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See NASA quote.

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Why NASA Used
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Animated Demo
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Torque Errors
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Why SureBolt?

Measures tension not torque,

Patented whole echo method,

Graphs tension changes in real-time,

Instrument is built into the PC,

  13.3" Color TOUCHSCREEN
ToughBook Open & Closed

Friction varies too much, bolt to bolt,

Not fooled by friction variations,

Using lubrication still leaves large friction variations,

Avoid flange leaks,


Prove to safety you took a reliable tension reading,

Far greater reliability,

All other bolt gages are one-point bolt gages,

No more zero-crossing peak jumping,

ALL other bolt gages have problems with peak jumping,

Dramatic improvement due to a new patented DSP technique,

Proven by NASA,

Can record over a million bolt tensions with their waveforms,

Playback built in,

Excel compatible data files,

Flange bolts easily grouped together,

Critical bolts,

Verify your design,


Tension verification,


Much easier to use,

Graphical help,

On-line help,

Dynamic help,

13" Color Screen instead of 5" black & white screen,

Full keyboard instead of a few cryptic keys,

Record field notes with your tension data,

You can use long file names,

Large on-screen buttons,

Familiar WinXP/2000 operating system,

Full featured laptop - Panasonic Toughbook Model 72 computer,

1 year limited warrantee,

No need to transfer data to another machine,

No hidden information,

To sum it up, vastly easier and more reliable.

Press here for a detailed point by point comparison to all other bolt gages.

Avoid The #1 Reason For
Bolt Failures & Flange Leaks.
Over 50 web pages on torque, tension, & bolted joints.

Number one reason that bolts fail?  Pre-load tension errors.  What causes this?

Even perfect torque control leaves 25% tension errors or greater. Why?

See this 10 minute video on how SureBolt uses ultrasonic strain to measure tension directly.

Before SureBoltTM, few engineers had enough experience and training in non destructive testing (NDT), to use a bolt gage. See the actual SureBoltTM screens of a typical use. (10 min video)

Real-time strip chartGraph Tension Changes In Real-Time.

Gone - 25% tension errors.

Gone - Torque wrench calibration & training, friction variations, long learning curves, peak-jumping, ..., etc.

Gone - Errors due to changes in lubrication or cross-threading.

The number one reason that bolted flanges leak and bolts fail?  Pre-load tension errors.  Why?  Because a perfect torque wrench leaves you with 20% to 30% tension errors (greater errors on flange bolts)See the graph below.  How can you cure this?  Answer: Use stress versus ultrasonic strain, not stress versus torque.

Before we can talk about the solution, let us understand the source of these tension errors. 

Identical bolts, when tightened to identical torque values, will vary substantially in their actual tensions (typically plus or minus 25%and not uncommonly plus or minus 50% on flanges).  Why?

Friction Variations:  Variation in tension happens because each bolt varies in the amount of torsional work consumed by the bolt's friction.  Usually only about 10% to 15% of the torsional work converts to tension in the bolt.  Only 10% to 15%?  Where does the rest go?  

Simple friction consumes about 85% (to 90%) of the torque --- 50% in the bolt head and 35% in the threads (see studies that confirm this).

And the friction varies so much, bolt to bolt, that your final error is +-25% of your target tension and it is not uncommon to have +-50% error (see source of errors), --- even with perfect torque control. (Friction variations cannot fool SureBoltTM.) 

This much error in pre-load tension complicates the design of bolted joints, especially lightweight critical joints and flange connections.  Flange bolts vary even more and this variation is the primary reason some flanges leak.  See the graph below.

Calculations: If 85% to 90% of your torque is consumed by friction, then this only leaves 15% to 10% for actual bolt tension. 10% is 33% less than 15%. 15% - 10% = 5%, but this 5% difference in friction gives you a 33% variation in bolt tension.
And if you use a much better lubricant, then maybe only 80% to 87% of the torque is consumed by friction. This leaves 20% to 13% for actual bolt tension. 13% is 35% less than 20% (20-13=7. Then 7/20 = 35%). So the 7% difference gives you a 35% variation in tension. But, this reduction in torque - needed to get the same bolt tension - leads to a 25% reduction in the required torque, but the variation in friction still leaves you with a 35% variation in bolt tension. So the friction variation is usually the same or worse, when you use better lubricants.

Email us the details of your bolted joint application. So how accurately can ultrasonics be used? See Bickford quote below.

See the flange example below.

SureBolt can never be fooled by friction variations.

This graph shows each bolt's tension in a typical 16 bolt flange.

only a torque wrench, on flange bolts, can give very large tension variations. 

Notice that after 3 passes, bolt #3 had over 10 mils of tension, while bolt #7 had less than 4 mils of tension. (10/4 = 250% variation, or (10-4)/10 = 60% variation. Either way the variation is large. And bolt #15 is even worse.) More passes did not help the tension variations.

Torque pass, after pass, after pass. But look what happens --->>>>>

Notice the "typical" variation pattern in bolt tensions on each of three passes with a torque wrench. Their Y axis's "Stud Stretch (mils)" shows the actual bolt tensions.

What if the extra tension (for example bolt #3) causes your bolt to go into yield? Now you affect the bolt's fatigue life and other safety factors.

X-axis = bolt position. 16 different bolts
Y-axis = bolt stretch (tension). 
Large tension variations are typical with torque control. Notice the > 40% to 70% variations.

Graph of 16 flange bolt tensions.

Notice John Bickford's statement: "The final sawtooth pattern is typical of gasketed joints tightened under torque control."

If you use ultrasonics to do the final pass, the variations can be greatly reduced. This is how many petrochemical companies fix their leaky flanges.

Give the credit to John Bickford for this graph. Mr. Bickford is probably the world's expert on bolted joints.

Read below to see how to measure bolt tension using ultrasonic strain.


NASA said:  
" Using a digital signal processing (DSP) technique (patented), the gage (SureBolt) proved more reliable on every test and bolt than any other available gage.
"  Download the NASA story (pdf file, 264k).

NDT Update says:  
" SureBolt outperformed the one-point bolt gauges on every bolt and every test in reliability and accuracy."


Thread lubrication allows more of the torque to be applied to the bolt's tension, but the bolt to bolt tension variation is still the same, and sometimes worse. 

SureBoltTM does not get fooled by friction.

There are many techniques for reducing these frictional errors but the use of an ultrasonic bolt gage allows the actual bolt tension to be measured more directly --- in particular, the ultrasonic pulse is not affected by the bolt's friction losses. 

And if you think calculating the correct torque is easy, just see either of these two web pages (no affiliation with FAST-DAQ), nut factors or torque is not easy

With SureBoltTM, instead of calculating the correct torque, you just measure the tension more directly.  You can even use SureBoltTM to determine the correct torque and its variation.  How does this work?

Customer said:  
"We have finalized our investigation of the UT (ultrasonic technologies) gages currently available on the market and we would like to purchase the Surebolt Gage."
This is why we give you the links to our competition. Our competition is our best salesman.

Tension, not torque. Accuracy and reliability. 

SureBoltTM can be thought of as a super accurate ruler (micrometer) that measures how much a bolt stretches under load (sometimes within +/- 0.00001 inch or better).  How?

SureBoltTM sends a sound pulse (ultrasonic) into one end of a bolt, and then measures the time for the echo to return (like sonar).  When you tension the bolt, the echo takes longer to return! See an animation!

SureBoltTM uses  a special (patented) digital signal processing (see animation) system to  increase the reliability, accuracy, and repeatability of tension measurements (press here for a short ultrasonic bolt gage explanation).  

The SureBoltTM correlation bolt gauge was first developed for NASA's Space Station.  SureBoltTM takes most of the guesswork and frustration out of ultrasonic bolt gage use. See why NASA switched to SureBolt. 

Competing ultrasonic bolt gages track only one point on the echo.  The echo often
(10% to 30% of the time) distorts when the bolt is tensioned.  This distortion of the echo - which can destroy the performance reliability of competing gages - has little affect on SureBoltTMSee diagrams. 

This is because SureBoltTM uses all the points of the waveform, not just one zero crossing point, and is therefore not as prone to the infamous problem of "peak jumping" (see graphics).  

SureBoltTM is manufactured by FAST-DAQ.

Press---here, for a step by step example of how to use SureBolt.  You will see two typical examples and one typical calibration process.

Read the "In Conclusion" section below and all the problems that are "GONE", when you use SureBoltTM. Some case histories follow the conclusion section.


Tell us about your bolted joint application.  Email us, write us, or phone us.  We may already have an answer.  Or maybe between both of us, we can come up with another solution. Purchase SureBolt or lease with option to buy.


In Conclusion

Avoid tension errors. Bolt tension is your goal, not torque. Torque is an estimate of the actual bolt tension. So, Measure Bolt Tension Directly, NOT Bolt Torque:

Torque wrenches, turn of the nut, better lubrication, ..., etc. still leave you with +/-25% and it is not uncommon to have +/-50% errors on flanges.  

Use of a one-point ultrasonic bolt gage will give you far more accuracy than a torque wrench, if you somehow know when you can rely on its reading. 

A new technology developed for NASA's Space Station is now available.  NASA needed accurate tension data on very critical Space Station bolts (see NASA story).  This patented technology uses the entire echo instead of just one point (see animation).  

Compared to competing bolt gages, the calibration process is tremendously simplified and the user interface is the familiar Windows 2000/XP (buttons, graphs, sliders, pictures...). 

Click here for a simple explanation of how SureBoltTM works  and see a simulation of the difference between SureBoltTM and all other bolt-gages.

In addition, SureBolt gives you a fully loaded,  Panasonic Toughbook laptop computer (13.3" TFT color touchscreen screen).

SureBoltTM uses Windows 2000/XP to make your learning experience easy.  You will not have to suffer with short file names, buttons with multiple uses, small black and white screens, ... and so on.

SureBolt uses industry standard hardware/software and operating systems. Therefore SureBoltTM has a longer useful upgradeable life.


GONE - 25% to 50% tension errors.

GONE - Torque wrench training, procedure errors, special washers, friction variations, lubrication errors, ..., etc.

GONE - Large variations in tension on typical flange bolts. Even with many passes, and tensioning the bolts in a special order, flange bolts have large tension variations if torque or turn of the nut methods are used. Multiple passes do not help.

GONE - Many extra torque passes, star patterns, and many procedures for flange bolts.

GONE - Long learning curves, cryptic bolt names, small B/W screens, limited keyboards, peak-jumping, ..., etc.

GONE - ASTM procedure that says you must calibrate your torque wrench daily.

GONE - Defining "snug-tight" condition for the "turn-of-the-nut" method.

GONE - Bolts with less than 1/2 turn to fully tightened have large errors when using the turn-of-the-nut method.

GONE - Torque wrench regulation that says "Installation procedures shall be calibrated at least once per day, on 3 or more bolts, to determine the actual bolt tension.

GONE - Proprietary operating system. Totally proprietary hardware. Questionable life expectancy due to total dependence upon the manufacturer's limited resources.

GONE - Requirement for hardened washer under the turning element (nut or head).


Case Histories from "An Introduction To The Design And Behavior Of Bolted Joints (3rd ed. by John Bickford) Probably the best bolted joint resource available. Again, no affiliation with SureBolt or FAST-DAQ.

(pg 410) The additional examples below will help illustrate the fact that ultrasonics allows you to see things you cannot see as conveniently by any other means. In fact, I think it gives the bolt mechanic or engineer the same sort of insight the electrician gets from an oscilloscope. The mechanic can make a change in lubricant, tools, fastener material, etc. , and, thanks to the bolt gage, see immediately the results which that change has produced -- instant feedback in either a static or a dynamic situation. For the first time we can go into the field and determine actual results on actual bolted joints -- not just on a few laboratory or field samples specially prepared with strain gages or the like.

The things you will see will not always be pleasant or understandable. Bolted joints are a very complex subject, and their behavior is not well known. They are not very stable, either-- they flex and shift and relax under environmental changes and/or variations in external load--as well as just "all by themselves." When you start to use ultrasonics, therefore, you should be prepared for a number of unpleasant surprises. ... Laplace who said, "Getting an education is like climbing a flagpole; the higher you go the more horizon you can see." Using ultrasonics on bolted joints gives you such an education. Here's a typical example.

A. Connecting=Rod Bearing Caps on a Large Diesel Engine

The fasteners were 1 3/4 - 10 x 17,  4140 studs. The problem: Fatigue failure of one stud had created a chain of events which lead to the failure of the entire engine. Ultrasonics was used to answer some of the questions raised by the analyst.

First question: What would failure of one stud do to the load distribution in the other seven studs holding down the bearing cap?

To answer this question, eight new studs were used to fasten a bearing cap onto an actual engine. Ultrasonics was used to control the elongation in each. One stud--that corresponding to the one which had initiated the original failure--was now loosened completely. The residual preload in the remaining studs was measured, with the results shown in Fig 11.13.

+3.6 %  Bolt 1        Bolt 5 0.0 %
+17.8 %  Bolt 2        Loose (-100%)
+16.0 %  Bolt 3        Bolt 7 +26 %
+0.6 %  Bolt 4        Bolt 8

-22 %

Second question: How much residual preload is there in a typical bearing cap stud 1.5 years after initial tightening? The engine has been running most of this time.

This question was answered by measuring the loss in length (bold not in original) in 16 studs (two caps in another engine) when they were removed for routine maintenance purposes. ... These results were somewhat surprising ... 

In any event, use of ultrasonics gave the analyst some joint behavior and joint condition information that would have been difficult or impossible to obtain by any other means.


Other valuable information.

See how NASA used SureBolt's Whole Echo patented technology to greatly increase reliability, accuracy, and ease of use.  

All other bolt gages use just "One Point" (one zero crossing), that leaves you susceptible to peak jumping (30% or more error).  SureBolt is a more reliable bolt gage due to this new patented technology.  See product comparison table.

Bolt gages have been around for over 20 years.  Their "Peak Jumping" problems and long learning curves, have kept them from being widely used. 

When your bolted joint fails or flange leaks, then you find out your one-point bolt gage may have jumped peaks.  And you still cannot be sure, because you only recorded "one-point", not the whole echo.

With a lot of training and laboratory testing, NASA has used bolt gages for years.  NASA physically takes a Polaroid picture of the echo before and after tensioning. 

Then they use their trained human experience to determine if the echo has distorted "too-much".  Even after all this, they have to throw away approximately one third of the ET (External Tank umbilical bolts) measurements because they are not reliable. 

When NASA used the SureBolt prototype on even more difficult bolts, no measurements had to be thrown away.

And if you think calculating the correct torque is easy, just see either of these two web pages (no affiliation with FAST-DAQ or any bolt gage manufacturer), nut factors or torque is not easy

With SureBolt, instead of calculating the torque to get you the correct tension, you just measure the tension more directly. SureBolt is like a strain gage, only SureBolt measures the strain in time (echo return time).

You can even use SureBolt to determine the correct torque, and its tension variations (friction variations, different procedures, different lubricants, ... etc.).

SureBolt gives you a 13.3" TFT touchscreen, portable PC (Panasonic Toughbook Model 72).  The bolt gage hardware is built into the CD ROM and PCMCIA slots.  Click here to see the actual SureBolt screens. 

See the animated DEMO page to see how an ultrasonic bolt gage can measure tension.  SureBolt has been used on a wide variation of bolts from special high strength titanium bolts to standard "off the shelf" bolts.  SureBolt handles more bolt types than any other bolt gage.



And how does SureBolt compare to all other bolt gages?


Quotes from "An Introduction To The Design And Behavior Of Bolted Joints (3rd ed. by John Bickford) Probably the best bolted joint resource available. No affiliation with SureBolt or FAST-DAQ.

(pg 373) Measuring or controlling bolt stress or strain ultrasonically is not uncommon at the present time. The equipment and techniques are relatively new, ...  ultrasonic equipment is used primarily in applications involving relatively few bolts in critically important joints, or is used for quality control audits, or to set up and calibrate other types of assembly equipment (torque, torque-turn, etc.), or to conduct laboratory or field experiments.

Currently available ultrasonic equipment is ideal for the QC (Quality Control) and laboratory roles because it can monitor bolt tension not only as it is being developed in a bolt during assembly, but at anytime afterward. It can measure residual preloads after embedment or elastic interactions, it can observe changes in bolt tension as external loads are applied, it can monitor the effects of temperature change, etc. It's a low-cost alternative to strain-gaged bolts in all sorts of studies -- "low cost" because such bolts can cost several hundred dollars each.

Currently available instruments can be used on virtually any kind of bolt material, including steel, aluminum, titanium, Inconel, MP35N, and other exotic materials. There are however, some practical limitations ...

(pg 403) ... As a result, we feel that the equipment is capable of residual preload measurements with an accuracy approaching +-5% in most field situations, and can approach +-2% in laboratory work. There are even well-documented examples where +-1% was achieved consistently in aerospace applications; but ...

See our technical information page for Barnes & Nobles links to where you can buy Mr. Bickford's books. Again, Mr. Bickford has no affiliation with SureBolt.


Side Note: SureBoltTM is built into a Panasonic ToughBook (pdf flyer 817k). SureBoltTM uses industry standard hardware & software for a long support life, and allows you to have the familiar PC user interface. 

Your computer becomes the instrument. SureBolt uses the CD bay and PCMCIA slots.

SureBolt - handle


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 No more guessing as to which "one point" is the right point.


The FIRST whole echo method (patented DSP Technique).

SureBolt picture

Built into a 
Panasonic Toughbook

Weather proof keyboard.

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