Rod Bolt Stretch Gauge recs?

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Eric P

Member
Anyone have a recommendation for a good rod bolt gauge? There seems to be quite a range from ~$40 to over $250. Both Jegs and Summit have what looks like decent ones for $60 but this isn't an area I want to take too much risk on.

Thanks in advance,

Eric Pickering
 
Just buy yourself a micrometer the right length with pointed tips. Be very carefull with the tips or you'll poke a hole in yourself.
 
If your bolts have a hole in the head- like an Allen bolt or some of the 12-point hex heads with a drilled center, you can consider using a small ball bearing as a tool. It will self-center in the hole and give a good point to measure to. I used about a 1/4 inch ball bearing. You can buy these at hardware stores like ACE or bicycle shops, since they use loose bearings in the hubs, etc. (Actual length does not matter- you want to see a few thousandth inch change. Make sure there are no burrs in the hole in the head of all bolts so the bearing always sits the same way, and also sand or grind FLAT the threaded end, which is often a little crooked....) Then you can place any micrometer over the theaded end, then slip the ball bearing into the hole in the head of the bolt. Measure, torque, recheck, etc. Write it all down, also the torque value required to get that stretch and which lubricant was used. If you do not use a lubricant, the friction will vary so much to make this effort useless. Joel
 
With a dial gauge, you can watch the stretch as you torque the bolt. No stopping and remeasuring. Also the stretch gauge , i find, fits into the tight areas better. Summit or Jegs both have nice gauges. I wouldn't scrimp on a cheap one though.
 
RonInSD":nelef0vi said:
Please note this a only if you run in - EP, GT1, AS, T1, T2, T3, SSB, SSC
Click to expand...

Thanks for pointing that out, I saw my own class and didn't look any further!
Still, It's a good product at a good price and they are supporting Club Racing.
 
Interesting approaches. Thanks for the ideas. I'm a little unsure of the "simple" micrometer approach though. Seems like a lot of room for error. Whereas the dedicated bolt gauge (with micrometer built in) should be fairly consistent and easy to use.

I guess maybe I don't understand how using a generic micrometer would be set up. I understand how you could put a ball bearing in the depression (Carrillo rod bolts) but how do you hold the micrometer on the bolt head relative to the bolt tip? Just using a magnetic base leaves WAY too much room for error methinks. Maybe I'm dense here...
 
The dedicated stretch gauge is the most foolproof. Just install it on the bolt, Zero the dial gauge and tighten until desired stretch is achieved. Accurate and repeatable.
 
Eric et al,

Save your $ for shiny stuff, carbon fibre stuff, tires or liquid refreshments.

So long as both ends of the bolt are either perfectly flat and perpindicular to the bolt axis or have counterbores or countesinks to engage a 1/4" ball bearing (retained on the micrometer by a small rubber cylindrical boot...any machinist has one ($3 ea or so)) the measurement will be highly accurate. Of course you must know how to properly use a micrometer as well but I suppose that's another discussion.

Thanks, Jay
 
If you're only going to do this once... ever... then yes, mess around with the micometer & ball trick (assuming you have the right length mic). It will only take you 5 times as long to do it. :shock:

If you're ever going to this more than once, let the moths out of that wallet and spring for the proper tool. :)
 
I agree with you Mark...........if you're seriously in the biz. 90% of us on this forum are not however. And yes 5* 10 seconds = 50 seconds.. Not really a bid deal for the amateur....... BUT, Plenty of pros like Grumpy Jenkins (pro stock drag racing....man did he build a lot of engines and take them apart more times than we can count) used a mic and did just fine.
 
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