TR2/3/3A Body Mounting Bolts.

[Skellyt]

Hello Forum. Is anybody aware of whether there are any torque specs. for body mounting bolts on my TR3B. I have checked the workshop manual (reprint), my Haynes manual and searched the forum, but could not find any. Since I couldn’t find any, my thoughts were to tighten them as tightly as possible after adding some lock tire to the threads.

Thanks, Tom

 

[sp53]

You probably will not find a number; the bolt is not a steel to steel attachment because the bolt goes through the rubber shims. I would tighten the bolt until the lock washer closes and perhaps a few pounds more and not so tight as to rip the thin rubber pad. With the lock washer closed, the vibration of driving is less apt to loosen the bolt. However, others might have a different view.

 

[Madflyer]

My TR 6 book states what should be the same for your TR 3 10 to 14 Lbs 3/8 fine thread. As they may have any number of shims and rubber to fit doors ect. it just holds body true. NOTE fine thread bolts strip easy at any location. here a some basic torques Spark plugs 14/20- 1/4 UNF 6/9
5/16 UNF 15/20 - 1/2 UNF 50/65 - Gear box top cover 5/16 UNF 15/20 - motor mounts 3/8 UNF 24/32. Valve cover 1 to 2 lbs note to bend cover
Madflyer
.

 

[Skellyt]

Thank You for the quick replies. That’s pretty much what I thought, just wanted to verify.

 

[Joel Lester]

Can someone define what those numbers are that Madflyer used? for example... what does 14/20- 1/4 UNF mean? Just curious because I'm trying to figure out how I can "chase" the square nuts on the body work on my TR3A. I know they are fine threads but if I were to buy a tap and die set (or thread chaser kit) I'd like to know what size etc. to get?

Joel

 

[bobhustead]

I don't know what the 14/20 means, probably torque applicable to spark plugs. 1/4 UNF is a phrase in itself and means 1/4 diameter and 28 threads per inch, 28 being standard fine thread in 1/4 diameter. 1/4 NC is coarse, or 20 threads per inch. Fine and coarse thread pitch vary with the diameter of the bolt.
Bob

 

[Joel Lester]

Thanks Bob!

 

[charleyf]

I don't know what the 14/20 means, probably torque applicable to spark plugs. 1/4 UNF is a phrase in itself and means 1/4 diameter and 28 threads per inch, 28 being standard fine thread in 1/4 diameter. 1/4 NC is coarse, or 20 threads per inch. Fine and coarse thread pitch vary with the diameter of the bolt.
Bob

I would suggest that 14/20 is really 14 to 20 lbs torque. These numbers have nothing to do with the threads per inch.
Charley

 

[DavidApp]

Coarse and fine threads also vary with the material they are intended for. Cast iron tends to get a coarse thread whereas steel will have a fine thread.
1/4" 20 is the UNC standard and 1/4" 28 is UNF standard.

David

 

[Madflyer]

Yes sorry that is the torque rang 14/20 14 to 20 lbs The Bentley TR book list every bolt and thread. You can be safe with fine thread taps and dies. But note there are three taps in most every size tap. STARTING- RUNNING- AND BOTTOMING taps they are used like they sound . Madflyer

 

[Graham H]

You would always be safe using the old mechanic's method, tighten it up until it strips then back it off half a turn, never fails.

Graham

 

[DavidApp]

Where I worked years ago we had an inspector who would go around an assembly checking the bolts were tight. He would always find that he could get another bit of a turn on the bolt and marked it lose on the inspection sheet.
One day an assembler got fed up with his attitude so the assembler tightened every bolt to the yield point so when the inspector did his normal thing every bolt failed. The assembler told him "put the spanner on the bolt and check it Don't add 1/2 a turn because I have got them done up correctly" He never had a problem again from the inspector.

David

 

[Joel Lester]

This is what I love about these forums... you gain knowledge, insight and... a great sense of humor as we learn about these fine British sports cars. Always good to have a handle on who is being sarcastic though! LOL!

 

[Madflyer]

Those that can do those that inspect well you know the rest. I had cement anchors inspected on a FED job 25% required a pull test. The test required a number of threads above the nut for his tool. I made sure they were the hardest to get to. A big job when 25% could be 50 test. I would walk away and the inspector would paint tested anchors. I think he spent more time painting than testing. Yes they all past. 5/8 3/4 and 1 inch anchors. Madflyer

 

[Madflyer]

I was a Elevator installer for 40 years. It is a trade that you do not mess with the good old boys. You name is our word and your work. As in the Ghost Buster's movie WHO YOU GONA CALL when things don't fit. Not the Engineer. Madflyer