repairing threads in hardtop

Body, Paint, Interior and Trim questions and answers

Moderators: timk, Stu, zombie, Andrew, -alex, miata

User avatar
Alex 2550
Racing Driver
Posts: 561
Joined: Mon May 11, 2015 12:01 pm
Vehicle: NA8
Location: Far south coast NSW

repairing threads in hardtop

Postby Alex 2550 » Mon Jul 17, 2017 2:45 pm

Hi everyone,
just thought i would share my experience from the weekend to hopefully benefit others and hopefully save someone some time and potentially a hardtop.
so my drivers front hardtop latch was loose with around .5mm of clearance under two bolt heads, i know this latch had been off before because the 2 bolts didn't match all the others, i also suspected that they were a fraction too long because there is a very slight crack in the paint directly above the rear inner bolt hole. the factory looking bolt came out easily with a orange thread sealant on it.
the two strange bolts were phillips head but massive, number 3 or larger, anyway you can see that the bolt must of bottomed out on the hard top skin and the installer tried harder to seat it so the head was chewed out a bit. i suspect they are a household bolt of some description.
anyway still hopefull that i could remove them i grabbed my Kinchrome screwdrivers, KC screwdriver ratchet kit and my Snappy-tom (snap-on) set and went to work, the Kinchrome was the best fit...... no luck it was too far gone.
next was the screw extractor, i figured this will make light work of it so drilled the pilot hole inserted the extractor and snap! the bolt snapped further down level with the internal metal plate, drilled again for round 2 and snap! the welded nut on the inside of the hardtop bracket snapped off. :evil: so now i had a screw extractor stuck in a bolt and nut in the hardtop, luckily i removed the extractor and got the broken bolt and nut out of a plug nearby with a magnet.
on inspection the thread had a loctite on it and it was red so i think 277 perhaps, so i had no chance with a phillips head.
i also removed the passenger front latch to see if i could access behind somehow, all bolts also had orange thread lock like the factory bolt i removed from the other so again shows me the mongrel latch had been taken off before.

so now i had a hole in the hardtop with no thread, and a bolt i knew wasn't coming out in a hurry. the metal plate is too thin to tap a thread so i thought what can i do? hardtop shed ornament was looking good?.

after a bit of pondering i remembered a thread insert gun we used when i was a mechanic by a company called Worth, i knew it would work if the depth of the insert fitted inside the hardtop. a bit of measuring and googling and it turns out that supercheap sells one, not the greatest quality but for the amount of use it would see i grabbed it.
i drilled out the stuck bolt and the other hole so now i had two holes the diameter of the insert to be fitted.
to get the head of the gun in i had to dremmel the fibreglass out about 1mm. this can not be seen with the hardtop latch on.
inserted both inserts and crimped them in, they work similarly to a pop rivet.
grabbed some stainless alan key head bolts the same size as the factory and test fitted it all, works perfectly!! hardtop saved!!
so if this happens to you don't stress and save some time, drill the offenders out and get one of those thread rivet guns. i wasted hours on mine.
a couple small tips. if you start looking to buy one.
- make sure the inserts are open straight through and not a blind hole, you will get more use.
- dont go over the top squeezing the tool, when i was a mechanic i went too hard on one and it distorted the thread making the tool a pain to remove and the needed bolt wouldn't fit so i had to do it again. the beauty of these little things is you can do a bit, remove the tool, check the fit and reinsert the tool if needed easily. the Worth one had alloy and steel inserts but i think i stuffed a steel one.
- there is better quality out there than what i got and i have seen some on ebay which look the same with something like 1600 inserts and i would look at these perhaps, mine came with only 40 inserts. however i wanted it straight away so got what i got. which is here http://www.supercheapauto.com.au/Produc ... ool/523129
i hope this helps someone. :beer:
Alex

User avatar
Alex 2550
Racing Driver
Posts: 561
Joined: Mon May 11, 2015 12:01 pm
Vehicle: NA8
Location: Far south coast NSW

Re: repairing threads in hardtop

Postby Alex 2550 » Mon Jul 24, 2017 3:52 pm

update.
i have broken the supercheap insert tool, supercheap were great offering me a refund or replacement straight away, even let me keep the spare inserts.
i have now purchased a Kinchrome one for $71 and its much better quality of course.

Mr Morlock
Speed Racer
Posts: 6444
Joined: Mon Feb 04, 2008 11:40 am
Vehicle: NB8B
Location: Melbourne

Re: repairing threads in hardtop

Postby Mr Morlock » Mon Jul 24, 2017 6:48 pm

good to affect a fix. Whats also relevant is that a consumer get's a warranty on items purchased. Sure SCA gives a refund or replacement and certainly does not want the thing back- for low cost items they fix nothing and and tolerate a certain number of returns. Who said consumer protection is not of great value and something that the nanny state has done for us.

Magpie
Speed Racer
Posts: 7468
Joined: Fri Feb 11, 2011 12:49 pm
Vehicle: NA6
Location: Purga, QLD

Re: repairing threads in hardtop

Postby Magpie » Sat Sep 16, 2017 7:11 pm

An alternative to using rivnuts are helicoils.

Supercheap does sell them http://www.supercheapauto.com.au/Product/TOOLPRO-HELICOIL-THREAD-REPAIR-KIT-131-PIECE/533029 these are a lot cheaper than genuine ones.

I had only 1 screw left on one side and even this was starting to worry me. So off with the hardtop today to and set about repairing at least one thread and removing a broken screw. The broken screw has been there for almost 3 years...

These have been waiting at home specifically for this job
ImageDSCN4801 by Eipeip, on Flickr

Complete kit, the drill bit was already on the drill :)
ImageDSCN4802 by Eipeip, on Flickr

One broken screw and a stuffed hole.
ImageDSCN4800 by Eipeip, on Flickr

Decided to do all 3 holes with helicoils after doing the first. Was a bit worried about slipping with the drill and damaging the hardtop, but this did not happen.

Drill hole with drill bit provided
ImageDSCN4804 by Eipeip, on Flickr

Tap hole and insert helicoil
ImageDSCN4806 by Eipeip, on Flickr

Insert the tool to snap off the tang on the helicoil, tap with a hammer and bingo job done.

User avatar
beavis
Forum sponsor
Posts: 1405
Joined: Mon Feb 02, 2009 12:31 pm
Vehicle: NB8B - Turbo
Location: Melbourne

Re: repairing threads in hardtop

Postby beavis » Sun Sep 17, 2017 5:44 pm

I use rivnuts all the time for the track car, but almost always M6 or larger.
My tool is an ebay one, but probably better quality than the budget spec stuff from supercheap.
Anyway, the point is, they do work well if they are used in the right place. Also I try to use steel nuts as often as possible over aluminium ones as the alu can tear the threads much easier.
Turbo NB Build Thread | BeavisMotorsport.com | YouTube.com/bbeavis | Cars: NA6, NA8-VVT, NB-Turbo, ND-2L


Return to “MX5 Body, Paint, Interior & Trim”

Who is online

Users browsing this forum: No registered users and 92 guests