup than just slipping a drill bit into the drill press. But if I'm using a standard size hole -- I generally use 3/16" -- then I can just leave the punch set up with the 3/16" die set in it. It can sit on a lower shelf, ready to pull into action whenever I need holes.

                          I like the cleanup; there isn't any. I guess when I've punched enough holes, the slugs will start to fall out of the bottom of the die, but that's still almost no mess. I'll brush a little dab of grease on the punch and the die when I'm finished each time to keep them lubricated and rust-free.

                          If I just use it to make the holes at the end of slots, it's an improvement over drilling. The resulting holes are very clean and smooth-edged, and don't need any filing until final cleanup of the parts.

                          I made a quickie bracket for a temporary system I was building, and needed holes in a piece of bent sheet metal. I marked the holes with a center punch, stuck the metal in the punch a couple times, and BAM!, BAM!, there were holes, perfect holes, right where I needed them, with no finishing required. I've never made holes so quickly and easily in my life. Oh, I like this tool.

                          The verdict so far? While this is a handy tool for surprisingly low cost -- especially on sale -- it isn't the total answer to making slots. With the standard tooling, I'll still have to use the cutoff tool to complete the slots. The punch makes the process easier, but it doesn't produce instant slots, so I'm not ready to call it the "solution".

                          If it can accept the Roper Whitney tooling and punch slots, it could be the answer I wanted. I'll research that this week.

                          Even without that capability, it's a keeper.
                          .
                          If just enough is really good, then too much ought to be perfect.

                          2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
                          .

                          Comment


                          • #14
                            Hmmm I like the fact that it's not messy like drilling stuff. I may get one myself! Another thing I don't like about drilling is that the holes are sometimes not really 100% round because of the way the drill bit bites into the material.
                            Kids, don't play with too many knives! -Crack Stuntman

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                            • #15
                              Originally posted by kibble View Post
                              Hmmm I like the fact that it's not messy like drilling stuff. I may get one myself! Another thing I don't like about drilling is that the holes are sometimes not really 100% round because of the way the drill bit bites into the material.
                              I've punched enough holes with it that the slugs are falling out of the bottom, now. They just drop onto the workbench. When I'm done with the punch, I put it away and sweep the slugs into the metal scraps bin. I wish all my tools were as neat and easy to clean up after.

                              Hurry, if you're going to get one on sale -- it ends July 22, I believe. But, even at its full $37 price, this is a really good tool, terrific for quick holes. And, now that I'm used to it, changing the punch only takes about a minute.

                              I still have to check on getting the Roper Whitney slot punch and die to see if they fit.
                              .
                              If just enough is really good, then too much ought to be perfect.

                              2006 Scion xB with in-dash Atom & Lilliput 889GL -- Worklog at http://www.mp3car.com/vbulletin/work...res-links.html
                              .

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