Benefits of line drilling rivets 1

[ddelaiarro]

I've read in multiple locations that line drilling rivets is beneficial, but I've never seen a technical (comprehensive or otherwise) discussion of why. Does anyone have any links to resources that discuss the why behind this suggestion?

 

[SWComposites]

do you mean drilling both sheets at the same time?

 

[ddelaiarro]

Yes, in a semi-assembled state.

 

[SWComposites]

that is the preferred approach, as it is unlikely to get holes to match up if drilled in each part separately. and its typically not acceptable to drill oversized holes to get them to line up, as the rivet will not fill the holes properly.

 

[IFRs]

Remember to separate the plates and remove any shavings prior to riveting.

 

[Compositepro]

Is "line drilling" a common term. I've never heard it before. I would call it "match drilling".

 

[ddelaiarro]

Is "line drilling" a common term. I've never heard it before. I would call it "match drilling".

I've heard it called both. I think "line drilling" is used because it's a (production) line function. Match drilling more accurately describes the process, however.

Back to the original question, though, does anyone have any technical articles on the topic? I understand the conceptual "why" as SWComposites mentioned above, but I'd like to dig into the analytics of it.

 

[SWComposites]

Not really sure what "analytics" you are looking to dig into. ??
Rivet install specifications (rivet supplier or internal company) typically call out a hole tolerance. Match drilling is typically the only way to meet those tolerances.

 

[ddelaiarro]

I guess what I'm looking for is an analysis of why those specs are the way they are.

What's driving this is a Quality Manager who is more concerned about FOD on the floor from match drilling than proper assembly.

 

[Tmoose]

"a Quality Manager who is more concerned about FOD on the floor..."

FOD = Foreign Object Debris ??

I'd have thought a shop vac would clean up the drilling process.
I think IFR's comment about deburring is worth noting. The non-aeronautic holes I drill in my garage are sometimes pretty ragged. Even when two panels are held together for "match drilling." A few times burrs on the faying surface panels resisted the (pop) rivet's efforts to pull the panels tightly together. Probably steel panels, not aluminum, but still.

 

[SWComposites]

Well, WTF does the QM propose doing? Drill the parts separately? And how does that genius expect the holes to line up?

Are you working to internal or customer specs? If customer specs then will the customer accept parts that are not match drilled?

And the hole tolerances are likely linked to proper rivet install and the tested rivet/sheet strength.

 

[ddelaiarro]

Well, WTF does the QM propose doing? Drill the parts separately? And how does that genius expect the holes to line up?

Are you working to internal or customer specs? If customer specs then will the customer accept parts that are not match drilled?

And the hole tolerances are likely linked to proper rivet install and the tested rivet/sheet strength.

I don't disagree with you, SWComposites. He thinks holes drilled separately will be "good enough" and not require the extra work and potential FOD on the floor. It's kind of ridiculous, and frankly, the arguments over dimensioning vs. strength are what's driving me toward this question.

It's our design, so most specs are ours, but your point on the customer specs may be important. I'll have my Project Engineer look into any Fastener specs the customer has.

I appreciate the feedback.

 

[IFRs]

It's not out of the realm of possibilities that a CNC punch would work on individual parts better than drilling.

 

[SwinnyGG]

Much depends on the scale of the part you're arguing with your QC guy about.

Match drilling happens a lot in the aerospace world because they are very frequently assembling very large, flexible parts which may have hundreds of rivet holes per part, and they are often riveting three or more of these parts together, using rivets with very tight hole diameter requirements. Delivering parts with all the holes drilled such that they properly align on parts like these is very difficult.

If you're riveting smaller parts, it gets much easier to use pre-punched assembly components.

You may be able to demonstrate this easily by performing a tolerance stack analysis on your parts, and showing clearly how hard it may be for your vendor to supply pre-punched parts that will assemble correctly.

 

[SWComposites]

Yes, should have mentioned/asked, how many rivets in the part? if only a few, it may be possible to pre-drill/punch the holes and have the tolerances acceptable
Please post a picture of your assembly
And what type of rivets are you using - squeeze, driven, blind? material? into what sheet material?