I've got a two-handled handheld capper. Twice, I've snapped the neck while trying to put the cap onto a bottle. Considering how few bottles I've actually capped, that's a failure rate of over 5%. Is there some technique I should be using to avoid this problem? New caps seem to require a great deal of force to apply.
We had this exact issue with our second capper, except our failure rate was approaching 10%.
We had been using twist off caps (that was what was available to us at the time) we switched to a stand capper and the failures were eliminated.
We have also switched to non-twist bottles and when we cap with a hand capper (we don't do this often now), but we haven't had a failure with non-twist.
I have a habit of breaking the handles off the two handed cappers. ;-) Quality construction there for sure. I have not had the pleasure of breaking bottles, yet. But what I switched to was the upright capper:
Works like a charm. I tend to push down and spin the bottle an then push again to get a nice circular pattern on top, which makes me fairly certain the caps are on. Also I don't have mine mounted anywhere (it has four screw holes in the bottom so it can be mounted to a table or bench), although that would make it even easier.
When using the two handled "red baron" capper, i prefer to use the weight of the capper to seat the cap without pushing down. When the handles are lowered, i try to use a slight lifting motion with the portion of my hands facing center.
I've only ever busted one bottle, and it was my first. On that bottle i was pushing down with quite a bit of force and sheared the neck off the bottle.
I've also had wider neck bottles that seem to not fit the red baron capper very well...i could see those have necks sheared as well.
I believe most commercial breweries that use glass bottles, accept a 2% breakage factor. I also believe that a glass bottle can only be used so many times before the glass becomes weak and requires melting and re-firing. The Red Barron caper has worked for me for about 3 years, and I've probably averaged about 2% broken bottles over that time (more when my friends use it!).
I haven't had any problems with using the manual hand capper but I've had a problem on occasion when I take the cap off and the top of the neck of the bottle breaks. I've had this happen on several occasions, maybe one or two bottles per case. I'm wondering if I'm putting to much pressure on capping some bottles.