tap size for 17/64" hole

[raingolfer]

I'm replacing a few loose rivets that connect the boom skin to the boom end piece/insert (Selden boom)

I drilled off the first one, and have a hole that's approximately 17/64" measured with calipers and another drill bit.

Looking for info on what size to go with for tap (and redrill as necessary) and what size machine screw to use?

I've only tapped for 1/4-20 and smaller so don't have anything this big.

[Spot]

A drill and tap chart used to be a mandatory poster in an engineering office or machinists' work area.
Now I just look for 'drill tap chart' on a search engine when I need one.
https://www.google.com/search?q=drill+tap+chart

[GordMay]

“F” Drill 17/64" (0.2656") diameter hole for 5/16" - 18 Screw/Bolt tapped for 75% depth of thread.

[raingolfer]

Awesome. Thanks for the responses.

[RaymondR]

You would be better off in the long term to use monel rivets with a chromate paste. Blind rivets are much easier to remove by drilling through than screw threads.

[Boatyarddog]

Originally Posted by raingolfer

I'm replacing a few loose rivets that connect the boom skin to the boom end piece/insert (Selden boom)

I drilled off the first one, and have a hole that's approximately 17/64" measured with calipers and another drill bit.

Looking for info on what size to go with for tap (and redrill as necessary) and what size machine screw to use?

I've only tapped for 1/4-20 and smaller so don't have anything this big.

I agree, this shouldn't be machine screwed together.
Think about how difficult it'll be to drill that out if it gets corroded, and you need to remove it for service.
At least tuff gel the threads of the screw.
The proper size rivet would be best.
Cheers
SV Cloud Duster

[deblen]

MM to Inch Chart.pdf


What about 1/4" dia. aluminum pop rivets?
https://www.homedepot.com/p/Surebond...-100/204285932

[Eigenvector]

But............If you tap it you want at least 3 threads trhough the thickness. Maybe that's why it had rivets. Just saying.

[GordMay]

Originally Posted by Eigenvector

But............If you tap it you want at least 3 threads trhough the thickness. Maybe that's why it had rivets. Just saying.

3 Threads on an 18TPI bolt requires a thickness of only 0.166" or 1/6 inch (<5mm).

[Benz]

Originally Posted by Eigenvector

But............If you tap it you want at least 3 threads trhough the thickness. Maybe that's why it had rivets. Just saying.

Beyond the thin-walled boom section is a thicker casting, which will have plenty of meat for tapped threads. Rivets tend to get baggy and work loose over time--far better to tap and screw. Tef-gel will keep them from seizing up in future, as will blue loctite.