make your own rod bolt stretch gauge for 23 cents... works great
 

I have too many tools. Really didn't want to buy another one... So....


You need to already have a digital caliper...

2 large paper clips, clamping style

2 pop rivets

1 rubber band

bend pop rivets as shown, clamp on. Use rubber band to apply tension... Put on bolt, reset gauge to zero, and turn bolt to correct stretch...

SHOULD WORK GREAT!!!! Any size bolt!!!

Yes, in the example thats not a rod bolt... mine have been sent out for machining...http://forums.pelicanparts.com/uploa...1506366103.JPG
http://forums.pelicanparts.com/uploa...1506366103.JPG

You're joking right? A digital caliper doesn't have the precision required to do this. When I was a jet engine mechanic, calipers were not allowed to measure parts. Micrometers, depth mics, and others were ok, but not calipers. Too much error in those and you don't calibrate them.

+1

Always willing to learn... Explain why this is worse than a dial indicator... ( ps. I now own 4 micrometers, an expensive dial indicator, and these calipers...)

Both read to .001 with most having a .001 error range.

I can use my calipers over and over on a 1 inch calibrated piece of stock, and it's spot on. We are looking for a relative difference, so calibration is moot.

I haven't used arp studs before. If I understand it, you are looking for a stretch of .009 to .01 or so. Easily within the scope of quality calipers...

You put it on the bolt, tighten to a bit less than 40 foot lbs, reset calipers to read 0.000 and torque until you get the stretch that arp recommends...

Sincerely asking, in this application looking for a .009 difference, why would this not work?

I don't mind buying tools... I suspect I own more tools than any man has a right to own. That said, why wouldnt a digital caliper be able to measure such a huge difference?

I can alway buy a stretch gauge, but thought this might help someone out too...

I mean, I'd trust a mic over the bolt ends with lots of readings making sure you're not inducing error, but even so....... I think most would frown upon that, too. :)

The stretch gauge uses hardened pins in the dimples, you're using a soft rivet. It'll deflect and induce error IMO.

bpu699

You have been getting some really good help from many trying to find why you cannot get higher Oil pressure.

I am now thinking you do not have an oil pressure problem.

I think your problem is not the engine.

Wow, harsh. Sorry I suggested it might be a neat idea and might work...

For the sake of science, when I get ready to assemble my crank I will buy the stretch gauge and correlate with the calipers. Will see what the precision difference is up...

Will also see how reproducible a measurement of the arp bolt is with the caliper with protrusions to go into the indents...

And this was supposed to be the alternative to torque, which many here thought inaccurate??

I'm curious about this statement. I have the fancy Mitutoyo electronic micrometers that are like $600 each. They are about as accurate as it gets.

For routine work, I have a set of mitutoyo calipers, which cost $250. Very accurate.

But I am curious as to what application calipers have in that case. What would you use them for?

Glad I suggested this idea, seems to garner universal acceptance ;) maybe it's a stupid idea... So be it.

Without simply saying its wont work... Why not? Where does the imprecision come from?


Most of the guys on this board buying tools to measure bolt stretch aren't buying the $500 tool. Probably, getting the $60 Summit special. I doubt those tools are super precise to start with. Yes, the pros have good tools.

My calipers are fairly good. Can measure a fixed distance to .001 reproducibly. Done 10 x, I get the same reading within .001.

Measuring rod bolt stretch is simply measuring a distance. If you can do it reliably, and the instrument is precise, you can measure a change. Calipers are not great for measuring rod bolt stretch for the same reason a micrometer isn't...the surface of the bolt needs to be measured at the indents... That's what makes it reproducible...

Maybe using pop rivets was silly... And rubber bands :)

I simply introduced a way to put points onto the calipers to set in the indents...

The accuracy of the measurement is based on the precision of the instrument, and user technique.

From a practical purely science based point, as long as the caliper isn't twisted and distorted, and the points of contact don't move, it should measure to whatever specification it was designed to do...

Is it the pop rivets and rubber bands that people object to? ;)

Calipers are great for quick measurements when on a lathe or figuring dimensions for putting stuff in CAD, at least for me.

The problem with calipers is the repeatability. There isn't!

The pads of a mic allow for more precise measurement keeping the anvil perfectly perpendicular. Calipers can measure at slight angles skewing the results.

From a practical point of view, if you put the caliper on what you are measuring, and apply pressure to the head pinching the object, it seems to align it perpendicular to the face. Not sure I am explaining that in a way that makes sense...

If you hold it at the ruler portion, you get a lot of variance...

Metrology........
 

Bpu,

I will give you high mark for creativity. But a low mark for accuracy using your improvised paper clips venier caliper.

Tony

0.001 is meaningless without the units.

To say that the caliper measures the same length 10 times doesn't take account of uncertainty and to correctly calibrate this type of device usually needs a reference measurement that is 10 times more accurate than the instrument being tested.

High quality digital calipers sold with UKAS Calibration Certificates are specified as having a 0.01mm resolution with an accuracy of +/- 0.02mm

This would imply that if you measure 73mm the distance could be between 72.98mm and 73.02mm.

This is an uncertainty of approximately 40 microns (1.6 thou) and would mean preload would vary by around +/- 10%.

A typical micrometer would have an uncertainty of about 7 microns and is more likely to be used correctly.

I am quite sure you do understand these issues :confused:

What sort of rubber bands?

OH MY GOD!!

Use torque, its not perfect, but hard to mess up, unless you plan to make your own torque wrench from office supplies...

Calibrated ones

;)

That makes more sense to me...

What is the error range on the basic stretch gauges folks are using? Not talking about the $500 ones. Curious... Is the dial indicator that much more precise/accurate? I assume so...

My recall from college: precision is the ability to repeat the same measurement over and over. Accuracy - how close to the actual measurement you really are.

I looked but none of the commonly sold consumer models list a precision/accuracy range...


Mea culpa... seemed like a neat idea... I have seen the error of my creative thinking :)

Not sure of the accuracy but I have the ARP gauge, the billet one. It's biggest feature is the rigidity of the aluminum beam that connects the bottom pin and the dial gauge. This rigidity is what makes it repeatable and accurate.

I have a huge amount of respect for the knowledge base on this board. Individuals who have had the fortune to acquire a base of knowledge many of us will never achieve. The intestinal fortitude and bloodied hands to obtain this level of acuity is commendable to the highest degree but I must state those of us who come here for guidance do not deserve condescension. This is one of the few places where the level of maturity and knowledge sets the bar for all other sites imho, and any comment to the contrary is merely self serving and arrogant. The individual who posted had and has genuine intent and in my opinion is beyond reproach.
Dan.