Stripped Le Mans 480Gold mounting holes

[Frankentruck]

The tough thing about a stud screw from the inside is that there won't be any can threads for that screw to bite into, so bonding is strictly by adhesive. Tightening and loosening a nut on the outside has potential to break the adhesive bond loose and make it difficult to tighten or loosen the external nut.

I think a round bottom punch (or a ball bearing with a regular punch driving it) could be used from the inside of the can to move some metal and close up the diameter of the stripped holes a little so there's some material to cut new threads with a tap. But there is some risk of distorting the flatness of the can bottom if going too "caveman" with the hammer blows to the punch.

[juicedcoupe]

M3X0.5 is the common size.

I have that exact kit. After slightly modifying the tool, it works fine.

Thanks! Could you elaborate on the tool modification?

I haven’t done a helicoil before but have seen a couple videos so have a basic understanding at this point.

It wasn't much. The tip of the tool wasn't grabbing the tang of the coil properly. I just tweaked the tip a little.

It would probably be fine for installing short coils into metal. I was putting medium length ones into plastic. The plastic contracts after tapping, requiring more effort to install the coil.

[morrisey0]

M3X0.5 is the common size.

Not sure why I had .35 pitch in my head, but as usual, JC is right on it and dead on.

With M3 .5, a rivnut could be an option. With such small hardware, I wouldn't think an actual rivnut tool would be required, as a jerry-rigged pulling / prying device shouldn't be difficult to come up with.

[coxbros1]

I have repaired many Le Mans motors with 3m knurled inserts from Ebay...works perfect....make sure u drill properly and I used a vice to press them in

[b027]

With M3 .5, a rivnut could be an option. With such small hardware, I wouldn't think an actual rivnut tool would be required, as a jerry-rigged pulling / prying device shouldn't be difficult to come up with.

i didn't know these existed. very interesting! The M3 ones I've found seem quite long (9mm) so may not work so well for the motor face.

I have repaired many Le Mans motors with 3m knurled inserts from Ebay...works perfect....make sure u drill properly and I used a vice to press them in

thanks for this -- now I see that was what Dadio was recommending also:

I'd try a thread insert , they are designed to be used as metal thread inserts for plastic parts ,I have some in M3 , you stick them onto the tip of a soldering iron and push them into a plastic hole meeting them into place , they are knurled on the out side to grip , I think if you drilled out the thread to just the right size hole you could press one into the ally .

I apologize, but I misread this earlier and thought the picture was a helicoil. now i see it's a knurled insert!


I'm uncertain whether the helicoil of knurled insert would be best - but it sounds like both are known to work!

At this point I'm leaning towards the helicoil since the kit juicedcoupe recommended is easy to source and has a good selection of depths. I also like that the coil would contact the entire inner diameter of the hole in the motor face plate.

The knurled inserts I've seen look like it would be harder to get the knurls to align just right with the motor face (some of the knurls may end up inside the motor and not really contacting the face plate...).

[b027]

The tough thing about a stud screw from the inside is that there won't be any can threads for that screw to bite into, so bonding is strictly by adhesive. Tightening and loosening a nut on the outside has potential to break the adhesive bond loose and make it difficult to tighten or loosen the external nut.

I think a round bottom punch (or a ball bearing with a regular punch driving it) could be used from the inside of the can to move some metal and close up the diameter of the stripped holes a little so there's some material to cut new threads with a tap. But there is some risk of distorting the flatness of the can bottom if going too "caveman" with the hammer blows to the punch.

you are right. i was imagining the remaining threads (which engage a tiny bit but can't be torqued) would be enough to hold the screw but if it broke loose could definitely be a pain to remove....

I've decided to try the helicoil or knurled insert approach, but definitely appreciate the variety and creativity of different suggestions here.

one of the things i love about the hobby is the many ways to solve problems

[b027]

I have repaired many Le Mans motors with 3m knurled inserts from Ebay...works perfect....make sure u drill properly and I used a vice to press them in

Coxbros is there a specific product you would recommend? per above i'm seeing a lot of different knurl patterns/designs for the M3 inserts and am wondering what works best for the depth of the Le Mans face? --thanks!

[morrisey0]

With M3 .5, a rivnut could be an option. With such small hardware, I wouldn't think an actual rivnut tool would be required, as a jerry-rigged pulling / prying device shouldn't be difficult to come up with.

i didn't know these existed. very interesting! The M3 ones I've found seem quite long (9mm) so may not work so well for the motor face.

That would be the uncompressed length. Once compressed, I would think they would be 5-6mm. And if too long, you can grind off excess. I found an interesting article online about installing M3 rivnuts with a standard pop rivet gun, and now I am going to order some just to have them.

[coxbros1]

I have repaired many Le Mans motors with 3m knurled inserts from Ebay...works perfect....make sure u drill properly and I used a vice to press them in

Coxbros is there a specific product you would recommend? per above i'm seeing a lot of different knurl patterns/designs for the M3 inserts and am wondering what works best for the depth of the Le Mans face? --thanks!

I will get a pic of the inserts, might not be till tomorrow, i bought them awhile back and have no link to actual units

[coxbros1]

[b027]

It took me a while to follow-through but i obtained the helicoil kit and completed the repair tonight.

I'm happy with the result! I repaired the 3 stripped holes and IMO it looks good (well, the repair, not necessarily the motor!) and holds securely on the Ultima. The motor has perhaps been too well loved by its previous owner, but this will certainly do to get it going again as a light runner

A few things I learned:

* drilling and tapping was pretty easy in the aluminum as expected. the only issue I had was i did't have the right driver to fit the square end of the tap (I assumed this would be the handle in the kit, but that's a larger bit size), so used a small 4" adjustable wrench that fit in my hand and just went slowly to keep the tap straight. not as good as a proper driver but it worked ok. I'd be interested to know what others have used with this same kit?

* as indicated the insertion tool did need some modification to grab the insert tangs more securely. I used a file to cut the notch in the tip a bit deeper and that seemed to work ok. See pictures below attempting to show a closeup of the tip after I adjusted the profile. A few of the coil inserts got bent out of shape before I figured this out sufficiently.

Lastly, if you're interested, here's the Ultima I've been working on that will get this 480Gold. It still needs quite a bit including a new body, wheels (have some ready to go), and tires, but the chassis and drivetrain have been fully rebuilt and are in pretty good shape

Thanks again to everyone for the suggestions and creative options -- This place rocks!

cheers - Brian

[juicedcoupe]

I use one of these for many small bit/tap/reamer tools.

https://www.amazon.com/General-Tools-93-Adjustable-Vise/dp/B000COYPG4/ref=asc_df_B000COYPG4/?tag=hyprod-20&linkCode=df0&hvadid=312003160272&hvpos=&hvnetw=g&hvrand=12904358575370371494&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9014054&hvtargid=pla-423287065598&psc=1