[bowersjack]

Does anyone know of a chart or formula to help me find drill depth for KEO combined drills and countersinks to give me a finish countersunk hole in my programming? Or do you use spotting drill instead? Thanks Jack

[Geof]

Does anyone know of a chart or formula to help me find drill depth for KEO combined drills and countersinks to give me a finish countersunk hole in my programming? Or do you use spotting drill instead? Thanks Jack

They call them 'combined drills and countersinks' but they have a 60 degree taper on the 'countersink' part which is not correct for a flat head countersunk screw. Right now I can't remember exactly, but the angle for a countersink is 87 or 89 degrees so even a spotting drill at 90 degrees is not exactly correct. I have been told it is possible to get spotting drills with the correct angle but have never seen them; for non-critical work the 90 dgrees is often okay. Using a spotting drill also gives the advantage that you can spot for the hole location to stop the drill wandering on entry, and go deep enough to leave the countersink at this step; saves a bit of time on multiple holes.

[mixdenny]

They call them 'combined drills and countersinks' but they have a 60 degree taper on the 'countersink' part which is not correct for a flat head countersunk screw. Right now I can't remember exactly, but the angle for a countersink is 87 or 89 degrees so even a spotting drill at 90 degrees is not exactly correct.

The SAE standard is 82 degrees. Aircraft standard (thin panels) is 100 degree, although you don't come across these very often. Metric flatheads are 90 degrees. I have lots of 82 degree countersinks, but only a few 90 degree for the occasional metric job.

Dennis

[Geof]

The SAE standard is 82 degrees.....Dennis

Thanks, I try reciting that to myself a few times .

[cnc-king]

Does anyone know of a chart or formula to help me find drill depth for KEO combined drills and countersinks to give me a finish countersunk hole in my programming? Or do you use spotting drill instead? Thanks Jack

may be this will help. this is a table i created when i first started in the trade before the days of excel

[MetalZilla]

Does anyone know of a chart or formula to help me find drill depth for KEO combined drills and countersinks to give me a finish countersunk hole in my programming? Or do you use spotting drill instead? Thanks Jack

Go to ï¼·ï½…ï½‚ï½ï½ï½“ï½ƒï½ˆï½‰ï ½Žï½‰ï½“ï½” - Internetagentur Bayern: Webdesign & SEO Passau
they have the formula there.

[wizard]

These angles are also available from multiple suppliers so I don't think it is odd or special order. The common size may be 60 degree but that is mostly due to use as a center drill.

They call them 'combined drills and countersinks' but they have a 60 degree taper on the 'countersink' part which is not correct for a flat head countersunk screw. Right now I can't remember exactly, but the angle for a countersink is 87 or 89 degrees so even a spotting drill at 90 degrees is not exactly correct. I have been told it is possible to get spotting drills with the correct angle but have never seen them; for non-critical work the 90 dgrees is often okay. Using a spotting drill also gives the advantage that you can spot for the hole location to stop the drill wandering on entry, and go deep enough to leave the countersink at this step; saves a bit of time on multiple holes.

[SF Giants Fan]

this is from txcncman...don't know how well it works.

[recordhound]

TXCNCMAN thanks this works well - I Used to have a printed chart that had a formula for standard center drills - it had coffee stains all over it. I lost it and now I can't believe it is so hard to find another one.

[SumDumPhuckr]

I took some time to review the posted excel file and found the numbers were not the same as what I use when programming. So I have added some additional information. Let me know if I'm on the right track or not.

[MetalZilla]

Try here: Center Drill Dimensions

[SumDumPhuckr]

A No. 5 Center Drill will make a MAX 0.4375 Diameter Chamfer. The example on this page [URL="http://www.webmachinist.net/centerdrilldimensions.html"] may NOT work

[TampaCNC]

I know this is an old post but awesome share guys. Very useful excel sheet!

[Dwanef]

I was looking to see of anyone had the math to calculate center drill depth, every I looked I got a different answer. I drew a #4 center drill on MasterCam and found a solid solution. If you have a Texas Instruments TI-84 Plus, below is the code that calculates the depth needed for a given diameter. This code does account for the pilot tip, which no one else seems to do...weird. Calculate the depth, touch the tip to your material surface, set Z, go.

Disp "DESIRED DIA.":Input A
Disp "PILOT DIA.":Input B
Disp "CENTER DRILL DEPTH IS..."
(A/2)-(B/2)?C
C/tan(30?D
(B/2)/tan(59?E
D+E+B

[maxspongebob]

stet