Time for new rod bolts?

I broke high gear last SUnday in the dragster, and it revved pretty hard......

Opinions on replacing the rod bolts?

Rods are Eagle 4340, 6" with L19 bolts. They have 24 passes on them.

http://www.youtube.com/watch?v=rxKQXTKVOV0

 

I would think a set of L-19 bolts could handle anything an eagle rod could. But while you have the trans out pull the rod bolts and measure them if they measure within .001 of new they are fine if not they have suffered to many dislocations and have entered into plastic deformation (O-K there stretched) and need to be replaced.

 

Rod Bolts

Hey Mike:
I like that idea of a go/no-go for rod bolts. I have never heard of one (not suprising). Sounds like it would be good to have in the tool box. Can you get them from ARP? If not where should a guy be looking?


Thanks
Corey

 

Threads

I found them , they call them a thread plug guage. I think I'm going to get one.

Thanks again
Corey

 

Threads

Did a little more research and I found the plug guages only come in a 2B thread fit,( a least the ones I can get) which is what is considered the "most common" This might be the reason that some guages thread in a little farther. Having said that, I guess it would be wise to get a no/go when using a fresh set of rods to get a baseline, and then you will have something to compare to.


Corey

 

You can get plug gauges for all classes, internal and external.

Class 2B has more manufacturing tolerance than 3B does. Most bolts used in aerospace are 3B and sometimes even tighter.

On Class 3B, the spec states that the gauge could enter up to 3 full threads as long as on or before the 3rd turn, a definite drag is felt. Don't try to force the plug gauge in, you'll ruin the part you are checking and the gauge. Class 2 has more tolerance in the minor and pitch diameters than Class 3. Use the gauge with the part and gauge both clean and dry, no lubricants.

If you go to my sight, www.ConceptsEngineering.com, and then got to the Tools section and select Thread Data from the drop down list. Then find the thread in question and compare the results between Class 2 and Class 3 and you will see difference.

Almost forgot, a thread with an oversize or oblong minor can check good with the gauge and still be bad as long as the minor is not as big as the pitch. That type of thread will be very weak and would likely fail under load. The gauge also only checks the begining or end of the threads, not the middle where all the strength is.

A thread plug gauge is useful on newly threaded parts where the manufacturing process is controlled, using it on used parts is no guaranttee of acceptable threads and could give false optimism.

 

Rod Bolts

Paul:

I was able to find the Ring Guages (for external threads) in all the various fits, but plug guages(internal threads) were only for the 2B. Who makes the plug guages for the other fits? I am interested because I have a new set of rods and as you stated, the guages are best used on "new" parts

Thank
Corey

PS to GregM784
I'm sorry for hijacking your thread I didn't think my question would get everything so far off topic. Next time I'll start my own.

 

No worries.

 

Corey, you can try places like MSC, Carr-Lane and other suppliers but be warned, some of those gauges can cost as much as a whole set of rod bolts! You also might want to see if you can "rent" one from a machine shop just make sure they have a calibration sticker attached that is current.

And I wouldn't buy used ones, they are probably out-of-spec and that's why they're selling them.

 

Corey, years ago, when I was in the aerospace industry, we used to use Osborne Products for thread plug gauges, you might want to check out their site.

 

if you have a wholesale tool co. they have them for around 20.00$..Dave