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Posted

they are known as fostner bits, for drilling  thru or flat bottom holes...not that terribly old they were designed long ago to remove knots in wood so the hole could be refilled....but they are used for more and more things 

and the straight one are called straight flute reamers.....used for very tight tolerance holes 

Posted

I was clean out my grandfather tools, and I thought they where for anther tool that was near it so I thought that those bit went with that tool. I get that they make hole but why would someone need these bit

Posted

Are used on a regular drill or hammer drill

well you can use either but Ideally a drill press if the hole needs to be perfectly 90 degrees to surface.......

  • 2 weeks later...
Posted

Yup. Forstner bits. Lots of uses. It can be quite challenging to use in a hand drill as they tend to skip. If you must use in a hand drill, and you have the depth to work with, a pilot hole of the exact same diameter will help with alignment and flatten out the bottom of the hole.

  • 1 month later...
Posted

Forstner bits are used when you need a hole that doesn't go all the way through the material. Using a forstner bit will ensure the bottom of the hole is smooth and the bit will not 'pull through'

If you try do drill a hole halfway through material with a regular 'twist' bit, the bit will mostlikly 'pull' too far through the material. A similar bit know as a hole saw is used when you want to bore large holes all the way through material.

As for the reamer, ... Drill bits are not exactly precise in diameter. If you needed a hole with a precision tolerance, you would first drill with appropriate twist bit, then come back and 'drill' with the reamer.

I assume you're grandfather did some metal work? Often those tools are used with mills & drill-press

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