Centerdrill or Spot Drill?

[Michael Sullivan]

Material = 17-4 PH Stainless Steel.

 

I was thinking to order center drills for this job. I typically use spotters for everything since 80 % of our work is Aluminum.

For anyone who has not cut it before 17-4 is nasty.

 

What do you think?

[ToolMan184]

To me you should always use a spot drill to spot the hole and a center drill to put centers into a shaft. JM2C

[chowquoe^]

We like to use 145° spots in our shop. Seem to give us the best result as far as size and location goes.

 

And yes 17-4 is a little nasty, if you need any help with cutting it let me know, 98% of what we do is 17-4.

[robk]

I'm not a big fan of center drills, but they have their place. Are you running carbide drills or HSS/Cobalt? Are you drilling on a flat face? Are your drills walking now? How deep are you drilling?

[Guest]

quote:

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I'm not a big fan of center drills

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+1 rob

 

Spot drills all the way, carbide if the material requires it.

[Michael Sullivan]

I need to spot and make a lead in for a 3/8-12 acme thread. It is a thru hole and the part is about .9 tall.

I will be using carbide drills mostly. I have not started cutting yet, just programming and ordering tools at the moment.

we have cut a bit of the 17-4 lately with mixed results. Originally they were ordering general purpose endmills and such which, I quickly decided was not in our best interest. I just wanted to get an Idea how everyone is spotting holes. I've heard some people preferring centerdrills for steel.

[Michael Sullivan]

Oh yeah, the hole is on a flat surface. Centerdrills do work well on a curved surface but here that's not the case.

[htm01]

with carbide drills you don't need to spot

[within a thou]

if you are using carbide drills why do you need either especially if you are only going .9 deep. But to answer your question I find centerdrill pilots to chip carbide drills I use spots whenever I can and if I am going on a round I flat bottom the hole with a endmill then use a spot. to me centerdrills are useless.

[robk]

If you have coolant through then I would run just the drill... No spot or center. If no coolant through then make sure your spot has a bigger angle then your carbide drill.

[Slixmix]

Here, we use centerdrills for all steels and spot drills for aluminum. Centerdrill, drill, c'sink, tap.

[Michael Sullivan]

I don't necessarily need the spot for the drill but, as a lead-in for the thread.

[jeff]

Spot drill only if the surface has slag on it like HRS.

Or if your location needs to be held closely.

Other than that,just use the carbide drill,chamfer tool, then tap.

[robk]

quote:

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I don't necessarily need the spot for the drill but, as a lead-in for the thread.

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Definitely use the spot drill, but after you drill the hole. They work great as chamfer tools

[Michael Sullivan]

Thanks peeps,I appreciate all the input!