Q: I string my racquets two-piece and I've been having a lot of problems lately with my cross string starting knot pulling back through the grommet. Do you have any advice?
A: I've run into this problem more than a few times and once it happens it can create some serious headaches, often turning a 20-minute string job into a 45-plus-minute job. I've found this problem to occur most commonly when you're stringing with a particularly slippery string (a few different polyester varieties come to mind) and/or when you're stringing a racquet with particularly large grommet holes. Also, in my experience, the issue seems to occur a bit more frequently when stringing on a constant-pull machine versus a lockout machine.There are a few different approaches you can take here in order to mitigate the issue or avoid it all together. Some of these tips work better in certain scenarios than others, and you'll have to decide which approach best suits your particular situation. I'll do my best to list the pros and cons of each, and explain when and where each could be used. Here are some of the tips and tricks I've had success with in the past:
String the racquet one-piece – Stringing one-piece eliminates starting knots altogether as the entire string job is made up of one, long, uncut piece of string. Obviously if you're stringing a hybrid, stringing one-piece is impossible by definition. You also need to be careful going this route since some manufacturers dictate that their racquets be strung two-piece and stringing them one-piece can void the warranty.
Tie a different or bulkier knot – There are a few different starting knots that can be used and most of them can fairly easily be "looped" an additional time to create extra bulk that will keep them from slipping back through the grommet. When I use a starting knot, I typically tie a "fisherman's knot." The "fisherman's knot" can be looped around an extra time to create more bulk, but when I'm working with a particularly slippery string or the grommet hole is extra-large, I'll usually revert to a "figure 8" knot. The "figure 8" knot doesn't need to be anchored around the main string—though it can be—and, like the "fisherman's knot" can easily be made larger by adding extra "loops." The "bulkier knot" approach can work virtually without fail since you can potentially make a knot as large as you want, but that doesn't mean you should; larger isn't necessarily better and this isn't always the best approach. Very large knots can look sloppy or unprofessional and they can even sometimes stretch out or crack the grommet.
Use a starting clamp to start your crosses – are extremely useful gadgets. If you string frequently and don’t have one, I definitely recommend getting one. Starting clamps have saved me lots of work—especially in my early stringing days—when I may have measured strings a little too short and didn't have enough to reach the tension head. But, as their name implies, starting clamps can also be used for starting your string job—or in this case, starting your crosses. Before weaving your first cross, leave a tail long enough to reach the tension head and put the starting clamp flush against the frame. Then proceed with weaving and tensioning the crosses until you have three or five installed. Then, pull tension on the tail you left at the beginning and remove your starting clamp while the tension head holds the tension. You can now move one of your regular clamps back to the first cross string, release the tension head, and "tie off" the first cross using any standard finishing knot. This method removes the need to pull tension against a starting knot, thereby eliminating the possibility of the knot pulling through the grommet. Because you need to leave a tail, this method is not ideal if you think you might be short on string. The starting clamp method also doesn't work as well for older machines that use a glide bar clamp set up. Since there's usually only one clamp used for the crosses on those machines, you'll have to install all the crosses and tie them off before returning to the top. This increases the risk of something catching the starting clamp and knocking it off. I've also heard some people complain that they feel they get less tension on the first cross using this method—which may be true—but it isn't necessarily a bad thing; leaving the last mains and first/last crosses a bit looser actually creates a more forgiving feel when you really mishit a ball off-center.
So, as you can see, there are several ways to deal with starting your crosses and avoiding pull-throughs, and I'm sure there are many, many more. I personally favor the last two since I don't really like stringing one-piece, though all three methods have their own pros and cons. Hopefully these tips point you in the right direction and get you back to headache-free stringing! Good luck!