Re: Torqueing scope rings?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Plange</div><div class="ubbcode-body">Hey Rob01,
I totally understand. Just wanted to make the point. But I am glad it is working for you (and probably many others out there).
Tburkes,
I have seen similar designs that were hand made items based upon the whole force and distance calculation. Now keep in mind I have not handled one of these-they do look cool though- but I have handled the "home made" ones that are very similar and the problem I had was after a lot of use the handle where it folds when the correct torque is hit can wear down, thus possibly lowering the torque value that was intended. I mean if you don't use it much then maybe you will be fine, but I would be concerned about heavy duty use of the wrench. Again though since I have not actually handled that particular unit I don't know. For shop work I need something that can be calibrated and checked regularly hence the Seekonk.
Paul </div></div>
Several SH members asked this question before, here is one of the detailed answers (in bold blue font) I've posted a few months ago:
<span style="font-weight: bold"><span style="color: #3333FF">Realistically, ball/detent arrangement will not wear out to the extent that will change torque settings more than 1-2% after, say, 100,000 cycles. Driver arm is made from 301 SS 1/2H (so called half hard, means HRc 36-38). This is a type of SS which is hardened thru "cold working", not heat treatment. So, the ball, which is made from E5200, heat treated to HRc 60, acts like a tool against softer material of the arm, forms 0.002"-0.003" deep groove for itself and in fact, increases hardness of the 301 SS in contact area to the considerable degree. So, wear actually stops at this time. The biggest change, up to 5-7%, happens during the first 5-10 "handle breaks" on brand new parts - sharp edges are being killed, ball running groove is being formed, etc. So, before driver final calibration is completed, handle is always being pivoted (cycled) to each side at least a dozen times, as a part of "break-in" procedure required to compensate for the 5-7% inital change mentioned above.
In this case of torque driver being a "hand tool", with no high rpms and no high working temperatures involved, torque settings will change with time, but not with use. The reason is the same as for any device which uses spring - spring under permanent compression/tension load does loose some portion of inital spring rate. This is applicable to any torque driver or device which uses spring as means to control force/torque. Good news is that springs I use are supplied by Lee Spring Co, good quality, stock items and can be replaced with fresh ones if needed. In time, I'll have relatively simple calibration check procedure developed, for home use, which would allow the user to find out if re-calibration is needed. I'll be also offering a service of spring replacement and torque driver re-calibration for a very modest fee. At the moment, spring is estimated to last between 15 and 25 years before replacement may be considered.Criteria for spring replacement would be the torque values change of 10+%</span>.</span>
"Home made" break-over torque wrenches, which you're refering to in your post, are something that I'm not familiar with, but I can imagine that if components are not made from appropriate materials, and geometry of the contact surfaces is not optimized or lack required level of accuracy, premature wear may indeed become an issue. Borka Tools multi torque driver is certainly <span style="font-weight: bold">NOT</span> a "home made" type of a tool. While I only have 30 years of engineering experience, Ph.D. in mechanical engineering, P.E. in state of Michigan, and specialized in R&D of certain aspects of tribology (science dedicated to effects of friction) for approximately 15 years, I do feel comfortable that my torque driver design is functional, sufficiently accurate and resistant to wear to the extent that would allow the user to torque fasteners with both accuracy and consistency for at least 15 years (most likely up to 25 years) w/o need for re-calibration. It is not the most accurate torque driver in the world, although "break-over" type of torque wrench is considered to be generally more accurate than "cam-over" and "slip clutch" types. But it has no torque accuracy issues at any settings (low, middle or high), which is, indeed, may happen with some other designs, based on use of only the spring itself for the adjustment of torque settings. I was very encouraged when Brad Mountz of Mountz, Inc., the maker of industrial grade high quality torque tools, including single torque setting "break-over" wrenches, gave Borka Tools driver his positive evaluation, and even kindly agreed to work with me.
While Seekonk T-handle torque driver is without doubt a very high quality tool, perfectly suitable for the application and has a long term success track record, Borka Tools multi torque driver provides 12 fixed torque settings with comparable accuracy, and in fact, replaces 12 of single setting Seekonk T-handles, has approximately half weight of single Seekonk T-handle, and is priced just a bit higher than a single Seekonk T-handle. Some people find it to be an attractive option to have...
Boris
www.borkatools.com
