3 8 vs 1 2 torque wrench

Needed some advice on what size torque wrench to buy. I have a basic socket set that has a 3/8 wrench. I thought I'd buy a 3/8 torque wrench, right? Or, are 1/2" better?

This will be mostly to work on the car. I want to swap out the spark plugs and do the valve cover gaskets on a friend's car. Thanks.

I have both but the 1/2" gets most of the use. It all depends on what type of work you are doing. Engine work requires a 1/2" but sometimes you need the 3/8th.

Better to buy both.

For common maintenance chores around the motor, like spark plugs (18-25 ft lbs range?), you'll use the 3/8" torque wrench.

Most Valve cover fasteners are down into the few foot-lbs range, likely to be at or below the minimum torque range for a 3/8" torque wrench. I use a 1/4" drive torque wrench in a low range of inch-lbs range for this.

Of course, most lug bolts or nuts will require a range at the high end of a 3/8" wrench, or even higher than they can go. Typically, a 1/2" torque wrench would be used here, but it's worthless for spark plugs and vc gasket jobs.

The problem you face is that most torque wrenches fall off in accuracy when used at the extremes of their ranges. The best solution is to buy the torque wrenches that cover the fastening torques that you will be using ... and if that means buying a couple of torque wrenches, then that's the best solution. Torque wrenches of decent quality are far less expensive than they were years ago, so it's not such a daunting expense anymore.

Another possibility to keep your expense down would be to purchase used. Have you looked at eBay, visited with your local tool van dealer to see if they have used ones, or checked out your local pawn shops?

Quote:

Originally Posted by PDD

I have both but the 1/2" gets most of the use. It all depends on what type of work you are doing. Engine work requires a 1/2" but sometimes you need the 3/8th.

Better to buy both.

Can't agree that "engine work requires a 1/2" " torque wrench ...

Most of the car motors that I work on have all their fasteners with little more than 40 ft-lbs torque on them, even the head bolts. With the exception of a crank pulley bolt at well over 100 ft-lbs, everything else is much less and a 3/8" torque wrench is ideal for these applications.

When I torque fasteners in the over 100 ft-lb range, I bring out the 3/4" torque wrench. Most 1/2" wrenches don't get into those ranges.

The thing that counts most is that the OP is using 3/8" drive tools at this point, and projects of much lower torque than a 1/2" drive will be used for. You won't be putting spark plugs in with a 1/2" torque wrench, nor torquing valve cover fasteners.

But I agree that having a set of torque wrenches that cover the ranges of the work to be done is the way to go.

Quote:

Originally Posted by sunsprit

Another possibility to keep your expense down would be to purchase used. Have you looked at eBay, visited with your local tool van dealer to see if they have used ones, or checked out your local pawn shops?

Used ... unless it's been recently calibrated, I wouldn't put my faith in them.

Valve cover and other items with smaller fasteners ... 1/4".
Plugs and many other things under the hood ... 3/8"
Lug nuts and suspension ... 1/2"

FWIW, buying Craftsman's torque wrenches is not a wise choice. Complaints abound about its plastic components, and unlike their other hand tools, they only have a 1 year warranty. In other words, you have the cost without the quality. You're better off going higher end, or if that's not in your budget, HF.

Quote:

Originally Posted by Narfcake

Used ... unless it's been recently calibrated, I wouldn't put my faith in them.

(snip).

Similarly, any torque wrench that's out of date on it's calibration certificate doesn't warrant your faith in them, even the one you bought brand new two years ago and has been in your tool box ever since.

When I buy a used torque wrench, especially from a tool dealer, I want it to have a current certificate, especially if it's used on critical work that's got to be signed off. But for most routine automotive work, I've never yet had a torque wrench be out of standard ... and I've got several that are now 40+ years old that still test accurately.

Quote:

Originally Posted by sunsprit

Can't agree that "engine work requires a 1/2" " torque wrench ...

I only work on V-8's so I need a torque wrench for 65-75- 110-115 ft lbs and the 3/8 ain't gonna cut it. If I worked an a lot of tiny motors I would break out the 3/8th.

My 1/2" does up to 250 ft. lbs so no need for a 3/4".

One thing about this forum is if you answer somebody's question with a reasonable answer there is always somebody to point out you are wrong.

I bought the one from TireRack, 1/2" drive with a 3/8" adaptor, as well as an extension piece. Nice tool, I used it for brake work few weeks back. 20-100 ft-lb I believe. I think it was $39.99 + S&H

Quote:

Originally Posted by PDD

I only work on V-8's so I need a torque wrench for 65-75- 110-115 ft lbs and the 3/8 ain't gonna cut it. If I worked an a lot of tiny motors I would break out the 3/8th.

My 1/2" does up to 250 ft. lbs so no need for a 3/4".

One thing about this forum is if you answer somebody's question with a reasonable answer there is always somebody to point out you are wrong.

Tiny motors?

How about 470-550 cu inch flat-6 motors that are critical for their torquing on assembly and don't need a 1/2" torque wrench? These go together with 3/8' and 1/4" torque wrenches.

How about all the alloy V-8 motors in BMW's and MB's that don't have torques over 42 ft-lbs on the head bolts? I've done a lot of valve jobs on these motors; many of these use a very low torque value for a stretch type head bolt which is torqued by rotation degrees, not torque wrench settings.

Even my old cast iron JD 4020 Diesel, with a 404 cu in motor that dwarfs a lot of car V-8's uses the rotational torque assembly technique and a 3/8" torque wrench is the tool to use to start the headbolt installation. After that, it's the degree card on the 1/2" breaker bar, not a torque wrench to finish the assembly.

I've even done a few overhauls on 289 Fords, many years ago ... when all I owned was a 3/8" torque wrench.

In any event, the OP was needing to install spark plugs and valve covers, and I'll bet all those mighty V-8's that you're working on don't use a 1/2" torque wrench for that purpose ...

Best bet is to get one of each. In my shop the 3.//8 and 1/2 get used about equally. I've never used or owned a 1/4 torque wrench. I know many people will tell me i'm doing it wrong but if something only requires 10lb/ft then I just snug it down and call it a day. Never had a failure resulting from this.