How much of the part needs to be in a (toolmaker's) vise?

[WobblyHand]

I have a 3" wide tool makers vise with 35mm high jaws. My 3" parallels are not tall enough to raise my part up high enough. I have a piece of 5/8" thick stock that I want to mill a 3/8" deep opening (9.525mm). So the thickness will be 0.250". Therefore the parallel needs to be such that the final surface is over the top of the vise. I do have some 6" parallels that are 1-1/4" high. This would give me 0.128" of the part in the vise (3.25mm). Since I am trying to hog out 3/8" of material, is that enough of the part in the vise? A very good size would be a parallel that's 30mm high, but from what I have seen such a beast is unobtanium.

The stock is 5/8"x1"x2.5" long. (The 1" depth is into the paper.) I need to mill out a channel that is 22.23mm x 25.4mm, so I intend to have at least 3/8" of material sticking out of the vise. Is there a simpler way to do this? I could just clamp it to the table, is that the best option?

 

[markba633csi]

Hmm. Well, I've seen videos of parts held by the very edges for cnc work, but I've also seen parts be ripped out of the vises and thrown across the room, very dangerous to anyone nearby
I would take the safer option and clamp it to the table if you can. Always take the surer, safer option if there is a choice. My cat told me that.
-Mark

 

[WobblyHand]

Yeah, I don't want to throw the part. Or break an end mill. I've had pieces lift before and jam the mill. I'll take the safer option and clamp it to the table.

You have a smart cat. How can you tell if a cat is smart, anyways? (Had cats for 15 years...)

 

[markba633csi]

Good question, maybe it's just inherent cat-wisdom? Or just self-preservation LOL
-M

 

[MrWhoopee]

You have a smart cat. How can you tell if a cat is smart, anyways? (Had cats for 15 years...)

You can tell by how well the cat has trained you.