[danrudolph]

Just wondering if you more experienced members can make an recommendations:

303 Stainless, .089" dia hole, thru, 3.84" part length.

Current approach:

Main Spindle
#43 MA Ford 205 series drills, 1" deep, .002 ipr, 6000 rpm, .050 pecks.
#43 Gurhing 336 series parabolic, 1.85" deep, .0015 ipr, 2000 rpm, .050 pecks.

Sub Spindle
#43 MA Ford 205 series drills, 1" deep, .002 ipr, 6000 rpm, .050 pecks.
#43 Gurhing 336 series parabolic, 2.20" deep, .0015 ipr, 2000 rpm, .050 pecks.

Tolerances are .089"+.005/-.010. Some mismatch is allowed, but the go pin must slide entirely through the part. I can only reach about 2 inches deep on the main and 2.2 inches on the sub on my Citizen A20. No HPC on the machine... for now.

The process above worked well but would like to look for improvements in tool life and mismatch (the long cobalts look used up at 400 pieces and mismatch was increasing). Thinking Titex might have something that would work better?

Dan

[txcncman]

What angle drill point? Recommend 135 or 140. Why 6000 on one drill and 2000 on the other? Recommend 75 SFM for both. Recommend peck at 1/2D max. Less peck at more depth.

[danrudolph]

The shorter drills (MA Ford 205 series) are carbide, the longer are HSS/cobalt.

Both are 140º drill points.

[jessebpm]

Do you have high pressure coolant. I have done a lot of deep hole drilling using Mitsubishi carbide coolant through drills. They make drills as long as thirty times the diameter. Much much faster than conventional drills. With these drills there is no pecking you simply drill a starter hole then enter you starter hole with the long drill turn on high pressure feed to bottom of hole then retract.

You do have to have a min of 1000psi.

[jbrookes]

Would you or someone clarify what .050 pecks means? Are you withdrawing the drill .050 every so often? If so, how often? I am looking for the procedure. Thanks in advance.
JB

[danrudolph]

Alas, no HPC... it's on my list for the future though.

Yes, .050 pecks means full retract, in this case. I use my own drilling macro to do it, which gives me more flexibility.

[jbrookes]

OK, full retract. That must take you around 3 sec. per retract? (at least...)
So, if I'm drilling 2.50 inches, that is 50 retracts...or about 3 minutes....Have you timed the retract, re-entry cycle time?
I have had some broken drills, and I can see I am not pecking enough....may use G83 canned cycle to do multiple retracts...

[danrudolph]

What diameter are you drilling and what material?

From the bottom of a 2.5" hole, rapid out and back in, might be 3 sec, probably more like 2 on my machine with 32m/min rapids. I use a excel macro to estimate drilling cycle time, it's fairly accurite.

I like a little dwell at the bottom of the hole and a longer one outside the hole to get more oil on the drill. I don't like the G83 cycle for this reason.

[jbrookes]

I am drilling 303 ss, 1/8 dia., 20XD. Currently using a black sulfur oil with some motor oil added to it.
JB

[SirDenisNayland]

OK, full retract. That must take you around 3 sec. per retract? (at least...)
So, if I'm drilling 2.50 inches, that is 50 retracts...or about 3 minutes....Have you timed the retract, re-entry cycle time?
I have had some broken drills, and I can see I am not pecking enough....may use G83 canned cycle to do multiple retracts...

3 seconds? Have you even worked on a machine? They will peck (that is, rapid retract and rapid back into the hole) faster than you can blink my friend...

[jbrookes]

My estimate is based on having a second pause on full retract...I have been hesitant to write code like this:
G0 z.3
G4 K100
G0 z1.95

What is the code ou you are writing? If retracts are this fast, why bother with coolant-through drills at all? mmmm?

[SwissBeast]

At that depth and diameter I would suggest some good coolant first and foremost. I personally would gun drill the hole but obviously thats not possible without high pressure coolant. I also have no experience with that alloy. If you tried a worthy drill company I would call their tech support and get some good starter dimensions. You could always write a while-do loop and set a pretty good depth with large pecks to start and smaller pecks for the second half. don't overlook how long to pause outside of the hole to cool the drill tip off. i personally keep one flood line on the tip of the drill and one aimed at the end of the workpiece when pecking. i also generally pause my drill for one rotation at the bottom of the hole.

[jbrookes]

I am now using HPC drill - Kennametal 1/8 20XD to drill 2.5 inch hole. Coolant is Rustlick 300A (for SS 303) at 1000 psi in an er16 collet.

Workpiece turns at 4500 rpm and feed is .0025. Pilot hole is .7 inches drilled with 3 flute carbide drill with 150 degree angle.

The time for the coolant drilling cycle is 10 seconds. I am running it slowly at first - later will try its full speed which takes 6.2 seconds - 5500 rpm and .003 feed. (180 sfm)

jb

[jbrookes]

I am cncerned about how straight the drill should be. Over a 2,5 inch length with 1/8 drill, how much misalignment allowed?
TX JB

[elsanch]

why not use a smaller drill for the first passes..i see you are using #43 for both. use a smaller drill (long drill) for the first roughing passes, then follow it with a reamer? same on back?

[SirDenisNayland]

Dan,

I work in a lot of 303 and for cost of drill vs tool life vs parts made Ive not found a better drill than a guhring gt100. I've tried everything, hsco, their firex 55xx series with or without high pressure, different coatings, different everything but always returned to the gt100.

On one particular job with the firex and hp I drilled my hole twice as fast, but the drill cost 150 and blew up in just over 24hrs at the recomended starting speeds, not pushing it at all, whereas I get 18hours out of a gt100 and it costs me 8 dollars. Sure, I made a few hundred more parts in 24hrs, but is it worth it? Not in my opinion.

[SirDenisNayland]

My estimate is based on having a second pause on full retract...I have been hesitant to write code like this:
G0 z.3
G4 K100
G0 z1.95

What is the code ou you are writing? If retracts are this fast, why bother with coolant-through drills at all? mmmm?

I use g83 unless I need more flexibility. No dwell on retract.

We bother with coolant thru because you can drill in one shot, which is faster in a production environment, but as my previous post details can be somewhat cost prohibitive..

Example if I'm not using g83 (which I will for various reasons like wanting to turn on an airblow or something at a certain position)

G1Z.25
G0Z-.05
Z.23
G1Z.5
G0Z-.05
Z.48
G1Z.75
...
Etc

The distance you rapid back into the hole is up to your discretion and what you're comfortable with, and is also a changeable parameter for the g83 cycle. My star came with it set to zero.. so it was rapiding itself right into the bottom of the hole which I wasn't comfy with personally.

I apologize for being a bit of a smartass with my prior comments.

[jbrookes]

Sir Denis,
Thank you for that tip. I would appreciate knowing more about the pecking cycle you are usin with the hsco drill. I am likewise using 303. I nvested in a hpc plus Kennametal coolant through drill. Due to a machine breakdown, I haven't drilled with it yet. But the whole area of deep hole drilling is a no-man's land of uncertainty, clouded with smoke. That's why it's good to hear actual experiences from users. I am drilling 20xD - 1/8 inch (3.18 mm) to 2.5 inch deep. Lets take that hole. They say that speeds giving a 12 second drilling are possible. But the fact that 1/8 inch is on the bleeding edge of size is an issue, I believe.

Another thing: I put the drill in an er16 collet and measure its straightness by backing it up to a fixed metal piece. I sense touch with a ohm-meter. And here is what I find: I believe the drill is curved. Measuring from near the end of the $200 drill bit, I get a variation of .002. Then for the next inch, I get a variation of .007. If my numbers are right, that will cause rubbing against the pilot hole.

Your comments about hsco drills are a welcome insight. In questioning high speed retract, I actually don't know if its a bad idea. I came up with the number of 3 seconds per retract - out of thin air. If that's reasonable, we are talking about an extra 45 seconds per hole, assuming the first inch is done without retracts with the pilot drill. (actually say 3 retracts - so add 8 sec.)

Thanks
JB

[jbrookes]

I note your code retracts every .25 inches (or is that mm?) Some in this thread say every .1 inches. I think .25 would work...
Any opinion onion?
jb

[SirDenisNayland]

Your peck depth is all dependant on your drill size. I was just providing a general example is all.

Cheers.

Edit:

I'll be honest, I've never done anything crazy like 30xD drilling, but at that depth hsco and carbide are probbaly your better options because of their inherent higher rigidity and lesser tendency to "walk"

The one job I mentioned was 7.5xD, but I have done upwards of 15xD with regular hss with minimal walk.

Generally you don't want your pecks to be larger than your diameter, and even lesser depending on the material (for instance I'm drilling 304ss with a .320" drill at .1" pecks right now at 50sfm and it will run and run without fail), and as mentioned in the thread, when you get into deep drilling you reduce the pecks even more. Some people write their own custom macros so that the peck depths gradually reduce as the drill drills deeper, eg. First peck is .1 then .09, .08, etc. The whole point is to prevent walk, tool burn up, and to evacuate chips. The deeper the hole and the smaller the drill and the chips end up with nowhere to go. Without HPC your drill tip down a hole especially in a lathe gets dry very quickly..

Trial and error and figuring things out for yourself is the best way my friend! Get ballsy, give'r! You can listen to people all day long giving reccomebdations that all contradict each other yet seem to work for that person lol, but I do understand being a tad wary about givin'r with a $200 drill lol. I drill the 7.5xD hole in 303 at 200sfm at .005"/rev with the HSS drill. Lasts 18-20 hours and in total drills about 1500"

Interesting method for checking the straightness.. if your drills are indeed curved find a new drill manufacturer.. I'm willing to bet though your square is against the tool block which your drill sleeve is held in. Play with your screw tightness and remeasure and get back to me

Lot of guys think you can just throw in a drill and let it fly.. and you generally can, but if things are critical like they are in deep drilling you want to be nuts on. It's why I don't particularily like double end drills like I can utilize in my A20 or stars, you can only really dial in one drill or find a middle ground between the two.

Also, everyone is a speed demon.. but where is the sense in speed when you're popping drills left and right? Think of all the down time.. slow down a tad and let it run and forget about it.