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tonyjohnson

Well Known Member
I would think that the appropriate size hole for a CS4-4 blind rivet would #30. When I tried to test fit the rivet in the canopy frame of my 8A, where the skirt will attach, I found that the CS4-4 would not fit in the hole I drilled with a #30 bit.

Other size 4 blind rivets that I have do fit. The CS4-4 is just a tad too large around. Have any of you had this problem? What size hole have you used for the CS4-4 blind rivet?

I should mention that I got the CS4-4 rivet out of a bin labeled for that rivet, that came with the kit when I bought it from another builder. It is possible that the rivet is not actually a CS4-4, but I think it is.

Thanks,

Tony
 
rivet chart

With my kit 2007 model 9a, i got a rivet chart with to scale pics. It is a perfect way to hold up all the various blind rivets and ensure you know what you have incase the bins got mixed or you find a few on the floor. Someone might have it in pda form. If you get stuck let me know and pm me with a fax number and I will fax you mine. It is a very handy time saver.
 
thanks

Bob and Rick,

Thanks for your responses. Rick, I looked and found the chart that you refer to, thanks for the heads up on that.

Bob, After I identified the rivet as a CS4-4 I checked it and found that you are of course correct, 7/64 is the right size.


Thanks again,

Tony
 
At Van's catalog the correct hole size for CS4-4 is actually 1/8"... Also the name of the rivet would idicate same. :confused:

I'm having similar problems: manual calls for MK-319-BS rivets for the difficult parts of the RV-7 rudder and the drawings are talking about CS4-4s. But they both seems to require bigger hole than #40, and to be precise 7/64" hole is likely the size we look for (both) as said earlier in this thread.

I quess it's not so important when these CS4-4 are mostly used to attach fiber glass parts... and blind rivet dimples has very likely 1/8" tip.
 
I know rivets (mainly pulled rivets) sometimes don't fit in drilled holes that they should. However, run the same size reamer through the hole and they fit great!
I can't remember if a CS4-4 should fit in a #30 hole, but if it "should", use a reamer.
 
tonyjohnson said:
I would think that the appropriate size hole for a CS4-4 blind rivet would #30.
Click to expand...
Measured with a micrometer and cross referenced with a drill index chart, you will discover that a 1/8" (.1250) drill bit is the correct drill bit to prepare a hole for a CS4-4.

fuselageassembly26615cb6.jpg
 
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Rivets are mfr'd with a +/- tolerance.

Drill bits are mfr'd with a +/- tolerance.

Take a drill bit that is at the small end of the acceptable size range. Take a rivet that's at the large end of the acceptable size range. What do you get? That's right, a tight fit. (Same reason you don't want to use a #41 or #42 drill bit on these RVs prior to dimpling...dimple dies could be at the large end of the tolerance range).

Rick, your calipers read 0.12435". Time & tradition have shown you want .003-.004" clearance for a rivet. I'm sticking with #30 (regardless of this discussion). I've never had a problem using a #30 drill bit for CS4-4 rivets, and I don't anticipate a problem popping up now.

Did the original poster try a new drill bit from a different mfr? Did you measure your #30 drill bit? And did the parts shift...even just a few thou...since you drilled the hole? A tiny misalignment often makes the difference between the rivet being able to fit and not being able to fit.

IT'S USUALLY THE SIMPLEST OF THINGS. Check the simple things before deciding to reengineer the hole size.
 
dan said:
Rick, your calipers read 0.12435". Time & tradition have shown you want .003-.004" clearance for a rivet. I'm sticking with #30 (regardless of this discussion). I've never had a problem using a #30 drill bit for CS4-4 rivets, and I don't anticipate a problem popping up now.
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Dan,

That is certainly your option. I don't know about time and tradition but at McDonnell any blind rivet hole that was .003 over was cause for rejection and the hole had to be brought up oversize. Granted, we are not building fighter planes but out of habit (tradition?) I tend to adhere to the same tolerances on my plane that were expected on the production line.
Sure, a #30 drill bit will work for our purposes but if the builder seeks optimum hole quality, hole preparation with a 1/8" drill bit is the better choice.
 
Putting a different spin on this, what exactly would happen if a hole used for a blind rivet is .003 oversize instead of being a line (exact) fit? In real world terms, not theoretical ones, where only a few out of many rivets are pulled rather than driven?
 
Another guess

My other guess - again, emphasizing guess - is that the rivet would not be as tight in the hole.

Pulled rivets are designed to deform by "squishing up" the non-puller end to grip the metal sheets.

A driven rivet will "squish out" sideways and fill an oversize hole before the shop end forms over, hence hole size is less critical.

Of course, all of this depends on the rivet material and the mechanical design of the mandrel, but in general, pulled rivets need better holes.

Now does 0.003 make a difference? It might, but who knows how much....

CherryMax does give a total hole tolerance of 0.003 for a -4 rivet... details here...

http://www.peerlessaerospace.com/pub/Productimages/TAF_CHERRYMAX.pdf

NOTE: the above is for structural applications

gil in Tucson
 
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What are the real chances using any hand drill and your typical drill bit of getting a hole that is actually the dimension of the drill bit, especially when drilling through multiple pieces? (Not a rhetorical question).

And, Dan, you're probably correct.
 
I'll bet on it....

Bob Collins said:
What are the real chances using any hand drill and your typical drill bit of getting a hole that is actually the dimension of the drill bit, especially when drilling through multiple pieces? (Not a rhetorical question).
......
Click to expand...

Bob,

Actually, the real world chances are very good to get a hole within the CherryMax specifications.

A #30 drill is 0.1285 inches

The specification for the Cherrymax rivet hole is 0.129 to 0.132

Use a good sharp #30 drill and you will get that size hole. The CherryMax document I referenced earlier has warnings on multiple sheet holes that don't align (don't do it... :) ...)

Where most folks might get out of specification is by not making a hole that is perpendicular to the surface...

gil in Tucson
 
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