Compressor and Air Tools

[DCASonex]

That Bosch 3/8" drill is my all around favorite, but for drilling a lot of holes at one time, air drills are hard to beat for both their speed, and their light weight. Drilling holes in the the thick spar will go much faster and easier with a good high speed air drill. Like Noel, I had a Pan American palm drill, and it is a good buy, but also splurged on a similar Sioux drill, and it is a real step above the others. With any air drill, get small light weight 25 ft. 1/4" ID hose and install quick connect coupling into a ball swivel in base of the drill. Small light and powerful means less hand fatigue and that means fewer errors. Select your drill, then look at what PSI and CFM is recommended for it and purchase a compressor larger than that. Pay no attention to the often phony HP ratings on compressors.

If you live where compressor noise will not be acceptable, battery operated will do the job, just slower. If you are the only one likely to be bothered by the noise, can compressor be located outside of your work area ?

To save time when switching between tools like the riveter that most folks recommend using at low pressure and an air drill at 70 - 80 PSI, fit a flow control (with quick disconnect) in the port of the rivet puller and set it just barely open so that bit takes about 2 full seconds to pull each rivet when operated from same line and PSI as your air drill.. Internal pressure when rivet pops will be no higher than when operated from a low pressure line. Flow controls can sometimes be found combined with swivel fittings saving weight and space. The slow action also allows time for the pulley to self align with surface once you get used to loosely holding it, and this minimizes the occasional cocked rivet that needs to be drill out and replaced. (Use your low speed battery operated drill for drilling SS rivets.)

With battery operated drills do not waste time of money on anything that does not use lithium battery, and stick to quality name brands.

David A.

[dxlusby84]

Several of you make good points about air tools having their own attraction, regardless of whether a cordless will do the job. Do I hear the thread right - the general quality equation here is: Both Air and Cordless drills will make a clean enough hole for the job. Both will require deburring, the cordless will likely require more. Of key importance to the drill itself is the form factor required to get in some places where larger or heavier drills would create the potential for a bad hole.

On that last point - if you drill a bad hole, do you have to throw away the component/assembly? How critical is it on a piece to do them all 'perfectly' (or at least 'good enough') and what is 'good enough'?

[kmacht]

For all practical purposes you won't find any difference in the actual hole shape or size for what is needed in building a sonex with pulled rivets whether you use a cordless drill or an air drill. A correct size sharp bit in either one will make holes in sheetmetal perfectly acceptable. As far as making one bad hole a tech counselor once told me not to fret over it. One bad hole or rivet is not going to make your airplane fall out of the sky. There is so much margin built into the structure that a few bad rivets out of the 10,000 holding the plane together won't matter. Trust me when I tell you that you will see every flaw in your plane when done but others won't see any of them.

Keith
#554

[Bryan Cotton]

I've worked at a couple airframers. The design guys assume the shop will screw up 10% of the rivets. Our standards should be higher. I don't redo a rivet if I think it will be worse from fixing it.

[mike.smith]

Like Keith said, both will work. I used an air drill for about 2 days. I had a very large air tank but still got tired of waiting for the pressure to come up, dragging the darn cord around, and wearing hearing protection. I spend the next 5.25 years using nothing but a cordless hand drill (and the drill press of course). I found the cordless to be much faster to use, and quieter. If I had 10 more planes to build I'd still do it with my cordless. Sharp bits make much more of a difference than the drill that drives them.

[NWade]

On that last point - if you drill a bad hole, do you have to throw away the component/assembly? How critical is it on a piece to do them all 'perfectly' (or at least 'good enough') and what is 'good enough'?

Just wanted to follow-up on this question...

There is no blanket answer that will cover all situations. You will have to learn to judge what is safe & acceptable; but AC-43.13 has a ton of good info to help. And if you haven't been to an EAA SportAir workshop on sheetmetal, that will help too. And there are other resources (such as Ron Wanttaja's "Kit Airplane Construction" book).

Having said all of that, here are some of the questions I ask myself, when looking at a hole or a rivet:

1. Is the hole within ~1/32nd of an inch of where the plans said it should be?
2. Does the hole have enough space / edge-margin (see AC 43.13) from other holes and from the edge of the part? Note that having a tiny amount less than the minimum (such as 1/64th of an inch) does not doom your aircraft to immediate destruction, and there are parts on the Sonex where it is nigh-impossible to meet the edge margin requirements unless you are 100% accurate. But consistently failing to keep edge margin (or undershooting it egregiously) should be grounds to disqualify a part and re-make it.
3. Does a rivet (or bolt) of the appropriate size fit in the hole without excessive slop? If not, can the hole be drilled to the next-larger size of fastener and still preserve edge-margin minimums?
4. Do the parts fit together nice and tight/flush with no gaps? If not, can burs or other material be safely removed to allow the parts to fit together snugly?
5. When the rivet is inserted, does the rivet head fit nice and snug/flush against the part?
6. When the rivet is pulled, to the parts end up pulled tight against each other with no gap between them? Its possible for the rivet to expand with the parts not sitting tightly together and they get locked in place with a slight gap - this weakens the part noticeably and the rivet(s) should be drilled out and the part re-riveted properly.
7. When the rivet is pulled, does the rivet mandrel snap off flush with the rivet and/or below the top of the rivet head? If a "spike" sticks out the top of the rivet head afterwards, then the hole was too big (or was widened during the rivet pull), and the rivet is not actually joining the parts with the proper amount of force. i]Personally[/i], I am OK if this happens 1-3 times on large parts (like fuselage side skins) - provided that they are widely scattered across the part and do not appear to be in an area that has special structural significance (for example, on a splice plate). As others have mentioned, some areas of the aircraft structure have a bit of margin built in; but you need to acknowledge that each time you allow a sub-standard rivet to remain you are eating into that margin, and its a cumulative effect. If they are clustered together or are in an area of significance then its time to decide whether to replace the part, or decide if you can use some kind of a shim to ensure that the rivet doesn't pull all the way through. The decision has to take into account what loads the rivet area is likely to take, and in what direction (i.e. in shear or in tension).
8. After the rivet is pulled, look at the two (or more) materials that you're joining. Are they being held together flush across a wide area? Riveting isn't just about pinching items together at a particular spot, where the hole is. Riveting its about pressing items together over a broad area - in the spaces between the rivets. This direct contact across an area provides friction & strength to help spread loads. So look at the part and make sure that the rivets aren't the only points of contact between the parts. If the material is "sagging" or separating in the spaces between the rivets (with the exception of some curved or fluted areas, like the leading edge of the wing ribs/skin), then your holes through the parts were not drilled with them clamped properly together and you should think about re-making one of the parts so that they join more-consistently and strongly.

I hope this helps!

--Noel
Sonex #1339

P.S. One final note about cordless drills: I think your statements about deburring and form-factor are correct. Its important to note that a cheaper air-drill will be almost as bulky and heavy as a cordless drill; but an air-driven "palm drill" is a lot lighter and smaller (making it easier to maneuver and less-fatiguing on your wrists and hands). This is going to come down to a personal preference and a work-style. If you work in short bursts or have large/strong hands then you may not be affected by the differences in form-factor. If you work on the aircraft for long stretches at a time or have smaller hands or have any kind of hand/wrist issues then you may find the form-factor playing a larger role in your decision. Additionally, personal sensitivity to wearing hearing protection (either plugs in the ears or the clamping pressure from a set of muffs) may sway you away from air-tools. Almost nothing about aircraft construction is a one-size-fits-all solution - it is a pain in the butt sometimes, but it is also quite liberating! ;-)

[pfhoeycfi]

Hi,
I ordered my first B kit and there are a couple of tools I need to consider. I do not have a pneumatic rivet puller or drill. The last time I did a build (sonerai in 86) I did it the hard way, hand puller and 120v drill. Anyway I would love to hear what other builders are using in the way of pneumatic drills and pullers...manufacturer, model, supplier. It would appear that I can get the comp and hoses at depot or lowes.

thanks,

peter
doylestown, pa
Sonex B

[NWade]

Anyway I would love to hear what other builders are using in the way of pneumatic drills and pullers...manufacturer, model, supplier. It would appear that I can get the comp and hoses at depot or lowes.

The Harbor Freight rivet puller is cheap and works just fine. I think something like 90% of Sonex builders use it. *smirk* One should get you through the entire build, but even if you have to buy a second one its a low dollar item.

My personal favorite for a pneumatic drill is the ATS Pro Palm Drill (4,000 RPM version). At ~$120 its a little spendy; but its much smaller, lighter, and quieter than any of the $40 - $80 drills you can get for cheap from Harbor Freight or Aircraft Spruce. Yet its still much less expensive than the high-end air drills.

Hope this helps!

--Noel

[x3 skier]

Hi,
Anyway I would love to hear what other builders are using in the way of pneumatic drills and pullers...manufacturer, model, supplier. It would appear that I can get the comp and hoses at depot or lowes.

thanks,

peter
doylestown, pa
Sonex B

I started my tail kit with the HF Pneumatic Rivet Puller and it quit working about halfway thru. Got one from ATS Tools and it’s been fine thru the rest of the tail kit and an almost complete fuselage. HF Tools seem to be either very good or very bad. Others have used a HF Puller with no problem. I just got a bad one. Since I only use air for the Puller, I’ve been fine with a small compressor from lowes. It’s actually the 8 gallon one I originally got with a brad nailer and stapler. It runs more than a big 40 gallon tank but it is ok for me to use.

I’ve used Porter Cable and Dewalt cordless drills for all my drilling with good results. If you really want a pneumatic drill, check out The Yard for surplus/refurbished ones.

Cheers