HELP! Drill bits keep breaking up...

[ryans]

Hello everyone,

This is my first post here.

First let me explain a bit: I am a computer guy but I love working with my hands and fixing everything that needs fixing at home and in friends homes (and some that dont need fixing as well ), and i usually do a pretty good job.

I have moved and now live in Sweden, beautiful place but unfortunately still don't know where to get some stuff done, so have little choice but to do it myself.

Here's my latest problem:
I have a hand drill (meaning that its not attached to anything to give it support) and i need to drill through 3-4mm of a cast iron "plate".

After reading online, i saw that its not wise to use a punch to make a hole through it but instead use a small bit and then when i have a hole through the sheet keep increasing the bit size till i have the desired hole size.

Problem is as i started on the first two smallest bits, they just broke one after another in 5 minutes without me getting even one hole
Checking the settings on the drill i see it was in "hammer mode" (guess i forgot to change that when i last drilled the concrete walls to put up shelves) was that why they broke?
also was not sure if I should use the maximum revs for the drill when trying to make the hole (seems a bit too fast, and was scared too high revs would shatter the bit... true?)
* and lastly *
not sure if i should lean on the bit (put some weight on it) or just push gently when trying to make the hole.

Tips, tricks,suggestions and read-up-weblinks would be most appreciated, otherwise i just see myself burning money on bits that are going to keep breaking

I'll try to post pics in a day or two (if anyone wants them).

Please help... and thanks in advance.

Cheers (and happy holidays)!
Ryan

[pushkins]

Most definitely never punch cast iron...ever never.
Never try to drill any steel while the drill is on hammer mode, I'm surprised you didn't break more bits on hammer.
Any good quality metal drill bit should do he job, put the drill on it's lower speed and apply a small amount of pressure while your drilling, give the drill time to "cut" the cast don't try to force the bit through the cast.
You have to be very careful drilling into cast, take your time and work your way up gradually to the size hole you need.

Sweden huh ?....never been there but want to go one day, what's better....summer or winter ?

[ryans]

Hey!

Thanks for the quick reply,was not expecting anything esp since its the holiday season.

"Never try to drill any steel while the drill is on hammer mode,"

first time touching steel... but learnt my lesson!

"you didn't break more bits on hammer."
Actually, ran out of small bits or am sure would have racked up an impressive number
the other bits were just too big to use.
gotto buy some new ones.

I dont know if this is a good thing, I bought a box of bits when i bought the drill... something like 5 or 6 bits for wood, same for metal and same for concrete, are these "packages" good or better to buy them individually?

" "cut" the cast don't try to force the bit through the cast."
Thanks! Will remember that

" You have to be very careful drilling into cast"
Is there a high chance of splitting the sheet?
any other (hopefully, easier)way to get two holes there to put a hinge?

I did think about welding the hinges in (as the old hinges were welded on,) but I'm not sure a complete novice could/would do a good job on that.

" Sweden huh ?....never been there but want to go one day, what's better....summer or winter ?"
Summer is beautiful... I see you are a pro handyman so let me just say: coming here in winter.. you might get your nuts frozen off

seriously tho, the above is just imho because I am more of a warm weather person.. if you are into snowboarding or such and like -10 to -20 weather (without windchill) then maybe winter would be better.

Cheers!
Ryans

[HayZee518]

cast iron is not the best "drillable" material but it can be dealt with. most twist drills have a web angle of 60 degrees with a negative rake. take a grinding wheel and slightly remove the cutting edge on both flutes. then drill on low speed and use kerosene as a lubricant. don't worry it won't start burning it'll just smoke. cast iron is porous with air spaces in it. it is a dense material that's why it's so difficult to cut up with a torch. it draws heat away from the line of travel. when you tap threads into cast iron either cut it dry - very slowly or use some kerosene for a lube.

[mrcaptainbob]

Would the titanium bits work better for this? Also, You need not start off with really small bits, as they most likely will snap when using a hand drill. I pop them quite easily if 3mm or less.

[HayZee518]

just about any high speed steel bit will work. cut slowly. 300 rpm or slower and use pressure with that semi dulled cutting lip. the chips will come out as flakes, not a spiral.

[ryans]

Hey guys,
Thanks for replying.

I dont have a grinding wheel so i dont think i will be trying to remove the cutting edge... i think thats a bit advanced for me anyway so would most likely screw it up.

Thanks for the kerosene tip, will remember that.

"I pop them quite easily if 3mm or less."
Good to know! First time i was trying to drill into metal and was wondering if i was the screwup/weak link in the chain and was wondering what i was doing wrong.

"the chips will come out as flakes, not a spiral."
Its not coming out as flakes... which kind of makes me question my pal telling me its cast iron or not (i honestly had/have no idea).
I'll post a couple of pics soon so you guys can give me your opinion.

When drilling i was getting a fine "mist" of "iron dust" (best way i can describe it)... i did find a nice way to catch the dust... two powerful magnets next to the hole i was drilling ) no mess and easy to clean up plus keeps the drilling hole very clean and easy to see what i'm doing.

Going out to buy some bits..

Thanks again!
R

[HayZee518]

a machinist once told me how to drill a hole. now, this shouldn't be a problem - you just doit! well doing it efficiently is a science. Brass, copper metals will draw your bit rather quickly through the stock. [because it is very soft] Regular steel requires constant pressure with a lubricant to release the metal - metal contact at the cutting edge. Cast iron is a dense material that chips out because of the way it is cast. the size of the bits determine the drilling speed. from very small very high rpm to about 1/4 inch - 400 rpm or so. when you apply pressure the drill bit bites the metal and tends to draw itself into the work. the cut material goes up and around the flutes. release the pressure now and then and continue to drill. when the bit starts to penetrate the material goes easy, the drill will start to speed up. increase sizes gradually until you reach the bit size you want.

[ryans]

Hey! Thanks everyone for replying. Got new bits, the titanium kind.. and was not getting anywhere much (they didnt break though) then discovered something that still makes me feel realllll foolish and should give you more experienced people out there a laugh.. When the drill was not in use, and was kept in its box... someone accidentally flicked the switch to reverse instead of forward... which is why the damn bits were not biting into the metal!!! I was too inexperienced to immd get what was wrong, hopefully will know next time. I flipped the switch and it was like a hot knife through butter, got perfect holes in exactly the place I wanted with exactly the sizes i wanted and no more broken bits (kind of a pity coz I bought extra bits this time!). Did such a good job, am willing to oursource my skills to people in this forum i work cheaper than india... only thing is you gotto send the parts to be drilled to Sweden (J/K) Thanks again to everyone who replied and esp for the tips and tricks. Have a very very good year! Cheers! R

[mrcaptainbob]

A different twist on an old problem. Glad it's working right for ya!