Do center drills have runout ?

[compact8]

As someone pointed out earlier, measuring the runout with the center drill in a chuck, collet, or any other tool holder, you're not going to be able to tell what is causing the runout. The spindle, the chuck/collet, the center drill, a little of all of the above? Put the center drill in a v block and eliminate the other variables.

My point is not so much about the absolute amount of runout but the difference between the main body of the center drill and the tip. All the mentioned contributing factors such as the spindle, arbor, collet, etc should affect the tip and the main body of the center drill equally right ?

 

[akjeff]

There is no guarantee that the tool is being held dead straight by whatever is holding it, so the runout you measure is going to vary the closer to, or farther away from the point that the tool enters the tool holder. Again, put it in a v block and remove all doubt.

 

[jwmelvin]

All the mentioned contributing factors such as the spindle, arbor, collet, etc should affect the tip and the main body of the center drill equally right ?

That was my point about parallelism. In my experience, a drill chuck especially can have issues in that regard, as a single worn jaw will let the tool tilt relative to the chuck axis. Trying in a v-block would not have that issue and would be interesting in this case.

 

[Superburban]

I could not watch the video on this tablet.

Are you accounting for the relief ground into the cutting surface?

 

[RJSakowski]

I could not watch the video on this tablet.

Are you accounting for the relief ground into the cutting surface?

I thought about that too. But you have to look at the difference between the readings at each cutting edge. It looks to be about .1mm as opposed to the .02 mm on the shank.

 

[compact8]

Okay .... here is the checking result of the recommended Vee block method. I hope I have done it right because I have not used Vee blocks for such purpose before.

 

[woodchucker]

so what you are showing is not very helpful.
All drill points have relief behind the cutting point.
The tip is what sets the hole in this case.

is your tip wandering.

for what you are showing ; you would only need to show 2 points to us , right on the cutting edge. showing the rotation its normal for the needle to wander ...

 

[compact8]

.... need to show 2 points to us , right on the cutting edge....

I have thought about that but I am afraid I don't know how to check the runout right on the cutting edge.

 

[brino]

so what you are showing is not very helpful.
All drill points have relief behind the cutting point.
The tip is what sets the hole in this case.

is your tip wandering.

for what you are showing ; you would only need to show 2 points to us , right on the cutting edge. showing the rotation its normal for the needle to wander ...

Hey Jeff,

I think it's valid.
Showing the full, slow rotation lets us see the maximum points.
How would you easily "clock" the cutting edge directly under the indicator tip....not easy.

As @RJSakowski stated earlier it's the difference between the two edge maximum readings and we can see that from the video.

The only thing I would do differently is to rotate the centre drill the other direction for two reasons:
i) not presenting the sharp cutting edge to the dial-indicator tip; that is making the ball climb up the larger sharp step, and

ii) it would be easier to sneak up of the maximum reading as you'd be slowly climbing the relief.

Just my thoughts......

-brino

 

[woodchucker]

Hey Jeff,

I think it's valid.
Showing the full, slow rotation lets us see the maximum points.
How would you easily "clock" the cutting edge directly under the indicator tip....not easy.

As @RJSakowski stated earlier it's the difference between the two edge maximum readings and we can see that from the video.

The only thing I would do differently is to rotate the centre drill the other direction for two reasons:
i) not presenting the sharp cutting edge to the dial-indicator tip; that is making the ball climb up the larger sharp step, and

ii) it would be easier to sneak up of the maximum reading as you'd be slowly climbing the relief.

Just my thoughts......

-brino

yep, good idea rotating it the other way, but I would simply find the high points..
And still, the tip is the most important aspect. The tip is what sets where it is going initially.
a D bit and it only has one cutting edge... while not a great drill, have you watched clickspring? he drills perfect holes with a dbit.