Drill Depth/Tap Depth Reference 1

[TomFin]

Hi all,

Anyone have a quick web reference for determining how deep to drill with the "pre-tap" drill before tapping, given the depth of thread required? Typically I use hole wizard in Solidworks, but it would be great to have some sort of table to understand.

Thanks a bunch

Failure is a prerequisite of successful design

 

[TomFin]

A machinist came to me with a drawing with a hole callout of "1/4-20-.28" I thought this was sufficient enought on a drawing for the machinist to figure how far to drill the pilot hole to attain ~.28" of thread, but apparently not. I know there are quite a few styles of taps so maybe a magic reference table is not available due to the variability of tap styles.

Failure is a prerequisite of successful design

 

[TomFin]

If anyone else is curious take a gander here...

http://www.championscrew.com/thread_sizes.htm

Failure is a prerequisite of successful design

 

[byrdj]

The depth will also be effected by the type of stud or bolt used. for example the studs I most commonly see have a one diameter reduced tip.

 

[JDana]

The required usable thread depth + the length of partial thread on the tap (depends on type of tap and possible manufacturer) + the length of drill point (depends on diameter and angle) + a thread or two for "safety".

Best to make your own chart based on your answers to the variables above.

 

[FredGarvin]

http://www.cnc-training.com/tandp/aug06.htm