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MG TD TF 1500 - Thread pattern and bolt size

I posted this message over on the USA Forum, and surprisingly, not one response. Very unusual for such a vocal and active group. Never mind, this is my post............

......I need to know what thread type and size the bolt/stud is, for the handbrake mounting bracket on the mgtf 1500

This the bolt/stud, fixing the handbrake mounting bracket to the interior surface of the transmission tunnel.

It would seem that a Dopey Previous Owner (DPO) has attempted to force an incorrectly threaded bolt into the mounting bracket bolt/stud opening.

I could tap it, but given that there may be some previous thread damage, I wouldn't want to do more damage, so I thought maybe you fellows would know?


Maurie P
R M Prior

5/16”BSF, 3/4” long, use 1/4” Whitworth Wrench.

Now, if you mosey back over to that other forum and do a search for Fasteners in the T forums you will find that Bruce Cunha has published a list with every fastener in the TD/TF.

Good thing to print and keep a copy in the garage or in your big thick book of good gen about your car.

Happy hunting.

P G Gilvarry


Thank you for the link to that information, however it doesn't help me in this instance, as the bolt/stud that came out, is a 3/8" and not 5/16" as you indicated. I am also assuming that it isn't a BSF threaded bolt/stud.

I am guessing here, that there is a captive nut in a cage, and like a lot of captive nuts in cages, it is loose. I will try to run a 3/8 BSF tap into it, but I am concerned that there is some damage and I do not want to have the tap bind on a bad thread, or have the caged nut start to spin in the cage. Brains trust anyone?

R M Prior

If you take out the seats, gearbox cover, floorboards you will be able to remove the transmission tunnel to replace the captive nut..

Only took me about 6 hours, might be better to tap it and stick in a suitable bolt. Length of bolt is important.

I took all of that out to replace the gearbox, slowly putting it all back in and updating fasteners at the same time.

I guess the issue is a loose handbrake handle as your original inquiry was about size of original bolt, to which I replied.

3/8” tapped would probably work after drilling the handbrake base.

Good luck.

Did you download Bruce’s guide, very useful.

P G Gilvarry

Thanks for the Acknowledgement Peter. I tried to check and double-check every entry in that list, but there is still a possibility some are incorrect. If you do find bolts that are incorrect, please let me know and I will update the list.

Tapping the nut with a bsf would be my recommendation. They are not that deep that you should not be able to get the tap through. It should hold fine.
Bruce Cunha

Just checked an original unmolested h/brake and the holes are 5/16" clearance size and a 3/8" bolt won't go through the holes
I guess your bracket has been drilled for the 3/8" bolt size
So tapping out to 3/8" bsf would be the logical step to take to keep all the fasteners bsf
William Revit

Bruce I had mine off about 3 months ago, they were not 3/8”, I stored the bolts on the nuts on the tunnel while removed so as to not confuse them.

P G Gilvarry

Just found a picture of the area during my restoration and the guys are right that there are threaded sleeves fastened to the cover, not captive nuts. I also agree with the 5/16ths size. As there are no as originally marked bolts available (unless you can find used ones), just find a bolt with the most correct head you can and tap the hole to that one and go with it. George
George Butz III

Thank you all gentlemen,

I am attaching an image of the handbrake lever, and it shows a chrome plated flange on one side (RH-side) with a single 3/8" hole.

George you mention a threaded sleeve? Could you enlarge upon that for me please? Is that like a Rivnut or similar?

Also thanks to William for the comparison, and thanks Peter for the link to bolts file and Bruce for compiling it.

Like all things mechanical, it is no big deal, but age and experience now trumps rushing to fix something which could lead to a harder to fix problem later. (like having the tap bind etc)

R M Prior

Providing you use the correct diameter drill flowed by a "Taper Tap" used correctly by reversing its direction of travel every few threads you wont have an issue with the tapping process.

To retain the 1/4 Whitworth head size you might want to consider modifying the heads on bolts that match your tapped thread diameter.

Helicoils could also be your best friend to resolve your issue.
G Evans

My whole chassis bolt hole threads were messed up, due to someone putting the car back together from an accident, where the whole tub was removed. Evidently they lost the bolts and put fine thread US bolts in their place, doing so messed up the threads. I took a 5/16 BSF thread chaser and it rolled the original threads back in position where they belonged, a long drawn out project. Actually I made my own thread chaser from a new tap. Bought a batch of BSF plated WW head bolts from Brown & Gammons and that's what's in the car today. PJ
PJ Jennings

I have another picture not available at the moment from the rear view. It shows the "sleeves" or whatever that stick up about 1/4" from the sheet metal. It appears they were brazed or welded into place. George

George Butz III

George Butz, many thanks for that image. It is a big help to be able to see the application.

I was travelling blind on this, because of only just obtaining the car and images like this are gold, so thanks again.

Hope you don't mind me mentioning that you had me intrigued though, when you called it a "sleeve"

I am not sure whether "caged" nuts were used back in 1955, or whether they used "captive" nuts.

The first (caged) being the nut enclosed in a square metal shroud which is spot welded to the sheet metal,or a "captive" nut being a nut that is fused to the blind side or the underside of the sheet metal?

In any event, I can see how mine may have been badly done by some careless DPO, and I am happy to know what should be there to hold the handbrake fixing bracket. I might pull the seats and carpet out and the job correctly, not only from an originality thing, but the tradesman in me will not allow me to do anything other than a decent job on it.

Maurie P
R M Prior

This thread was discussed between 03/03/2020 and 06/03/2020

MG TD TF 1500 index

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