Do you drill to final size or ream?

  • Drill

    Votes: 49 51.6%

  • Ream

    Votes: 46 48.4%
  • Total voters
    95
Kobwo

Kobwo

Active Member
Mornin,

What is your preferred method of making the prepunched holes their final size? Drill or ream? I've read a few posts that reaming makes a more perfectly round hole with a smaller burr.

Cheers
 
Properly set, rivets swell to fill the holes so there is no need to ream for solid rivets. Not even the large manufacturers go that far. Reaming, however, is always recommended for the final pass through bolt holes.
 
What Rick said...

Rick6a said:
Properly set, rivets swell to fill the holes so there is no need to ream for solid rivets. Not even the large manufacturers go that far. Reaming, however, is always recommended for the final pass through bolt holes.
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Reaming is not necessary for rivet holes. Drilling is mostly necessary to remove the small material fractures that exist around punched holes. Dimpling a punched hole mihgt result in cracks growing from the fractures that will be further stressed by the dimpling process.
 
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Difference in difficulty / time

Over several months of reading here, I've often seen recommendations for reaming vs drilling, and that reaming results in a nicer hole, but this is the first I've heard that reaming may be over-spec'ed. Is there a difference in effort or time? I understand the reamer bits may cost more, but once purchased, is there any reason NOT to use them?

--Stephen
 
Have at it if that's what you choose..

Like Rick says, drilling is quite sufficient for nearly all riveting requirements. I suppose you have the same chance to elongate a reamed hole (marginally) because of angle of entry when you ream a wing skin or rib. I think of reaming along with drill guides to maintain correct angle of entry for bolt holes. Perhaps you are steady enough to get the ream you are expecting in all those holes without making them look like drilled holes anyways. There are also quite a few holes that require a long 6 or 12 in bit. I don't see where you're going to hurt anything.
 
Ream to final size

Drilling may produce acceptable results under most circumstances, but reaming generally produces results that are at least as good, usually better (rounder, cleaner hole). Reaming doesn't require any greater effort than drilling, nor has any other down side that I'm aware of. So the obvious question is: is there any good reason not to ream?
 
It depends...

The aft spar hole I reamed.

The holes that hold the HS and VS in place were also reamed.

Every other hole was drilled.

If you are talking about the rivet holes, just drill and deburr them and move on. Just think about how many thousands of RV's were drilled without any problems.
 
Rick6a said:
Properly set, rivets swell to fill the holes so there is no need to ream for solid rivets. Not even the large manufacturers go that far. Reaming, however, is always recommended for the final pass through bolt holes.
Click to expand...

Rick,

What size reamers do you recommend to get through the entire project?

Cheers
 
Tolerances

Rick6a said:
For the entire project, I suggest using a .310 or .311 reamer for AN5, .2490 or .2495 for AN4 and .1875 for AN3 bolts.
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A #12 might be better for AN3 bolts if you are using it correctly.

AN3 bolts are 0.186 to 0.189 diameter.

A #12 reamer is 0.189.

A good 0.1875 hole will be tight - almost a force fit - if your particular AN3 bolt is at the high end of the tolerance rance.

Buy a #12 reamer, it's probably the same price as a 0.1875...:)
 
Prepunched holes

I think the original post referred to the prepunched holes in the skin and ribs. I got some nifty #30 and #40 reamers and have indeed found the holes have less of a burr when using these reamers and prefer them to the #30 and #40 drills.
 
terrye said:
I think the original post referred to the prepunched holes in the skin and ribs. I got some nifty #30 and #40 reamers and have indeed found the holes have less of a burr when using these reamers and prefer them to the #30 and #40 drills.
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I agree. This has been my experience, too. I used reamers as much as possible for all the pre-punched holes. They do a beautiful job. I bought one #30, one #40, and one each of some of the other sizes mentioned in this thread, and they have held up very well throughout the entire project so far.
 
The thing I like about reamers on pre-punched stuff is that it's much less easy to make an accidental mark in the skin when you're tiring after a match drilling a bunch of holes.

I guess one shouldn't be waving a drill around when one is tired, but mostly it takes a slip-up to tell you that it's time to let it rest for the evening.
 
I used

1/8" and #41 reamers for my 7A build whenever possible. When you dimple a hole, the diameter increases. The slightly smaller reamers leave you with a hole closer to the ideal size after dimpling... Besides, the reamer leaves smaller burrs.

Learned this at the Cleaveland Tool metal working class.
 
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A mechanic told me that since rivets take the shape of the hole, it is preferred to have slightly irregular holes because the correspondingly irregular rivet body will be less likely to "spin" in the hole and cause smoking rivets.

The more perfect the hole, the easier it will be for the rivet to shift in the hole.

Don't know if it is true or not, but the science makes sense to this non-mechanic.
 
Rivets are shear fasteners, not tension fasteners. As such, the holes have to be sized properly, but the rivet expands when it is driven to fill the hole. As a result, the hole does not need to be more accurate than what a drill can achieve.

Bolts, however, are primarily tension fasteners. In airplanes, however, they are many times used as both tension and shear fasteners at the same time. Since they don't expand when driven, because they aren't driven, they need very precise holes to make sure that the shank of the bolt is in contact with the edge of the hole in the stackup of materials being fastened together so that they can properly perform the shear function. As a result, a reamer is required to get the proper hole precision.

There is no problem with using a reamer for rivet holes, it just isn't necessary. On the other hand, bolts in airframes should be in holes made with reamers.

Make sense?

Tim
 
Clarity welcome

tjo said:
Make sense?
Tim
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Yes, Tim, that makes sense to me now. And like all the best answers to VAF questions, your answer had the clarity and precision needed to teach not only the "what" and "how" of building, but also the "why" that is needed by beginning builders like me. So thanks for taking the extra effort to explain this "simple" issue so clearly.

--Stephen
 
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