Rules on peck depth

[Alarm Hero]

What are the main factors to consider when calculating peck depth? Should peck depth be a percentage of the hole depth or cutter DIA.? Or both? Differences between free machining steel and aluminum? Stop asking questions and experiment?

Thankies

[cnc wizard]

I was taught 1 1/2 - 2 times the drill diameter for a standard drill.
So for a 1/2" drill in steel, peck every 3/4"
For aluminum you could go every 1"
But a lot depends on coolant delivery, drill point, number of flutes, coatings and on and on and on....

[kalmah]

What are the main factors to consider when calculating peck depth? Should peck depth be a percentage of the hole depth or cutter DIA.? Or both? Differences between free machining steel and aluminum? Stop asking questions and experiment?

Thankies

With free machining steel, you don't need pecking cycling until 7XD if your twist drill produce short chip (due to good geometry). I suppose it's the same stuff when drilling aluminium (I haven't a lot of experience with this material).
- With high alloyed steel, you can go until 4xD without pecking cycle
- With stainless steel it's difficult to drill. Personally I use 0.5-1xD of pecking cycle.
- With hardness tool steel, I use 0.3xD of pecking cycle.

[HuFlungDung]

Well, I hate big snarls of chips, so I peck about .05 to .1 in stringy materials if using an ordinary twist drill that has no chip breaking features. Fortunately, my Haas has lots of nifty so called 'high speed peck cycles' that help to optimize this sort of short peck drilling so that retractions are not occurring every peck.

[Rekd]

It depends on mat'l, tooling, depth, dia etc.

I typically do alum, so here's how I do it.

Small holes going deep: Initial Peck 150% to 200% of dia, reduced by 50% per peck finishing at 25%.

Small holes shallow: Peck 50% or Drill straight thru if less than 1 dia thick.

Bigger holes (1/4" or more typically) deep Initial peck 250%, reduced by 50% finishing at 50

Bigger holes less than 2 dia's deep drilled straight thru.

HTH

[cdlenterprises]

All this talk about pecking is making me dizzy...Just send it in there!! If you push hard enough the chips will take care of themselves

Seriously though, I'm with Hu. I usually keep the pecks to .200 or less. In difficult materials I try to keep the pecking to a minimum(not peck as often). I was always told that pecking in hard materials is a good way to lose the tips of your drill.

[lerman]

What are the main factors to consider when calculating peck depth? Should peck depth be a percentage of the hole depth or cutter DIA.? Or both? Differences between free machining steel and aluminum? Stop asking questions and experiment?

Thankies

Others have given you directions, but haven't really answered the question. Peck drilling does two things. It breaks the chips by stopping Z axis motion (so you might want to do that often), and it clears the chips by retracting out of the hole. Unfortunately, retracting from a deep hole takes some time. So, in materials that have stringy chips, you might want to break them more often than you want to clear them.

Since I use EMC, I've written my own peck cycles that break chips by stopping the Z feed for a short time and, less frequenctly, do a full retraction. I assume that is what the Haas peck cycles that Hu refers to does.

Ken

[Geof]

What are the main factors to consider when calculating peck depth? Should peck depth be a percentage of the hole depth or cutter DIA.? Or both? Differences between free machining steel and aluminum? Stop asking questions and experiment?

Thankies

Even with free machining steel if you are pushing both the speed and feed it is a good idea to peck just before breakthrough on a through hole. This lets coolant in to cool off the thin section of material remaining which does not have anything behind to act as a heatsink. In my experience if you are bordering on burning the corners off your drill the most risky time is at breakthrough.