We use a plug cutter in our pro-shop and have yet to have a major issue with it. But in using one there are a few things that can happen if you use it incorrectly:
1. Forget to set the press to a zero-zero pitch and hit the ball. Ofcourse if your press is out of alignment then it will also hit the ball.
2. Going to fast / applying to much pressure will make the ball wobble and it could make the ball kick some. My old shop did this to a ball and it wasn't pretty as it took a good sized chunk out of the ball and sent it flying.
Basically it's a good tool for plug, but I still think the router can be faster depending on how much over flow / height you have within the plug damn. The cutter also has the same issues cutting down slugs that have only been put into the ball. If the hole has been drilled in the ball the cutter works great though!!
I would say to get one and try it, but you must be carefull with it.
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-Chris
DJ's Pro Shop
Auburn, MA