Thread depth

[3strucking]

If a thread calls for .030” depth, is that total depth or per side? I am assuming it’s total depth but I would rather be sure.

 

[benmychree]

That would be per side, with a sharp pointed tool, straight in, not depth of compound travel. The depth figure would be more for purposes of calculating root diameter than in cutting the thread. In cutting threads in the lathe, one just starts feeding the tool in for each successive cut until the thread nearly comes up sharp, starting with a relatively heavy cut and reducing the infeed with each pass until nearly on size, gaging the fit with a thread gage or a nut that has had a tap run through it to make sure it is not burred, or, thread wires can also be used for sizing the thread or a thread micrometer can be used, having referred to the tables of pitch diameter in a machinist's handbook.

 

[magu]

Depends, what size threads are you cutting? On 1/8" Dia I would say total, on 1/4" dia I would say per side.

 

[3strucking]

I’m going to cut a bastard internal thread. It’s probably going to wind up being a .855 id after I bore to clean up the inside. I think I am going to use 24 or 28 tpi

 

[Wreck™Wreck]

Some machine controls call this thread height, Bridgeport lathe controls for example, the only way to be sure (or nuke from orbit) that the PD is correct is to measure it, plug gauges for internal threads and ring gauges, thread micrometers or wires for external threads. There is for the most part no other way with internal threads short of cutting a sample in 1/2 so that one may use an optical comparator, either buy or make a plug gauge.

If making many parts make GO and NO GO gauges, this will save a good deal of time.

 

[3strucking]

Its going to be around .885 id, not .855