Drilling slotted holes through 1/4'' angle iron with Mag Drill


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Old 09-22-21, 04:59 PM
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Drilling slotted holes through 1/4'' angle iron with Mag Drill

I have galvanized fabricated steel triangles - this is for a marina - and I need to drilled some slotted holes in one side. Given it is already fabricated I can't get it under a drill press or end mill. I have mag drill and have used it on this piece to drill singular hole with a annular cutter with no issues. Thing is I can't use the annular cutter to try and do slotted holes as the drill will catch and lift.

Would a step drill bit work for slotted holes? Holes need to be 13/16 or 7/8. The annular cutter I have is 13/16.

Thanks
 
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Old 09-22-21, 05:10 PM
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Sounds to me like you will need to drill 2 holes on each end and then connect them by cutting the waste out between them with a jigsaw. A step bit will work if you buy one that is 7/8" maximum.
 
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Old 09-22-21, 05:20 PM
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Didn't see 1/4" material. My way wouldn't work.
I'd be using my torch.
 
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Old 09-22-21, 09:59 PM
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Just drill over sized holes, trying to do slots is a pain and will look like s#@t.
 
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Old 09-22-21, 10:01 PM
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A step drill will not grab like a twist drill, but it still just makes round holes.
 
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Old 09-23-21, 04:08 AM
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A picture might help as I don't see why you can't hold the triangle in a vise and mill a slot. I am assuming you have a milling machine with a vise. Regrip the triangle and mill a slot. Repeat as many times as needed.
 
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Old 09-25-21, 01:39 PM
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Each side is 4’ x 5’ x 6’ or so, and is therefore too large to fit into a Vice on a mill
 
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Old 09-26-21, 08:30 AM
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If one side of the 3 pieces of angle stock of the triangle is parallel to the ground, is it this side of the angle stock you need the slot in or the side that is at 90 degrees to the ground?
 
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Old 09-27-21, 07:16 AM
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If you do this often you could fabricate a jig and use a plasma cutter.
 
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Old 09-27-21, 10:51 AM
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Old 09-27-21, 11:09 AM
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Pretty expensive magnetic drill.
 
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Old 09-27-21, 01:29 PM
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Create slot ends with mag drill and bit. Use a saws-all with steel cutting blade (at least 16 tpi) to cut the sides. May take multiple cuts as the blade thickness prevents starting cut from center of hole. Can finish off the sides of the slot with a file or flat grinding wheel on right angle grinder. Good luck.
 
 

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