Mounting hardware size?

[®smpr_fi_mac®]

I'm mounting a 56HZ frame motor. The mounting holes will pass an 11/32" drill bit but not a 23/64" bit.

Is that a 1/4-20 size bolt hole? If not, what size do I need?

Thanks!

[museumguy]

5/16-18. standard size bolt.

[®smpr_fi_mac®]

Thanks!

[Stwood_]

Google drill bit chart, print, insert in plastic cover, hang on shop wall. Yer welcome.

[®smpr_fi_mac®]

That's not a bad idea.

[KyleD]

I'm mounting a 56HZ frame motor.  The mounting holes will pass an 11/32" drill bit but not a 23/64" bit.

Is that a 1/4-20 size bolt hole?  If not, what size do I need?

Thanks!

Here is how I do this in my head. The hole is at lest 11/32 but I know the bolt needs a little wiggle room. so I subtract a 32nd and end up with 10/32. Now the trick is to start halving (simplifying) the fraction until I get a proper fraction. 10/32 becomes 5/16. In this case I only needed to halve it once. Many times the fraction can be halved multiple times. For example 24/64 becomes 12/32 which becomes 6/16 which finally becomes 3/8.
Please don't think I am trying to be patronizing. I tutor non-traditional students in algebra and calculus at the local college. I see students who are otherwise smart and capable people struggle with this because they never learned the subject in high school. My personal nemesis is spelling. Thank goodness for the dictionary and thesaurus programmed into my computer.

[Steve N]

Google drill bit chart, print, insert in plastic cover, hang on shop wall. Yer welcome.

Steve I'm partial to this one, seems to always save me from myself
 







This guy at Pinterest must be even worse off than I am he's got a whole web page to saving himself from the wrong sized hole. He has that chart I posted in a much clearer version, which can be upsized to put onto a bigger paper. I love Kinko's for that stuff, big paper, they can plasticize anything, never costs a lot, winning......

[Stwood_]