[dataway]

I working on a project to 3D print 68 GTO grill mounting pins, the ones that always break off. Not sure if the 69 uses the same type or not.

Anyway, when I was restoring my 68 I turned up a couple of needed pins on the lathe, smoothed off and drilled out a hole in the original pin location and installed the pin setup you see in the rendering below.

Kind of a pain and tedious to make them on the lathe out of aluminum so I thought I'd try 3d printing them. Results are good so far, they would mount the same way ... using the original location/pad with the remnants of the broken pin ground off, and a hole drilled to mount the new one.

Since the original project I have lost my measurements for the OEM pin and I don't have a spare grill here. I was wondering if someone could measure the pin diameter, length, and how large the circular base can be (seems like I remember some support ribs on the grill that limit the base size).

Strength of my test prints seem more than adequate.

Not sure if anyone needs a solution like this .. but pretty easy, do the prep on the mounting location, use a screw and washer on the back side, thread it into the new pin from the bottom ... done.

3D printing file, CADs file etc .. free for all when perfected. And I'm sure I could send out some for just the price of postage (please, just if you need them as opposed to "in case you need" them).

Also a picture of my other problem solver ... rivet on tabs for 68 defrost vents with tabs cracked off.

Thanks

[Greg Reid]

Those are an excellent contribution to the hobby dataway. Kudos!
I have an extra set of grilles somewhere in my stash. As soon as I get a chance I'll measure them if no one else does first.

[dataway]

I think I have the diameter right, but not sure how long, or how big the built in base washer can be.
Thanks, no hurry.

Eventually as the 3D printing hobby matures it would be nice to have a topic with DIY replacement parts people can print.

[Greg Reid]

Oops... almost forgot about this..lol.
Funny thing is, this is the only pin that survived on this set...so yeah, I'd say there's a need alright.
On the set in use on my car I needed one or two. I drilled a hole in the center of where the pin was previously moulded in and inserted a 1/2" #10 or so panhead screw with a piece of vacuum hose pushed over the threads. The rubber hose holds it in place and makes up the diameter needed.
I like your idea better.
My idea works fine for one or maybe two missing but they need to be a firm fit for rigidity. Yours will provide that.

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[dataway]

Excellent, thank you, very helpful.

I'll adjust the CAD drawings and print up a bunch of them.

[dataway]

Greg I printed up a batch of four pins (as seen below).

I made them a tad larger in OD than OEM, and tad longer than OEM.

Hopefully for a bit more secure fit than OEM.

Anyway ... if you PM your address I'll send them out for you to test. You'd have to supply the hardware (unless in the meantime I find the appropriate stuff in the shop). I realize you aren't going to disassemble your car to check the fit ... but I trust you can eyeball them and see if they will work.

To be honest my GTO is right down in the shop, but I also don't want to take anything apart So maybe compare these to the one remaining pin you measured to see if you think they will work. I don't have any more old grills lying around.

When it comes to the screws .... big enough to bite, not big enough to split them. Holding them still to install the screws might be sketchy. If too sketchy I could add flats for a wrench.

[Greg Reid]

I'll be glad to check them on my spare. We're not talking machine tolerances here. I'm sure they'll work.
pm coming.

[dataway]

Greg, check your PMs ... package on the way.

[Greg Reid]

PM rx'd

[Greg Reid]

Ok, finally got around to checking these out. I think you have something here that'll be useful.
I started by filing the remnants of the old broken pins flat. There's a parting line there that might need to be dealt with but I didn't concern myself with that and just filed the pin "stump". I forgot to take pics of that.
I then drilled a pilot hole making sure that it was centered on the old pin location and enlarged it to just a fraction over 5/16" ... I think it was 21/64 or something, not critical there.
The mounting method is fine but I would suggest an Allen head screw because you need an "L" shape on the driver. "L" shaped Allen wrenches are much more common in the average toolbox than similar Phillips head drivers.
Overall I think they'll work great!
Pics of typical broken state and your repair pins next to unbroken originals.
Actually, the final pic shows that you could just about use it without the screws if you insert it from the back, just not sure what type of adhesive will bond to the material.

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[dataway]

Greg, excellent, thank you for the testing.

When I installed a similar fix on my grills I did use socket head screws (the pins were machined aluminum) I ended up sending you whatever hardware I had on hand that would fit. I'll modify the design so the hole is the right size to just thread in a allen bolt.

Looks like they may be a tad too tall? I figured they can stick through the mounting grommet as far as they want .... but too tall might make the grill hard to install.

I thought about the installation from below ... but I'm skeptical of the strength of the pin without a screw inside to strengthen it. Of course ... I guess if they did install from below I could print them with solid pins for more strength.

Hmmm ... makes me wonder if I could print them with flexible (think hard rubber) material ... and then print up insert pins that would push in from the bottom and lock them in place .... like a late model plastic fastener where you put in the a pin, then push another pin into to lock it in place (wheel wells, trim etc.)

[Greg Reid]

Yeah, there are options when it comes to how they are secured. I don't think they are too tall but they are probably a hair taller than the original the way they are mounted with the screw because of the thickness of the pedestal.. Inserted from the bottom they are probably about the same amount short but I think either way it will work fine.
If I feel energetic and the day is nice I might actually mount one but as you know they're kind of nit-picky to R&R...
The rubbery material is actually nice but something stiffer and thinner might be better for the pedestal part. Don't know what if that's possible or even needed. I really think they'll work as they are.

[Shiny]

What a great idea!

How about a push-on retention clip to secure the pin? This would minimize the shoulder height and probably be strong enough. The pin is just to align, correct? So drilling a "press-fit" hole for the pin or even printing the pin with a split or tapered shank to keep it tight in the hole should be good enough.

[dataway]

Jeez, good idea, ... push it through from the bottom and use one of those clips ... it's not like they should ever need to be removed. I know from experience those clips grip plastic very well.

On a 68 the pins do actually hold the grill in place, one on each corner, and they slide into rather loosely toleranced oval rubber grommets in metal brackets. But the grill is very light, they are under very little stress. Probably more stress during installation than they ever see in use.

See .. now I have to buy a box of 100 of those from McMaster and pay $10 in shipping just so I can try it out
I don't like releasing anything into the wild unless it's as bullet proof and simple as possible.

Greg ... do you think it's easy enough to get a fairly flat surface on the underside of the mounting points?

[Greg Reid]

I think that's the perfect approach. From the bottom with a retainer on top. The length seems closer too.

That's a good question. I don't recall if that prominent parting line is present on the underside. I believe that it's flat from the way the screw and washer went on but I will verify it and confirm here.

[dataway]

I'll print out some solid pins and source some clips. I can drill a hole in something and test them. I'll reference your measurements and adjust the design to equal the OEM height when installed from the bottom.

[OG68]

I don't have any problems regarding the pins, but it's nice to know that there is a viable solution available in the event I do break one. Thanks to you both for being proactive with this.

Now I should go out and find out where I hid the grills lol.

[Greg Reid]

Verified that the interior side is perfectly flat. If you minimize that radius at the pin/base junction close to 90* you're going to get a good flat mount.


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[dataway]

I'll have to do some strength tests without the radius ... it's there because the sharp inside edge there tends to break off without a transition. Should be less of a concern with the solid pins. Worst case scenario a slight chamfer on the bottom of the hole would work.

[Greg Reid]

Exactly.. just a small inside radius I would think to avoid the stress risers.