How To Remove A Broken Center Drill

[shopandmath]

How To Remove A Broken Center Drill
At the end of this video is a short bit on what to look for in a center drill
The cheep junk (split grind) center drills are not worth what you spent on them
I am having to remove broken tip about 2 to 5 each class
The number of people trying to drill out a HSS center drill with a HSS center drill is just upsetting
Ray


Video URL

[high-side]

How's the end of that 3 flute carbide end mill looking after machining HSS?

[shopandmath]

The choice of the three flute end mill was one of convenience
I have a half dozen of them in my toolbox and we can’t use them for anything because the tapered
There was no chips or anything I noticed that the time wrong with the end mill
I’m on vacation for the next little bit when I go back I’ll trying take a picture of it
Ray

[Paul Alciatore]

On the tip at the end on better center drills, can you explain why the spiral cut one is stronger? The one on the left that you refer to as a straight cut is what I have seen and most, if not all of my center drills are that style. But the one you show looks like it has a very poor finish, possible already cracked. None of mine are like that. They have nice, ground finishes like most of my drill bits and end mills do. Is that the reason why the one on the left is no good? Or what? I would think that they both have about the same amount of cross sectional area at the base of the small diameter area, which is where center drills normally break.

AND, just where do you get those spiral cut ones? What brand? What are they called, other than center drills?

[shopandmath]

Hi Paul
Thank you for your email
I’m going to try and answer each question in point form

first question
can you explain why a spiral cut is stronger
The spiral cut has a Web just like a drill it starts off small at the top and tapers down wider as you go into the centre Drill Like a skinny pyramid almost or triangle The straight cut doesn’t taper

Second question
Most center drills are straight cut
When I complained about straight cut It was explained to me the cost is almost 10 to 1
That is why the quality of the grind on the Straight cut in the photo is so low
The only time we get the spiral cut centre drills is when they are solid carbide

Question three
Do they have the same amount of cross-section
This is where the problem lies if they have equal cross-section the spiral flute will be stronger
Scenario. Have you ever picked up a Centre drill looked or measured the Cross section?
If you’re machining an expensive part would you use a no-name tap or a high-end tap
The only time you’re going to look at the cross-section thickness is if the Centre drill breaks then it’s too late

If you’ve never broken Centre drill keep using them they are just fine

Question four
Where do you get the spiral cut
I have rarely ever bought centre drills I’ve told other people to get them for me and they just show up When I have ordered Centre drills I purchased them from Sowa tool and machine Co.
In Kitchener Ontario
I have also purchased them from Sowa in Calgary for the 2009 world skills competition

If I have missed any other questions or have not quite explained everything or if you have any other questions Please let me know

I went to my toolbox at home and got all of my center drills
And was surprised there are no straight cuts
Added photo
Ray

[high-side]

If your using center drills to spot holes for general drilling & tapping, why bother searching for the strongest center drill when you should just use a proper spot drill instead. No small tips to break off, and more accurate spotting.

[shopandmath]

Thank high-side you for your response
You are correct (what can I say) right is right
In the circumstance my students are in the toolbox they buy only have center drills in it
The CNC have spot drills
Spot drills work best with rigid equipment/setups center drill are a little more forgiving
Ray