How to melt a drill bit

[rake60]

That brings back memories.

I used a center drill in a CNC program to spot a tapped hole. No problem.
Then I had programed the drill bit too fast. It snapped off in the hole when it broke through.
Of course the machine didn't know that so it attempted to tap the hole.

It wasn't pretty! :

I do have spotting drills at home but rarely use them.
They are in the tool box and the center drills are within easy reach at the lathe.

No matter what you use to center a hole, all you really need is a spot slightly larger than
the chisel point of the drill bit to keep it from walking.

Rick

 

[lee9966]

I don't use spotting drills cuz I don't own any. I do know though one of the easist ways to get a hole off center is to start it with a center drill. I've got lots of work arounds if its important to get a hole dead nuts on. Maybe I'll buy some spotting drills. I often start holes for small drills using a ground point on a piece of drill rod to create the starting hole.

For soft materials and small hole sizes I have been known to use a dead center to make a small very centered indent in spinning material in the lathe, something like .010 to .020 deep maybe. Dont try to do more than create a small dimple, you dont want to hold the center against the material for more than a second or so. This has worked for me on brass and aluminum, but I am perfectly willing to hear why this is a bad idea

Lee

 

[rake60]

Other than possibly damaging the dead center, that will work Lee.
That first .010 or .020 is rarely used on a center anyway.
I wouldn't do it but it will work!

I've also seen people who know nothing about machining, (or a machinist who is in a hurry),
carefully position a center punch on the mark and smack it with a hammer.

Again, if that punch mark is larger than the chisel point of the drill bit the bit will not walk.

It can be as simple or as complicated as one wants to make it.

Rick

 

[milotrain]

I needed a nice little 45˚ chamfer bit and found that a 1/4" carbide 90˚ bit works wonderfully as a spotting drill as well. Much much bettter than my center/countersink bits, and works in multiple capacities. I understand that the angle is not ideal but for now it is an upgrade.

I've found many uses for this little 90˚bit and highly recommend picking one up.

 

[Andrew_D]

Since spotting drills are essentially regular drills with a very short fluted section, I've often made spotting drills by resharpening broken drill bits. It may take some work, especially for larger sizes, but for those of us in a home shop environment, time is usually pretty cheap!
:big:

Andrew

 

[steamer]

Hey Kvom,

Similar experience....thought I had 303 stainless...but it was really 17-4 stainless!

half way through the hole with a center cutting endmill and I wondered why the motor started to bog down...the endmill was WHITE hot :big: :big:...the mill could have cared less!

Dave