Number 2 Center Drill Speeds and Feeds

• #1

Hey all...

When i need to use the tailstock center for support of a long parts, i usually use a #3 or #4 center drill...

I ussually go about 750-1000 rpm...
And i usually feed at .001 ipr :|

Is this too slow ?
Sometimes if i want to feed my center drill into my work about .250 it takes about 15 seconds...

Is it ok to feed at, lets say .002 ipr ?
Or is this asking for trouble ?

I dont have too many center drills and i like them to last... Will .002 ipr hurt my center drill ?

If feeding at .002 should i have a 1 second dwell (G04 P1.0) at the end of the .250 feed, so that all the centers come out the exact same depth ? because uniform depth is very important...

We use our center holes to help guide us with hole drilling afterwords... so its important that the center holes are very close to the same...

Anyway... just wondering because i do the same thing on the mill as well...

S1000 + F1.0 so basicly .001 ipr
VERY slow!!!

What say you ?

thanks

• #2

MATERIAL, MATERIAL, MATERIAL!!!!!

3t3d

Diamond

Joined

Nov 1, 2004

Location

WI

• #3

That sounds really slow for Balsa wood.
For tungsten that might not be right either.
So, you are someplace in the middle. Therefore you must be -just right- Carry on.
Pete

• #4

The guideline I used for teaching c/drilling has been F.005 per rev for mild steel, so if you are running at S1000, the feedrate would be F5.0. That's for 1018 Steel, for Aluminum you can about double it and for tool steel you have to slow it down.
It also depends on the size of the c/drill, but its pretty close. I don't see any real reason to dwell at the drill depth.
Heinz. [email protected]

• #5

my bad... sorry...

this is 8620 steel (mild)
about 8-10 Rc

How about 316 (Rc = soft and gummy) and 17-4 (28-30 Rc)?
what would you do for these 3 materials ?

thanks

• #6

S1000 + F1.0 so basicly .001 ipr
VERY slow!!!

What say you ?

^%[email protected]{:'';[#~~~];'']'~~##`% *&^%*& ^&^%£^ ^%$%^$%£ @:}@~#;' ^$!"£!`` !!!!!!!!

Boris

Rough translation leaving out the rude words :- you trying to rub the metal outa the way?
The S1000 sounds fine for a #4 into steels, maybe drop to 900 for the #5
The feed is waaaaaaaaay too low
Roughly speaking feed should be 4 thou per rev, which gives 4 inch/per sec.. oops not slam drilling per minute or 100 mm per minute

Normally drilling harder stuff I only drop the spindle speed and generally keep the feed at about 4 ipm/100mm/min, this stops the drill rubbing so much, on really hard stuff use cutting oils instead of slurry

Boris

<<used to drill 1000's of holes in PCB press tools so I should know what works

Jeff

Hot Rolled

Joined

Jun 11, 2001

Location

WI

• #8

Anyway... just wondering because i do the same thing on the mill as well...

slapping forehead!

• #9

1200 rpm 6 ipm. no.3 on a mill cutting h12 works well for me.

• #10

i always peck with a center drill g83.

g81 with a spot drill.

• #11

I run the rpm at bout 1000 what you are running. feed at .004 then grab the feedrate override and turn it up to see what happens. I am new to cnc lathes to and the best way i have learned how to do stuff is look at another program that is good and go from there. these cnc's are a completely different animal than warner&swasey 5 spindles. But as my dad always said Quote " cutting metal is cutting metal and this is just another way to do it" another favorite my dad use to say is "if one monkey can make it another one can make it just like it" You never stop learning in a machine shop.

• #12

I dont have too many center drills and i like them to last...

I bet if you only used them in the lathe for drilling center holes, and quit using them in the mill where you shouldn't be using them, they would last a lot longer.

Get a spot drill! Get a few! They are not expensive; I bet even your boss would buy you some if you asked him nicely!

• #13

and quit using them in the mill where you shouldn't be using them, they would last a lot longer.

what do you mean you're not suppose to use them on a mill???

if anything they should last longer if you use them on mills only because its harder to center on a lathe.

on a mill you don't have the issue of possibly not being concentric with work.

I agree that spot drills are better though.

I use them over a c'drill whenever avail.

• #15

How did centerdrills end up being commonly used to spot drill with?

When I first started out I was taught that centerdrills were used to spot with, what a huge mistake, they wander a bit and the hole they make lets your drill wander all over the place, might as well not even use it.

• #16

Maxh,

You beat me to the punch. Who the heck uses a center drill for production cnc work unless the print calls out for a specific c'drill or you are prepping for center work later. C'drills are SLOW because they have terrible chip evacuation. Look at one up close Solar, BARELY any flute at the end and you have to bury the tip( fat web and all) before you get any appreciable countersink diameter. And you are feeding a lot farther to get the same diameter. If you're just spotting for a drill, quit being silly and get a spot drill or spade drill(lathe or mill ). You only use centerdrills because that's all you have there, Right? Time to be a trendsetter again, Solar.

Ted

PS--Solar, you will love these things. You can really push 'em.

• #17

I will use a ( sometimes Carbide) center drill on harder materials. Softer stuff I always go spot drill.

Tool pressure comes into play on certain parts and you have to use a center drill and i dont burry the center drill i just spot with it .

i will come back and chamfer with another tool if part has chamfer call out.

• #18

Center drills are OK if nothing else is available.
But then again, how can that be in a reasonably equipped shop is beyond me... But I degress...
What kills me is one of the local shops is flat out refusing to use anything but centerdrills to spot holes, and to top that off, he feeds the miserable thing to below the body diameter.
Obviously, the next thing is he comes over and sharpen drills on a weekly basis, all the while bithchin' about the sucky 316 eating the outer edges of all his drills to a point that a double pass has to be taken on the grinder.
I'm tempted to take every one of his centerdrills and shove'm up his you know where!!!

• #19

Who the heck uses a center drill for production cnc work

I DO!!

• #20

more advantages of using a spotdrill:

you don't have to go as deep as you would a centerdrill to get a countersink for a tapped or drilled hole

you can use the same tool to chamfer,

you can feed faster,

better finish,

and im sure theres more

sykesthise1986.blogspot.com

Source: https://www.practicalmachinist.com/vb/cnc-machining/center-drill-feed-rate-question-121046/

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