'TR' Head Markings on Bolts

[Ronald L.]

I have noticed two distinct TR sizes on 1/4" bolts, probably off 327 or 427 engines. One is about 1/8" high and the other is large, abut 1/4" high letters.

Is one from the 60's and the other from the 70's?

[William L.]

Re: 'TR' Head Markings on Bolts

I think you can apply what John Hinckley said about Voltage regulators covers to bolts.
"Don't over-think this thing. The covers were made in a multi-stage deep-draw progressive die operation, and there was more than one set of tools running at the same time, plus at least one spare set of dies to be run during normal die maintenance or wear replacement. Anyone who thinks that every cover made was absolutely identical during the production life of that cover when running well over 20,000 per day with multiple sets of tools doesn't understand high-volume manufacturing."

[Ronald L.]

Re: 'TR' Head Markings on Bolts

In the case of fasteners, I do not think so.

I agree with John with respect to a common part that had general usage on high volume car lines.

Let's talk about that a bit.

Plastic molds generally get a 60 second cycle time +/- so if you ran that tool round the clock, the most efficient process, you can get about 240,000 parts a year, given down time, maintainence, etc.

A stamping die on the other hand, some get a hit a second, something as large as a hood, 30 parts a minute.

On the VR cover it had to be a prog die due to how much that had to be stretched, trimed, etc. Still you could pound out a lot of parts with one set of tools. And yes there were times we had backup sets, sometimes that was not the case though and the tools were down until repaired.

Fasteners are the same, one thread rolling -cold heading machine can pop out a part in less than 10 seconds, 400 plus an hour, 10,000 in 24 hours.

The fastener identifier was also specificed on prints, so there was a time frame for the change...

[Bruce B.]

Re: 'TR' Head Markings on Bolts

Ronald,
Your comment about plastic molds running 60 second cycles and producing 240,000 parts a year needs some qualification.
How many cavities in the tool?
If a small high volume part, cycle times could be greatly reduced.
Also cool the mold and get faster cycle times.

[Jack H.]

Re: 'TR' Head Markings on Bolts

You're getting into a very obscure area now! While most JG descriptions ocassionally cite the headmarks for this/that fasteners that have been observed on factory original cars, they don't get down to the detail you're discussing now (exact font, postion, and detail)...

Tooling wore out on various screw machines and was periodically replaced. For items produced in the millions of units per annum, there was probably MORE than one set of production tooling active at a given time.

Last, producing corporations changed their corporate logos for various reasons AND headmarks changed in subtle fashion when a given supplier was acquired/absorbed by another in order to distinguish parts made before the acquisition from those made after the acquisition...

Bottom line, these minor details are known by SOME judges and not by others. Some headmark differences do, in fact, associate a given fastener to a specific time frame, while other differences are simply the result of multiple production tools used side by side.

I know I don't know and can't comment specifically about changes in the TR headmarks. But, there WERE changes in the Anchor headmark that resulted from specific corporate acquisition.

Bottom line, BEWARE of any answer(s) you get on this one UNLESS the person who comments can tie his reply to industry cited documentation. Fastener manufacturers DID list their headmarks for industry-wide source identification purposes...

[Ronald L.]

Re: 'TR' Head Markings on Bolts

Bruce,
Yes, and yes.

Many molds run at a faster cycle, and others slower, SMC, slower yet.

For the example I mentioned, it was a 1 cavity tool running 2 shifts.

If you went to 3 shifts and weekends, volume doubles.

[Michael G.]

Re: 'TR' Head Markings on Bolts

The size and specific shape of the supplier's head marking was usually not specified on GM prints. Additionally, it was entirely the decision of the supplier as to what to use as their marking. Some had several different marks, often a given mark varied significantly in size and shape from lot to lot of parts.

The tooling utilized on the heading machines used to produce fasteners was disposable, ie, a punch (the part of the die that produced the "TR" you speak of) could last anywhere from 10,000 pieces to 100,000 pieces (maybe more).

When making a punch the tool maker tried his best to copy the "standard" mark for that company, but, given the available methods of the day, this was not an exact science. As such, the marks varied in size and shape, often widely, every few thousand parts. This goes for head forming as well.

Then you must consider that dies wear and "load-up" with oil and dirt during production, metal cut-off sizes change, and a myriad of other things occur, further changing the shape of the mark and/or the head. A broken-out or "loaded" die may produce a strange mark - or none at all! If such a "defect" did not affect function, chances are it was shipped with the "correct" parts from the same run. This happens with almost every single run of parts. Fasteners constantly change during production.

As I've said here before, head markings should not be considered "absolute", nor should slight variations in head shape, height, or quality. There are perhaps two people in the hobby who have seen most of the "expected" variations, and I will guarantee that those two have not seen every one that occurred on each part. Remember, most Corvette fasteners were used all over GM, millions were made each year, with hundreds of die changes, and just as many head variations.

It should never be assumed that a fastener is "incorrect", just because someone has not seen a particular variation before.

If its not an obvious, known repop, it may be real.

[John M.]

Re: 'TR' Head Markings on Bolts

1969 is the first year I have seen the large TR valvecover bolts used, I have no way of backing up my statement, I have spent alot of time in the wrecking yards though............John

[John H.]

Re: 'TR' Head Markings on Bolts

A stamping die on the other hand, some get a hit a second, something as large as a hood, 30 parts a minute.

Ron -

With today's best world-class tri-axis transfer press technology, parts like hoods run at 13-15 strokes per minute; with the multi-stand tandem press technology used in the 60's, they were lucky to get 6-8 strokes per minute. A small deep-draw part like a regulator cover, running in progressive dies in the 60's, would run about 15-20 parts per minute on a good day; the shuttle cycle hobbles the rate in progressive dies.

[Brett H.]

Re: 'TR' Head Markings on Bolts

I have seen several variations in original chassis of 53-54 Corvettes. The repro's are obviously not very correct for 53-54 either. Dead giveaway.

[Doug F.]

Re: 'TR' Head Markings on Bolts

all right since we're talking about TR bolts, maybe someone can explain this one to me, if memory serves me it came from a horn on a 62, it's not trick photography or photo shopped it's just backwards

[Mike G.]

Re: 'TR' Head Markings on Bolts

all right since we're talking about TR bolts, maybe someone can explain this one to me, if memory serves me it came from a horn on a 62, it's not trick photography or photo shopped it's just backwards

and you can bet that was not the only one.

[Bruce B.]

Re: 'TR' Head Markings on Bolts

all right since we're talking about TR bolts, maybe someone can explain this one to me, if memory serves me it came from a horn on a 62, it's not trick photography or photo shopped it's just backwards

Doug,
It's not really backwards such as "RT".
The problem I believe is that die was engraved wrong. Sort of a positive image versus a negative image or a photographic "flip flop".

[Tom M.]

Re: 'TR' Head Markings on Bolts

1969 is the first year I have seen the large TR valvecover bolts used, I have no way of backing up my statement, I have spent alot of time in the wrecking yards though............John

John, That is what i have seen too,
Large "TR" IS THE ORIGINAL & SMALL "TR" re-pop

[Michael G.]

Re: 'TR' Head Markings on Bolts

Probably a die made by a trainee. It would have looked like "TR" in the die. It also probably wasn't noticed until the die was loaded in the header, and a few parts were run. Nobody was going to throw out a perfectly good tool at that point, or go to the significant effort to change it, so it was likely run that way until something wore out or broke. I'd expect to find at least 30K of those were produced and sold.

Tom, unless you're sure someone made a repop with larger letters, there is no guarantee that a random letter size change (or mirror image, for that matter) did not occur at the manufacturer.