Split-point drill question

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dml66

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I have the setup shown below ready to drill tomorrow, figured I'd ask a question before I make a mess of things.

First, this is not a precision 1/2" diameter hole; it's a pass-thru hole, but I'd like it to be nice of course. Hole depth will be 2".

I purchased the drill from McMaster-Carr; it's a split-point which, according to the description, may not require a pilot hole. I have no problem drilling a pilot hole but I don't want to do that if it creates problems for the spilt-point drill.

So, should I drill a pilot hole? If so, what would be the best diameter for the pilot drill?

The small center hole in the part was made on the lathe just to double-check center on the drill press using an edge finder on the ER40 square block; the two methods agree nicely :).

Thank you.

Split Point Drill.jpg
 
Personally, I have always started with a pilot hole, then upsized drill sizes in various stages before using the intended finish size drill.

You have to remember, it is easy to remove a little at a time without the drill bit wanting to "Grab" Vs trying to bore a 1/2" hole right from the start.

Been there, done that. It was when I was being taught and shown the reasons NOT to do it and instead pilot drill, then upsize.
 
Only a tiny divot is needed to help center the drill. There is no need for a significant pilot hole. What is already there is plenty. Use cutting oil. Steady pressure so you always take a chip. No need to step drill but you can if you want.
 
A good pilot hole will help keep the bit from wandering.
Since you have a divot, you should be fine.
Peck drilling is a good way to start until you get a 1/8” deep bore started, then use steady pressure all the way through .
12L14 drills wonderfully
 
A 1/2 inch bit in a drill press does not need a pilot at all.

It does need SLOW speed, lots of pressure, and be careful on the exit.

We drill 1/2 often, never a pilot. Sometimes, we use a 1/16 to 1/8 just to spot the mark, and it makes a tiny spot for confirmation.

A pilot hole adds stresses to the cutting edges that can damage the drill.

The pilot should not exceed the size of the web.

Sent from my SM-G781V using Tapatalk
 
I skipped the pilot hole, used cutting fluid and, as long as the drill kept making nice, meaty chips, I let it ride.

Very satisfied thank you all :).

20240313_120323.jpg
 
Nice curls! 8^)

I still wonder about those split-point drill bits.
 
CraigH said:
Nice curls! 8^)

I still wonder about those split-point drill bits.
Click to expand...
There is a reason the drill point is called a chisel point.
If you take a chisel the size of the chisel point and try to drill with it you will see a rubbing action Not really a good cutting action. Once the flutes engage they act as a centering action.
I split every thing I can by eye but I have been a machinist for 70 years And learned how to split points by hand many years ago.
 
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