Monday, October 31, 2011
Torque Limiting Spark Plug SocketI happened upon this tool while assisting a friend with his Beemer M3 and ordered one for testing and evaluation--to minimise the suspense here it is:
What it is, is a spark plug socket with a built-in torque limiter. It works because in the head is a a spring-loaded one-way ramp "ratchet" type device. The input to the tool (a standard 3/8" drive socket recess) is ground to have 4 ramps against which a spring-loaded ball acts. The pre-load on the ball is calibrated such that it climbs and then quite noticeably jumps (releases from) the ramp at a a calibrated input torque--in the case of the 16 mm (5/8") socket typically used with tapered seat plugs this torque setting is 20 Nm (Newton meters), or 14.75 lbft.
Note: This is intended to be used ONLY with hand tool input--NOT powered wrenches, torque or otherwise--I.e. it is not a torque stick.
While a bit higher than the 11-13 lbft recommended by Ford, it happens to be the torque most plug manufacturers specifiy and that I have been using for nearly 5 years on my 2003 Mustang GT and others with no issues--and it beats the crap out of not torquing the plugs at all.
In addition it is a very nice plug socket, long enough to keep the socket from canting in the plug bore. It also has the typical plug socket rubber gripping insert, and a somewhat atypical (meaning well designed) shallow 12-point drive socket to minimise the plug's cocking in the socket itself.
My initial tests proved it to release at 175 to 180 lbin (14.6 to 15.0 lbft) just at it's spec. I then ran it through 450 to 600 rapid cycles¹ using a Milwaukee drill/driver at 600 RPM and found it to continue to cycle at 170 to 178 lbin, 14.2 to 14.8 lbft. Letting it cool back to room temp got single releases in the 174 to 179 lbin (14.5 to 14.9 lbft) range.
Short story is I like it! It is accurate and convenient as heck! I got mine from Norwalk Tools--click here...
¹ - This is the equivalent of torquing a set of 8 plugs, 70 times in a minute or so...