implmex
Diamond
- Joined
- Jun 23, 2002
- Location
- Vancouver BC Canada
Hi again nissan300ztt:
All excellent advice here.
A thing you may wish to consider though:
As some have alluded to, the failure usually happens very quickly from the first premonitory "Squeek" of the drill to total catastrophic failure.
Since that is so, there is something to be said for doing this on a manual machine where you have tactile feedback as well as aural feedback and can interrupt the job as needed to re-group and re-sharpen and whatever.
I had to drill deep holes in Inconel 718 once upon a time on the manual lathe, and I found I had best results using a pilot drill no bigger than the web of the final drill (as garychipmaker recommends in post #20) and piloting in an inch, then opening out the hole in one shot to final size, piloting in another inch, and opening out etc etc until I got to the bottom of my hole.
Breaking up the hole this way meant I could always get lube down the hole and I never had flute packing to deal with.
I drilled undersized for the first increment and bored right to size, so my final drill would just slip in the hole and the stock acted as a drill bushing.
I could sharpen the drill as often as I needed to, and those who commented on the importance of watching the corners of the drill and the lands are spot on.
I got in the habit of re-pointing both drills after every inch whether they needed it or not, and the whole job went uneventfully (5/16" final diameter, 10" deep, 8 pieces).
As I recall my peck increments for both drills were something like 0.050"
My drills (after 80 sharpenings) were a lot shorter after the job than they were before the job!
So it IS possible, but the ability to feel what the drills were doing was important to my success.
If I was doing this in production however, I wouldn't even try it without all of the goodies...carbide TTC gundrills, HPC for the machine of at least 1000 PSI, a gundrilling capable machine, the ability to grind a drill to new specs, a torque sensor on the drill, maybe an auditory alarm to catch that first "Squeek".
This is all pricey stuff and takes a long time to tune so the process is stable.
For one hole, once in your life, you can never hope to do it this way.
So there is much to be said for abandoning the CNC for this job and running it the old fashioned way, with alert senses and a clenched sphincter on a manual machine that's in good enough shape you can feel what you're doing.
Demand your bonus when you pull it off!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
All excellent advice here.
A thing you may wish to consider though:
As some have alluded to, the failure usually happens very quickly from the first premonitory "Squeek" of the drill to total catastrophic failure.
Since that is so, there is something to be said for doing this on a manual machine where you have tactile feedback as well as aural feedback and can interrupt the job as needed to re-group and re-sharpen and whatever.
I had to drill deep holes in Inconel 718 once upon a time on the manual lathe, and I found I had best results using a pilot drill no bigger than the web of the final drill (as garychipmaker recommends in post #20) and piloting in an inch, then opening out the hole in one shot to final size, piloting in another inch, and opening out etc etc until I got to the bottom of my hole.
Breaking up the hole this way meant I could always get lube down the hole and I never had flute packing to deal with.
I drilled undersized for the first increment and bored right to size, so my final drill would just slip in the hole and the stock acted as a drill bushing.
I could sharpen the drill as often as I needed to, and those who commented on the importance of watching the corners of the drill and the lands are spot on.
I got in the habit of re-pointing both drills after every inch whether they needed it or not, and the whole job went uneventfully (5/16" final diameter, 10" deep, 8 pieces).
As I recall my peck increments for both drills were something like 0.050"
My drills (after 80 sharpenings) were a lot shorter after the job than they were before the job!
So it IS possible, but the ability to feel what the drills were doing was important to my success.
If I was doing this in production however, I wouldn't even try it without all of the goodies...carbide TTC gundrills, HPC for the machine of at least 1000 PSI, a gundrilling capable machine, the ability to grind a drill to new specs, a torque sensor on the drill, maybe an auditory alarm to catch that first "Squeek".
This is all pricey stuff and takes a long time to tune so the process is stable.
For one hole, once in your life, you can never hope to do it this way.
So there is much to be said for abandoning the CNC for this job and running it the old fashioned way, with alert senses and a clenched sphincter on a manual machine that's in good enough shape you can feel what you're doing.
Demand your bonus when you pull it off!
Cheers
Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
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