Which choice of: Bolt pattern, Bolt Torque
specification, Bolt Heater, Bolt grade, Shear bolt, High strength bolt, Stainless bolt, Aluminum
bolt? Why all these choices, just to get tension into a joint?
Engineers take classes on bolt & nut specs, so why do some bolts fail? Because getting the correct pre-load
tension into a bolt and nut is even harder to implement, than it is to calculate.
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 directly. You
can even use SureBolt to determine the torque and its variation in
Verify your bolted joint design. Bolt and
nut selection are affected by many factors:
1. Friction. Engineers know
that bolt and nut friction consume over 80% of the torque measurement.
But, how does the actual tension vary bolt to bolt?
What if you use the same type of bolt? It still varies more than 20%
(flange bolts vary even more: see #7).
Update says: " SureBolt outperformed the one-point bolt gauges
on every bolt and every test in reliability and accuracy."
2. Bolt failures. What do bolted joint
designers say the number one reason, stated by bolting experts, for bolt
failures? Lack of proper pre-load tension. What are some of the factors that cause pre-load
tension errors? Why are the bolt torque specifications not enough? Can't I
just choose a good wheel bolt pattern?
3. Measure Tension errors. How can an
engineer measure torque wrench errors?
Do these bolt tension errors matter? And If you think calculating the
correct torque is easy, just see either of these two web pages
with FAST-DAQ). Do you think nut
factors or torque
calculations are easy? With SureBolt, instead of calculating the torque, to get you the
correct tension, you just measure the tension directly. You can even use
SureBolt to determine the torque.
4. Bolt gage. Your bolt's stress analysis
can be verified using a bolt gage. What is an ultrasonic bolt gage? See an animated demonstration of
an ultrasonic echo inside of a bolt. Mechanical engineering labs
rarely have enough resources to let each engineer learn ultrasonics.
Are bolt gages reliable? Are they easy to use? New
patented technology has finally made ultrasonic bolt gages reliable and easy
5. Bolt tension, not bolt torque.
Tension not torque. You want to put a known amount of tension
into your nut and bolt combination, not just a known amount of torque. Your
bolted joint design often relies on proper pre-load tension.
6. Stress, strain & yield. A stress strain curve can be plotted using SureBolt. Stress strain
and yield. SureBolt can help a engineer verify
his bolted joint
design. Did his bolt reach yield?
7. Flanges. Flange joints sometimes leak. Why does the tension in a flange bolt
vary so much, bolt to bolt? Tightening one bolt loosens some others. No
matter how many passes, the tension can vary over 50%.
How can you tighten each flange bolt to closer tolerances?
How can you use SureBolt on a flange?
Notice the variation in bolt tensions on each of three passes with a
Credit Integra Technologies for this graph. They have taken data on 94
joints. They mislabeled the first pass (it should
show 100 Pound-Feet instead of 200 Pound-Feet)
X-axis = bolt position. 16
Y-axis = bolt stretch (tension).
Large tension variations are typical with torque control. Notice
the > 250% variations.
8. SureBolt. How does SureBolt differ from any other ultrasonic bolt
gauge? What is the difference between a one-point bolt gage and SureBolt's
patented whole echo method? Are the prices similar? (Yes)
9. Engineering. Some engineers use a strain gauge to measure bolt tension because
they know a torque wrench is not directly measuring tension. This site is an engineering resource for torque versus
tension in bolted joints.
SureBolt's Whole Echo
patented technology greatly increases the reliability over all other bolt
gages, by using the patented whole echo method, instead of just one point.
See NASA story. All other bolt gages use just "One
Point" (one zero crossing), that leaves you susceptible to peak
jumping (20% error, and much more). Surebolt is a more reliable bolt gage due to
this patented DSP technology. See comparison table.
Bolt gages have been around for over 20
years. Their "Peak Jumping"
problems and all the training required to take a reliable measurement,
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. You cannot be sure, because you did not record
the whole echo.
Example, with a lot of training and laboratory testing, NASA has used
gages for years. NASA physically takes Polaroid pictures of the echoes
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 measurements
(ET umbilical bolts) because they are not reliable. When
NASA used the
SureBolt prototype, no measurements had to be thrown away.
SureBolt gives you a 13.3" TFT, portable PC
(Panasonic Toughbook Model 72). The bolt gage 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 SureBolt can measure tension. SureBolt has been used
on a variety of bolts, from special high strength titanium bolts to standard "off the shelf"
Time". See animation below of how to ultrasonically
measure the change in bolt tension using echo time.
This animation requires FLASH
(version 4 or higher).
FAST-DAQ Let us know how we can help you.
1022 Antelope Trail, Winter Springs, FL 32708, USA
Send your email to
comments about how we can help. Contact us here,
or type in the email address shown above (Due to spam, we have replaced the text
email address, with the image email address shown above).
Note: Privacy. We will NOT give your contact information to
No more guessing as to
which "one point" is the right point.
The FIRST whole
echo method (patented DSP Technique).
Built into a
Visitors Since 1-22-02
September 27, 2011