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Drill Bit selection for a drill press


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I just scored a gently used 1 hp drill press with a 5/8 inch chuck (a craftsman to be exact). I had my last shop class in Jr High. and I'm pushing 50 now. What kind of drills bits do i buy for drilling the mild steel we use for smithing? There are ones coated in cobalt or carbide or titanium. And what about the angle of the point 118 vs 134 degrees?

I currently have a nice set of bullet point dewalt drills bits but they are specifically for wood.

Any advice for what kind of set to purchase would be helpful.

and any comments on the best cutting oil to use would be great too


Edited by mod07
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I won't claim to be any type of expert but I do use my drill press alot. I drill alot of large holes, 3/4"-1" in mild steel, and alot of 3/8" and 1/2" holes in hardened steel.
I use the cobalt bits for the hardened steel and they work great. They'll also work great in mild steel but are a little more expensive than non-cobalt.

I'd say if you don't plan on drilling into alot of hardened, just go buy a quality set of steel bits and if you need to drill through hardened for something, just go buy the size you need then.
Otherwise, go buy a full set of cobalt bits and you wont have to worry.

Also, when drilling steel, use a low speed. I use mine only for steel and have never changed the speed off of it's lowest 150 RPM speed and it cuts great!

I'm not sure but when I was buying those larger bits, I had the Grainger guy call the manufacturer and they suggested the 135 degree bits I think.

Again... no expert, but I've drilled alot of holes in my 1 hp Westward drill press.

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My personal preference for everyday drilling of aluminum, mild steel, annealed high carbon steel, cast iron, and whatever else I get my hands on, is the TiN coated HSS bits. The only time I've ever actually needed cobalt was drilling out some sheared off studs on an engine, although if you can afford a whole set of cobalt bits, go for it, they sure are slick :) Carbide drills (I am thinking of the indexable ones) are mostly for production and machine shops, imho.

If it can be squeezed into the budget, check into getting a Drill Doctor for keeping whatever you buy nice and sharp. We've got one of the more basic models (the kind that doesn't sharpen split points) and I am not sure how I ever lived without it. (Usual non-affiliation disclaimer here)

-Aaron @ the SCF

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in a blacksmith shop , on a drill press i reccomend a drill point angle of 118 degrees
for most work .
the equation for, is the more mild the material the steeper the angle
hence 130 degrees for stainless
stay away from split points although they cut great at first but are real vulnable to chipping .

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  • 8 months later...

I'm thinking of buying drill bit sets but would like to know if there is a prefered system, fractional, letter, number , metric.
Or a combination.

My use is general shop, and knives ,clearance holes for pins, thong holes.

Metric sounds like it would provide the most logical step arrangement but I have no machine shop experience so just a guess. The letter-number system seems confusing, and the fractional bits seem to take large steps.

Maybe a combination of systems or just have all?

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I have a set of high speed steel fractional drill bits for routine work and Cobalt drill bits in common sizes for drilling steels that are hardened. Cobalt drill bits will drill most hardend tool steels when sharp.
I have selected metric, letter, and number drill bitsthat I have aquired as I needed them.

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I'm back on this drill size thing again. I guess it's more of a rant.
Seems the system is illogical (refer to chart).

I started using micrometer to measure my blades, (thousands of inch) thinking in decimal terms, but not metric :confused: so trying to pick a drill a little oversize for a given dimension (pick one) :mad: still confused

What would be easier: metric micrometer, metric stock, metric drills?

Letter,#, fraction, metric drills:o

Whats standard machine shop measurement system?

I guess this is an old argument, I'm just becoming aware of it.

OK I feel a little better, back to my chart.
Drill Size Conversion Table

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The ultimate is one of those 3 in one sets, fractional, 1/16-1/2x64ths, letter and number. I personaly have no use for metric sizes, though I do keep both metric tap and die sets as well as metric thread files for repair work.

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If you do not have the right drill size ,you can grind one side of the flute angle a little longer . So one side will be slightly longer, which will drill over size little practice needed but works. Thats if you haven't the right size drill
Hope this helps
ONYA Mate :rolleyes:

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The Chicago/Latrobe 135dg split point drill bits are the best you can get. A set is quite expensive but they last and last so they are an excellent investment. I have a drill bit index for wood and another drill bit index from 1/32 to 1/2 in Cobalt which I use the most.

You can get good quality cobalt bits from MSC or most supply outfits. Even ebay has them, just make sure your getting good quality as not all cobalt drill bits are created equal thats why its important to buy them from a good source.

Far more important then the grade of drill bits themselves is actually learning how to sharpen them. Even a low quality drill bit can cut quite well if its sharpened well, it just won't hold the edge as long as a higher grade bit. Learning to sharpen bits is not something you learn overnight but you can learn with some patience and practice. You can perform this with a drill doctor or even better on a bench grinder. I've often used my drill doctor to get it close and then my fine stone on my bench grinder to take it to final sharpness.

If you can, find someone who knows how to sharpen drill bits well and have them teach you and practice with you for about an hour sharpening them on a bench grinder and then having you test them. One of the best ways is to experiment with a hand power drill and sharpening your own bits. With a powerdrill you will feel the cutting or lack thereof if your sharpening is off. You will also feel eccentricity if your grinding is off. Time learning how to sharpen bits is time very well spent. It will save you considerable money and time. Once you get the hang of sharpening a 135dg split point drill bit and get that picture memorized in your head you'll be able to grind a blunted or broken bit into an excellent cutting edge by hand. This is an invaluable tool as even the best bits dull quick enough when drilling repeatedly through hardened materials and relying on drill doctors is rather frustrating as their little diamond wheels die out pretty quickly.

Edited by Avadon
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I use the bullet point Dewalt drills for everything on a regular basis (their only real drawback is that they are not readily resharpenable). When I am drilling on the drill press though I find that regular HSS cheapies are fine. The smooth powerful feed of the drill press and a little oil makes quick work of drilling in mild steels. I try to hot punch and drift anything very heavy when I can (especially tool steels).

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in a shop in the us using inch sizes:

fractional inch set to 1/2 by 64ths 118 point hss
these cover 99% and easiest to sharpen

if you tap a lot of holes you will need letters and numbers as well.

i would buy a good quality set up to 1/2 inch to get started. and see what your needs are from there.

a drill doctor might be a wise investment as drills are useless when dull.

my 2 cents

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I have one good drill index set. I BELIEVE it was American tool. I will just add that I buy replacement bits from time to time and this is a good thing to consider when you buy an index. I'm not into buying bits if I can't hold them in my hand first. Call me old fashioned. I will also add that the post drill will drill HARD stuff at a few rpms cranking by hand with a lot of down pressure on the automatic feed. I use La-Co cutting fluid. Just google it.

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  • 2 weeks later...

An old machinist set me up with some "baby poop" it's some sae20 oil, baking soda, and chalk. There may be something else in it too, but I don't remember seeing anything else when he mixed it. If you are dealing with work-hardened holes, or larger bottom tapping, this stuff is the best. Keep it in a closed container, glass or metal. I wish I had the exact recipe, but it was about getting consistency. If you have had kids, you will understand (I didn't at the time, but do now). It's non-fluid, but slightly runny and sticky, sorta like what the name implies. It tends to not separate for WEEKS after mixing, and then only a slight amount of oil comes to the top.
The summer I spent in a machine shop we were cleaning up some parts that failed inspection, threaded sleeves something like 1 1/2 or 2 inch diameter threads. We would lock them in a vice, goop up the bottom tap with "baby poop" and thread it in as far as it would go by hand, then put a wrench and a 6 ft cheater bar on it. Then 2 of us would crank it through the last 5 or 6 turns. Good times! The first unit we wasted a pint of tap magic on (might have been 4 oz really).
I do like tap magic for "normal" holes though.
I have a small jar of this stuff from that summer, and it is fantastic for drilling in easily hardened metal too. I think I need to experiment and make more soon.

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