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How much runout OK for a 0.006" cobalt micro-drill?

rklopp

Diamond
Joined
Feb 27, 2001
Location
Redwood City, CA USA
I need to drill some 0.006" holes 0.004" deep in 360 brass. I set up in a 1-mm ER-16 collet and checked the runout. I got 0.001" TIR, which seems like way too much (analogous to 0.1" runout on a 5/8" drill). My spindle taper runout is about 0.00005" and the ER collet taper runout is nearly the same, so I know it's not the machine or holder, and is most likely the collet. I have done 0.008" holes previously without breaking anything except chips, so I know I can do it. I forgot how I held the drill in that instance.

How much runout can I get away with?

When I did 0.008" holes, I fed at D/64 feed per revolution at 6300 RPM (max), and it worked a charm. I am worried that the CNC might not be the best for this, because the feed moves in "digital" jumps around 0.0001" (probably 2 µm, since it's a Deckel). It won't feed smoothly at such tiny increments. My fallback is to use my manual Aciera. It has a separate feed motor with a belt variator and VFD, so I can get a nice smooth "analog" feed as slow as I need (limited to 3400 RPM max on that machine).
 
you can tap the ER nut that is lightly tightened into practically zero TIR measured on the tool, it helps it seat more evenly, then tighten it down further, with some luck the runout will be minimal if the collet is good, if it isn't, I'll undo the nut and rotate the collet slightly and repeat the tighten/tap/tighten again till it's good

edit: and by "rotate" I mean the orientation of the collet against the holder, mark with sharpie before undoing the nut, and have to hold it in the different orientation till it starts to seat and grab the holder
 
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Yes, the runout is really nice. I was more surprised at how little runout the ER-16 toolholder taper had. The spindle taper on the horizontal spindle of my other Aciera is also almost undetectable using a tenths indicator. I had the vertical spindle on that one reground, and I get about 0.0003 TIR on it.
 
Honestly, in those sizes we use CB drills, with as little flute length as possible. Harvey makes a .0059 with a .066 loc.

We rarely even check runout and have good luck drilling brass and aluminum.
 
When I did 0.008" holes, I fed at D/64 feed per revolution at 6300 RPM (max), and it worked a charm. I am worried that the CNC might not be the best for this, because the feed moves in "digital" jumps around 0.0001" (probably 2 µm, since it's a Deckel). It won't feed smoothly at such tiny increments. My fallback is to use my manual Aciera. It has a separate feed motor with a belt variator and VFD, so I can get a nice smooth "analog" feed as slow as I need (limited to 3400 RPM max on that machine).

Just because that is the increment it feeds at does not mean it starts and stops each step. The motors receive continuous power adjusted according to where it senses it is and where it needs to be. They may be AC but the concept still applies. The controller is not sending 2um pulses to the motors like it would if it were a stepper motor, and even those have far less prominent steps at speed.
 
I watched the drilling through a cheapie USB microscope when I ran the 0.008" drill, and I could actually see the motion increments. Perhaps this has something to do with the fact that the machine has glass scale positioning feedback and brushed DC servos with tachometers.
 
I need to drill some 0.006" holes 0.004" deep in 360 brass. I set up in a 1-mm ER-16 collet and checked the runout. I got 0.001" TIR, which seems like way too much (analogous to 0.1" runout on a 5/8" drill). My spindle taper runout is about 0.00005" and the ER collet taper runout is nearly the same, so I know it's not the machine or holder, and is most likely the collet. I have done 0.008" holes previously without breaking anything except chips, so I know I can do it. I forgot how I held the drill in that instance.

How much runout can I get away with?

When I did 0.008" holes, I fed at D/64 feed per revolution at 6300 RPM (max), and it worked a charm. I am worried that the CNC might not be the best for this, because the feed moves in "digital" jumps around 0.0001" (probably 2 µm, since it's a Deckel). It won't feed smoothly at such tiny increments. My fallback is to use my manual Aciera. It has a separate feed motor with a belt variator and VFD, so I can get a nice smooth "analog" feed as slow as I need (limited to 3400 RPM max on that machine).

ER are often spec'ed - at least in ADVERTS .. to "average" six tenths for the common ones, TWO tenths for the "precision" ones. This over a nominal 1mm "collapse" range.

Half-mm range ones should at least have a better CHANCE at holding or beating that "average" if only because it is measured over only half the collapse range. Not that I need it, but I have TG-100, inherently half-mm for that.

Which grade of ER are you working with? How far off optimal collapse is the shank?

And "of course" one "clocks" it to take advantage of countervailing errors canceling each other out... same as any other stacked tooling, big bang, onward.

Magazine fed, auto toolchanger CNC? Even the best of off-machine preseting loses that manual "clocking" last-tiny-fiddle advantage, if only because it is not yet in the actual spindle that will run it.

So the tooling has to be as good as can be had and everything squeeky CLEAN and undamaged as well.

That said, it is done "somewhere" every day of the week, so not TOO hard.

Rego-Fix's best grade of premium-spec goods instead of my merely adequate "Asian No-Name" ER collets, I'd surely expect an improvement!

Rego-Fix are in the bizness of BEATING "averages"!

They get to charge more MONEY that way.

2 ER worth. 20 and 40
 
"
And "of course" one "clocks" it to take advantage of countervailing errors canceling each other out... same as any other stacked tooling, big bang, onward."

Bill you do not do any work, you entire post is meaningless, read some of the others and try to learn something of value.
Stop the drunk hick in the barn talk!
 
I watched the drilling through a cheapie USB microscope when I ran the 0.008" drill, and I could actually see the motion increments. Perhaps this has something to do with the fact that the machine has glass scale positioning feedback and brushed DC servos with tachometers.

I'm curious how well tuned the servos are.
 
How much runout OK for a 0.006" cobalt micro-drill?

The servos are tuned per the manual, which is probably aimed at ordinary milling. The job isn’t worth the science experiment that would be needed to figure out the optimum tuning for super-low feed rates.


I changed to a much better collet and now I have about .0002 TIR. I’ll take it.


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I changed to a much better collet and now I have about .0002 TIR. I’ll take it.

Even the medium-priced Taiwanese offer that, so yes, by all means. Good value for money, and not much justifies chasing further.

The collets for the Precise jig grinder are a whole 'nuther animal.
Priced accordingly.

For the size you are working?

Those - or current version - and on a spindle of the sort current-owner, Fischer Spindle, supply to uber-precise machine-tool makers - are probably a better choice than anything "ER".

Page Two:

Already by the 1980's were were dealing in rather good clarity and colour commercial "fine white" diamonds that had been improved by burning-out unconverted Carbon inclusions, often six or so in one single diamond.

A laser drilled that Diamond in a diameter so tiny it left only a fine thread of a boreline visible under 10X loupe. AND NOT visible to unaided vision.

Once it reached the inclusion, it heated it, burned it, left a clean cavity. The diamond - even with documentation it had been enhanced by drilling - fetched a price higher by enough to justify the cost.

That was a long time ago, now. '74 to '84, that "Day Job" as Manager of Jewelry Manufacturing.

the tools of Production have gotten steadily better and cheaper.

Might there be a CNC laser "drill" in YOUR future?
 
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"Even the medium-priced Taiwanese offer that, so yes, by all means. Good value for money, and not much justifies chasing further.

The collets for the Precise jig grinder are a whole 'nuther animal."
Priced accordingly"

Thats pretty good Rooster Fish Bill, but there is the rumor you have died, "Goldstein" made a bottle of urine art out of you!
We must have a proof of life photo!!
 
Ha, it would surely cause some gastric disturbance to see a photo from the troll.
But we must weather the storm!

Bill, people like photos of machines, and some interesting content to go along.
Why are you compelled to interfere with others work and efforts with your worthless and long posts?

"Nowhere NEAR as weak as your TDS-rotted mind!" Bill, anyone that goes against you is really going to get it! As you have clearly shown in my direction.

I do like the little face icons showing your rage, you like to use!

I stated in the other dreadful thread, I was here 8yrs before you, doing projects and showing photos!
And you bring it to a dead stop. Mr Rooster Fish Bill thermite!
 
I was here 8yrs before you, doing projects and showing photos!
And you bring it to a dead stop. Mr Rooster Fish Bill thermite!

Oh? "been HERE' have you? Best you could find, was that?

Or just the LAST forum you have not already been RUN OFF OF for your insane vicious behaviour?

Lesse.. 1953 was it? You probably didn't yet have adult TEETH when I entered the workforce!

What? A month or so short of 12 years old when I LAST worked for an hourly rate at the tool-tip and moved up to managing the resources. US, Europe. Asia?

You brought yourself to a stop, fool!

Back when you went barking, obscene, profane full-throttle mad as a hating-hatter two or three of your sad "cycles" ago, hating-on and "threatening dire consequnces" to ... several members, forum moderators, and even .. the FOUNDER of PM, personally and directly in a PM THREAD!

YEARS worth of your fingerpainting with your own feces still sit in the record "right here, on PM".

And PM is a website important enough to be mirrored. Even PM could not make your sad shite-slime-trail vanish no matter how hard they tried.

Assuming they even wanted to do....rather than preserve the clear evidence of your insanity as is now the case .... for anyone who cares to look.

https://www.practicalmachinist.com/vb/search.php?searchid=24529241

I can only WISH your s**t actually WAS "brought to a stop"... rather than simply going stoopider and siller with each passing pathetic-pity-me-party wound collection cycle!

Teats.. on a Boar hog... actually have a FUNCTION, however minor.

Wound-collector drama-queens?

No more welcome nor useful than pubic hair on a rosebud Oxy-Acetylene torch!
 
Bill, you started the fight with me because I called out you lying about cutting screw threads on a lathe, and I point out you have done nothing in your time here but be the troll you really are.
No photos, because you are a troll with the intent disrupts others threads.
It is the no photos that hang you out to dry, like the slug you have become.

" hating-on and "threatening dire consequnces" to members, moderators, and even the FOUNDER of PM."
Bill, DT and I have gotten along over many years.

You have been threatening me with a violent beating, I somehow get from the locals here in Walla Walla, broken bones, pins and screws. You have brought that up three times now.
Bill, no one here is going to war with me, its only you looking for trouble, come to me, pimple of a man....
 








 
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