Calculating rivets lengths question

mikehoover · #1 05-24-2013, 10:48 AM

Is there an excepted industry standard for rounding rivet sizes up or down?

I have calculated the required length of many rivets during my build using the:
(1.5 x rivet diameter + metal thickness ) x 16 to get the length of the rivet in 16th inches. This leaves decimals so at first I would think you would always round up to the next size (half or whole as available). Sometimes this leaves the rivet longer than you would want, rounding up from a small decimal.

A few examples with a rivet diameter of 4/32":

1. Metal thickness: 0.064 calculates to a rivet length in 16th " of 4.024. Would you round this down to a -4 or up to a -4.5?

2. Metal thickness: 0.1280 calculates to a rivet length in 16th " of 5.0480. Would you round this down to a -5 or up to a -5.5?

3. Metal thickness: 0.2560 calculates to a rivet length in 16th " of 7.0960. Would you round this down to a -7 or up to a -8? (not sure they make 1/2 sizes after -5.5)

I guess my question is: is there a decimal point where it is technically correct and acceptable and industry standard to round down, ie, anything 0.010 or less for example, then round up it is greater than that?

jdeas · #2 05-24-2013, 10:55 AM

May be over thinking this. Purchasing a rivet gauge and a rivet cutter is faster.
There were several places in my build where I used the combo to get the longer pulls to 1.5x value. Saves drilling out shorts or toppling 2x.
I always went tall when there was a question. As long as I was +.5x I never had a problem.

David Paule · #3 05-24-2013, 11:11 AM

Also download the spec for riveting on Van's site. It lists the minimum and maximum sizes for the shop heads, and a bit of experience will help you decide which rivet will get you there.

Dave

aerhed · #4 05-24-2013, 11:48 AM

Also, your shop head will vary with hole size. A larger hole will use more rivet to swell leaving you with a shorter shop head. Since each hole is slightly different.........

agirard7a · #5 05-24-2013, 02:27 PM

Exactly what David said. Check out table 3.
There is no max diam for shop head just a min.
and max and min on the height.

My experience is that a shorter rivet vs. a longer (1.3 vs 1.5 of diam. out of the material)
will most often get you into spec. As the shop head
Given the correct spec on the driven height will easily
Give you the min diam. Experiment and you will see.
Use a 1,000 gauge caliper to measure both height and diam.

http://www.vansaircraft.com/public/Specs.htm#TABLE%20II

longranger · #6 05-24-2013, 04:26 PM

I never knew there was a problem with shop heads too thick. What's the problem if the driven diameter is sufficient and the rivet is not clenched?

RVRC · #7 05-24-2013, 04:40 PM

Mike, I have a rivet cutter in my hangar if you need it. I should be there tomorrow, but you know how to get in if you want to.

az_gila · #8 05-24-2013, 11:03 PM

Quote:

Originally Posted by longranger

I never knew there was a problem with shop heads too thick. What's the problem if the driven diameter is sufficient and the rivet is not clenched?

I think it might be a clearance issue in assemblies. Not really a RV problem, but the spec would set a limit on how close riveted assemblies can be mounted.

I haven't had this confirmed though.

az_gila · #9 05-24-2013, 11:04 PM

Quote:

Originally Posted by aerhed

Also, your shop head will vary with hole size. A larger hole will use more rivet to swell leaving you with a shorter shop head. Since each hole is slightly different.........

And round up when dimpling is involved.

This enlarges the holes somewhat and the holes also loose their straight sides.

DaAV8R · #10 05-24-2013, 11:42 PM

It has been awhile since I visited this question. I had the same question when I started my project. Initially, I just tried to use the 1.5 dia. protrusion but I quickly discovered that didn't always work. As I don't generally accept things at face value, I set out in search of some data to support the 1.5 diameters. I started with some simple volume calculations. Allowing for the swelling of the rivet within the hole, my calculations ( to the best of my recollection) showed something closer to 1.3 diameters to be ideal for the relatively short rivets we are using.

I have a copy of the Riveters Manual, fourth edition, 1 Aug 1967 on my shelf. A check of this manual finds a paragraph with illustrations which states, "As a general rule, the rivet should protrude at least 1.0 to 1.5 times its diameter before driving, with a protrusion of 1.3 times the diameter desirable".

I generally use 1.5 diameters as a maximum but never less than 1.3 diameters. The exception would be long rivets where more material is required to fill the hole. Protrusions greater than 1.5 diameters are easy to clinch if you are not on your A game.

On a side note, I don't see who published this Riveters Manual, although I think I have found reference to one of the big manufacturers buried somewhere in the manual in times past.