Loscaldazar
Well-known member
- Joined
- Feb 23, 2013
- Messages
- 2,385
Got my PI 1/4 drive micrometer torque wrench in a week or two ago, and realized I didn't need my trusty HF 1/4" drive torque wrench anymore (taiwan made). Contemplated selling it to someone, but realized it probably wasn't worth the time to get maybe $5 out of it. So what else to do other than tear it down for science!
I've always had mixed feelings about my HF torque wrench. I tested it, and it was accurate, but it was super large for a 1/4 drive torque wrench, and the scale was hard to read as well as the markings didn't line up the best on it...but it was cheap and it served me well for two or so years, doing many water pumps, tensioners, and other important low torque bolts. Never had a problem with any of those repairs.
Here's a pic next to a PI 1/4 TQ wrench. Pittsburgh Pro one is of course the larger one.
Cut off the pin holding the head on first..
Pulled out the innards! The ratchet head sits on a block (which was marked as 25, indicating that different blocks/sizes are used to bring these torque wrenches into spec, and that they can indeed be recalibrated if you so desire). The block sits on top of a holder with a plastic sleeve and ball bearings, allowing the block and holder to be pushed higher without having to rotate (since the handle is rotating to reach higher torques). Obviously the higher the block is, the more torque it takes before the ratchet head slips off the block. The holder does appear to be machined, not cast. That seems like it would be some expensive machining for a $9 tool! Both the holder and the head have slots where the block fits into, so it's not just held in by pressure.
Next part to come out is the spring. And it's a heavy duty spring for a 20-200 in-lbs torque wrench. Probably why they hold their accuracy fairly well even when stored improperly (according to another one of Popular Mechanic's tests). Would take a lot to fatigue this spring!
Last thing was to remove the handle and see if anything neat was there (because why not???). Little more work with an angle grinder and the handle was cut off, and I found something that actually truly surprised me.
The body of the torque wrench has a slot cut through it that mechanically limits how far the torque wrench can be adjusted up or down. Meaning that you cannot loosen these torque wrenches too far and have the internal springs and such fall out of alignment/fall apart, and you can't over tighten it and stress the spring. Not a bad feature for a $9 torque wrench!
The ratcheting mechanism is also pretty familiar. It's the classic proto design, but unlike the 72T Taiwan design, this only has 2 teeth on each pawl, and 44T overall.
Pretty cool for $9. Some reasons to not like them (hard to read scale, rough locking mechanism that I always need pliers to unlock, and it's way too large for a 1/4 drive torque wrench), but also some surprising design features showing that these weren't just assembled to be as cheap as possible, but there was some though that went into them.
So here ends the factual part of this post, please feel free to start telling me about your 3rd cousin's uncle's brother's old college roommate who used one on his engine and had his suspension fall apart, his dog shot, his wife divorce him, the IRS investigate him for tax fraud, and had terrorists threaten to kill him because he used a Harbor Freight torque wrench.
I've always had mixed feelings about my HF torque wrench. I tested it, and it was accurate, but it was super large for a 1/4 drive torque wrench, and the scale was hard to read as well as the markings didn't line up the best on it...but it was cheap and it served me well for two or so years, doing many water pumps, tensioners, and other important low torque bolts. Never had a problem with any of those repairs.
Here's a pic next to a PI 1/4 TQ wrench. Pittsburgh Pro one is of course the larger one.
Cut off the pin holding the head on first..
Pulled out the innards! The ratchet head sits on a block (which was marked as 25, indicating that different blocks/sizes are used to bring these torque wrenches into spec, and that they can indeed be recalibrated if you so desire). The block sits on top of a holder with a plastic sleeve and ball bearings, allowing the block and holder to be pushed higher without having to rotate (since the handle is rotating to reach higher torques). Obviously the higher the block is, the more torque it takes before the ratchet head slips off the block. The holder does appear to be machined, not cast. That seems like it would be some expensive machining for a $9 tool! Both the holder and the head have slots where the block fits into, so it's not just held in by pressure.
Next part to come out is the spring. And it's a heavy duty spring for a 20-200 in-lbs torque wrench. Probably why they hold their accuracy fairly well even when stored improperly (according to another one of Popular Mechanic's tests). Would take a lot to fatigue this spring!
Last thing was to remove the handle and see if anything neat was there (because why not???). Little more work with an angle grinder and the handle was cut off, and I found something that actually truly surprised me.
The body of the torque wrench has a slot cut through it that mechanically limits how far the torque wrench can be adjusted up or down. Meaning that you cannot loosen these torque wrenches too far and have the internal springs and such fall out of alignment/fall apart, and you can't over tighten it and stress the spring. Not a bad feature for a $9 torque wrench!
The ratcheting mechanism is also pretty familiar. It's the classic proto design, but unlike the 72T Taiwan design, this only has 2 teeth on each pawl, and 44T overall.
Pretty cool for $9. Some reasons to not like them (hard to read scale, rough locking mechanism that I always need pliers to unlock, and it's way too large for a 1/4 drive torque wrench), but also some surprising design features showing that these weren't just assembled to be as cheap as possible, but there was some though that went into them.
So here ends the factual part of this post, please feel free to start telling me about your 3rd cousin's uncle's brother's old college roommate who used one on his engine and had his suspension fall apart, his dog shot, his wife divorce him, the IRS investigate him for tax fraud, and had terrorists threaten to kill him because he used a Harbor Freight torque wrench.