What is the difference between screw plates that just have threaded holes vs those that have threaded holes with area for cut material to gather?

[GregG]

I am looking to buy a screw plate to fabricate a #14 Bourgeaux screw.  There are two types that I am finding, ones that have just a threaded hole (or sometimes the hole isn't even threaded, maybe it's like a draw plate?), and ones that have two additional holes flanking either side, presumably for where cut material can accumulate.  What is the difference between these two?  Is the one with just the threaded holes for identifying which screw size you have?

 

Edited September 18, 2024 by GregG

[tomh207]

The one with the extra overlap holes is so that threads can be cut, there needs to be an edge to create the chips and somewhere for them to go. The one with single threaded holes is probably a screw guage so you can size a screw then you would use a matching threading plate to make a required screw.

 

Tom