[beanbag]

When I drill on a manual mill, I am able to pull a continuous chip. On the Tormach, I often get these small broken chips. Sometimes these chips cause clogging or rubbing, so the hole turns out bellmouthed or oversize. Specifically, I am talking about using a .100 drill, running 5k rpm (or a bit less) in aluminum and feeding at 10 ipm or a bit more or a bit less. That should give about the right chip load for drilling. Is the problem that the Z step rate isn't smooth enough relative to the time it takes for the drill to make one rotation?

When I use a larger drill like 3/8 I am able to pull a continuous chip just fine.

I use flood coolant in this case.

[Steve Seebold]

How deep are you trying to drill? Are you going straight through or are you peck drilling? G81 or G83?

I'll bet that on your conventional mill you are feeding faster than 10 IPM. And I'll bet your conventional mill is not going 5,000 RPM.

[Don Clement]

I got excellent results when switching from a standard drill to a parabolic drill with a 0.125" hole when drilling through 1/2" 6061-T6 aluminium plate. Also Relton A9 work extremely well for drilling in aluminum. [ame=http://www.amazon.com/Relton-PNT-A9-Aluminum-Cutting-Fluid/dp/B0000DD2EY]Amazon.com: Relton PNT-A9 16 Oz A-9 Aluminum Cutting Fluid: Home Improvement[/ame]

Don

[Steve Seebold]

I got excellent results when switching from a standard drill to a parabolic drill with a 0.125" hole when drilling through 1/2" 6061-T6 aluminium plate. Also Relton A9 work extremely well for drilling in aluminum. Amazon.com: Relton PNT-A9 16 Oz A-9 Aluminum Cutting Fluid: Home Improvement

Don

A-9 and parabolic flute drills is an excellent combination. Under the right conditions you can actually make them cut undersize.

[Don Clement]

from the Domer product description:
"The Dormer A976 PFX series allows for single pass drilling, which eliminates the need for pecking in up to 10 times the drill diameter deep holes, thus offers improved efficiency, and increased productivity. The parabolic design, combined with a parallel thinned web, allows for smooth and efficient chip (also called swarf) evacuation. "

This has exactly been my experience with parabolic flute drills in drilling deep holes in 6061-T6 without pecking.

Don

[beanbag]

ok, I get it that parabolic drills and A9 are awesome, but I am still trying to figure out why I am having trouble here with a "regular" drill.

In this particular case, the holes were 1/2" deep, and I usually use g83, and sometimes g73 if I am feeling lucky. On the manual mill, I have used from about 1k to 4k rpm. I can't be sure, but I think I can pull a continuous chip manually even at feed rates much less than .001 ipr. Yes, I am using the same drill in both cases.
Sometimes on the first peck of the drill on the Tormach I can get a continuous chip, but not afterwards.

[Don Clement]

ok, I get it that parabolic drills and A9 are awesome, but I am still trying to figure out why I am having trouble here with a "regular" drill.

You can lead a horse to water, but you can't make it drink. Yeah I had trouble using a "regular" drill on aluminum with my Tormach @5.1K rpm also.

Don

Insanity: doing the same thing over and over again and expecting different results. ~Albert Einstein


"[while Peter Cronk is staying with Dr Martin Ellingham, he persuades Martin to let him rent "an educational video". Later, Louisa is horrified to see that he is watching an X-rated horror film]
Louisa Glasson: What are you watching? Turn it off!
Peter Cronk: Oh, but they were just about to eat the virgin's eyeballs.
Louisa Glasson: Off! Martin?
Dr. Martin Ellingham: He told me it was educational.
Louisa Glasson: Yes, and he just said the words "virgin's eyeballs".
Dr. Martin Ellingham: Is that bad?"

[gjvander]

I think it is reasonable to ask why a standard drill works on the manual mill, but not on CNC.

Maybe 5000 RPM is too fast. A quick test at different RPMs to see if it changes results?

Regards,

Geo

[bostosh]

Calculate the feed per tooth to get the answer
5000rpm is too fast for 10 IPM

[beanbag]

10 ipm at 5k is .001 feed per tooth, which is about right for a .1" drill, or maybe a bit on the low side. I have also drilled 4k and 13ipm and still got broken chips.

I am starting to think that with drilling aluminum, the higher the sfm, the more curled the chip is. When I drill on the lathe below 1k rpm, I get straight chips that shoot out the flutes. On the manual mill, I either get these long strings, or moderate length broken curls. On the CNC, when I dropped the rpm down to 2k, I at least got chips that looked like they made 1 or 2 curls before breaking.

I tried to get a parabolic drill, but on closer inspection, it doesn't look like one. I think the guy just gave me a regular drill but high helix. It made very small and crumbly chips, but at least the hole came out ok.

[Steve Seebold]

I ran a job yesterday that I drilled 12 .0995 holes, 4500 RPM 15 IPM and it made a very nice short broken chip with just a regular HSS drill.

[Don Clement]

I ran a job yesterday that I drilled 12 .0995 holes, 4500 RPM 15 IPM and it made a very nice short broken chip with just a regular HSS drill.

How deep were the holes? Blind or through holes?

[Steve Seebold]

How deep were the holes? Blind or through holes?

The holes were through 6061 aluminum ,375 thick. I used 4500 RPM G83G98X?Y?Z-.45R.1Q.075F15. I probably could have used deeper pecks, or a higher feed rate, but that worked for me.

[beanbag]

So how did the holes turn out? Does the shank of the drill fit back in? Is it bellmouthed at all?

[Steve Seebold]

So how did the holes turn out? Does the shank of the drill fit back in? Is it bellmouthed at all?

Holes came out great. No bellmouth, nice straight holes.

I also did some parts last week that had a .125 hole, 4.5 inches deep. That was a trick because I drilled in to a pitce of 7075 aluminum that is .188 thick, so there is no room for the drill to walk sideways. It took 7.5 minutes to drill that part. Almost 6 minutes just to drill the deep hole. And I had to do 130 of them.

[beanbag]

I got excellent results when switching from a standard drill to a parabolic drill with a 0.125" hole when drilling through 1/2" 6061-T6 aluminium plate.

What does "excellent result" mean? And what is a "non-excellent" result from a regular drill?

[tbaker2500]

When I drill on a manual mill, I am able to pull a continuous chip. On the Tormach, I often get these small broken chips. Sometimes these chips cause clogging or rubbing, so the hole turns out bellmouthed or oversize. Specifically, I am talking about using a .100 drill, running 5k rpm (or a bit less) in aluminum and feeding at 10 ipm or a bit more or a bit less. That should give about the right chip load for drilling. Is the problem that the Z step rate isn't smooth enough relative to the time it takes for the drill to make one rotation?

When I use a larger drill like 3/8 I am able to pull a continuous chip just fine.

I use flood coolant in this case.

I pull a continuous chip in 6061 T6 with a standard jobbers bit, #9 drill 2400rpm 7IPM, if I recall the speeds right. But I still need to peck if the hole is deep, it can still clog the flutes.

[TXFred]

And what is a "non-excellent" result from a regular drill?

[beanbag]

An update on my parabolic drilling experiences. Yesterday I used a 5/16 parabolic drill (Guhring 549 series) to make a deep hole on the manual mill. I was very impressed that I could do one continuous plunge, without pecks, all the way until there was only about 1/2" worth of flute left. The drill just shoots small chips out the top of the flutes. (which in retrospect matched my experience in post #10) So in fact small broken chips is what you want with this kind of drill after all, which if I think about it makes sense. A "normal" drill tends to make long stringy chips, which is partially why they clog easier and need peck cycles.

I am still a bit apprehensive about doing a g81 on the Tormach, though. Sometimes, the flutes still clog up a little bit, and you can feel that on the manual mill with a little more drag and vibration.

Anyway, thanks to Don and Steve for mentioning this type of drill.

[esmondperry]

For the small hole drilling and you have to use the low rpm like 2k per rpm or lower...
So, your problem solved for it...