"The Entrances Holes on my Factory Crescent Supergourds are 1/16 of an Inch too Small!"
From: James R. Hill, III - Edinboro, PA
It is possible the factory crescent SuperGourds you have are a few 1000’s of an inch under 1.1875" (1-3/16"), but I would be highly skeptical of a measurement done with a tape measure and doubt they are off by .0625".
Here’s what I would suggest: borrow a digital set of calipers and take 5 consecutive readings, using the part that measures inside measurements, then average the five readings. Be sure you are taking your readings at the highest part of the arc. The piston that punches the crescent entrance hole in the gourd is about 5% larger than 1-3/16" as the coefficient of shrinkage in this material is about 5%. The end result is that the entire gourd (including the entrance hole) shrinks down to the proper size as the gourd cools. Measure several gourds. By the way, when you use a ruler to measure these openings, instead of calipers, these holes LOOK like they are off by 1/16", but they are dead on with calipers.
We just measured a bunch of crescents openings from the last two manufacturing runs and they are dead on. If your gourds are actually under by a few thousands of an inch, I wouldn’t worry. Martins, like humans, vary in size significantly from individual to individual. Most will get in. IF you measure the gourds with calipers, and find they are on the "short" side, you could take a few quick swipes with some fine sandpaper inside the arc and on top of the flat part of the hole. Most experts say a hole can vary by 1/32" on either side of 1-3/16" and still admit martins and exclude starlings. Hope this eases your mind. By the way, PLEASE let me know what you measure when you do it with calipers.
James R. Hill, III/PMCA