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Hot Bob
03-17-2010, 05:52 PM
This is driving me nuts! I'm trying to arrive at a 1.001 through hole in 1.750 360 brass hex. I drilled a .250 pilot hole and then jumped to a 31/32" drill. I was planning to finish with a 1.001 chucking reamer. This whole process worked great in aluminum. Not going so well in the brass. The drill keeps catching and turning the chuck off the arbor. Everything is firmly clamped in the mill vise. I tried running it with the power downfeed at .005 and that didn't work either. The backlash in the feed allowed it to grab. Also tried stepping up with smaller drills but I get the same result. This is a part that I would like to be making in quantity. I read in another thread about knocking off the rake of the drill for drilling in copper. Is that what I need to do? Is there a drill that is better suited to this operation?

Bob

oldtiffie
03-17-2010, 05:58 PM
Knock the positive rake off the cutting edges of the drill. Reduce it to zero.

Only needs to be/have a 1/16" wide "flat" - same as on a centre drill.

Should be OK then.

Kibby
03-17-2010, 05:59 PM
Knock the positive rake off the cutting edges of the drill. Reduce it to zero.

Only needs to be/have a 1/16" wide "flat" - same as on a centre drill.

Should be OK then.

Beat me to it! :p

gwilson
03-17-2010, 06:04 PM
Also use that same technique when drilling brittle acrylic plastic. It breaks when you come out the other side. I taught that trick to some guys who were ruining a lot of acrylic making transparent speaker cabinets.

krutch
03-17-2010, 06:09 PM
The flatting of the cutting edges help to stop the drill from 'screwing into' the material. That is why the chuck pops of the arbor.
Krutch

Scishopguy
03-17-2010, 06:17 PM
Same holds true for sheet PVC. O* rake, and slow but steady downfeed by hand.

Hot Bob
03-17-2010, 07:24 PM
Wow! Thanks guys. Night and day! I just took about .050 off the cutting rake and it worked beautifully. I've said it before; I'm no machinist. I'm sure this is something you would learn early on in school. I have read Machine Shop Practice I & II and I never saw this in there.

Bob

airsmith282
03-17-2010, 07:56 PM
??? what speed/rpm are you running it at.. i have never moded a drill bit for drilling brass ever, i center drill it then i take the drill size i need and run my lathe or even the drill press when doing it on it at the fastest the machine will run. And it just goes in nice, I also use a very slow feed , and my drill bits are sharp as i can get them, works great for me,
on the lathe oyu can take up some of back lash by just lightly snugging the quill lock or what ever you want to call the screw on the top of the tail stock, that also can help..

Oldbrock
03-17-2010, 08:34 PM
Sorry Airsmith but that is dead dangerous. 0 rake for brass. You just need to hone a 5 thou flat in line with the centerline of the drill to stop it grabbing. Special drills for brass are straight flute. Peter

airsmith282
03-17-2010, 10:49 PM
Sorry Airsmith but that is dead dangerous. 0 rake for brass. You just need to hone a 5 thou flat in line with the centerline of the drill to stop it grabbing. Special drills for brass are straight flute. Peter

'
ok come to my shop and ill show you how to drill brass.. i been doing it this way sence the lower speeds where a problem and sence i been doing it the way i had mention i never had an issue..

but this is just me and i have done alot of drilling in brass ..

so if itss wronge then i guess iam one lucky SOB then , that or i know what iam doing, iam voting for my second option...

the only part of working on the lathe that makes me scared is parting off large dimeters of steel. now thats scary crap with a flexable parting tool, hence its time for me to up grade to a pro level parting tool and part with the old flappy blade style i have now...

Paul Alciatore
03-18-2010, 01:59 AM
I bought a set of fractional drills, 1/16 to 1/2 and resharpened them for brass. Only took about 1/2 hour with the Dremel. Now they are always ready for any brass drilling.

Circlip
03-18-2010, 03:00 AM
so if itss wronge then i guess iam one lucky SOB then , that or i know what iam doing, iam voting for my second option...

Well I (and ALL my mentors) would go for the first option, strange how all the others who have replied have ALSO got it wrong in your opinion.

Wonder how a claim would sit in the event of an industrial accident ??

We need to try to PROTECT newbies from the Bull***t :rolleyes:

Regards Ian.

John Stevenson
03-18-2010, 04:10 AM
Try drilling a 1/2" cross hole into another one using a hand vise and a drill press.

That will certainly cure your spelling :rolleyes:

Astronowanabe
03-18-2010, 05:08 AM
I have also have never had more than a slight hiccup drilling brass, but was warned and am careful. My very limited understanding of the issue is copper is soft but work hardens, brass is mostly copper and there are all sorts of alloys with different properties, but if a drill gets away and starts to screw itself into the soft mostly copper alloy the area where the drill is feeding work hardens ...something fierce, possibly freezing the drill in place.
Corrections to the theory are most welcome.

Your Old Dog
03-18-2010, 07:16 AM
I have seen drills with less or very slow twist rates per inch, almost straight. Are these the ones used on softer metals?

Also, when we mention 0 rake, are we talking about the tip of the drill bit or the sides which also cut. I'm thinking we are talking about the sides of the bit which might not cause it to screw into the material so much.

TGTool
03-18-2010, 07:26 AM
I have seen drills with less or very slow twist rates per inch, almost straight. Are these the ones used on softer metals?

Also, when we mention 0 rake, are we talking about the tip of the drill bit or the sides which also cut. I'm thinking we are talking about the sides of the bit which might not cause it to screw into the material so much.

Just the cutting lips on the tip of the drill - the place where the drill is sharpened. I was taught to use a hand stone a few strokes held in line with the drill and flat against each lip.

Hot Bob
03-18-2010, 08:17 AM
After I posted this question I searched google. I found a good thread on the matter over at Practical Machinist. Includes pictures of how to properly sharpen a twist drill for use on brass.

http://www.practicalmachinist.com/vb/general-archive/drilling-brass-stuck-drill-chuck-76515/

Bob

johnl
03-18-2010, 08:23 AM
I had trouble drilling some brass also. The fixes were the 0 rake on the drill,
use of a straight fluke bit, or drill with an end mill. All worked fine
John L

Carld
03-18-2010, 08:32 AM
I must be doing it wrong too because I almost always have issues using a standard drill to make a hole in brass. It almost always sucks the drill into the brass at some point.

To remedy this I flatten the cutting edge of the drill bit which is by some the wrong way to do it. Since it works I will keep on doing it wrong.:D :rolleyes:

Black_Moons
03-18-2010, 08:39 AM
What kinda hand stones do you tend to use for dressing/sharpining drill (And lathe) bits?

(Name of stone and aprox size/grit of the stone you use would be very helpful)

airsmith282
03-18-2010, 09:45 AM
Well I (and ALL my mentors) would go for the first option, strange how all the others who have replied have ALSO got it wrong in your opinion.

Wonder how a claim would sit in the event of an industrial accident ??

We need to try to PROTECT newbies from the Bull***t :rolleyes:

Regards Ian.

i never said anyone was doing it wornge,so dont go putting works in my mouth there dude.

what i have been doing and works for me is what i do, what i have found that did not work for me i dont do plain and simple, as we all know a drill bit when not going all the way threw leaves a sholder or concave shape so if you sharpen the drill as mention my question is would this still give that concave shape providing its a needed shape , i have 1 drill bit in my collection i got it used and it s been modded flate accross the tip now i was told it was for drilling brass , if this is true then the needed inside concave would then not be there so there goes the project if this is the case.

.

gwilson
03-18-2010, 09:53 AM
Lose the dude,airsmith. You are just plain wrong.

japcas
03-18-2010, 10:06 AM
i never said anyone was doing it wornge,so dont go putting works in my mouth there dude.

what i have been doing and works for me is what i do, what i have found that did not work for me i dont do plain and simple, as we all know a drill bit when not going all the way threw leaves a sholder or concave shape so if you sharpen the drill as mention my question is would this still give that concave shape providing its a needed shape , i have 1 drill bit in my collection i got it used and it s been modded flate accross the tip now i was told it was for drilling brass , if this is true then the needed inside concave would then not be there so there goes the project if this is the case.

.

Airsmith what you have is a flat point drill. You can modify a regular 118 or 135 degree drill to drill brass and still get the point if your project needs that shape at the bottom of the hole.

Toolguy
03-18-2010, 10:07 AM
I sharpen mine like the pictures on the PM site using the side of a bench grinder wheel. It takes about 5 seconds per flute. This grind is also what to use on anything soft like plastic, bronze, lexan and sheet metal. It will still drill steel too.

TGTool
03-18-2010, 10:29 AM
What kinda hand stones do you tend to use for dressing/sharpining drill (And lathe) bits?

(Name of stone and aprox size/grit of the stone you use would be very helpful)

I use 1/4 x 1 x 4, mostly a medium grit. It works for de-burring, honing lathe bits after grinding, stoning dings in tables and generally looking for anomalies on surfaces. The toolmaker I learned from had us keep a stone constantly on hand in the apron pocket. I've actually got a collection of round, square, triangular, conical, etc. which find use frequently.

Before setting anything on a flat surface including mounting a vise or workpiece on the table, stone everything to find raised spots. You'll recognize them by the change in drag on the stone, and then if you look you'll see a bright spot or half-moon where a ding has been raised on the table. Dress it down. Same thing for parallels before use and the vise jaws and bottom. Those are the little things that will throw your part off a thousandth or two and parts won't quite fit when they're supposed to.

MSC and McMaster Carr I'm sure has them and likely other industrial suppliers.

Circlip
03-18-2010, 10:48 AM
Wow,never been called a Dude before, is this some American term of endearment?? Have you spulled it write?? Should it reed Dummy??

Regards Ian.

airsmith282
03-18-2010, 10:54 AM
test done on 360 brass round
the peice on the left was drilled with a brand new never used 8.1 mm drill 1620 rpm max speed of my lathe. the peice on the right was done on a well used 11MM not so sharp drill and as you can see it did not go so well. runing the 8.1 was nice and smooth then 11 mm not so smooth , neither one grabed..
now i tried slowing the 550 rpm and the 8.1 was fine, the 11mm was not so fine at the slower rpm so to me id step drill when going past 8.1 mm that or make sure you got a really sharp edge and you can run 550 at the 11mm unmodified drills..
now the feed must be constant on the smaller but you need to go in and out slowly on the larger diameter this i did notice as well.

thanks for the info on my modded drill i added a pic of it,

i have not had the experience in drilling copper but i did try turnning it once and its not a nice metal at all ..

iam sure and ill admit i still have alot to learn when it comes to machining , and iam sure we can agree i do things at times that make some of you cringe a bit , but for me some of this stuff i do thats scary works for me, ...

at the price i pay for the higher end drills i buy i smiply cant afford to have a set for steel and a set for brass doubles of each..

the 2 drills in the pic together cost me over 100 for both.

i buy my drills like i do my taps and dies for the job needed , i have cheap master craft ones but thoes are for other stuff and they can't drill as nice or propery in compairson to the more costly drills.

you get what you pay for with drills taps dies and so on ,

anyhow here are the pics

http://i26.photobucket.com/albums/c124/airsmith282/leftgood.jpg

http://i26.photobucket.com/albums/c124/airsmith282/Drillsused.jpg

http://i26.photobucket.com/albums/c124/airsmith282/moddeddrill.jpg

chrisfournier
03-18-2010, 11:02 AM
Try drilling a 1/2" cross hole into another one using a hand vise and a drill press.

That will certainly cure your spelling :rolleyes:

Please read the above quote and get back to us with the results.

mochinist
03-18-2010, 11:10 AM
You guys need to stop being so jealous of airsmith282's superior mind. Throw everything you know about machining, taught to you by old dumb machinist and open your minds to our own "Rainman" of machining.

Circlip
03-18-2010, 11:12 AM
the peice on the left was drilled with a brand new never used 8.1 mm drill 1620 rpm max speed of my lathe

But how did you mount the drill vice in the lathe DUDE????

airsmith282
03-18-2010, 11:16 AM
Please read the above quote and get back to us with the results.


ok chris i read your little note and now iam getting back to you , my answer is simply this

back off on my spelling, my spelling is my spelling iam not the only one that can not spell..at least its my only weakness in life other then writting, so praise god for the man that invent computers,, ok i know your next comment is .use the spell checker ,
my answer the more pratice i get at spelling the better i get and i dont have alot of time to waste so ill take things my way ,

now back to the topic at hand,

my experiment is complete as far as drilling into brass goes..

and look not one spelling mistake how about that,, and i never even used the spell checker

chrisfournier
03-18-2010, 11:28 AM
I should have clipped the quote to the relevant portion which has nothing to do with spelling but everything to do with time honoured machining practices.

I can see how you flew past the first line of the quotation and got in a twist about the second line. This was not my intention, I have grown fond of your posts.

I was referring to the cross drilling through a hole in brass portion of the quote.

airsmith282
03-18-2010, 11:32 AM
I should have clipped the quote to the relevant portion which has nothing to do with spelling but everything to do with time honoured machining practices.

I can see how you flew past the first line of the quotation and got in a twist about the second line. This was not my intention, I have grown fond of your posts.

I was referring to the cross drilling through a hole in brass portion of the quote.


ok my bad sorry man ..

Willy
03-18-2010, 11:42 AM
Airsmith, look at how much time you've wasted explaining spelling in your posts.
Yet you don't have the time to click once on spell-check?
It will help show you where you went wrong, it's not a crutch, it's a teaching aid.
I think if you don't use it you'll be havin' to do a whole lotta more splainin'.

Not only that but I think it's a little arrogant on your part to expect the rest of us to conform to your lingo...it's not an easy read. We certainly don't expect this to be an English lit. forum, but just a little effort on your part will go a long way to make it easier on all, especially yourself.

As far as your arrogance and rudeness to people that have been in a production machine shop environment all their lives, and have intimate knowledge of what works and what doesn't... well spell-check can't fix everything.

Circlip
03-18-2010, 12:14 PM
Pity there isn't a READ check, as the O/P seems to be talking of a vertical machining operation.

Regards Ian.

EVguru
03-18-2010, 12:37 PM
BRASS; A yellow metal that's not Gold.

You can get away with all sorts with leaded free machining 'Brass', but some of the 'mystery Brass' I have lying around will give you palpitations (often tin plated and with crowsfoot markings). Much of it screams when machined giving off a violent spray of hot slivers. You'd damn well better have zero rake on your tools or it'll grab any backlash in the machine and probably ruin the job. Even with the cutting edges flatted back drills will sieze in it if you're not careful. My boss tried drilling some with a cobalt bit and the bit grabbed and shattered.

Circlip
03-18-2010, 12:51 PM
Tried a magnet on it Paul??

airsmith282
03-18-2010, 01:44 PM
But how did you mount the drill vice in the lathe DUDE????

are you smoking crack lets see on the lathe mounted the brass in the chuck drill bit in the drill chuck

if you like i can do the same thing and put the brass in the drill press and then mount the brass in a vice to drill a side hole in it. what this is going to accomplish for you i have no idea.

krutch
03-18-2010, 02:13 PM
Airsmith,
Just because you have gotten away with your method so far, doesn't mean you should ignore the advise you have been given here. No one here is trying to blow smoke up you a**! Your method will some day cause you some kind of grief. But you are going to have to find out for yourself, as you are too smart to take advise from any of us. So I guess maybe you should stop visiting this site, 'cause it is not doing you any good. And may cause harm someone new to machinework.
Just my opinion.
Krutch

Hot Bob
03-18-2010, 03:01 PM
After seeing how much difference this made I had to dig out my Moltrecht books. Sure enough it was in there; bottom of page 85 in Machine Shop Practice Volume 1 and diagramed out on the following page.

Airsmith, I'm not bashing you but I suggest that if you really want to run a test, you should try duplicating what I was doing in my original post. Of course, wasting a $35 piece of brass for a test may not be cost effective but I suspect the test will go the same way with any piece over .125 thick.

Thanks again everyone,

Bob

Circlip
03-18-2010, 03:05 PM
Long as you're safe Bob and can STILL count to ten, (Five each side)

Regards Ian.

S_J_H
03-18-2010, 04:13 PM
Great stuff so far. :D .

I use brass quite often and I'll admit I don't use special bits for it very often. Have I had bits grab in brass? You betcha! But I can usually make do with a standard bit with careful attention to feed rate and readied for quick action if the need arises.:eek:
But that is hardly good advice for a noobster.

A bit designed/modified for drilling brass will eliminate most of the drama and might just make for a calmer day in the shop.

Steve

Gavin
03-18-2010, 04:41 PM
you should ignore the advise you have been

Krutch - a small point certainly but given that you are correcting airsmith's language you may want to note that the word you were looking for is advice. Advise is the verb, advice is the noun.

Personally I'm happy reading any post on these forums irrespective of the makeup of the language, life's too short to get hung up on pedantic matters like this.

Oldbrock
03-18-2010, 04:53 PM
'
ok come to my shop and ill show you how to drill brass.. i been doing it this way sence the lower speeds where a problem and sence i been doing it the way i had mention i never had an issue..

but this is just me and i have done alot of drilling in brass ..

so if itss wronge then i guess iam one lucky SOB then , that or i know what iam doing, iam voting for my second option...

the only part of working on the lathe that makes me scared is parting off large dimeters of steel. now thats scary crap with a flexable parting tool, hence its time for me to up grade to a pro level parting tool and part with the old flappy blade style i have now... But in your first post you now have a problem and we have told you how to fix it, so listen up. Peter

gwilson
03-18-2010, 05:04 PM
Now,come on,Airsmith. I CANNOT understand WHAT you were trying to say in your post #38.

I even use spell check myself,though I am well educated. It's surprising how many words a person will spell wrong. The spell check helps you LEARN how to spell.

I did very little writing for some time,and have forgotten some of the spelling I learned when I was young. The use of the spell check is useful to everyone.

At LEAST TRY to make your posts understandable.Otherwise,you waste your time posting them,and our time TRYING to figure out what you mean.

ABOUT BRASS: One night I had a piece of 1/2" X 2" X 2" brass CLAMPED in my drill press vise. I thought it was secure enough,and was in a hurry. I didn't grind the bit fir use on brass. I drilled the block of brass,and when the drill broke through the brass,it SUCKED the brass right up out of the vise. That brass sliced open my index finger,causing the end of the finger to have no feeling. It took 10 YEARS before feeling returned to that finger.

That was all because I didn't bother to spend a minute grinding the drill. The brass was 260 alloy,a very common brass.

I have NOT FOUND any decrease in the drill's ability to drill steel with the edges ground vertical. So,don't worry about ruining your drills. They still will drill steel just fine.

airsmith282
03-18-2010, 05:32 PM
enough is enough on the spelling get of my fu****g back for the last time.

mochinist
03-18-2010, 05:34 PM
enough is enough on the spelling get of my fu****g back for the last time.you spelled "off" wrong

airsmith282
03-18-2010, 05:45 PM
your wish is to see me leave this board is what its comming down to so , you can all have your wish then ,,

see ya ill not be back to this place again..

Kamala
03-18-2010, 05:46 PM
are you smoking crack lets see on the lathe mounted the brass in the chuck drill bit in the drill chuck...
Capitalization and punctuation can be just as important as spelling. I too, had trouble understanding Post #38 quoted above. Took the time to figure it out. Maybe it should have gone like this.

Are you smoking crack? Let's see. On the lathe, mounted the brass in the chuck, drill bit in the drill chuck.

And then there is this famous example.

that that is is that that is not is not is that it it is

That that is, is. That that is not, is not. Is that it? It is!

gwilson
03-18-2010, 05:48 PM
My post was entirely friendly advice. I tried to explain to the dummy the benefits of spell check. He listened to NO ONE's advice about ANYTHING. In another post he blew up a parting tool in his face. It hit (may have cut) his lip twice. If Airsmith does not want to listen to constructive advice on improving his safety in drilling brass,or in improving his mind,then he can go jump. Good riddance. I'll bet he's back,though.

Black_Moons
03-18-2010, 06:32 PM
I think its a little sad to see personal 'attacks' rather then informative discussion in this forum, and think it bodes kinda poorly on the rest of us.

That said, iv never seen airsmith apologize or admit when hes wrong, or even that he could ever be wrong. He does seem to rather continuely give advice that has little or no basis to back it up and is sometimes even dangerious. His spelling is slightly problematic but I think the real problem is grammer that is incredabley hard to understand and could be misinterpeted a few diffrent ways.

This seems to overall frustrate a lot of people in this forum.

Personally I try to just ignore him. I wish he would learn and improve but he does not seem open to learning from the rest of us here. A shame really when there is such great information going around.

i'll admit, iv tryed my own wacked out methods myself against advice.. but iv also tryed the real recommended methods to compair them to and try and learn why the recommended method are recommended, and if there is any merit to my wacked out methods.

Black_Moons
03-18-2010, 06:36 PM
lets see on the lathe mounted the brass in the chuck drill bit in the drill chuck

Is an example of the grammer problem. I have no idea whats going on with that sentence. it is painful to try to parse, like a bad newspaper puzzel.

Gavin
03-18-2010, 07:13 PM
Is an example of the grammer problem. I have no idea whats going on with that sentence. it is painful to try to parse, like a bad newspaper puzzel.

Guys - this is a machining forum, not an english forum. There are 3 mistakes in the the post from Black Moons quoted above in which he tries to correct airsmith. None of us are perfect, not even those who take the high moral ground.

Black_Moons
03-18-2010, 07:31 PM
Gravin: its an english forum, Not an engrish forum. 'mistakes' are acceptable, Sentences that belong in chinese lathe manuals are not.

Gavin
03-18-2010, 07:41 PM
Gravin: its an english forum, Not an engrish forum. 'mistakes' are acceptable, Sentences that belong in chinese lathe manuals are not.

Sad really, and ironic.....your spelling mistakes and punctuation mistakes are acceptable but others are not. Will chinese machine discussions be the next item of flame-wars here?

chrisfournier
03-18-2010, 07:48 PM
you spelled "off" wrong

Thanks to you I wasted a perfectly good gulp of my end of the day beer(s), found out that beer really burns your nasal passages and spent 5 minutes cleaning up my laptop.

All of this being said I'd like to thank you for some of the finest comedic timing that I've ever seen on a forum.

Bravo!

Willy
03-18-2010, 07:58 PM
Gavin, no one wants or expects English language perfection here.

I use spell-check and I still make lots of mistakes, like using "to", when I meant "too", for example. I also constantly have to go back and correct grammatical errors, never mind sentence structure, and I'm sure my posts still look like hell to an English teacher.

No one here is on a witch hunt to ostracize those with less than perfect English. But when someone posts here and half of the people here can't comprehend what the poster is trying to convey, then I think we have a problem.

Airsmith has been asked repeatedly, and very nicely too I may add, to make his posts easier to read. His reply was that it was our problem and to back off! His lack of willingness to help himself was only exceeded by his complete arrogance toward anybody that questioned anything he did.

I feel bad for him as I do believe he meant well and could make some worthwhile contributions.

mconlee
03-18-2010, 08:19 PM
The procedures mentioned here for drilling brass.. do they also apply to drilling bronze?

macona
03-18-2010, 08:24 PM
spelling iam not the only one

and look not one spelling mistake how about that,, and i never even used the spell checker

iam is not a word.

gwilson
03-18-2010, 08:34 PM
My post to Airsmith was not a personal attack. I mentioned that I even use it,and tried to help him see the benefits. Then,I advised him that grinding his drills for brass doesn't seen to affect their performance in steel. He had expressed his concern about ruining a set of bits and not wanting to buy another.

If he didn't bother to read my post,it's his problem. He doesn't even write so we can understand him. That's over the top,when you don't care enough about your fellows to ATTEMPT to make your posts readable.

Spelling REASONABLY well,and making yourself understood is acceptable to everyone,I believe.

spope14
03-18-2010, 09:20 PM
If you are seeking a 1.001 inch hole in 1 3/4 hex brass, could you mount it in a lathe instead, drill it with zero rake drills, then bore the last bits? Even with some "zero rake" drills over the years, after the pilot drilling I still get some
"wants to grab" just by the nature of drilling a second hole after a pilot due to the lack of the chisel point of the drill engaging and guiding and just the cutting edges engaged. Maybe even bore to that 3 to 5% "leave allowance" for a ream.

Single part jobs and such, mill or lathe with tight tolerance or dimensions +/- over or under a miminal size, I tend to bore because of the control allowed by the boring bars.

Suit yourself, just a hint from one who has this preference.

dorsey
05-19-2010, 08:23 PM
I just had the same problem drilling brass - the workpiece "screwed" up the drill bit and pulled the chuck out of the drill press. Very scary. Fortunately, it did no damage to me or the workpiece because I had drilled undersize for later finishing (see below). I also had the vice clamped down, so that didn't spin around and chew up my hand.

Because this hadn't ever happened before, it caught me by surprise. Upon reflection (something I do more often now that I'm 60), I thought it might be because every bit I happened to use had recently been sharpened on my drill doctor. After reading this thread and the referenced thread at Practical Machinist, I now think that in the past I was using dull drills that mitigated this tendency. Zero rake makes perfect sense to me as the solution, and I will use that technique from now on.

Another solution is to use drill rod to make a D bit, something I learned while building a Stuart steam engine model. Apparently they like those bits in England, because I had just never heard of it before. For example, using .375 drill rod, I quickly and easily made a D bit that absolutely will not grab on exit, and also leaves a beautiful finish inside the hole. D bits are also great for finishing the bottom of a blind hole, should the need ever arise.

Sportandmiah
05-19-2010, 10:40 PM
So to modify a drill to zero rake essentially means dulling the cutting edge?

J Tiers
05-19-2010, 11:44 PM
Not quite dulling, but reducing rake to zero.....

BTW, for plastics and soft metals there ARE slow twist drills available. Just bought some a couple weeks ago for work, to drill into a thermoplastic housing. Got them from McMaster, because we order from them a fair bit..... MSC surely has them also. Cheap, buck or so for a 4-40 clearance hole.

They work really well. No "grab and pull" as you break through.

The other good thing is that you get a different and different-looking drill, really hard to confuse with a standard one.

doctor demo
05-20-2010, 12:19 AM
iam is not a word.
Yes, but Iams is a dog food brand.

Steve

Paul Alciatore
05-20-2010, 04:25 AM
A dull drill would be one with rounded cutting edges. This would make it hard to drill with it. Reducing the rake angle to zero while keeping a good sharp edge is not dulling it. It is simply matching the geometry of the drill to the work at hand. Many lathe and milling cutters even have negative rake angles, but the edges are sharp.

Get a good text on machining and read the sections on tool geometry.

Black Forest
05-20-2010, 06:00 AM
You all remind me of a joke I once heard.

A man asks a woman if she will have sex with him if he gives her $100.

She gets all mad and tells him she is not that kind of woman and is not a whore.

Then he offers her $1,000,000 dollars to sleep with him. She thinks a few seconds and accepts his offer.

He then tells her that she is indeed a whore, but just high priced!

A little bit like the spelling here. As to post number #38, I still have no idea what the poor fellow was talking about!

John Stevenson
05-20-2010, 09:39 AM
I took one of Airsmiths posts and put it thru a red-neck spell checker and it made more sense than in the clear


test done on 360 brass round
the peice on the left was drilled with a brand new never used 8.1 mm drill 1620 rpm max speed of my lathe. the peice on the right was done on a well used 11MM not so sharp drill and as you can see it did not go so well. runing the 8.1 was nice and smooth then 11 mm not so smooth , neither one grabed..
now i tried slowing the 550 rpm and the 8.1 was fine, the 11mm was not so fine at the slower rpm so to me id step drill when going past 8.1 mm that or make sure you got a really sharp edge and you can run 550 at the 11mm unmodified drills..
now the feed must be constant on the smaller but you need to go in and out slowly on the larger diameter this i did notice as well.

tess done on 360 brass roun' th' peice on th' lef' was drilled wif a bran' noo nevah used 8.1 mm drill 1620 rpm max speed of mah lathe. th' peice on th' right was done on a fine used 11MM not so sharp drill an' as yo' kin see it did not hoof it so fine. runin' th' 8.1 was nice an' smooth then 11 mm not so smooth , neifer one grabed, cuss it all t' tarnation.. now i tried slowin' th' 550 rpm an' th' 8.1 was fine, th' 11mm was not so fine at th' slower rpm so t'me id step drill when gwine past 8.1 mm thet o' make sho'nuff yo' got a pow'ful sharp edge an' yo' kin helter-skelter 550 at th' 11mm unmodified drills.. now th' feed muss be cornstant on th' smaller but yo' need t'go in an' out slowly on th' larger diameter this hyar i did notice as fine.

.

Tony Ennis
05-20-2010, 09:48 AM
What did you do, run it through a "Kentucky" filter?

edit - why yes you did!

Hot Bob
05-20-2010, 10:32 AM
If you are seeking a 1.001 inch hole in 1 3/4 hex brass, could you mount it in a lathe instead, drill it with zero rake drills, then bore the last bits?

Probably would be a little impractical to do in the lathe.

http://img.photobucket.com/albums/v205/badman14/IMG_4121.jpg

These are handlebar risers for choppers. The 1.001" bore is where the black tube runs through on the display. Once I adjusted the cutting rake on the drill, I had no problems. I've streamlined my process to the point that I can produce five sets of the fluted style in about 8 hours. The hex style take about an hour less.

Bob

Sportandmiah
05-20-2010, 10:34 AM
Back to the topic at hand: I can't picture what zero rake would look like if I wanted to modify a drill. I'm assuming zero rake on the cutting edge would be flat, but at what angle do I start? What is the rake before I modify it? I'm probably making this harder than it needs to be, but I cannot picture how to do this. I've seen the pics on here and PM but am still not sure how to do it.

Hot Bob
05-20-2010, 11:55 AM
Back to the topic at hand: I can't picture what zero rake would look like if I wanted to modify a drill. I'm assuming zero rake on the cutting edge would be flat, but at what angle do I start? What is the rake before I modify it? I'm probably making this harder than it needs to be, but I cannot picture how to do this. I've seen the pics on here and PM but am still not sure how to do it.

Here's what I did. First I sharpened the twist drill as usual then I laid it flat on a workbench with the point at the edge of the bench and the cutting edge parallel to the top surface. I used a small diamond file also held parallel to the bench surface to bring down the front of the cutting edge on the drill. The file works within the flute of the drill. Very quick and easy; maybe 8-10 strokes for each cutting edge.

Bob

EVguru
05-20-2010, 12:06 PM
http://www.drill-tech.co.uk/dubbed-side2.jpg


http://www.drill-tech.co.uk/dubbing.htm

That's a 'Dubbed' drill point, if just doing a quick mod to an ordinary twist drill, then putting a facet on the cutting edge in line with the drill axis will do the job.

Sportandmiah
05-20-2010, 12:21 PM
Thanks fellas for the tips.

Paul Alciatore
05-20-2010, 12:33 PM
Back to the topic at hand: I can't picture what zero rake would look like if I wanted to modify a drill. I'm assuming zero rake on the cutting edge would be flat, but at what angle do I start? What is the rake before I modify it? I'm probably making this harder than it needs to be, but I cannot picture how to do this. I've seen the pics on here and PM but am still not sure how to do it.

Here is a somewhat crude drawing showing the rake angle and how to modify it for brass and other soft materials.

http://img.photobucket.com/albums/v55/EPAIII/DrillAngles.jpg

As for how to do it, there are several ways. A small, hand held stone can be used. It would have to fit inside the flute. It would be held with the flat face parallel to the axis of the drill and that flat on the cutting edge. Then just move it parallel to the axis of the drill to grind the flat.

Or I did it with a Dremel and one of the reinforced abrasive disks. The Dremel was held perpendicular to the drill and the disk was inserted into the flute. I used the side of the disc to grind the flat. For small drills, this goes very quickly and a quick touch is enough.

Mcgyver
05-20-2010, 01:55 PM
just to pile on, here's some pics I put up years ago showing zero rake and how to grind/stone it.

you really need a second set of drills as its a pita restore to positive rake

http://i20.photobucket.com/albums/b201/michael0100/drills%20brass/DSCN0159.jpg

http://i20.photobucket.com/albums/b201/michael0100/drills%20brass/stoningzerorake.jpg

http://i20.photobucket.com/albums/b201/michael0100/drills%20brass/grindingzerorake.jpg

small.planes
05-20-2010, 02:03 PM
http://i20.photobucket.com/albums/b201/michael0100/drills%20brass/grindingzerorake.jpg

Just a quick one on that, watch out the drill doesnt grab and slip, the flutes can make a nasty cut.
I recently sliced my thumb on a drill edge holding it in a similar manner to deburr a hole.
I often use a much larger drill to clean the edge of a small hole, eg 2mm hole, use 8mm or so drill.

Dave

Mcgyver
05-20-2010, 02:19 PM
good point Dave, in this example that a chicom drill, flutes as sharp as butter knives ...... no side milling with that bad boy :p

Sportandmiah
05-20-2010, 07:25 PM
This is precisely what I was looking for.
Thank You!


http://i20.photobucket.com/albums/b201/michael0100/drills%20brass/grindingzerorake.jpg[/QUOTE]

rohart
05-20-2010, 08:44 PM
Thanks EV for the comment about screaming and showers of slivers. I never knew there was leaded brass. All the brass I can remember machining screamed - shrieked would be a better way of putting it.

I'll have to have some strong words with my supplier.

Did anyone answer the question about whether bronze behaved the same way ? And phosphor-bronze ?

I think antimony's quite fun to machine - it doesn't scream so much as leave a surface that looks like it's been etched. Maybe you need alomost a burnishing rake, but using normal geometry seems to tear the top layer off the crystal structures.

J Tiers
05-20-2010, 08:46 PM
Actually, I think the use of a powered grinder is excessive for this....

If you want to make a brass drill, it is easy to just do that yourself with a small hand stone. A flat edge of more than 10 thou or possibly 20 thou is of no help, and if later you want to sharpen again for steel, it means much more grinding....

A few strokes with a hand stone give you enough edge flatting to be fine.

darryl
05-20-2010, 10:44 PM
If you were to compare the angles on a drill bit to a lathe bit, the angle of the flutes equates to the top rake, and the relief angle on the drill bit equates to the lathe bits' front relief angle.

Oh, and thanks John for clarifying that- Now I unkdrshtund parefckalylie!