Derek Cohen (in Perth, Australia)
The Gramercy holdfasts are notorious for poor holding. Here is a video of Frank Klaus trying to use one. It came loose half a dozen times in three minutes.

Some have suggested work-around solutions, but the truth is that a well designed holdfast does not have these problems.

Warren, I also note that Frank is using a Wood is Good mallet, which is wrapped in Sorbothane. This makes it spongy and I wonder if Frank miss-read how hard to strike the hold down? If you look at his second use of it, for the tails, he strikes it a little harder, and does not repeat this at all.

The experiences I have are very positive. I made a video which demonstrates that mine hold with a rap of my hand or a small 7 oz hammer, never mind a hulking 20oz mallet.

Some benches are not suited to these 3/4" shaft hold downs, and that is simply because they are too thick (and this reduces the angle of the shaft inside the hole). The Gramercy are not recommended for 4" and above. My bench is 3 1/2" thick.

Here is my video. I am not sure why I sound breathless or doing an impersonation of Winston Churchill. I am not usually this dramatic ...

https://www.youtube.com/watch?v=OaI_E2Yv1O0

Regards from Perth

Derek