What size drill bit for 5/16" tap?

Want to tap repo. '40 steering wheel hub so I can use my steering wheel puller. Puller bolts are 5/16," what size tap do I use?

 

17/64 drill for 5/16-18 threads

 

Thank you!

 

Letter Drills
5/16-18=Letter F
5/16-24=Letter I

 

Something I've got bookmarked.

http://frentzandsons.com/Hardware References/tapanddrillsizes.htm

 

Here's an opportunity to print a reference on tap drill sizes.

 

If the tapped hole engages 2 full diameters of the bolt/screw, the tap drill size can be enlarged a little bit and decrease the "probable % of thread" and still maintain 100% of the fastener strength. That can be handy when tapping tricky materials or scary deep holes with smallish thread sizes.
I think Machinery Handbook has a few extra columns in their tap drill charts for reduce probable % of threads.

 

X2, ....will def. reduce the oh shit factor

you should be good with an "f" drill, .257" dia. & it will probably run out a few thousands also, up around .259-60"

 

There's one in the back pages of a book I needed for my welding classes. Came in handy a few times.

 

you can always google drill tap chart

 

Many times the drill size is marked right on the tap. Old repair manuals usually have a chart in the back for reference.

 

in general different metals require specific tap clearances. aluminum should be drilled tapped with lubricant for aluminum to prevent galling. turn tap a 1/4 turn at a time then reverse about a 1/2 turn. it is very easy to break a tap off in aluminum even though it is soft than steel. chamfer the drilled hole so as not to create a paper thin thread at the top of the hole. there are also chamfer charts for this. get a machinists handbook. it can be a great help when working with metals. use a drill block to keep drill and tap straight in hole.

 

In what I thought was a very simple question with a simple answer turned out to be a thread with a lot of interesting facts.

Thanks to all for the info.

 

Good rule of thumb. Hold drill in front of tap and be able to see the threads of the tap and not the shank. Also works for metal screws etc.

 

Yes for the most part it is. I just went though hunting down the right drill bit size for a tap last weekend. The drill bit/tap charts are invaluable to have in your shop info binder.

 

did you know......

the tap-drill size for metric bolts is..

the major diameter less the pitch, (both in millimeters)

for instance; M8x1.0 , tap drill is 7mm

M24x3.0, tap drill is 21.0mm


of course, most people don't have metric drills (me included), so a close English equivalent would work.

 

Yep, glad I didn't post some snappy answer like "look it up dummy".