To Peck drill or not to peck dril.....

[Crashmaster]

Hello guys. I need to drill a 1.5" deep hole in 12L14 mild steel. I am using a HSS 118 degree 37/64(.5781) drill. In the past, I wouldn't peck anything shorter than three times the dia of the drill. However, this is close to that mark. Was wonder what you guys would recommend for this application. 12L14 is like machining butter anyways. How about a feed and speed recommendation?

[Abacus]

If it was me I would would probably drill it right through, especially if you have a lot of holes. You can always throw a gold drill in there if you are worried about it dulling or snapping. Speeds n feeds I always believe are up to personal preference depending on the material, machine, and equipment being used. If you go by sound you will know. A good center drill, if you decide, may eat up .4 of your overall stock. If the drill is squealing or crunching (lol) and no chips are coming out of the hole you got a big problem. Then you may want to sharpen, readjust your specs and decide to peck.

[Crashmaster]

OK, I am used to my chips being just that when I drill, chips. Based on my feed/speed chart I am currently drilling it at S625 F5. and I am getting long stringy chips. This may be due the the material, 12L14 but it is bothering the hell out of me.

[Abacus]

A long time ago on the boring mill I ran, I would be drilling away and getting those long stringy chips. Every so often they would stick around the drill and then one would fling off and either land on the lights up on the roof or whip straight into the foreman's office when he had his door open (kept him awake anyways). I even had one long stringy one somehow go airborne and find its way into my coca-cola can opening... go figure.

[Crashmaster]

So do I need to let those long stringy guys stop bothering me?

[Abacus]

Usually whenever I got what you describe as chips, was when I was drilling very hard material, pecking too small, or the drill was dull or improperly sharpened. The drills web is designed to remove the material. If it was all chips spinning around inside of the hole and nothing coming out it would only be a matter of time before you weld a new dowel into that location. I have seen many poorly drills sharpened and many times the only reason the chippy - chips are not breaking the operators drill is because the high blast coolant is saving his ass. Two stringys are better than one, so keep a ear on it, huh?

[Crashmaster]

That makes sense. I am usually used to drilling stainless. I appreciate the insight Abacus.

[ragman]

I'm suprised at all to hear you are getting stringy swarf. Being 12L14, I would expect short chips like cast iron.

Maybe try a higher RPM like 850?

[mactec54]

Hi crashmaster

I would start at 950rpm with F10 & peck you could go up to 1150rpm with no problem & more feed like F12 with lots of coolant but you do need to peck to break up those long
ones

[Geof]

Originally Posted by Crashmaster Hello guys. I need to drill a 1.5" deep hole in 12L14 mild steel........

You are not drilling through?

If this is a blind hole that does not get anywhere near the opposite side of the material you can almost double your speed and feed and not worry about pecking. You should find you get broken chips with a faster feed but if that does not occur then maybe pecking is needed.

If you are breaking through you may need to be conservative on speed and feed because just before break through things can get very hot, if you are pushing the speed and feed. For through holes your speed and feed is probably about correct; I also find it useful to do a single peck a littler bit before breaking through to fill the hole with coolant and cool things down.

[davereagan]

More feed per tooth makes the chips thicker and therefore less ductile and sooner to break. With 12L14, you need even more feed than 1018. If your machine has the thrust, you could feed up to .015" without hurting the drill. That would be 625 rpm, F9.4 A peck at 1" deep would be nice to break chips and give the drill some coolant.

[Crashmaster]

Geof, no it is not a through hole. I did fail to mention that I am drilling this on a lathe, on the face of the part into 1 inch round stock. Correct me if I am wrong, as you know I usually am, doesn't pecking serve a dual purpose. Not only does it break the chip but doesn't it also allow coolant to the cutting area? I did try, at my original feed and speed to not peck and it seemed to work fine, I just worry about wearing my drill bit faster than needed due to the lack of coolant I perceive is getting in the hole.... Thoughts?