Stringing Machine Maintenance
Posted 29th December 2019
Stringing machines have numerous moving parts, each of which require regular cleaning in order to maintain a well-functioning machine. Although most routine cleaning and maintenance can be done only periodically, stringing machines benefit greatly when this is done as regularly as possible in proportion to usage, as it will not only ensure smooth operation of the mechanical parts, but will prolong the machine's working life.
The following suggestions on how to implement effective maintenance require a variety of cleaning products that are both readily available and inexpensive. The tips herein are compiled from written guidance produced by several leading stringing machine manufacturers, and also include helpful tricks adopted by other professional stringers.
The stringing machine should be cleaned often enough to prevent dust or dirt from accumulating on or in it. Clean off dust by wiping the outer surfaces of the machine with a soft cloth. A brush can be used to remove dust from around the tension mechanism.
Hardened dirt or grease may be removed with a cotton-tipped applicator dampened with a solution of mild detergent and water. Cotton-tipped applicators are inexpensive and fantastic for cleaning small areas as well as hidden parts and grooves. They can be bought online or from any laboratory supply company and are usually supplied as a bag of 50 or 100.
Ideally, the stringing machine should be covered with a polythene-backed cotton sheet when not in use, to protect the machine from dust.
Cleaning & Lubricating the Turntable Tracks
The tracks of the turntable should be cleaned at least once a week (depending on usage) to allow the clamps to move freely. Clean the tracks and the base of the clamps using a soft, clean cloth that doesn’t shed fibre, applied with isopropyl alcohol. Isopropyl alcohol (IPA) is generally available in two concentrations 70% and 99%. IPA 99% is pure isopropanol and is recommended for this purpose as it is a more effective cleaning agent. IPA 70% is isopropanol diluted with purified water and is used more for disinfection purposes.
As an alternative to a soft cloth, disposable medical isopropyl alcohol wipes can be used. However, these are generally soaked with IPA 70% so may not be as completely effective. Most stringing machine manufacturers also advise against using organic cleaning solvents (such as benzene, toluene, acetone or similar compounds) as they may damage the plastic parts of the machine. Abrasive cleaners or aerosol cleaners are also inadvisable.
Use a light machine oil (also referred to as sewing machine oil) to lubricate and protect the tracks of the turntable after cleaning. Do not use silicone spray or penetrating oils such as WD-40, as these either dissipate quickly or are not designed for long-lasting lubrication. A small amount of WD-40 should only be used if the machine has not been well serviced (i.e. if the tracks are pitted) and alcohol wipes are not effective.
Cleaning the Clamps
With time and use, the clamping surfaces of the machine may become oily or dirty. This can result in string slippage while stringing, potentially ruining the string's coating. The string clamps should be checked and cleaned often to ensure they hold the string properly. Tournament stringers may clean their clamps four to five times a day – this translates to about every five rackets strung. Ensuring the clamps are clean allows the correct clamp pressure to be maintained, avoiding over tightening and preventing damage to the string.
Clean the inside gripping surfaces of the string clamp jaws by inserting a cloth or pipe cleaner soaked with isopropyl alcohol between the jaws and rubbing back and forth. A clean shoelace is also effective. If the build-up is excessive, dismantle the clamp jaws to expose the gripping surfaces by removing the adjustment screw. Using a small nylon brush (such as a toothbrush), scrub the inside surfaces until all debris is removed. Fine emery cloth can also be used to remove accumulated oil and wax from the jaws of the clamps (do not use sandpaper). Use a cotton-tipped applicator dampened with isopropyl alcohol to clean the debris away, then re-assemble. Follow the same procedure for cleaning the string gripper on the tension head. Don't forget to clean the starting clamp as well.
Use a cotton-tipped applicator dampened with isopropyl alcohol to clean the inside of the clamp holder tubes. Use light machine oil to lubricate the posts of the string clamps after cleaning. The roller bearing channels on each side of the gripper jaws also require periodic lubrication with a sparing amount of light machine oil. Be sure not to apply too much, as this could cause oil to drip inside the machine.
Both electronic and manual stringing machines require occasional calibration. Manual lock-out machines require the most frequent calibration, as the accuracy of the spring in the tension winder can be lost over time. For stringers doing low-volumes of rackets or who string only their own rackets, calibration of the machine is only necessary every couple of months. However, professional stringers doing several rackets a day should check the calibration on a monthly or even weekly basis, to ensure consistency in their stringing. Tournament stringers are known to check their machine daily.
A range of electronic or spring tension calibrators are available. With whichever type of calibrator used, the calibrator will indicate the pounds of tension on the tension head under actual stringing conditions. When calibrating a manual stringing machine, start by setting the tension at 60 lb, or whatever calibration tension setting is recommended by the particular stringing machine manufacturer. Place a string attached to a tension calibrator in the string gripper. Place a second string attached to the other end of the calibrator, in one of the machine clamps. Lock the clamp and the turntable, then pull the string until the locking lever releases. If it releases before 60 lb or after 60 lb, adjustment is needed in accordance with the manufacturer's guidance. Be sure to release the string holding the tension calibrator before adjustment.
Electronic tension heads come pre-calibrated in the factory using highly accurate load-sensing devices. Recalibration is generally only needed when travelling with the machine often, if the machine is dropped, or after a sudden impact. It is important to note, however, that spring calibrators are not accurate enough to calibrate electronic tension heads. Electronic calibrators should be used on these machines. Many electronic machines now incorporate an automatic self-test / diagnostics check function that initiates on start-up.