Using a Mirror To Read Beam TQ Wrench

[thescreensavers]

How do I use a mirror with this type of wrench? Do I lay it right behind the numbers?

 

[SpatiallyAware]

Why would you need a mirror?

 

[thescreensavers]

To remove the Parallax Effect. I need it to be as accurate as possible. Its my only choice.

 

[996GT2]

To remove the Parallax Effect. I need it to be as accurate as possible. Its my only choice.

If you need as accurate as possible, I don't think that's the right type of torque wrench to use. Seems like it would be difficult to read it accurately while trying to apply a decent amount of force to it.

 

[The Boston Dangler]

you could close 1 eye

 

[The Boston Dangler]

If you need as accurate as possible, I don't think that's the right type of torque wrench to use. Seems like it would be difficult to read it accurately while trying to apply a decent amount of force to it.

it's accurate because it's simple, although that particular model has a large gap between the needle and gauge.

 

[996GT2]

it's accurate because it's simple, although that particular model has a large gap between the needle and gauge.

It could be more accurate in theory, but a good micrometer-style TQ wrench would probably be more accurate in practice, just because you don't need to worry about parallax or...mirrors.

 

[thescreensavers]

Thanks Guys but this is my ONLY option. If I could I would use a different tool.

Do I put the Mirror Perpendicular to the Number I am going to?

 

[someone16]

What exactly are you trying to tighten?

You know you can buy a click type torque wrench at harbour freight for like ~$12.

 

[thescreensavers]

37 inch-lb I need to tq in a somewhat accurate fashion

a 20-250 inch lb china freight click type will be off by a huge margin.

Ill stick to the beam type that's from 0-60

 

[LTC8K6]

Epoxy a small piece of bent paperclip to it as a pointer that's right on the scale?

 

[jaedaliu]

When was it last calibrated? without that information, I can't tell you how to best read it.

Assuming it's calibrated correctly, the dangler's suggestion of closing 1 eye should be plenty god. Your marks look plenty far apart that angle doesn't seem to be a big deal to figure out which mark is the closest.

 

[SpatiallyAware]

37 inch-lb I need to tq in a somewhat accurate fashion

a 20-250 inch lb china freight click type will be off by a huge margin.

Ill stick to the beam type that's from 0-60

What exactly are you tightening?

I mean just for curiosity's sake..

 

[phucheneh]

37 in lbs? LOL, good luck.

A torque wrench sensitive enough to give you an accurate read at ~3ft lbs...better bust out the credit card. And even then, you're probably just gonna break whatever it is.

...echoing the above, what are you tightening?

 

[SpatiallyAware]

Also, depending on what you're tightening, you might be better off using a bar and weights.

More info plz.

 

[JCH13]

Thanks Guys but this is my ONLY option. If I could I would use a different tool.

Do I put the Mirror Perpendicular to the Number I am going to?

Only for lack of imagination, or artificially constrained rules.

Epoxy a small piece of bent paperclip to it as a pointer that's right on the scale?

Winner winner, chicken dinner. This will eliminate any parallax issues. Or just bend the indicator beam down, if you're feeling ballsy.

you could close 1 eye

This will not help.

 

[thescreensavers]

For everyone's curiosity

I have a group project which I made this fixture above. We had Two of these with an aluminum "gasket" in between and we have to put it on a tensile test machine and see if our calculated preload was correct. Our axial load was not too high (2500 lbs)so this was the only way to cheaply tighten our bolts semi accuretly.

We tested it and we were about 10% off which was good.

 

[JulesMaximus]

If you need as accurate as possible, I don't think that's the right type of torque wrench to use. Seems like it would be difficult to read it accurately while trying to apply a decent amount of force to it.

:thumbsup: This.

I hate that type of torque wrench.

 

[sontakke]

I am confused; are you trying to tighten the four bolts to 37 inch-lb? Aren't they too big for such a low fastening torque? To me it looks as if it will take a 10-mm wrench to tighten it and if so, it has about 6mm diameter. I have never seen any 10mm fastener with 3 ft-lb tightening specification.

Something does not compute.

 

[thescreensavers]

^ its just for a class for a single static test

4 - 1/4 inch bolts socket is 7/16ths everything fits, just need a 1/4inch extension to fit the TQ wrench.

37 inch-lb was our calculated preload, yes per bolt each to that value

 

[rstrohkirch]

Buy a click style and then calibrate by hand to 37in/lb

 

[sontakke]

I am not a mechanical engineer (only electrical/comp science) but have just barely enough wrenching experience to know that for a 7/16 headed bolt (which is even *larger* than 10mm!) your calculated preload is way too low if the job of these bolts is to clamp things together. Even 37 ft-lb is on the low side. For example, 37 ft-lb is on the higher end on an oil drain plug bolt but NOT on a brake caliper bolt where that is too lose. What calculations have yielded the 37 in-lb value?

Where are the other engineers backing me up here?? This is sounding more and more like the proverbial guy who misreads in-lb vs ft-lb and ends up stripping the valve cover bolts :-(

 

[thescreensavers]

I am not sure what you are talking about. Are you saying 37 inch lbs isnt high enough to get the fastener to work properly? The Max torque for Grade 8 1/4-20 bolts is ~12ft/lb.

We are just preload failing. Our Specified Tensile Axial load is 2500 lbs. We need to apply a certain amount of torque to the bolts so that when using an extensometer the preload "fails" as shown on this pic below, we need to exceed the preload so at 2505 lbs

Basically using Toruqe = Force * K * D

K is the Nut Factor
Diameter

 

[sontakke]

Are you saying 37 inch lbs isnt high enough to get the fastener to work properly?

If used as a fastener to clamp two things to each other using the 7/16 headed bolt, yes, it will come off with a slightest of vibrations. In practical terms, 37 inch-lb is usually used on #2 (or #3) Philips screws. Very rarely a 1/4 drive would be used on a 7/16 headed bolt. If you pick up a generic 1/4 inch socket set, it will not go that high and there is a good practical reason for it. I am not really understanding your application.

Let me see if I can give another analogy. Suppose you had a flat and thin electronic gauge material (aka wafer film with embedded electrodes) which can measure surface pressure. Suppose a washer was made up of that material. Just to make it more fun, assume the washer had built-in wifi which relayed the pressure to your laptop. I can tell you that if you used a 7/16 mm headed bolt and used a torque wrench to tighten up to 37 inch-lb, the pressure displayed on your laptop would be too small to support 1000 lb of dead weight.

Given that you were within 10% of your calculations, that means you are doing right and I am just not understanding your experiment. So getting back to your original question, most torque wrenches are not going to be any better than 10% in terms of accuracy. So grab a cheap HF and calibrate it yourself using weights. That is your best option.

 

[JCH13]

Frankly, getting withing 10% is doing really well for a torque wrench. Friction and thread inconsistencies will tend to make things much, much worse than that.

I ran your numbers and they seem close enough.

If you want to go super-pro-legit, use an ultrasonic device to measure bolt stretch :awe: