Torque Wrench Accuracy Below 20%?

[Bleugrass]

So a quality torque wrench should be +/-2% accuracy from 20-100% of full scale I hear (Snap-on). I was wondering what would the torque accuracy be below 20%? Huge difference, highly inaccurate?
I'm looking at Snap on at Precision torque wrenches. Ill probably go with Snap on because the SEP discount puts them around the same price.

 

[Bleugrass]

I hear the Husky's are the good cheap ones right now though. And this says lifetime warranty? On a torque wrench? http://www.homedepot.com/p/Husky-1-4-in-Drive-Torque-Wrench-H4DTW/203541509
Where should I go for the quality discount torque wrench these days?

Btw when it says 20-100% of range, like in the above link, does that mean 20% of the MAX or 20% of the actual range? The range is 160 so 20% is 32, does the accuracy start at 32 or 32 +40 where it starts? If it starts at 72 then that *****. I'm very confused here so please help.

 

[Bleugrass]

I'm considering that Husky and this Gearwrench so I'll be able to measure every torque up to 200 in lbs. Lemme know if this is wise (I do small engines). HD's website says +/-4% and gearwrench says +/-7%. A little shady there.

http://www.homedepot.com/p/GearWren...tybaIDh9rUSTsOqvDqazcaAniq8P8HAQ&gclsrc=aw.ds

http://www.gearwrench.com/torque-wr...1-4-drive-beam-torque-wrench-0-60-in-lbs.html

I emailed Home Depot about the COO of the 1/4" Husky btw.

 

[JJThrasher]

Not sure about all torque wrenches, but here is from SO on an electronic one.

Techwrench® (standard models)
Torque accuracy ratchet head models: 2% CW, 3% CCW
from 20-100% F.S. 4% CW, 6% CCW from 10-19% F.S. 8%
CW, 10% CCW from 5-9% F.S. (TECH2 only)
Torque accuracy interchangeable head models: 4% CW,
6% CCW from 20-100% F.S. 8% CW, 12% CCW from
10-19% F.S. 16% CW, 20% CCW from 5-9% F.S. (TECH Y only)
Tolerance (early preset alert) - 2% of torque setting

 

[larry_g]

I'm considering that Husky and this Gearwrench so I'll be able to measure every torque up to 200 in lbs. Lemme know if this is wise (I do small engines). HD's website says +/-4% and gearwrench says +/-7%. A little shady there.

http://www.homedepot.com/p/GearWren...tybaIDh9rUSTsOqvDqazcaAniq8P8HAQ&gclsrc=aw.ds

http://www.gearwrench.com/torque-wr...1-4-drive-beam-torque-wrench-0-60-in-lbs.html

I emailed Home Depot about the COO of the 1/4" Husky btw.

Why shady? One of those wrenches is 20" long and the other 11" long. That will make the resolution of the scale change.

lg
no neat sig line

 

[Yankee]

Btw when it says 20-100% of range, like in the above link, does that mean 20% of the MAX or 20% of the actual range? The range is 160 so 20% is 32, does the accuracy start at 32 or 32 +40 where it starts? If it starts at 72 then that *****. I'm very confused here so please help.

I've always understood it as follows..... if the torque wrench is 10-100ft lbs, the total range is 90ft lbs. 20% of that is 18ft lbs, so I wouldn't use the wrench on anything lower than 28ft lbs..

 

[gte718p]

I've always understood it as follows..... if the torque wrench is 10-100ft lbs, the total range is 90ft lbs. 20% of that is 18ft lbs, so I wouldn't use the wrench on anything lower than 28ft lbs..

What he said.

It is just the nature of the materials. Torque wrenches are generally build around springs. At very low deflections you have affects from how the spring is seated, and the pressure it is putting on the head. It might not fully engage and slip instead of click on a clicky type torque wrench. Elasticity curves are not perfectly flat especially at the bottom and top end of the curve. This especially affects beam style torque wrenches.

As a result you get a sweet spot where the torque wrench is accurate and repeatable. That is generally 20%-90% of the stated range. The stated range is what it should be able to measure in a perfect world.

 

[woody 73]

You missed out on husky made in the USA 3/8 and 1/2 drive torque wrenches; unless you get lucky and find any old stock; The 1/4 was not made in the USA but rather Taiwan.

I believe they are all being made in China today, at least the 3/8 & 1/2 drive torque wrenches.

 

[Yankee]

What he said.

It is just the nature of the materials. Torque wrenches are generally build around springs. At very low deflections you have affects from how the spring is seated, and the pressure it is putting on the head. It might not fully engage and slip instead of click on a clicky type torque wrench. Elasticity curves are not perfectly flat especially at the bottom and top end of the curve. This especially affects beam style torque wrenches.

As a result you get a sweet spot where the torque wrench is accurate and repeatable. That is generally 20%-90% of the stated range. The stated range is what it should be able to measure in a perfect world.

I've never liked how they spec torque wrenches the way they do. You shouldn't have to do the math... a 10-100ft lb torque wrench is actually a 28-100ft lb torque wrench.

My guess a lot of people assume and use it at the described range. (10-100)...

 

[Loscaldazar]

It would be a 20-100Ft lbs wrench. It's 20% of the max reading.

Here's an excerpt from PI torque wrenches about one of their torque wrenches.

"Extremely Accurate-Accurate within 4% of reading from 20% of full scale to full scale. Guaranteed against defect in workmanship and materials for 1 year from the date of delivery providing that they have been used according to instructions."

As you can see, it says from 20% of full scale to full scale (i.e. 20% of 100, which is 20, all the way to 100), making the usable range from 20 to 100. This is the industry standard. If it is a 40 to 250 Ft-lbs torque wrench, it is usable from 50 to 250Ft-lbs.

Many torque wrenches are also accurate below their 20-100% of range, but they don't have to be. You won't know unless you test it against a calibration machine, so just stick to 20%-100% of scale.

 

[Yankee]

It would be a 20-100Ft lbs wrench. It's 20% of the max reading.

Here's an excerpt from PI torque wrenches about one of their torque wrenches.

"Extremely Accurate-Accurate within 4% of reading from 20% of full scale to full scale. Guaranteed against defect in workmanship and materials for 1 year from the date of delivery providing that they have been used according to instructions."

As you can see, it says from 20% of full scale to full scale (i.e. 20% of 100, which is 20, all the way to 100), making the usable range from 20 to 100. This is the industry standard. If it is a 40 to 250 Ft-lbs torque wrench, it is usable from 50 to 250Ft-lbs.

Many torque wrenches are also accurate below their 20-100% of range, but they don't have to be. You won't know unless you test it against a calibration machine, so just stick to 20%-100% of scale.

I doubled checked CDI's website and you are correct. It's 20% of max, not the range... I've copied from thier website below..


All mechanical torque wrenches are calibrated from 20% to 100% of full scale, therefore, they should never be used below or above those limits

To determine which torque wrench capacity is best suited for an application, many factors must be considered. However, as a recommendation, use a torque wrench in the middle 50% of the overall capacity of the tool. This will result in longer tool life, ease of use for the operator and increased accuracy from "clicker" type torque wrenches

 

[country83]

Btw when it says 20-100% of range, like in the above link, does that mean 20% of the MAX or 20% of the actual range? The range is 160 so 20% is 32, does the accuracy start at 32 or 32 +40 where it starts? If it starts at 72 then that *****. I'm very confused here so please help.

20% of MAX torque, so it would be calibrated from 32 to 160. I've tried calibrating mechanical clicker wrenches below 20% and it doesn't work. For some reason some that I worked on were marked 5-75 ft-lb, but we only started calibrating at 15 (20% of 75). When I tried calibrating that wrench at 5 ft-lb (to see if it could be done), I couldn't get it to click below 6 (20% over!), but at 15 I was easily within the +/-4% range.

 

[rsanter]

I have a high precision torque wrench and when reading the instructions it said that it was accurate to +\- 1% for the center 80% of the scale and +\-2% for the top and bottom 10% ranges

Bob

 

[Bleugrass]

I have a high precision torque wrench and when reading the instructions it said that it was accurate to +\- 1% for the center 80% of the scale and +\-2% for the top and bottom 10% ranges

Bob

Hell yeah, exactly what torque wrench is that?

 

[Bleugrass]

I doubled checked CDI's website and you are correct. It's 20% of max, not the range... I've copied from thier website below..


All mechanical torque wrenches are calibrated from 20% to 100% of full scale, therefore, they should never be used below or above those limits

To determine which torque wrench capacity is best suited for an application, many factors must be considered. However, as a recommendation, use a torque wrench in the middle 50% of the overall capacity of the tool. This will result in longer tool life, ease of use for the operator and increased accuracy from "clicker" type torque wrenches

I see. So either Husky is an exception or Home Depot messed up on their website. I figure I should get torque wrenches with these scales, so that I have everything covered up to 250 ft./lbs:
1/4(0-50 & 50-240in.lbs), 3/8(20-100ft.lbs), & 1/2(50-250ft./lbs.).

Should I heed that 50% recommendation and get even more torque wrenches? Would that apply to Bob's godly torque wrench as well? My first year I'll still only be able to get these 4 or maybe a 3/4 drive(200-600ft/lbs) as well ( if needed for automotive), but it'd be good to know for later on when I have enough funds and my own shop.

 

[Bleugrass]

You missed out on husky made in the USA 3/8 and 1/2 drive torque wrenches; unless you get lucky and find any old stock; The 1/4 was not made in the USA but rather Taiwan.

I believe they are all being made in China today, at least the 3/8 & 1/2 drive torque wrenches.

Damn.

Thanks for all the replies and answers people. Very helpful. Still could use some more answers.

I'm thinking about getting some Snap-on torque wrenches I saw at the flea market awhile back. I think they were around 30$, I dont remember the condition. What's my best bet? I have the SEP discount

 

[Steinmetz]

"...I'm thinking about getting some Snap-on torque wrenches I saw at the flea market awhile back. I think they were around 30$, I dont remember the condition…".

Forget it.

I recently bought a Sturtevant-Richmont clicker brand new to install cylinder heads on one of my classic cars. I bought it just for this job. Even though I had another suitable torque wrench re-calibrated, I didn't want to take a chance. Repeatability is the key, not necessarily accuracy.

In most cases, I strongly prefer the deflecting beam type with a rectangular cross section, but they aren't necessarily the most convenient to use.

 

[Bleugrass]

I recently bought a Sturtevant-Richmont clicker brand new to install cylinder heads on one of my classic cars. I bought it just for this job. Even though I had another suitable torque wrench re-calibrated, I didn't want to take a chance. Repeatability is the key, not necessarily accuracy.

In most cases, I strongly prefer the deflecting beam type with a rectangular cross section, but they aren't necessarily the most convenient to use.

Repeatability...just calibrated. How much life can I expect out of a snap on torque wrench?

 

[L.Cheapo]

Repeatability...just calibrated. How much life can I expect out of a snap on torque wrench?

The warranty is 2 years. Then I believe its a simple flat rate for repair...somewhere in the $50-$75 range. I really like my new Techangle! (they're on sale until 12/31!)