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S&S_ShovelHead
01-26-2011, 02:21 AM
I'm looking to get a new set of metal drill bits. Ill be drilling SS, mild steel, 4140, brass, aluminum, ect. I was wondering if someone could tell me the pros and cons of the different types of bits (cobalt, hss, TiN coated, ect.) and anything else I should keep in mind when shopping for bits. Any recommendations would really be appreciated. Thanks.

AllThumbz
01-26-2011, 02:38 AM
I personally want the cobalt 135 point USA set that Enco sells for about $250. These drills stay sharp longer in steel, and are worth the extra money.

The TiN sets are sharp the first or second time in steel, then dull quickly and need resharpened.

The cheap import sets are not a good value IMHO.

Best,

Nelson

mike os
01-26-2011, 03:44 AM
good quality cobalt is useful if you drill stainless or a lot of steel, otherwise a decent HSS will do just fine... assuming you keep it sharp...TiN on metal... i remain sceptical

Black_Moons
01-26-2011, 04:41 AM
IIRC, You may need to grind your drills a little diffrently for brass. So you might wanna buy a cheapo set for just brass drilling.

That said, iv seen cheapo drill bits do wonders in steel.. But you HAVE to use them slow (like 500rpm or less for drills over 1/4"), with lots of pressure, and lots of lube.

Watching little filings form at 1800rpm is not how efficent drilling is done in steel. Watching large curly swaffs form is. :)

And IMO, the number one reason people burn out drill bits is using them in wayy too fast a drill. Faster rpm is not faster hole drilling. More pressure is faster hole drilling, And you can only achive that with a low RPM tool that is geared for lots of torque. (No, using your 1800rpm drill at 500rpm by feathering the trigger won't work either)

DougC_582
01-26-2011, 08:49 AM
Warning: purely opinions...
...stainless is tough on HSS. Cobalt would do better. But....

...cobalt is more brittle than HSS, and will break easier if used in a hand-held drill on metals.

...tin coating is not that important.

...there is a lot of variable quality in HSS bits now. SOme work just fine but some can be very soft. Also I have seen that in some of the very-cheap China sets, some drills (particularly the smaller sizes) come bent and drill bigger holes than they should. Others break very easily the first time you try to use them.

-------

You also need to plan out a drill-bit-buying strategy.

If you got the money--you can spend a huge amount of money for a big complete set of good-quality bits from teh get-go.... but many of those drill bits you will NEVER use. Most people buy the 115-pc sets and then use maybe two dozen of the bits, and the rest just sit in the case collecting rust.

You can go the other way and buy a cheap set, but some of the bits may be basically defective from the get-go for whatever reason, and so you will need to order replacements one-by-one as you find the crappy ones. The upside here is that you can replace them with GOOD bits, and this way is nice (I think) because you only spend a lot of money for the bits you need to use (-the cheapo bits will make at least a few holes in a pinch, they're not totally worthless).

Alternately you can buy a good-brand set of a limited range of sizes (like 1/16 to 1/2 x 64ths cobalt, maybe) and then "fill in the gaps" by ordering good brands of whatever other ones you need.,,, but this way, you will be left waiting for the package to arrive because you need a #D or a #17 drill bit that you probably cannot buy separately at any local walk-in store.

Machinist-Guide
01-26-2011, 09:12 AM
IMO Tin coating is not good for much other than making them pretty. Tin coating is a good thing in some applications like a die punch for example it prevents galling with out lubing. As for cutters I think it's a waste because the first time you sharpen them the coating is ground off the cutting surface.

SGW
01-26-2011, 09:18 AM
Whatever you get, get good ones, which translates into "costs more." TiN coating may help IF the underlying drill is of good quality to begin with. I think all too often TiN coating is used to "powder the pig" as a sales gimick though, and for casual use the advantage may be minimal anyway.

I've got sets of bright HSS 118 degree Hanson jobber drills from 30 years ago that are very good drills. I don't know how Hanson quality is now.

I've also got a set of black oxide HSS 135 degree split point screw machine "made in USA" drills that are good, and I really like the split points. I can't tell much difference, from what I do, between bright finish and black oxide.

As somebody said, brass requires SHARP drills for best results, and a diligent machinist will have a set of dedicated slow-spiral drills just for brass; personally, I've never bothered.

You'll probably want a set of fractional drills 1/16" to 1/2" by 64ths and a set of number drills #1 to #60. You'll need about two letter-size drills for tapping sizes, maybe. If/when the time comes, buy the individual size you need. I've got a letter set and hardly ever use any of them. If you can afford cobalt, go for it, but top-quality HSS would probably win out over so-so quality cobalt.

For general use, jobber length is a good compromise. At some point a set of screw machine length drills may be desirable, but you can certainly get along without it until the need becomes apparent.

118 degree points are a good compromise for drilling all types of material. I'd like to find 118 degree split point drills, but split points seem to be offered only with 135 degree points.

Machinist-Guide
01-26-2011, 09:28 AM
Here is a link to a page with a drill bit material selection chart and a drill point angle chart. http://www.machinist-guide.com/drill-point-angle-chart.html

Mcgyver
01-26-2011, 09:38 AM
Whatever you get, get good ones, which translates into "costs more." .

+1. get a set of say HSS Dormers, run them properly and watch how long they go between sharpening. I don't do much stainless, but work in the shop a lot and feel zero need to seek longer wearing drills than something like Dormer HSS


Watching little filings form at 1800rpm is not how efficient drilling is done in steel. Watching large curly swaffs form is.

+1 Exactly, focusing on speed without considering feed/chip size is pointless; there needs to be balance. The speed you calc is theoretical max; anything slower is good and often beneficial. Also, as drilling imposes a very large DOC compared to say lathe work, few drill presses or even vertical mills have the rigidity to run at even close to theoretical speeds with a decent feed.


, brass requires SHARP drills for best results, and a diligent machinist will have a set of dedicated slow-spiral drills just for brass;

what brass really needs is zero rake so they don't grab. Putting the zero rake on is an act of sharpening so they'll be sharp....and you may never have sharpen them again if used exclusively for brass, as they should be. You can get away without zero rake on the small ones, but its dangerous with larger sizes. Keeping separate sets is the way to go; just because you'd go mental putting on zero rake then grinding it off every time you switched from steel to brass

Lew Hartswick
01-26-2011, 10:04 AM
what brass really needs is zero rake so they don't grab. Putting the zero rake on is an act of sharpening so they'll be sharp....and you may never have sharpen them again if used exclusively for brass, as they should be. You can get away without zero rake on the small ones, but its dangerous with larger sizes. Keeping separate sets is the way to go; just because you'd go mental putting on zero rake then grinding it off every time you switched from steel to brass

+ +++ At lest a 10. :-) Even if you keep them in a set of drawers
put the brass ones in a little envelope and mark it.
...lew...

airsmith282
01-26-2011, 10:22 AM
if your drilling alot of SS and regular steel then go colbalt its the best for thoes steels, can also be used on aluim, to help avoied and gum up on aluim use some cutting fluid ,also work great with brass and bronze to,

Bruce Griffing
01-26-2011, 11:01 AM
I would agree with the comments on cobalt drills for stainless. Excluding brass and stainless, HSS is fine for most other applications. Maybe I was lucky, but I bought an import 119 drill set made of M2 HSS for about $20 (25 years ago). I have resharpened many of them, but other than a few I lost, the set is still going strong. Some of the common sizes are a little short at this point in time tho.... I did look over several sets at the time I bought them and selected a set that seemed good to me - as I said probably just lucky.

projectnut
01-26-2011, 11:12 AM
Here's a link to the first page in the "drill Bits" section of the Enco Master Catalog. It's titled "Introduction To Drills". It covers all the basics of styles, grades construction materials, coatings, point angles, and more.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=1&PMCTLG=00

There's a similar page at the begining of each section for end mills and other cutting tools.

Boucher
01-26-2011, 11:31 AM
The new 2011 Enco catalog has some good information re Drill Bits on page 1.
The catalog comes with a 10% discount on your first order so it is worth your time to get one.