Snug/tight fit holes

[Barry63]

I'm currently making fuse parts in order to be prepared to start the fuselage assembly when the rest of the skin material arrives. I ordered 4 reamers from 3/16" to 3/8" in order to have nice snug holes for all bolts, etc.. So I tried a few holes on scrap, mainly 3/16" material and have yet to achieve a nice snug fit hole. Tried first on the drill press starting with a #40, then double margin #40 - #30 and finishing with a double-margin #30 - #13 for the final drilling. Chucked up the new 3/16" reamer and after reaming, the bolt slipped right into the hole. No effort needed at all. Tried the same thing in the same order using my good Sioux drill and drill guide bushings with the same results. Tried the same thing for a 1/4" hole after final drilling to D with the exact same results. The reamers are Cleveland, not China junk so, what am I doing wrong?? I'm about ready to final drill to #13 and put the bolts in the freezer for final install. Getting frustrated!!

[GordonTurner]

Hi Barry

I made the same small mistake. Start by looking up the specs on AN-3 AN-4 and AN-6 bolts. They aren’t exactly 3/16, 1/4 or 3/8. I ordered reamers that were in the middle to upper range of the bolts. Works perfectly. Once in awhile you get a bolt thats looser than you want. Just grab another and save the skinny one for somewhere that seems uncritical.

Gordon

[Bryan Cotton]

What Gordon said! All my reamers are a couple/few thou short of nominal. Practicing on scrap is absolutely the way to go - A+!

[Scott Todd]

I hate to be 'that guy' but you should consider how the bolt is used. Very rarely is a bolt in pure shear where its transferring the load from one part to another. And if it is, its probably WAY oversized for the job, and it has friends to help. Most applications in our airplanes count on the bolt to create a clamping force. The friction loads will overcome whatever shear loads are present. Things like our wing bolts where there is not much clamping force due to the box spar tunnel are more critical. These should be reamed to fit. I'm not sure where on the Fuselage anything is that critical. Do the plans call out for tight fits?

[Bryan Cotton]

I used the reamers and went for the awesome fit on the critical joints - wing and tail mostly. For the majority of the bolts I drilled up in several steps, which keeps the hole more round.

We all have our different comfort levels, but I do believe that Sonex calls out tight fits.

[Barry63]

Thanks for the tips guys. Just ordered a few different size reamers from McMaster-Carr so that should get me moving along again.

Thanks Scott for the input. I am making the aft spar attach fittings on F-03 currently and I want those (3) AN3 bolts on each side to be nice and snug on those fittings. I'll feel better having snug fits on the aft/fwd fuselage splice plates too.

Any and all input is much appreciated!