Drill ing life problems 4145 Q&T 330-341 Brinell

alphonso · Jun 21, 2017

Tougher stuff than chemistry/heat treat suggest.

.515"(or .531) clearance holes, 2 7/8" thru.

We have tried a number of different combinations and multiple variations and can't seem to find a decent balance between tool life and cycle time.

Current set up is Precision Twist Drill, cobalt bronze oxide finish drills. 40sfm, .008 feed, .5 peck depth, flood coolant( TSC is out of action at the moment). Stub drill as deep as it can go then jobber to finish. 8 holes per part, 84 parts(672 holes), cycle time is 18 minutes. Get about 6 parts before drills get dull. Seems to be about the best life/time balance so far.

Tried a Chicago-Latrobe AlTiN cobalt drill with same parameters and the cutting edge started chipping after 12 holes.

Tried some carbide awhile back and it did cut a lot of time out but it didn't cut any more holes before it dulled.

Years ago, when the TSC was working, we tried a spade drill which worked until it had a catastrophic failure. Don't want to repeat that.

Should be able to get TSC back in service soon. Rotary union was leaking and ate up $1200.00 worth of bearings in less than a week. New union is slightly different design and I'm not sure exactly how it is supposed to work. Need to call manufacturer and find out.

Suggestions, recommendations, WAGs?

Milland · Jun 21, 2017

Is this an abrasive wear failure most of the time? Maybe looking for a drill that works well in AR400 or similar would give decent life. And having to do the swap from stub to jobber doesn't sound good, it would be easy for chips to remain in the hole during both peck and changeover. Getting the TSC working again, and staying with the jobber may work best.

Talk to a Nachi engineer and see what they have to say. They have a range of powder metal Co drills that might meet your needs.

D Nelson · Jun 21, 2017

Drilling that many holes u have to use carbide probably in a shrink fit holder u can't have run out no pecking no centerfrill unless it has the same tip angle as the drill. Look on u tube for mega drill and watch how drilling is done

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gregormarwick · Jun 22, 2017

Once you get your TSC coolant back in operation (not before), look into carbide replaceable head drills. They are by far the most effective way to drill smaller holes in this kind of material.

Sandvik Corodrill 870, Iscar Sumocham, Tungaloy Drillmeister are all ones that I have had very good results with and would happily recommend. PHorn made a very good one that they unfortunately discontinued.

I have had poor experiences with Allied Gen3sys and Seco Crownloc and wouldn't recommend those.

Limy Sami · Jun 22, 2017

Suggestion only

Worm pattern will give better swarf ejection in dep holes
YG do a range of worm pattern that IMR work well in EN24T which is near enough what you have, .......without pecking.

Tool here DL58 - HSS Twist Drill | Hole Making Tools | Cutwel Ltd

Cutting Data here http://www.cutwel.co.uk/FileDepository//ProductId - 3377/Cutting Data DL508.pdf

Not too $$$ to find out

Oh and YG in the US http://www.yg1usa.com/

Mtndew · Jun 22, 2017

alphonso said:
40sfm, .008 feed, .5 peck depth, flood coolant( TSC is out of action at the moment).

That's about right for a HSS/Cobalt drill. Maybe bump it to 50sfpm, but any faster than that and you'll just wear out the drill faster.
You could peck with a carbide drill. I know it's not recommended (and I've done it many many times),but if you have a ton of holes to do, the tradeoff in cycle time will pay for itself in no time.
A non coolant thru drill isn't that expensive.

alphonso · Jun 22, 2017

Milland said:
Is this an abrasive wear failure most of the time? Maybe looking for a drill that works well in AR400 or similar would give decent life. And having to do the swap from stub to jobber doesn't sound good, it would be easy for chips to remain in the hole during both peck and changeover. Getting the TSC working again, and staying with the jobber may work best.

Talk to a Nachi engineer and see what they have to say. They have a range of powder metal Co drills that might meet your needs.

PTD bronze oxide: Abrasive edge wear, no chipping of edge.

We started using the stub and jobber option when the jobber wore out (and broke from chip jamming) after about 16 holes.

Looked up Tungaloy info. Surprised to see that for 8XD drills they recommend drilling a 1.5XD hole first.

Milland · Jun 22, 2017

alphonso said:
PTD bronze oxide: Abrasive edge wear, no chipping of edge.

We started using the stub and jobber option when the jobber wore out (and broke from chip jamming) after about 16 holes.

With plain drills or TSC?

Looked up Tungaloy info. Surprised to see that for 8XD drills they recommend drilling a 1.5XD hole first.

Hmm - solid carbide? Have you looked into carbide tipped insert drills as someone else mentioned?

Matt_Maguire · Jun 22, 2017

alphonso said:
Tougher stuff than chemistry/heat treat suggest.

.515"(or .531) clearance holes, 2 7/8" thru.

Get about 6 parts before drills get dull. Seems to be about the best life/time balance so far.

Suggestions, recommendations, WAGs?

WAG, 36-37 rockwell is where you start to test machine stiffness, HP and work your tools hard IMO.

Your settings are pretty standard for HSS with the feed being possibly a little heavy. Perhaps just add more jobber drills in the tool changer, swap at 40 holes & let it go??? Old data suggest M33 or T15 HSS is advised at this hardness.

I struggle when I have a bunch of screwdrivers but I need a hex key. I’m thinking if you get lots of these type parts a multi spindle drill would look good in the corner waiting to punch 8 drills through & just hand burr them (2 parts & 16 drills if you can find a 15HP one). Numbers suggest at .005” feedrate 1 part needs 7HP & 4 minutes to drill and drill life might improve 20-25%. HOLY COW! I Just looked at used Natco’s wish I had a few??? Maybe somebody could make a multi spindle attachment for the VMC???

Also... might ask why they think eight 1/2” stud/capscrews are gonna hold whatever load that 2 7/8” cross section at 170Kpsi tensile part could see in use...

Good luck
Matt

Ox · Jun 22, 2017

I have spades this size, but I would rather use a "tipped insert" drill and TSC for this app if I had the right size at hand.

Kenna - KSEM
Iscar - Sumo (?)
Allied Gen3

Otherwise - I'm sure the spade should be fine.
Just make sure that you don't overstroke with the spade.
It is possible for the back of the insert to catch the back of the hole on the way out if you feed too far.

----------------------

Think Snow Eh!
Ox

alphonso · Jun 22, 2017

Milland: Plain drills, flood coolant.

Matt: Cobalt drills. Certs say 331 Brinell at surface, 341 Brinell 1 inch down?? Does act like it is closer to 40 42Rc. Half inch SHCS. Holding a rolling die on a shouldered shaft. Previous incantations of this device have worked with this arraignment. Makes changing dies a lot easier and quicker than prying the die off a keyed shaft.

Checked with manufacturer of rotary union and am satisfied that it is correct and will work. Probably will install it in the morning.

Ordered Iscar Sumocham body and drill heads. Should be here tomorrow afternoon. Drill body: $310.65 Heads: $72.64 each. Iscar recommends 130-180sfm, .006-.013 feed. Cross your fingers.

Ox · Jun 22, 2017

alphonso said:
Ordered Iscar Sumocham body and drill heads. Should be here tomorrow afternoon. Drill body: $310.65 Heads: $72.64 each. Iscar recommends 130-180sfm, .006-.013 feed. Cross your fingers.

Don't feed over the rec on that!
Boy - I found that out the hard way!

I crept it up to just over spec, and instantly chipped a fairly new insert (in 316SS I think)
Ran razor wire the rest of the job as it wouldn't break a chip anymore. :willy_nilly:

----------------------

Think Snow Eh!
Ox

NAST555 · Jun 23, 2017

Ox said:
Don't feed over the rec on that!
Boy - I found that out the hard way!

I crept it up to just over spec, and instantly chipped a fairly new insert (in 316SS I think)
Ran razor wire the rest of the job as it wouldn't break a chip anymore.

----------------------

Think Snow Eh!
Ox

Or have an operator put a rectangular (YES RECTANGULAR :mad5:

) part in the vise wrong way up.... The drill sure was pretty impressive till I landed up with half of the body in the chip conveyor.

Mtndew · Jun 23, 2017

alphonso said:
Iscar recommends 130-180sfm, .006-.013 feed. Cross your fingers.

That sounds about right. Although 130 may be a bit TOO conservative.

gregormarwick · Jun 23, 2017

Mtndew said:
That sounds about right. Although 130 may be a bit TOO conservative.

Yes, that seems slow to me also.

Most important thing with these drills is to keep the cutting data above the functional minimum. Too little feed in particular is a disaster as they start to make longer chips which are more difficult to blast out of the hole. This is the quickest way to lose a drill body. When they are drilling properly they make small, heavy chips.

alphonso · Jun 23, 2017

gregormarwick said:
Yes, that seems slow to me also.

Most important thing with these drills is to keep the cutting data above the functional minimum. Too little feed in particular is a disaster as they start to make longer chips which are more difficult to blast out of the hole. This is the quickest way to lose a drill body. When they are drilling properly they make small, heavy chips.

Peck or straight thru like I do with my Kennametal inserted drills?

gregormarwick · Jun 23, 2017

alphonso said:
Peck or straight thru like I do with my Kennametal inserted drills?

Straight through. As long as your TSC can keep up.

alphonso · Jun 23, 2017

gregormarwick said:
Straight through. As long as your TSC can keep up.

That's what I thought. Pretty sure the TSC can keep up. It will shoot coolant 10 feet straight up over the machine with a 3 inch drill just before drilling starts. Must have deflectors mounted and wear raincoats.

gregormarwick · Jun 23, 2017

alphonso said:
That's what I thought. Pretty sure the TSC can keep up. It will shoot coolant 10 feet straight up over the machine with a 3 inch drill just before drilling starts. Must have deflectors mounted and wear raincoats.

Sounds about right

FYI, just went and picked these out of the machine. 14mm Tungaloy Drillmeister, 34CrNiMo6 (4340) @ 300Bn, 1600RPM, 320mm/m feed. CNMG 120408 (432 I think?) for scale.

mikespahn · Jun 25, 2017

I actually did a job very recently with a similar size hole (except blind 3.640" deep) in similar material. I got about 100 holes per drill, but with slower cutting parameters. Cobalt drills, split point 135 degree, 30 sfm, .005" feed, flood coolant. I spot drilled. Fed w/ reduced speed and feed (about 80%) until the drill got fully engaged. First peck .5", after that, pecked .050" without full retraction to break chip, fully retracting after .5, dwelling for .5 second to cool slightly and clear chip. Up to 2.5", then same peck but retracting every .250" and dwelling 1 second. Might want to slow down before breakthrough, not sure if it grabs, i didn't have to worry about that.

Can't say it was right or wrong, or that it didn't take a good bit of time. just telling you what was the most successful for me, in a similar situation and not breaking a drill in a part was a concern.

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