Spotting Drills

[rwm]

I have now played with spotting drills with both 90 and 120 deg angles and tried deep and shallow.
I like my old center drills the best!
R

 

[wrmiller]

I have now played with spotting drills with both 90 and 120 deg angles and tried deep and shallow.
I like my old center drills the best!
R

I bought some spotting drill as well, based on comments made here. I do use them, mostly on the mill, but they won't replace my set of carbide center drills for the lathe.

 

[mmcmdl]

With the advance of CNCs , spotting drills became a neccesity , The solid bodies allow long lengths to be held out of toolholders . Your cycle time is reduced because they do not have the small pilot drill , thus reducing your drilling depth on z axis . They are much easier to program for CNCs also . You know the angle and the desired width you need , so depth is a simple trig calculation . As far a the different angles ? Many DOD jobs require different angles for different applications . They tie them up and they check them closely . I use spotting drills over center drills for one reason . I can run them at a higher speed and feed . Center drills may go from 1/8pilot to 1/2" body which changes your surface speed dramatically causing them to break , dull , load up etc . They are also very easy to resharpen .

 

[ericc]

I use center drills. When they dull, I save them and sharpen them as usual, but grind off that nub. They work perfect.

Hi Andre. This sounds interesting. Do you have some details on how this is done?

 

[Bill Gruby]

With the advance of CNCs , spotting drills became a neccesity , The solid bodies allow long lengths to be held out of toolholders . Your cycle time is reduced because they do not have the small pilot drill , thus reducing your drilling depth on z axis . They are much easier to program for CNCs also . You know the angle and the desired width you need , so depth is a simple trig calculation . As far a the different angles ? Many DOD jobs require different angles for different applications . They tie them up and they check them closely . I use spotting drills over center drills for one reason . I can run them at a higher speed and feed . Center drills may go from 1/8pilot to 1/2" body which changes your surface speed dramatically causing them to break , dull , load up etc . They are also very easy to resharpen .

Reality check due here. Spotting drills were a necessity long before CNC work. Automatic Screw Machines used them in 90 - 100 - 120 degrees for years. They couldn't get a straight hole without them.

"Billy G"

 

[Jimsehr]

I grind old broken drills and broken centerdrills to make spotting drills and I don't pay much attention to the point angle. As . long as they are short and stiff'
jimsehr

I am CHEAP.

 

[Bill Gruby]

You aren't cheap, you're FRUGAL. Machinists are the original recyclers.

"Billy G"

 

[JR49]

I grind old broken drills and broken centerdrills to make spotting drills and I don't pay much attention to the point angle. As . long as they are short and stiff'
jimsehr
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Jimsehr,
You are the second guy to mention grinding/resharpening old center drills. Ericc, myself, and probably others are still waiting for details/tutorial on how this is accomplished. I've tried it a few times, but never had a good outcome. TIA, JR49

 

[Bill Gruby]

Easy way. To regrind a broken Drill I either cut the broken part off or if it's not to bad I grind the end flat first.

"Billy G"