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MG TD TF 1500 - Wiper Motor; mounting to frame; nuts

Among other things, there are four brass nuts that are used to mount the two posts of the wiper motor to the windscreen frame. What size are the nuts and where can I get them?
Thanks.
Milton
Milton Babirak


They are 3BA nuts, but I believe the originals were chrome plated. Doug Pelton "The Frame Up"
https://fromtheframeup.com/
Richard Cameron

Although I have no evidence for this I've always believed that each of the nuts were originally covered with a knurled cylinder held in place with four grub screws, in which case the nuts wouldn't have been chromed. The reason for this was the NOS LUCAS wiper motor that I purchased a few years ago, which was still in the original dust covered box. Inside were four of these. They can be seen in the dozen or so pics I have, none of which will upload. I have no hard evidence that they were ever fitted to TC's and TD's, but if so they would almost certainly have been one of the first items lost as it would be very easy to have them vibrate loose. It does make sense that they were originally fitted however, as the nuts are in a very prominent position on the windscreen. The inclusion with the motor obviously suggests that they were designed to be fitted on vehicles utilizing this wiper motor, where the nuts were visible, in order to dress them up. Happy to send a pic or two by email to those interested. Cheers
Peter TD 5801
P Hehir

Picking up on Peters comment, I have always felt that the un-chromed hex nuts wit the screw threads sticking out were unsightly.
I have always wanted to cover them with something more appropriate.

This post made me look again. The 3BA thread has a very similar diameter and pitch to an M4 - .7mm thread. (Angle of threads is different @ 47.5 vs 60 degrees).
I found some m4-0,7 mm Acorn SS nuts at McMasters, ~$5.00 for 10.
I will let you know how they work out.

Jim B.

JA Benjamin

The dome its from McMasters arrived. I love how they get the stuff to me the next day.

These are M4 x 0.7mm

Initially they threaded on only a few turned before becoming tight. Although the diameters of the M4 and 3-BA are close and the pitch is very close I reasoned that the depth of the 60 degree mm Thread was the problem. Had I had a 3-BA tap it would not have been an Issue. (My next tool purchase.) I opened up the root of the threads to 9/64 and the fit was much better.

The Photo on on the right shows my initial installation. There were two nuts on the studs. These were a very tight fit on my 3 BA wrench. I initially thought the hex was not 3=BA. I used a 9/32 ignition wrench which fit much better.

The left photo shows the new cap nuts. I think it looks finished. I left the first 3BA hex nut on and the dome nut is a check nut. I don't believe the dome nut has enough depth to replace both hex nuts.
The 9/32 wrench fits both the 3-BA and the dome. I believe the 3-BA will also fit both, so I don't think the nut size police will notice a difference.

Peter sent me a picture of, what he believes are, the original "finishing" nuts. As he noted these are round and knurled with two slotted grub screws holding them in place.

I may make a pair out of SS just to compare with the dome nuts, if I can sort the dimensions. I believe Peters nuts replace both hex nuts. I don't like the idea of the grub screws bearing on the 3-BA studs, unless there is a brass shoe under the grub screw.

For now I am happy. Perhaps not original but finished and period looking.

Jim B


JA Benjamin

Jim the fittings in my box don't replace the original nuts, they fit over the top of them to conceal them. Each of the four grub screws then bear on one of the flats of the nuts to tighten it into position. There were four in the box but only two are used. The other two were spares, perhaps an acknowledgement that they were easily lost? Still can't upload pics. This site's server wont accept them even though I've never had this issue previously. Cheers
Peter TD 5801
P Hehir


Peter;

Yes you had said that they go over the nuts in your previous posts. It just did not register in my mind.

Since you can't post I have taken the liberty of posting your picture.

Now I understand, there is an unseen counter-bore and the grub screws bare on the nut flats.

A little more complicated but not a large task.

I will need to secure a real 3-BA tap and give them a try.

JIm B.

PS the file you sent me was 2 Mb. The BB won't accept pictures that large.
Ones with the longest side containing about 1000 pixels are nearing the limit. Somewhere less than 200Kb.

If you have someway to reduce the picture size try again.


JA Benjamin

Here is an original setup. Don't pay attention to the black backing plate. It should be chrome. This car was oversprayed with black paint everywhere.


Christopher Couper

I believe the wiper motor installation shown in Chris's pic looks unfinished, ugly even, especially in such a highly visible area where all the other windscreen fixings are chromed, even the clips on the inside of the top rail that secure the wiper wire. The fact that the knurled nut covers shown in my pic that Jim posted aren't there in Chris's pic, doesn't mean that they weren't fitted originally. It could just mean that they are missing. Absence of evidence isn't evidence per se. I find myself asking if they weren't meant to be fitted why did LUCAS provide them in the box with replacement wiper motors? Cheers
Peter TD 5801

P Hehir

Chris’ picture is basically what I had before the Acorn nuts.
I agreed with Peter, it looks unfinished.
I plan on making some like Peters,
1) If I can find some slotted grub screws.
2) When my eyes get a bit better after Cataract removal.

Jim B.
JA Benjamin

Peter,
are you sure those are not splined wiper arm adaptors. They look like Land Rover Mk 1 adaptors.
Ray
Ray Lee

The truth is that these cars were pretty simple and did not go in for many decorative frills. These wiper motors were used on many British cars of the period with frame mounted wiper motors.

Here is a picture of an unrestored 1953.


Christopher Couper

For a better on a 1974 replacement (you can see the date in the plate) see this picture. Also notice how you can adjust the studs so the nuts just cover the end of the stud and the threads don't show.



Christopher Couper

Ray;
I blew up Peter's Hi Rez picture and it sure looks like threads on the ID.

But the counter sink has funny lines and Jagged edges like a spline.

Jim B.

Chris;
Where is the adjustment? From behind the wins screen?

Jim B.
JA Benjamin

Jim.
this is what I mean, these are modern ones but look similar.

Ray Lee

On the stud adjustment: IIRC you just turn them into the wiper motor to the height you need. Just trial and error.

Worst case scenario you figure out how long they need to be, cut them to length and make sure the cut end is in the wiper motor exposing the factory end for all to see.
Christopher Couper

Ray;
I think you have something there.
I am beginning to see your point.

I think I will just stay with the acorn nuts as a finishing embellishment.

Jim B.
JA Benjamin

Ray they could well be. I'm not at all familiar with the Land Rover set up. This could explain the inclusion. I'd always thought that the Land Rover ran a 6 volt system though? My NOS unit is definitely 12 volt. If the original nuts were chrome plated that would make for a perfectly acceptable presentation. It seems the ones in Chris's pic are chromed. I'll contact Doug at FTFU and ask how the TC wiper motor was originally fitted, as it should be the same for the TD. Cheers
Peter TD 5801
P Hehir

This thread was discussed between 10/07/2019 and 14/07/2019

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