What sized tap for .70" hole?
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TECH Regular
Joined: Aug 2005
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What sized tap for .70" hole? I'm trying to tap a .70" hole and I'm wondering what sized tap to use. The hole corresponds to 11.2/16" or 17.78mm.
The hole is already drilled and I REALLY don't want to have to drill it out to a bigger size, so what shoud I use: 3/4-16 (11/16" hole), 3/4-10 (21/16" hole), or 20x2.5mm (17.5mm hole)?
I don't know how much "wiggle room" you have when tapping. If it can't be done with the .70" hole I'll drill it out, but it would be vastly easier to do just tap the pre-existing hole.
The hole is already drilled and I REALLY don't want to have to drill it out to a bigger size, so what shoud I use: 3/4-16 (11/16" hole), 3/4-10 (21/16" hole), or 20x2.5mm (17.5mm hole)?
I don't know how much "wiggle room" you have when tapping. If it can't be done with the .70" hole I'll drill it out, but it would be vastly easier to do just tap the pre-existing hole.
TECH Apprentice
Joined: Jul 2004
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I’d love to know how you ended up with an exactly .70” hole…
The recommended hole sizes for a tap are supposed to be adjusted for the hardness and stickiness of the material (IE, the same size tap will use a tighter hole in something like non ferrous metal then in steel or stainless), and the end result when it’s properly sized is a thread that has the last 20% cut off (in other words, not perfect pointy thread peaks and valleys but missing 20% of the points), so real world you really should be considering drilling it to the next size up… barring that, the 3/4-16 looks to be the closest so that’s the one that I would use from your list of choices (well that and the metric size will be hard to find, depending on what this thing is to start with.
For that matter, at this point, what did you do?
The recommended hole sizes for a tap are supposed to be adjusted for the hardness and stickiness of the material (IE, the same size tap will use a tighter hole in something like non ferrous metal then in steel or stainless), and the end result when it’s properly sized is a thread that has the last 20% cut off (in other words, not perfect pointy thread peaks and valleys but missing 20% of the points), so real world you really should be considering drilling it to the next size up… barring that, the 3/4-16 looks to be the closest so that’s the one that I would use from your list of choices (well that and the metric size will be hard to find, depending on what this thing is to start with.
For that matter, at this point, what did you do?
