Deburr Dilemma

[wbpace]

From the Department of Minutiae and Other Small Matters.

OK, so this is going to sound like a silly question coming up, but bear with me for a minute.

First, the setup: I have drilled all of the holes for my myriad spar pieces slightly undersized, and am about to ream them to final size. (Yes, I know this is more work than to just drill straight to a #21 hole, as is called out in Fred's wing instructions, but lets leave that aside).

My question is: should I deburr my holes before I ream them, after, or both? Now, I know that right about now you are probably rolling your eyes : over such a trivial thing, but consider that there are almost 4000 deburring operations involved (~1900 holes, two sides to a hole). At one second per op, it will take an hour to do all of them. At three seconds, three hours. So if I only have to do it once, I can save a whole bunch of time (catch the pun there?).

See, not quite so silly after all!

It occurred to me that deburring before reaming could also reduce the net amount of material removed around the final hole. But that works only if a reamer does not leave a burr like a drill bit does.

So do we have any reaming experts out there?

The Other Bill

 

[pilotsailing]

If I was doing my spars again I would start off as you and drill them all slightly undersize first, deburr them all and then assemble with clecos. Just before you are ready to rivet then I would drill out using a #21 drill and not worry about the burr, there won't be any increasing the size of the hole that small amount. Doing it this way will ensure that all of the holes are perfectly lined up and the rivets go in perfectly.

 

[n3480h1]

Not a deburring expert, but minutiae . . . well that's another matter. Whether or not a secondary burr will be driven up depends on what type of deburring tool, sharpness of the tool, feed pressure and speed, lubrication or dry, : . If its a perfect initial fit of rivet-to-hole you are looking for, have you mic'd the rivets? You might be surprised. I'd avoid all this complication and try my options on a piece of scrap. By the time you've tried several methods on several holes, including riveting, you'll find the option that works best.

Let us know what works for you.

Tom

 

[pilotsailing]

No need to mike rivets if using standard drill bits, a no. 21 drill is .159 in and will make a hole very slightly bigger, while a no. 21 rivet is .156 in diameter . So there is at least .003 in clearance designed into the rivet and hole and this is necessary to insert the rivet without scraping and getting stuck while inserting, as well as scraping the protective cadimum off the rivet. The rivet swells when bucked and takes up the clearance.

 

[Mayday]

When I am locating critical #21 holes I usually pilot it with a #40x#30 piloted bit followed by a #30x#21 piloted bit to upsize and when installing rivets I would not worry about reaming but I would still deburr. I find that the piloted drill bits seem to keep razor sharp and make very nice holes. If I was doing that many holes i'd prbably just start with a

 

[mhflyit]

The holes on pre-punched kits aren't deburred but go together 'out of the box'. Thinking back to the RV8 I built years ago I either cleco'd pre-punched holes or drilled and cleco'd, then up-drilled to required size and then deburred both sides of those holes - lightly. Make sure your drill bits are sharp.

Hope this helps.