Thread: Internal threading help

Hi

I've got a M24 coarse bolt and I need to bore and thread a nut to fit it. How do I calculate the correct size hole to bore in the nut?

TIA

That information is in a Zeus book.
For M24, core diameter is 20.3194mm; tapping drill size is 21mm

Michael

Tapping drill size is 21mm

Thanks. I should have it clear I'm single pointing the internal thread. Is the hole the same dia as for a tap?

Depending on the class of fit (how much clearance you want or need for the bolt or the application your using it in) your bore should be anywhere from 20.752mm to 21.382mm.

Originally Posted by pipeclay

Depending on the class of fit (how much clearance you want or need for the bolt or the application your using it in) your bore should be anywhere from 20.752mm to 21.382mm.

Thanks. Is there a formula for calculating this eg for a non standard application?

There are charts for standards of fit but if this is just for a standard application I would either go either with the middle of the tolerance or if you wanted go towards the larger .
Seeing you allready have the bolt it might be better to go towards the smaller bore size as production bolts generally have the greater clearance.
This is the reason why a lot of times bolts and nuts bought through hardware and engineering supplies of feel loose.
If you went with 20.8mm to 20.9mm it might make the nut a better fit.
Either way if you go you should be fine.

Originally Posted by Bidgee

Thanks. Is there a formula for calculating this eg for a non standard application?

Here you go
http://www.woodworkforums.com/f65/ch...ml#post1466509

Dave

For 60 degree threads like your M24, as a rule of thumb:
Major diameter minus pitch = Minor diameter (hole size)

24mm - 3mm = 21mm

Jordan

Depending on the class of fit (how much clearance you want or need for the bolt or the application your using it in) your bore should be anywhere from 20.752mm to 21.382mm.

The size of the bore doesn't change the fit. It can only be changed by the pitch diameter.
If the bore is too small, the peak of the nut's thread rubs against the valley of the bolt. This only pretends a close fit. In fact, the chests of the threads don't get in contact. It's just a misfit.


Nick