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Thread: Slots in a bracket?

  1. #1

    Slots in a bracket?

    Hi all,

    I'm fairly new to all hand tools and learning as i go along. I need to make a very specific bracket to fix part of a machine. This bracket needs slots in it, like these;

    DlmKJwi.jpg

    How can I make these?

    I had thought a series of holes then some filing with a dremel to smooth out the slot.

    I have tried with a hand held power drill but lining them up was impossible. Each hole would be somewhat out of line with the previous despite all best efforts. Then i tried with a drill press, but the bit wandered into previous holes and wouldn't complete the new hole.

    I had thought a series of holes then some filing with a dremel to smooth out the slot.

    All advice would be appreciated!

  2. #2
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    I'd do this on a milling machine. Hold the metal firmly and use a short, inflexible end mill which can't wander even a little bit. Mill straight down on one end of the slot, then move the bed to machine the slot. Use plenty of lube/coolant. If you don't have a milling machine, an x-y table on a drill press might work with an end mill in the chuck. The speed may need to be lower than the drill press will handle though, I don't know. And a drill press may not be sturdy enough for precision. Do you know anyone in your area with a milling machine in their shop?

    Do the slots have to be perfect? One way that might work is drill each end hole then use one of the little metal-cutting disks on a Dremel to make a couple of parallel cuts between each set of holes, then file to smooth. I get a lot of use from the Dremel disks. One possible problem is the possible need to cut at a slight angle for tool clearance. Maybe the disk on flexible shaft would help.

    JKJ

  3. #3
    Join Date
    Feb 2007
    Location
    southeast Michigan
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    129
    As John indicated, a milling machine is the best tool for this job. But the cost to have a small machine shop make a part like that with 8 slots might surprise you. I used to have a very tight x-y table on an old drill press and it worked fairly well on aluminum but not so much on steel.

    Since you have a drill press you can drill holes that are exactly in line. The way to do this is by using a center drill (see picture) to start the position of each hole so the drill bit doesn't wander. Decent ones are fairly inexpensive and sets can be had for less than $15.

    You would need to lay out the position of each hole for all the slots on your piece. A scratch awl would help with this layout along with blue layout fluid, or a magic marker would also work. Mark the position of the hole at each end of each slot. Then mark the positions of holes in between the two. I would not go more than about a 20% overlap with each hole.

    Set up a fence on your drill press for the center line of the first 2 slots and drill away using the center drill first for the start of all holes in that line and then switching to whatever size drill you need. Move the fence for each of the other 3 center lines and repeat the process. You could use a dremel to grind away the remaining material but a vice, either bench or woodworking, and a decent file will probably get you there faster. Good luck.

  4. #4
    Join Date
    Feb 2008
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    E TN, near Knoxville
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    2,772
    Quote Originally Posted by John Ziebron View Post
    Since you have a drill press you can drill holes that are exactly in line. The way to do this is by using a center drill (see picture) to start the position of each hole so the drill bit doesn't wander.
    That's a great idea. I use the center drills with metal and a lot at the wood lathe for starting holes but using them to start a series of overlapping holes never occurred to me.

    JKJ

  5. #5
    Join Date
    Apr 2010
    Location
    Berkshire County in Western Ma
    Posts
    47
    Also a prick punch or center punch mark will assure your center drill holes will be right where you want them

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