Drill guide for airframe...

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jahall4

jahall4

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Does anybody sell a guide (or jig) to drill 3 or 4 equally spaced holes around the circumference of an air-frame?
 
^+1 If you are really anal you can use angle aluminium and install a drill bushing for an exact 90 deg angle to said airframe. (Yes, I've done it for shear pins) Pressure relief holes are not critical.
 
If you know someone with a 3D printer they can make awesome drill alignment jigs.

Normally I just use a paper wrap To get them in line, and measure each way around from a starting location and split the difference.
 
OverTheTop said:
If you know someone with a 3D printer they can make awesome drill alignment jigs.

Normally I just use a paper wrap To get them in line, and measure each way around from a starting location and split the difference.
Click to expand...

I do as well and have some other tricks too, but in this case I want to be able to repeatably drill the same holes in the same place on tube after tube.

The 3D printer is a good idea because the jig could position AND "plumb" the hole. I could always draw something up and have it printed, but I'm hoping someone has already addressed this issue.
 
OverTheTop said:
I would just run a pencil reference line up using an angle from the first marking.
Click to expand...

"First marking"?

I referring to repeating on multiple tubes. Say you had 1 coupler and 5 tubes... when I'm done drilling, all 5 tubes would align on the coupler in any rotation.
 
I've never heard of such a guide. You'd have to have a different one for each tube diameter.
 
OverTheTop said:
Correct. You print them as needed and throw them away when they fob out a little. Disposable items. Work really well.
Click to expand...

I suspect the guide holes themselves might be a challenge with the 3D print, but the design could "mark" where they should be so they could be drilled out. I don't think you would be throwing a lot of them a way if you use a drill press.
 
jahall4 said:
I suspect the guide holes themselves might be a challenge with the 3D print, but the design could "mark" where they should be so they could be drilled out. I don't think you would be throwing a lot of them a way if you use a drill press.
Click to expand...

That's a neat idea- I've always struggled getting my holes equally spaced, so I end up having to "key" everything. I'd love to be able to just line up one hole and know that the others are lined up too!
 
soopirV said:
That's a neat idea- I've always struggled getting my holes equally spaced, so I end up having to "key" everything. I'd love to be able to just line up one hole and know that the others are lined up too!
Click to expand...

Your "struggles" may be near an end. :) I'm talking to a 3D printer later today. Since the jig would be little more that some combinations of primitives it should be easy to model.
 
jahall4 said:
Your "struggles" may be near an end. :) I'm talking to a 3D printer later today. Since the jig would be little more that some combinations of primitives it should be easy to model.
Click to expand...

Would love to see what you come up with! My nephews are into 3D printing, or were, anyway, not sure if college has gotten in the way. If you're willing to publish a file, you could help a ton of people out (unless you're planning on commercializing, in which case I may be interested in ordering!)


Sent from my iPhone using Rocketry Forum
 
The guides are seriously simple. It is a ring of plastic (with enough length to keep it square on the tube) with a known diameter hole in the middle, radial holes in the locations around the ring guide the drill.
 
OverTheTop said:
The guides are seriously simple. It is a ring of plastic (with enough length to keep it square on the tube) with a known diameter hole in the middle, radial holes in the locations around the ring guide the drill.
Click to expand...

Certainly, although depending on printing costs I will take it a step further.

I'm beginning to suspect the reason no one already makes this product is due to cost to produce them. :(
 
jahall4 said:
I'm beginning to suspect the reason no one already makes this product is due to cost to produce them. :(
Click to expand...
The materials cost in printing them would be pretty low, but any 3d printed part takes time to make. I’d consider designing & printing some to put on Amazon for sale, but I’m not sure anyone would buy them. Also, I’d need to figure out what exact diameters would be popular...maybe start out with ones to fit Madcow’s thin-walled fiberglass 38 & 54mm rockets and go from there...?
 
GrouchoDuke said:
The materials cost in printing them would be pretty low, but any 3d printed part takes time to make. I’d consider designing & printing some to put on Amazon for sale, but I’m not sure anyone would buy them. Also, I’d need to figure out what exact diameters would be popular...maybe start out with ones to fit Madcow’s thin-walled fiberglass 38 & 54mm rockets and go from there...?
Click to expand...

Exactly, its one of those things where many may not understand why you would want (even need) to use them. Although, I think I can keep the print time to a minimum. As with most everything else in rocketry size is directly proportional to cost.
 
OK, I'm officially confused. I read through the thread and still don't understand why you need a drill guide for holes? If you are doing vent holes for a av-bay, just eyeball the locations and drill. The location tolerances for proper sampling holes in a av-bay are huge and an eyeball location is more then accurate.

If you are talking about shear pin holes, how many different rockets are going to use different av-bays or nose cones? I use one av-bay and one nose cone for each rocket. If you want to make sure the shear pin holes are always aligned right, you don't have to have them exact, you just need to use alignment pins at the joints, like this https://www.rocketryforum.com/showthread.php?140178-Blue-Baboon-One&p=1693535#post1693535
 
Handeman said:
OK, I'm officially confused. I read through the thread and still don't understand why you need a drill guide for holes? If you are doing vent holes for a av-bay, just eyeball the locations and drill. The location tolerances for proper sampling holes in a av-bay are huge and an eyeball location is more then accurate.

If you are talking about shear pin holes, how many different rockets are going to use different av-bays or nose cones? I use one av-bay and one nose cone for each rocket. If you want to make sure the shear pin holes are always aligned right, you don't have to have them exact, you just need to use alignment pins at the joints, like this https://www.rocketryforum.com/showthread.php?140178-Blue-Baboon-One&p=1693535#post1693535
Click to expand...

I'm 1:1 too, so my desire isn't to make avbays or cones transplantable, although that would be a nice benefit. I just like to know I've done my best on something, and not having to use a key alignment is a pretty good indicator of that. I'm not beating myself up over it, and have incorporated the "key" concept into paint jobs I'm pretty happy with, but it would just be the next level in skill building for me.
 
Probably not appropriate for shear pins, but when I've done screwed-together components (e.g. securing an av-bay), I do intentionally mis-aligned holes. So if I'm doing three, instead of doing them at exactly 120 degrees each, I'll do something like 110/110/130. I do this because that way, I don't have to worry about the hole spacing being precisely perfect.

Here's my thinking:
If you go for 3 *perfectly* spaced holes, then ideally, you can just slide the bits together and twist until two holes line up, then the other holes do. To get that to work, the spacing needs tiny tolerances - 0.5mm is enough that a screw won't line up with a hole. And if you have one hole that's just *slightly* off, you either have to make a reference mark for joining the pieces (OK, I know that if I align these marks, everything lines up, but any other configuration and one of the holes is going to be off by JUST a hair.) or you have to try each possible combination until you get the sweet spot.
Instead of dealing with that, and knowing that I don't have a machine shop and my precision just isn't where I want it to be...
I drill the holes so that they're close enough to "evenly spaced" that they'll share the load reasonably, but off by enough that there's only one way that fits and there's no "is this right? Why isn't this screw fitting? OK, let me twist it and try this. Nope, not that way. OK, one more twist and ...WHY ISN'T THIS WORKING" nonsense when I try to assemble it.

Does that make sense? I think I need more coffee.
 
There was talk not long ago of durable, metal drill guides for various airframe sizes. 3D printed ones that could easily and cheaply be replaced might be a better way to do this. Is there a place to openly share rocketry 3D designs so others can download and print the same object, royalty free? Could be drill guides, av-bay sleds, decorative add-ons, bulkheads for non-structural needs, fly away guides, etc.
 
Thingiverse is where to look for shared things to 3d print. I’ve shared a few rocket part designs there.
 
Viperfixr said:
There was talk not long ago of durable, metal drill guides for various airframe sizes. 3D printed ones that could easily and cheaply be replaced might be a better way to do this. Is there a place to openly share rocketry 3D designs so others can download and print the same object, royalty free? Could be drill guides, av-bay sleds, decorative add-ons, bulkheads for non-structural needs, fly away guides, etc.
Click to expand...

Maybe something like a rocketry CAD repository: https://drive.google.com/drive/folders/0B61IjVuE29dEQ2V5SVlIc21NcEU
 
OverTheTop said:
The guides are seriously simple. It is a ring of plastic (with enough length to keep it square on the tube) with a known diameter hole in the middle, radial holes in the locations around the ring guide the drill.
Click to expand...

Heh. It can be simple, as long as you don't over-engineer everything. :) I've printed several drill guides in different sizes, the current version looks like this:

Screen Shot 2017-09-21 at 8.27.59 AM.pngP9210001.jpg

The holes I print are rather large, a few years back I bought a tube drilling guide from Dog House (the thing next to my printed ring guide, Binder didn't pick this up, apparently, so it looks like it's no longer for sale), it's basically angle-iron with two spots for inserts, and it came with a few inserts for different sized drill bits. So my printed guide uses the same hole size to accept the smaller inserts (they fit a bit tight so there's no wobble), and I can use even smaller bits provided I build-up the bit with some blue-tape to make it a good fit in the insert. But that way my drill bits aren't digging into the plastic and growing my printed holes, and I can handle many different bit sizes as well.

The first time I drilled shear pin holes manually I always had to ensure I had the nose in the right position to have all of the holes align, once I started using my guides any of the positions worked interchangeably. I even care about my vent hole positions in AVBays, because I line up the LED on my Featherweight Magnetic Switches with the holes, both so I know where to swipe the magnet and so that I can visually confirm that the LED is lit. So to ensure my printed sleds "just work" I need fairly accurate positions on the airframe holes.

I will note, however, that even the different colors of RW/Madcow tubes come out to different ODs, I have a Double Shot sustainer and Go Devil 54 that are both RW 54mm tubes (purchased at the same time), but things printed for one don't work on the other (I think the green turned out slightly larger OD than the yellow, but that might be backwards). Not a huge deal when you're printing your own parts, but makes it quite a bit harder to try to make a one-size-fits-all part for sale. Not that the smaller tube couldn't be shored-up with blue-tape or something to make up the difference, just an extra complication.
 
You should size the holes in the printed guide to accept an aluminum bushing. That way your drill bit (1/16"?) goes in the bushing and then doesn't wear your guide out.

I made guides out of PVC for the sizes that I typically use like this. I used a dividing head for spacing.

Edward
 
Here is one (the black one) I had printed yesterday for my Vertical Trajectory System. It suits 4" airframe.

The orange one is for drilling 38mm NC to suit a GPS sled (thanks Chris!).

Note that the orange one has some thin extra height added to keep it aligned better. Also, the black one uses small bosses rather than a thick band, so it uses less print material. It is able to do this because it has a two-head extruder and uses support material (dissolved after printing).
Guides.jpg
 

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