Are all center drills the same? Frustrated here...

[mmcmdl]

Center drills are made for the use of turning a shaft between centers with the small tip providing clearance for the center point . Hence the 60 degree angle . A spotting drill is a much more rigid tool vs. the CD . Pretty darn tough to break one if at all possible .

 

[jcp]

Most of the center drills I've broken have been while doing 'gummy' steels (1018 etc.) with not enough rpm and too much pressure.

 

[compact8]

When would one use a spotting drill compared to a center drill, and visa-versa?

I just learned this recently. Spotting drill is used for starting a hole and center drill is more for drilling a hole to accomodate the tailstock center of lathes. Spotting drills have a much more pointed tip so it has lower tendency to wander. The angle of the tip is also optimized to minimize the wandering of the drill used after it.

 

[jcp]

I suppose the terminology is confusing. Reading 'center drill' leads one to thinking 'centering a hole for a drill' when in fact it means 'drilling a hole for using a center' (live or dead).

 

[Maplehead]

That's very odd ...... I have broken small-diameter drills ( talking about around 1 mm ) but never any center drills. I have got some really crappy center drills but they just refused to go into the metal instead of breaking. This is just wild guess but is it possible that the run out of the spindle or the tip of the center drill is excessive ? This is the run out of my crappy center drills but still they do not break :

I've never checked that but it looks like I'm going to switch to the spotting drill.

 

[Maplehead]

I did a qucik search on Amazon for Keo spotting drills and most are at 90 degrees. Considering most "jobber" drill bits are at 60 degrees, a 90 degree spotting drill would be incorrect. So that's odd. I am basing this off of this article I just read.

Spot Drilling: The First Step to Precision Drilling - In The Loupe

In high precision machining, drilling a hole exactly where it is needed is a challenge. The challenge comes with choosing the right spot drill for your job.

www.harveyperformance.com

 

[mmcmdl]

Can you imagine using a center drill vs a spotting drill on a cnc mill drilling thousands of holes ? The center drill must get that small point down into the stock which takes lots of time and it's also very weak . A spotting drill will plunge to the desired depth in seconds and create a true start for the drill . I realize we aren't production guys , but using the right tool for the job is why we're all here .

 

[mmcmdl]

Spotting drills come in different angles MH . I got a bucket full of them down the basement . What you googled is not a spotting drill either . I'll get some pics and load them here .

 

[compact8]

I did a qucik search on Amazon for Keo spotting drills and most are at 90 degrees. Considering most "jobber" drill bits are at 60 degrees, a 90 degree spotting drill would be incorrect. So that's odd. I am basing this off of this article I just read.

Spot Drilling: The First Step to Precision Drilling - In The Loupe

In high precision machining, drilling a hole exactly where it is needed is a challenge. The challenge comes with choosing the right spot drill for your job.

www.harveyperformance.com

Common jobber drills have a tip angle of 118 degrees, not 60. You will need spotting drills with slightly larger tip angle. All those I have got are of 120 degree type. The 90 degree type is designed to do spotting and chamfering at the same time at the expense of less spotting accuracy. Although they are much more common, I don't use them.

 

[Maplehead]

Spotting drills come in different angles MH . I got a bucket full of them down the basement . What you googled is not a spotting drill either . I'll get some pics and load them here .

Considering my tap drill is a #33 at .113" in diameter, can you recommend a spot drill for me to use? More precisely, can you link me to one on Amazon or eBay?