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-   -   Just broke 3 cobalt drill bits (http://forums.procooling.com/vbb/showthread.php?t=4451)

Puzzdre 09-20-2002 09:12 AM

Just broke 3 cobalt drill bits
 
Where did I go wrong?

Just broke 3 (three !) 2 mm HSS cobalt bits trying to make the wblock like Xjinn's, just to see how it performs.

I drilled on my drill press, with max speed (2800 rpm), with lots of in and outs with drill bit, lubricating with oil and WD 40. I even put the block into the freezer to make it less gummy, than drilled one or two holes...

Just wasted two good pieces of copper. Anyone have any good ideas how to take the broken bits out of the block?

The broken parts are fully inside the block (hole) so I can't take it out with pliers or similar.

All I can think of is to try to drill the hole on the opposite side of the block and try to hit the right spot to hit the broken bit out...

Any ideas,
and
WHERE I DID GO WRONG?????

Thx for all the help!

Fixittt 09-20-2002 06:10 PM

Prolly went to fast. And also if it was done on a "Cheaper" drill press. And you didnt use a level to make sure that the table and part were PERFECTLY flat then that might be what happened. You drilled in deep, flexing the skinny drill bit and.......... SNAP! Putting the block in the freezer really didnt do anything, as I am pretty sure that the block was above room temp before the first hole was drilled thrue.

jaydee 09-20-2002 08:22 PM

Yeah I would say you are trying to drill it to fast. You will have to pull down on the handle real slow with Copper. It will want to jump right in at first but you have to keep it slow or it will just bind up and break. Like Fixxittt said freezing it will do no good as the friction from the bit turning will heat it up to or above room temp real fast. Not sure how to get the bit out.

SCompRacer 09-21-2002 01:10 AM

Nows the time to have a friend that works in a machine shop that has an EDM machine, do some Electrical-Discharge Machining. Had broken studs/bolts removed from aluminum heads like that.

Puzzdre 09-21-2002 03:21 AM

Thanx, thanx, thanx !!!! :)

It came to me lately that if I broke first bit when drilling the very first hole in the first block, than managed to drill next 10 holes and than the second drill bit broke, not to mention the third, I was going still too fast.

The drill press is one El Cheapo, and I wanted to compensate that with good quality bits... It is bolted heavily to the table, and I tried to level everything (block also) to the maximum that can be done on the this kinda of quality drill, but...

You know that feeling...beginners feeling...Wow, I'm making it...it would be good...yes,yes, look at it, emerging from the piece of metal...mmm, gooood...that copper is not so heavy to work with as they all say...yeah, it's going fine...mhmmm...(snap!).....:eek: .....UHOH?!?!?!????.../bitching/......

so, I'll just have to control adrenaline level and take it easy on the lever...live and learn.

It's great to have the help from the people with lot's of experience...

Thanx again guys !

Puzzdre 09-21-2002 06:07 AM

Hmmm, dunno if anybody here in my city have EDM machine, but it's nice to know one more way out.

Thanx!

morphling1 09-21-2002 01:04 PM

Ok, first buying expensive bits doesn't mean it will do the job on all materials. I think that cobalt coated bits are meant for hard matrials. For copper normal bits or hss bits are good then the geometry of the bit is also important, ask for bits for softer materials : top angle 130-150°, angle of the helix 30-50° ...
Then you need to have right cutting speed and feed rate speed.
For speed you need to go with your top rpm for 2mm bit, then like other said as slow as possible, then lubrication, this is very important, but drop wd40 or lubricating oil, those will do more harm then good, you need to get cutting oil, this is special oil that help cooling and lubricting tool so machining is much easier, this is also a must if you're thinking of threading holes especialy M3 or M4 in copper

FRAGN'STIEN 09-21-2002 01:30 PM

So what RPM do you guys recommend for HSS bits on a drill press? Also would these be good bits to use on copper?

morphling1 09-21-2002 01:36 PM

Depend on material you're drilling and bit diameter

FRAGN'STIEN 09-21-2002 01:39 PM

Copper and the bit sizes would be 1/2" and 3/8".

morphling1 09-21-2002 02:05 PM

~600 rpm for 1/2" and ~750 rpm fpr 3/8"

Puzzdre 09-21-2002 04:35 PM

morph, first of all, thanx!

Can you post a tradename of some lubricating oils that can be found in this parts of the world?

THX!

morphling1 09-21-2002 04:46 PM

NICRO 860 plus swiss made cutting and drilling oil. It came in a spray can. I bought it in bauhaus, you got those stores in Croatia right.
Company is NICRO (SWISS) AG.
Realy great stuff.

Puzzdre 09-21-2002 04:53 PM

ah yes, second...

I know that I can dig it myself on the net or in the books, but I'd like to know for sure from you guys with experience, not sort of 'in general' stuff:

can you please post some sort of table containing drill bits dia / drilling rpm for copper and alu, say from 2 mm to 15 mm bits, with 1 mm steps? It would be a great help. Im sure that Im not the only one in need of this info.

Also, what is with endmills and the rpm? Is it similar to the drill bits or there is considerable difference? I'm sure that milling bits business is more complex than drill bits, considering various types and diameters...

I think that my wife will not be wery happy with my new junkie style of hobby, considering the prices of the mills...I'm seriously getting hooked up on this...:D :D :D

Puzzdre 09-21-2002 04:57 PM

almost forgot, a big thanx in advance!

Puzzdre 09-21-2002 05:21 PM

Yes, thank to God, we have Bauhaus in Cro!!! It's not close to me, some 300 km to the nearest one, but I'm going in that direction at the end of the next week... It's buying time, again!

Thanx!

FRAGN'STIEN 09-21-2002 05:25 PM

Quote:

Originally posted by morphling1
~600 rpm for 1/2" and ~750 rpm fpr 3/8"
Thanks for the info morph.

morphling1 09-21-2002 05:31 PM

Well, I have a technological reference book, covering all classic machining operations, and there are guidelines how to choose optimal operating parameters, but those are for profesional machines with cooling and everything where in large production tool wear in machining time is very important for final product price . But most of the time home machining is cripled by lack of power and cooling, required to do the job, so if manual say 3000 rpm and you got max of 2800 and then considering that at those rpm your torque will basicaly suck, and rpm will dropped even further down... so we must compromise a little,learn how the machine works optimaly and get more experienced with time, but still good to know the theory behind everything, so that you don't use wood bits for drilling in stone :D
So if you can't find any data, or books, I'll go to friend and scan needed pages, so tell me what exactly do you need

Can O' Beans 09-21-2002 11:44 PM

At my previous job (Wall length church chimes) I had to cut Brass, aluminum & copper. We always used Titanium Nitride bits and decent cutting oil. I would also follow the above suggestion of making sure everything is square (to the bit axis), especially with these cheap drill presses.

The thing about copper is that it will "grab" the bit, and draw it into itself. When drilling copper, it's a slightly different technique as you want to barely give it any downward pressure and back it off constantly. I would also let the copper block cool down every few holes (thermal expansion). Take your time, I usually went 1/8" deep then back off, another 1/8" then back off.... as the stuff I was drilling was already too far in the manufacturing process to get a broken bit stuck inside.

Puzzdre 09-22-2002 04:09 AM

@Morph:
Quote:

wood bits for drilling in stone
:D :D :D :D :D
LOL, I can tell the difference between the bits for various materials, I love making stuff, and I'm pretty good with tools, but this metal (thick pieces) drilling and machining is brand new (and very interesting) to me. All I'm trying to achive is to lower the experience=expensive equation to the minimum...for a start...:) :D...so I'm bugging you guys for advices...:p

El Cheapo':
The drill press motor says 350 W - S2 10 min. Dunno what S2 10 min means. It's a belt drive drill press, 5 speeds, ranging from 640 min to 2890 max. Max drill bit dia is 13 mm. I need to know the bit dia / rpm ratio to narrow (not exclude, where's the fun! :p ) the experimenting area for copper and aluminium.

Can you give me the title/author of that tech reference book, so I can try to find it here (I have Bojan Kraut's machining manual, helpful on some things, but not enough) before I continue asking questions ;) ? It would be a good start.

Also, do you know the good place to buy a smaller x-y table, can't find it nowhere near me...
THX!
@Can O' Beans:

Thanx for the advice!
Quote:

Take your time, I usually went 1/8" deep then back off
yes, this seems to be the first thing to do !!! :)

Quote:

as the stuff I was drilling was already too far in the manufacturing process to get a broken bit stuck inside.
I know what you mean, on the second block (with the second drill bit :D ) I managed to drill one full row of holes, than decided not to do what BB2K said (one row is enough), started second row and - snapped the bit. :mad: :cry: :confused:

Thanx guys, your'e wery helpful !

morphling1 09-22-2002 05:42 AM

Yes Kraut's reference book, well that's my bible :D (I need to buy new eddition with updated standards), but this book is mostly about elements.
For technology I have this book:
STROJNOTEHNOLOÅ*KI PRIROÈNIK

publisher: Tehniška založba Slovenije
Editor: Hinko Muren
written by: Mario Jež, Ladislav Kosec, Karl Kuzman,Evgen Marek, Hinko Muren, Viktor Prosenc, Jože Puhar, Daro Žvab, Janez Žvokelj.
Each expert in their own field.

X-Y table... I know one place that sells machines, tools... I need to take a look at their catalogue, I'll let you know later.

Puzzdre 09-22-2002 01:42 PM

1 Attachment(s)
I guess that I'll find Str. prirucnik easily enough here, at least equivalent one. thanx for the info!

My brother dropped by this afternoon with digicam, so I made some pics:

this is El Cheapo

Puzzdre 09-22-2002 01:43 PM

1 Attachment(s)
And this is the PAIN...:mad:

Puzzdre 09-22-2002 01:48 PM

1 Attachment(s)
And this is my copper I still didn't manage to ruin...:D
both bars are 10 mm thick, one 4 cm wide, and one 5 cm wide...
just can't find thicker copper here...:shrug:

Puzzdre 09-22-2002 01:54 PM

1 Attachment(s)
last one: some endmill bits I managed to buy till today, 3mm ones on the top, two HSS-E 5 mm, and small ones I bought for drilling PCB I occasionally make...:)

Just from the picture, can you tell me something more about them?
3 mm ones and small ones are manufactured by Jabro...
Can't read the manuf. name from the 5 mm ones...


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