How can this relate to TR's ?
It probably doesn't .... but it was the only thing I could come up with when pondering on an article that deals with very fine thread sizes and a bit of delicate engineering. What this article is really about is how to reclaim those damaged letters which spell out TRIUMPH on the front of TR3's, plus a better way to attach the apron medallion.
First the letters:
- these were designed to be attached by means of nasty things called "push-on fixes" (at least, that's what they are called by the Rageem Fastener Co. - 02-599 3132 who make them and numerous other types of clips).
The trouble is that the pin which is embedded in the letter suffers damage when the clip is repeatedly fitted and prised off. The pin is also metallurgically pathetic !
Anyway, the letters on my 3A had broken pins and others that were clearly ready to break. I wanted to replace them with threaded fastenings having tiny nuts on them so that I could easily place and remove the letters.
This is what I did:
- cut all the pins off and carefully file them back almost flush with the rear surface of the letter. I did this with a pair of large sidecutters and used a miniature fibreglass cut-off wheel held in a Dremel tool (or an Arlec) but a small file would suffice.
- lightly centre punch the middle of the pin which should be visible against the "muck-metal" from which the letters are made. Place the letter on a protective surface such as a smooth wooden block so that you don't mark the front surface. How do you know where the middle is ? The pin is only an 1/8" in diameter ! Use your eyes and a fine scriber to scratch a cross where you estimate the centre to be - if it looks wrong, dress it off and "guesstimate" again then use a sharp centre punch. It is remarkable how accurate the eye can be. If you can't see, use a magnifying lens such as a jewellers loupe or one of those cheap pairs of magnifying glasses which seem to be sold everywhere today.
It doesn't matter if the hole is a whisker off-centre.
- the tricky bit is drilling a hole down the middle of the remaining piece of pin without going right through the letter. We are going to use a 6BA brass thread and the correct hole to drill is:
- number 43 drill OR
- 3/32" drill OR
- 2.3mm drill (3/32" is probably easiest to buy)
I used a Dremel drill stand which has a nice depth stop and makes the job easy. If you haven't got one, you will at least need access to a bench drill of some kind as long as it has a depth stop. If the chuck in the bench drill won't hold such a small drill, you can use a gadget called a PIN DRILL or PIN VICE. Take the top swivel part off and you can hold the pin vice in the chuck of a large drill (virtually making a "sleeving down" device).
The depth stop needs to be set such that the point of the drill comes within 2mm of the protective block you will be sitting the letter on.
Drill the hole carefully using some light oil or WD40 as a lubricant - no ham fisted operators here! If you have set everything correctly, the drill will stop 2mm clear of the front surface. If not, you will have a completely buggered letter!
- Tapping the hole.
Obviously you will need to buy a 6BA tap. There isn't much thread depth so use a plug or intermediate tap - in fact you probably won't have any option - the supplier may only have one type and it will most likely be a plug (threaded most of the way). Hold the tap using the PIN VICE or a very small tee wrench or an old drill chuck and proceed carefully, supporting the letter on a wooden block. Use light pressure as this is a very small tool and continually reverse the tap to clear the chips. Frequently invert the letter to clear out chips from the bottom of the hole. You really only need 3 or 4 well formed threads but work patiently. Keep the tap at right angles to the surface.
- Insert the brass bolt:
I used 1/2" long brass 6BA bolts (head is unimportant as it will be cut off) and thread a nut onto the bolt. Screw the bolt into the tapped holes using a TINY dot of Loctite (say 601). Let the Loctite set then cut the head off the bolt with large sidecutters or Dremel. File the surface flush then wind the pre-assembled nut out to check that there are no burrs on the end (that's why we put it on first!). There should be about 5/16" of thread protruding.
- Install with small washers and lock washers. Tighten lightly with a nut driver.
It's fiddly, but the final product is worthwhile and it may help to salvage old letters.
Where to get the bits:
6BA bolts, nuts and taps: try model engineering suppliers and hobby shops. Railway modellers use this stuff. Otherwise try:
1 Copeland Ave Penrith.
047 - 31 3950
Pin Vice - again try model suppliers or electronic stores such as Dick Smith, Jaycar etc. as they are used to hold PCB drills.
Second - the Apron Medallion.
These are held on with the same dopey clip arrangement and are very difficult to fit when the car is completely assembled.
Try carefully tapering the end of the brass mounting pins so that you can start a 3/16" UNF die to cut a thread on each pin.
This whole operation needs to be done CAREFULLY and with VERY LITTLE FORCE. These pins would seem to be silver soldered in place so be gentle - I accept no responsibility for damaged medallions. None the less, it worked very well for me and the medallion can now be easily removed and replaced.
I filed the pin so that the die cut fairly easily. It was easier to hold the die with a pair of vice grips on end as the curve of the badge precludes use of a normal die holder. Use a sharp die and a little lubricant, reversing the die frequently to clear chips.
I have only threaded the pin for 1/4" of its length and have used nyloc nuts with a tap washer or O ring as a spacer.
Good Luck .... Rick Fletcher