6 replies to this topic

[clarkymini92]

Hi everyone,

I'm currently restoring a mini from ground up and come across a little issue. I had the front subframe powder coated as it was still in good condition, however had to replace the back one as it was shot! Now the problem I have found is that the tread for the tower mount bolt is all clogged up with crap etc and I really need to re thread it with a tap and die set, however i can't seem to find the size for it anywhere.

Does anyone know what size it is and where I can get the tap and die from? I do have a set but none are big enough to fit it!?

Thanks.

[ibrooks]

Since you mention tower bolt rather than bolts I'm assuming it's a single big bolt at each side with an inch and five sixteenths head. In which case the thread is 3/4"UNF a twin bolt subframe uses two 3/8"UNF bolts from memory.

 

It's a fairly common size for chucks on wood-turning lathes as it happens. It's also the same thread as the oil-filter.

 

As for where to get a tap - a decent tool supplier should be able to source one (I doubt they will have it on the shelf nowadays). I wouldn't expect it to be cheap. Ebay might yield one.

 

Since you are only looking to chase the thread you can probably do it with an old bolt with some grooves cut lengthwise up the thread. You'll need to clear the first couple of threads manually with a metal pick or scribe but it shouldn't be too hard.

 

Iain

[dklawson]

I cannot comment on the size of the subframe bolts. 

 

For the rest of the car you would be well served to buy 1/4", 5/16", and 3/8" taps in fine (UNF) pitch.  Dies will have occasional use but not nearly as much as the taps.  There are a few coarse (UNC) threads on the car but those are limited in number.  In addition to those there are some BA threads on the carb, early gauges, and some of the SU fuel pumps.  However, it is very likely you will never need those.

[Guess-Works.com]

As you're only removing powder coat I would take an angle grinder to a sacrificial turret bolt and run some grooves up the bolt through the thread....  I can imagine a tap of that size would not be cheap...

 

Also, I would avoid buying a tap set as most will probably be 1st or at best 2nd taps, ideally to clean threads you should be using a chaser or 3rd tap.

[Ethel]

You should be able to get a 3/4" tap from Tracy tools or RDG engineering for less than a tower bolt, both companies re online. Can't confirm it's 3/4 unf but it sounds right.

[Mini Manannán]

Have a gander here: http://www.tracytool...d-dies/UNF-taps  not too pricey at all/

[clarkymini92]

Thanks for all the info everyone. Bit tight on funds at the moment so think what guess works said might be the best option but il still have to buy a new tower bolt so not sure. But that website looks good and good prices. Thanks everyone. Cheers. Il let you know how I get on.