Mysterious Snap On torque wrench

[kshansen]

Left handed threads on older drivers' side wheels
that is LHD vehicles

Yep, know some Chrysler cars, and others, were that way at least in the 1960's. Actually had a drivers ed class one day where were were going to be taught how to change a tire. Driver Ed. teach told us that the lug nuts on the left side were left handed threads. Funny thing is when the first student was tasked with removing the lug nut the first stud broke off as did a couple more. Seems the people who had mounted the new tires on this car did not know about left hand threads and managed to force them on with and air wrench. Just lucky we found it before a wheel had fell off during driving class!

 

[bosco659]

A few pics of the innards - a bit blurry from my old phone. The brass mechanism in the bottom is the movement for the needle. The copper arm is attached to a beam that bends with the applied load. It moves the arm on the movement to cause deflection of the needle. The copper arm is twisted - I assume from misuse and / or abuse from a po. If Snap On can’t or won’t fix it, or it’s cost prohibitive, I’ll take it apart and attempt to straighten the arm. I found an old parts list on line that listed the rivets that hold the case together. They were expensive so if I do take it apart and “fix” it, I’ll reassemble with screws until I’m confident it’s working properly. Nit sure how to set the rivets. Looks like a special tool might be needed.

Moving the screw up or down changes the calibration.

 

[bosco659]

My Snap On dealer says $147.00 Cdn to repair the wrench (flat rate). That would put my total investment up to $200.00. I will probably go ahead with it because it sells for over $600 new. Once repaired I can sell it as a new tool if I want to part company with it (I think in many cases they just replace them vs fix them). Stay tuned.

 

[jetmechmarty]

I believe I would do the same. It’s nice to have a tool like that you can be confident in. $147.00 Cdn doesn’t go far right now.

 

[bosco659]

Well the torque wrench went to the repair depot and was returned telling me it was not repairable. Parts not available and internal damage from over torquing.
Since it was going to be a paperweight anyway, I decided to do a bit of surgery. 5 rivets drilled out easily exposing most of the innards. The long brass arm was indeed twisted but not from over torquing. What I learned is if you wind the dial around too far in either direction, that arm starts to twist.
A few minutes with a pair of pliers got the arm straightened out and centered. I took two of my smaller torque wrenches and adjust the mechanism until the torque agreed with the two that I’ll trust were fairly accurate. Now the wrench works well reading torque in the tightening direction. The dial needs to be rotated counterclockwise two allow movement in the opposite direction and that’s where something still isn’t right.
That said I’ll use it in the clockwise direction only. It can live in my garage toolbox.
Rivets from Snap on were over $6.00 each so I reassembled it with M4-70 x 10 button head cap screws and nylocks. Looks pretty slick especially for a $20 investment.
The light doesn’t work but I don’t care..

 

[bosco659]

In pictures 2&4 you can see the “post” that is welded to the wrench body on one end and the 3/8” drive is machined onto the other end. This is the core of the torque reading mechanism. The amount it twists when torque is applied, translates into rotation of the brass arm, which in turn actuates a rack and pinion that moves the needle. Pretty primitive but I guess that post is made from some alien metal that allows repeated torque application without permanent deformation.

The small screw in the slot is used to calibrate the tool. You loosen it off and slide it up or down to have the tool agree with a torque standard.

 

[AUTOMAN]

In pictures 2&4 you can see the “post” that is welded to the wrench body on one end and the 3/8” drive is machined onto the other end. This is the core of the torque reading mechanism. The amount it twists when torque is applied, translates into rotation of the brass arm, which in turn actuates a rack and pinion that moves the needle. Pretty primitive but I guess that post is made from some alien metal that allows repeated torque application without permanent deformation.

The small screw in the slot is used to calibrate the tool. You loosen it off and slide it up or down to have the tool agree with a torque standard.

The small screw is for GAIN.
ZERO is meter spring/beam position relative to CL of multiplier arm/pinion line.
Zero comes first then adjust gain.

The alien material is just elastic deformation, unless over torqued by 150%.

Well done!
cliff