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MG TD TF 1500 - 'Re-Re' tapping BSF nuts?

A previous owner tapped some of the 1/4 BSF caged nuts in my TF to accept 1/4-20 screws. Can the re-tapped 1/4-20 threads be re-re-tapped to 1/4 BSF?

The nuts are in the body frame of my TF and secure the rear fenders. The 1/4-20 re-tapped nuts work. But my Picky Gene wants to use BSF screws to stay consistent with the rest of the car.

Any pitfalls? Suggestions? Will they strip out easily?

Or should I just use 1/4-20 and move on?

Thanks,

Lonnie
TF7211
LM Cook

I've done it Lonnie. A few chassis threads were messed up by a PO screwing a wrong bolt in, I taped them with a thread chaser which I made using the appropriate tap and removing the cutting edges on the tap threads with a dremel type tool. It's a precarious project and takes some time and patience. At the time I couldn't find a thread chaser for BSF threads. I wouldn't use a straight tap as it will recut the threads taking out some of the thread material, a chaser will roll them back in place. I used cutting oil to lube them. You might have better luck than I did finding a thread chaser. PJ
PJ Jennings

Retapping is never really recommended. BSF nuts are not hard to find if you order from one of the usual suppliers. However, a BSF bolt may be easier t use and certainly easier to find than a BSF thread chaser.
Lew Palmer

You said "Caged Nuts"

I am assuming these are the square captive nuts in the welded on cages.

I had a similar issue with some. I may even been the DPO that did it.

I made square nuts, out of flat stock the correct width and thickness, cutting them to the correct length, and drilling and tapping them to the correct BSF thread. I repainted them.
You can then lift one side of the cage with a small pry-bar or screw/ nail remover. Then take out the buggered nut, and reinsert the new nut and seal in the cage.

I must have done about 8 to 12 nuts this way.

Jim B.
JA Benjamin

Thanks guys,

By the way, the caged nuts are in the rear quarter panels. The rear fenders attach to them.

I don’t want to go through the pain of replacing the cages.

I cut a gash across the threads of BSF screws with a Dremel or a cutoff wheel on an angle grinder to make thread chasers. Don’t know if the steel In the screws is hard enough to re-tap the 1/4-20 threads. I’ll try.

Lonnie
TF7211


LM Cook

Seems like you could try the re threading route and see how snug they get. If they skip then you will have to replace.

Jim B's method of pulling up the tabs is what I have done before in the same location. Since it does not show you could even apply something like JB weld to hold the nuts in place if needed but being loose is easier to assemble.

Can you get BSF square nuts? Have not looked.
Christopher Couper

British Fasteners has the 1/4 26tpi square nuts.

Pulling up one tab of the cage and replacing the damaged nut would be the best way to go. JB Weld or tack welding to secure. Also a great time to inspect all the tabs to the cages to make sure they are secured positively.

Frank
TF1414
Frank Cronin

Lonnie, I agree with Lew about the re-tapping. Like Jim I also made my own cages and nuts for the TD and fitted them on the bulkhead replacing the four that were missing there. I also used them for the rear fenders. Really simple task using 1/4" flat bar to make the nuts and some gal ant cap for the cages. A few hits with the MIG and job done. The only pain was accessing the bottom one on each side at the rear. I ended up riveting the cage and nut in place on a 1/8" plate and installing the assembly from below, using a piece of timber with a suitable cutout to hold it in roughly place while I tightened the bolt. It was then secured it with another couple of rivets and the bolt removed. I hid those rivet heads with some body filler to present a flat surface prior to painting. Probably not necessary because once the rear mudguard (fender) is fitted this area is covered by the piping flap as well as the mudguard and so is not seen. I have some pics showing the process but still having trouble posting them here. I can email them to you if interested. Cheers
Peter TD 5801
P Hehir

Thanks Peter and all.

This restoration has hit so many road blocks, I don't know if I have the time or energy to replace / repair the cages.

I've often pondered this … fill just the threads (not the entire hole in the nut) with JB Weld. Drill with the appropriate size bit, #5 or #6 for 1/4BSF. Then cut new threads with BSF tap. Might be a way to make BSF round and rectangular T-nuts for floorboards from off-the-shelf 1/4-20 T-nuts. Not that I would do it in my situation, just pondering.

Lonnie
TF7211
LM Cook

Idea---
Drill the nuts out
Fit a 6mm x 1mm pitch nutsert and then tap that out to 1/4 bsf
1mm pitch is 25.4tpi so over the short distance of a nut there wouldn't be much in it and 6mm is 0.240 so just a nice little bit to run the tap through
You could use aluminium nutserts to make it easier specially for the floor screws (no rust)
Worth a try---------?
William Revit

An update to my question from a few months ago.

Success!

Thanks Paul. I chased the SAE threads that had been cut in the 1/4" BSF caged nuts with a BSF thread chaser. The chased BSF nuts on the rear quarter panels hold the wings securely.

I'm too cheap to mess up a good 1/4 BSF tap by dulling it to make a thread chaser as Paul suggested. I used a 1/4" BSF bolt with a gash across the threads.

Lonnie
TF7211





LM Cook

Lonnie I know you’ve said you have fixed your threads. Should you ever want to put fresh square nite in the cages they can be obtained from FTFU
W A Chasser

Thanks Bill and others,

Fingers crossed that the "re-retapped" square nuts will hold.

Lonnie
TF7211
LM Cook

This thread was discussed between 16/08/2019 and 03/01/2020

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