Enlarge a hole


Old 09-04-14, 09:35 PM
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Enlarge a hole

i have a 25mm hole in 4mm steel that needs to be at least 28.5mm, is there a tool for this ?, i have a drill press, thats how i got the 25mm hole drilled, i would say thats about max for it though, thinking a hole rreamer or something like this.
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Old 09-04-14, 09:46 PM
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Welcome to the forums.

Have you ever heard of Unibits or stepped drill bits ? They are just what the doctor ordered.

There are many different sizes, types and manufactures. For your 28.5 mm (1.1") hole you'd need a larger diameter unibit like in the picture. These bits are a tad on the pricey side but worth every dime. As an electrician I use them all the time.

Most every electrical supply house, hardware store and home improvement stores stock them.

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Old 09-04-14, 11:51 PM
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thanx, knew there had to be something out there
Old 09-05-14, 06:02 AM
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4mm is getting thick for a step drill. A step drill can do it but make sure to keep the bit well lubricated, turn the tool slow and with hard pressure. Since you were able to drill up to 1" I'm wondering why it's suddenly become difficult to imagine simply getting the correct sized drill bit? They do made drills in sizes larger than 25mm. Just buy the correct size drill and many/most are available with a 1/2" shank to fit a standard drill press drill chuck.

Old 09-05-14, 06:22 AM
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Cobalt HSS Bits

These drill bits are precision ground from solid cobalt alloyed high speed steel and are very resistant to heat and abrasion.

cobalt bits work very good.
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