String Clamp Slippage Problems

True-Tension Stringing Machines (TTSM)
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String Clamp Slippage Problems:

Over the last few years Iíve been receiving increased calls about string clamp string slippage as the newer strings were becoming thinner. For a while the string clamps could be adjusted to make up for the thinner strings being used. The TTSM String Clamps were originally designed for natural gut and functioned fine up to the advent of the thinner 17 and 18 gauge strings. When the original TTSM String Clamps reached the maximum adjustment possible slippage occurred with the new thinner 17 and 18 gauge strings and many owners thought that their clamps were worn out. These clamps do not wear out and can be modified to work with the new thinner strings!

Since the first True-Tension String Clamps of the late 1970s were developed there have been many different versions of TTSM String Clamp String Contact Areas. The first clamps had no surface markings and as time progressed the surface areas have had many changes. Most of the clamps since the very early 90's have had a knurled contact surface as required by Yamaha. Throughout the 80's and into the early 90's Yamaha was the largest distributor of the True-Tension Stringing Machines throughout the Pacific Rim but has since stopped marketing Tennis Products. 

06/25/09 Update:
Starting back in August 2007 I've been re-machining the Cam Adjustment Slot of the original existing TTSM String Clamps allowing a tighter string grip for the 17 and 18 gauge strings. The cost to re-machine a True-Tension Stringing Clamp and replace the self locking adjustment set screw to allow more adjustment is $95.00 Plus Shipping and requires a complete disassembly, machining through the case hardening of the String Clamp Cam Assembly, lubrication, and reassembly. I basically break even or take a loss doing this modification as machining through the case hardening of the Cam destroys my expensive solid carbide end mill cutters after modifying only a couple of clamps.

If any registered True-Tension Stringing Machine owner decides that they want the modification but can not afford it with the tight economy of today contact me and I'll explain how to do the modification using a Dremel Rotary Grinding Tool.  The very first modifications that I did were done using a Dremel Rotary Grinding Tool to prove it was possible but the results were iffy trying to hold the required tolerances and could take up to eight hours per clamp but it proved that it could be done. I've had a few TTSM owners try it and then ask me to finish the modification which I did as long as the slot dimensions of the String Clamp Cam were not ruined.

I now use my Bridgeport Series 1 Model 2J2 Variable Speed Vertical Mill for an exact continuation of the adjustment slot.  Even then I sometimes have to assemble and pull test the clamp as many as five times before I'm satisfied.  Some, not all of the very early clamps required a complete change of the old original cam assembly.  The early tolerances were such that no matter what I tried I could not get the clamp to lock over center after the modification.

The original Cam Assembly went thru 3 design changes since 1978, the last being in 1991 until my final modification in August 2007. The design date of the original TTSM String Clamps still in use today is August 7, 1978. After that date there were 9 TTSM String Clamp design changes up thru early 1991.

Future TTSM String Clamp Modifications

As time allows I've also been experimenting with machining the string contact areas smooth and adhering a silicon carbide material that stops all string slippage without damaging the string. This silicon carbide material can be bought inexpensively at most hardware stores and easily replaced by the owner at minimal expense if the need should arise in the future. An owner can do almost the same by skipping the machining the string contact areas smooth.

Eventually all new TTSM String Clamps that I manufacture in the future will also have a more forward location of the Cam Assembly for easier closing with less hand pressure, and as stated above, a friendlier string contact area with owner replaceable Silicone Carbide string contacts. As time allows I will also modify existing clamps to have the more forward location of the Cam Assembly for easier closing. This mod was designed and then used by Mike Schenkhuizen, who manufactured all the clamps from the
late 70's until he left Tennis Associates in 1988.

Note that the original True-Tension Stringing Machine has had no major upgrades since the Classic Model 2020 was developed back in 1982 as no major upgrades were required. One area of the True-Tension Stringing Machine Tensioning Assembly that had to be addressed were  the Brake Assembly Synthetic Rubber Pads. In the early 90's a generic synthetic rubber was used which didn't meet the original design specs and, as a lot of owners found out, the generic synthetic rubber wore out rapidly or disintegrated after a few years whereas the older original pads even from the 70's were still like new. I now have new upgraded Long Life Brake Assembly Synthetic Rubber Pads available and you can read about them by clicking here.

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Jim Larsen, Tel: (575) 756-2737
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This site is maintained by Jim Larsen -- last updated on 10/30/14