Question about rivet spacing

[musigenesis]

I have 7" diameter circular steel plates, 1/8" thick. I am using them to cover the holes left by removing the flasher lights. I am going to be riveting them in place with 1/4" steel pop rivets. Should I use 8 total rivets around the circumference or 12? Is there some sort of handy rule for the ideal spacing between rivets?

Also, I've found that in order to drill holes that my 1/4" rivets will fit into, I need to use a 17/64" drill bit (1/4" holes don't seem to fit the rivets even after de-burring). Is this normal and expected, or should I use a 1/4" bit and hammer the rivets in?

[o1marc]

If they are 1/4" rivets, use a 1/4" drill, any bigger weakens the connection.

[PNW_Steve]

Originally Posted by o1marc

If they are 1/4" rivets, use a 1/4" drill, any bigger weakens the connection.

+1

I had to use a hammer to gently tap my rivets in on over half of them.

[musigenesis]

Hmm, this source: https://www.fastenermart.com/underst...nd-rivets.html

... says a 1/4" rivet needs a hole 0.257 - 0.261 inches in diameter, suggesting my 17/64" (0.2656) bit is too large but a 1/4" bit would be too small.

Aha, same table mentions an "F" bit. I've never heard these letter-designated bit sizes before, but that's apparently what I need. Yay, I already messed up one of my plates! Good thing they weren't too expensive.

[Sleddgracer]

Originally Posted by musigenesis

Hmm, this source: https://www.fastenermart.com/underst...nd-rivets.html

... says a 1/4" rivet needs a hole 0.257 - 0.261 inches in diameter, suggesting my 17/64" (0.2656) bit is too large but a 1/4" bit would be too small.

Aha, same table mentions an "F" bit. I've never heard these letter-designated bit sizes before, but that's apparently what I need. Yay, I already messed up one of my plates! Good thing they weren't too expensive.

l've used a 17/64 for 1/4" rivets in other applications and it worked fine - no problems later on

[musigenesis]

Originally Posted by Sleddgracer

l've used a 17/64 for 1/4" rivets in other applications and it worked fine - no problems later on

I did some experiments on doing waterproof patches using the 17/64" for 1/4" rivets. All the rivets leaked a small amount and required Dynatron-550 sealant to be watertight. I wonder if they would leak less or not at all if the rivets were a tighter fit with the holes (seems obvious but you never know).

I just ordered a bunch of cobalt F bits from Amazon, after wasting an afternoon driving to Blowe's and Home Repo to learn they don't carry them.