When to cauterise tail

In some states and provinces it's illegal. So take them to your vet to have it done if you must.

Whose tail? And why are you carterizing it?

To dock tails, it should be down within the first 3 days of life. After that, the pup supposibly feels more pain because the tail and dewclaws start to become more bone like instead of like cartilage.

To dock a tail, it is typically cauterized to stop the bleeding. I find it more effective then stitching because the mom will pick at the stitches and reopen the tails and basically chew them down.

Please contact your vet for this procedure. Don't think that you can do it yourself. It does need to be done correctly both for esthatic reasons and breed standard. Too many times have I seen tails either docked too short or too long, not to mention the large scars that occur when people do them at home.

And the cauterizing tool should be steril and not the one sitting in your garage for 10 years ;)

Wouldn't recommend you trying it, without having some experience in doing it.

Cauterizing is done to sear the tissues and stop bleeding, so it's done at the time tails are docked. It is a sort of ancient art, because sutures are now more commonly done to simply tie off the bleeding vessels. However, when you cauterize something, it scars, and you have no hair at the end of the tail... just a smooth spot. One of the good reasons to have the vet do both... dock the tail and sew the end closed so it will heal without a scar. With sutures done properly, neither mom nor the pup will bother them.