The Torque Wrench - A Critical Printing Tool
I would like to talk about a tool that has many uses in the press room, but one purpose is especially critical - torquing blankets.
We have found the need recently to get ours calibrated. The reason being is that, through use, they lose their calibration over time. We had a "specialist" come in recently to calibrate ours. They were not far out of calibration, but nonetheless were off the target.
A torque wrench's calibration is especially important when mounting blankets for the following reasons:
- Too much torque can cause the blanket to lose height over the cylinder. See also how blankets are made.
- Too little torque can cause the blanket to be loose and cause everything from web breaks to slur.
- Blankets can begin to tear over time at the cylinder gap if they are over tightened.
Tips to Extend Life of a Torque Wrench
I would like to share a couple of tips given to us for the sake of extending the life of our torque wrenches and maintaining their calibration longer:
- Only use it for one purpose. In other words, if you have a torque wrench that you use for mounting blankets, then only use it for that purpose. Use another one for lug nuts etc.
- Even if using it for blankets, use another wrench for removing the old one. Torque wrenches are usually able to be reversed for unscrewing something, but that is not their main purpose.
- Only two clicks. In other words, do not over tighten. We tighten our blankets to about 70 newton meters (50 foot pounds). Every time we "test" to make sure it's tight enough, those clicks made by the wrench will push it just a little further.
How Much Torque is Enough?
This is kind of a side point, but a good question. That answer can vary depending on the type of blanket and press you use. The principle behind it is this: tighten only what you need. In other words, all the blanket has to do is be flat against the surface and not move while running - that's it. How much torque you need to accomplish that may be something you need to trial test. As a start, get a recommendation from your blanket supplier or press manual.
I would be curious to hear how tight other pressmen out there torque their blankets. If you care to, leave a comment below. Thanks.
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