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Drilling larger holes in steel

Herbettehunter

Plastic
Joined
Aug 10, 2021
I am brand new to this forum, retired and have a woodworking and metal working shop for my own use. I am at best an amateur hack. My question that I posed to different people seems to get different answers so I'm just trying to sort it out. Specifically I want to drill 1 to 1.5 inch holes in steel plates using drill bits with reduced 1/2 inch shanks. I have a Jet 2HP 20 inch variable speed drill press. My question is about the chuck. If I use a Jacob's 20N Super Ball Bearing Chuck, the maximum drill capacity is 1 in. But can I use a 1.5 inch drill bit diameter with 1/2 inch shank in such Chuck? Or will I get slippage because of the excess torque exceeding the capacity of the chuck? Also I asked a supposed expert at MSCDirect this question and he said run it at a slower speed so the torque would be less which makes no sense to me as I thought torque increases at lower speed. Your feedback would be greatly appreciated.
 

john.k

Diamond
Joined
Dec 21, 2012
Location
Brisbane Qld Australia
Forget your chinee rubbish.......to drill 2" holes in steel with a standard MT drill,all you need is a ratchet drill driver ,and a chain pulldown.......you cannot believe how effective the 150 year drives are until you use one.
 

thermite

Diamond
What Scruffy said.

"Relative" example for conventional "Helical twist drill":

Capacity 3" in Cast Iron, 2 1/2" in steel.

What does that?

Four thousand four hundred pounds avoir and seven horsepower driving a # 5 Morse taper through a PIV Werner-Reimers metallic belt varidrive and reduction gears. Power downfeed alone has about the same power budget as the whole mini-drill press owns.

Seems like a lot of power? An Allied VP was kind enough to assess it for me as to use of "spade"drills with high-pressure coolant. No Joy. About an inch and quarter and it hits the wall.

I own a lot of annular cutters now!

Because.. a Hougen or Milwaukee annular may be, and usually ARE, driven with a portable, battery or corded, "mag base" drill.

But "not only".

Hougen Annular Cutters for Mag Drills, Sheet Metal, Machining and Industrial Applications

GEOMETRY is in play.

Twist drill has to convert 100% of the metal in the hole to loose chips.

So does a spade drill, just faster. Similar equation comparing helical in wood to an Irwin-pattern "Speedbore".

Mass goes up on a multiple as the diameter gets larger. Power required - both twist and feed - climbs with it. Non-linear equation.

An "annular" or trepanning process only has to chew-up a narrow cylindrical "wall". A tube shape, IOW. The rest of the "slug" is not disturbed

Bigger the hole? BIGGER the difference in favour of NOT arguing with 100% of the metal.

Deeper slug cavity, otherwise same plan as the "holesaw" in wood.
And/or metal, you but buy the GOOD ones.

Annular is too raggedy? Reamers exist, and they do NOT need massive power budgets.


Page Two:

Helicals are a Royal Bitch Kitty on "breakout", off-side. Most especially when the material is thinner than the depth of their point.

Annulars are MUCH nicer on thin material. Apron on a stainless sink top wants a hole for an extra item? You got it. No fuss. Not even a lot of muss.
 

Blazemaster

Hot Rolled
Joined
Oct 13, 2009
Location
Olympia, Wa
I have a cheap 1" drill bit with a 1/2" shank. It will drill steel plate just fine, but 1.5" may be too much for a 1/2" shank. I would also recommend an annular cutter, or a MT shank drill. What is the lowest speed on your drill press?
 

DJ2

Aluminum
Joined
Feb 12, 2007
Location
Ontario, Canada
I was going to try an annular cutter but my jobber said they were for magnetic drill only. Something about getting the core out of the drill after the hole was made. Is there a problem getting the core out sometimes?
 

atex57

Hot Rolled
Joined
Sep 6, 2006
Location
SW Wisconsin
I was going to try an annular cutter but my jobber said they were for magnetic drill only. Something about getting the core out of the drill after the hole was made. Is there a problem getting the core out sometimes?

It's always worked for me. I use a needle nose plier to pull out the core if it does not fall out. Worst case you pull the cutter and knock it out through the back.

Ed.
 

akajun

Hot Rolled
Joined
Jul 1, 2011
Location
Brusly, LA
I have a 20" wilton dp, 2hp. I have drilled 1.25" holes with it BUT
I use a mt3 taper shank drill, well sharpened bit, speed as low as it will go, and even then its on a vfd turning about half speed of that. My dp weight is abot 700 lbs, it has the hp but will chatter if I go to fast, which I think will be your limitation too.
Use an annular cutter or a hole saw, they work really well.
 

CatMan

Hot Rolled
Joined
Apr 12, 2005
Location
Brandon, MS
I was going to try an annular cutter but my jobber said they were for magnetic drill only. Something about getting the core out of the drill after the hole was made. Is there a problem getting the core out sometimes?

Find a different jobber. And then get the new guy to sell you an adapter that will hold an annular cutter in your drill press. The adapter will increase your tool length. Keep the coolant poured on it and you should be fine.
 

MichaelP

Titanium
Joined
Dec 7, 2008
Location
IL/WI border
APT Multi-Tool set will work for you. Try to find one that can get inserted directly into the drill spindle taper where your chuck shank goes.
 

thermite

Diamond
I was going to try an annular cutter but my jobber said they were for magnetic drill only.
The SHANKS he stocks surely are. One can get adaptors, but the Hougen link has several shank types already. Buy adaptor(s) and the mag drill ones IF you will ALSO have the mag drill.

Something about getting the core out of the drill after the hole was made. Is there a problem getting the core out sometimes?

Nowt to do with mag drill or such. Slugger has no klew what is pushing it, nor brains enough to act differently if it did have.

Universal and not uncommon that a core needs persuasion.

There are side slots, back holes, etc etc to get them out. Not a show-stopper at all - minor nuisance, now and then, rather.

Or they would not be so popular.

There is lore to it. Different techniques to get used to.

As with woodworking, where I have many "types" of hole-making goods, there is no "one and only". Most situations, there is only a ranking by preferable vs less-so.

Best machine-tools on-planet can't make wrong or s**t tooling look good.

Best tooling can make even a lousy machine-tool work OK, and if the craftsman minding it is experienced? Even right heroic.

Not new news, is that?
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
Divide 320 by the lowest speed on your drill press. This is about the largest hole size you will successfully drill rillo a hole this large, but trying a hole larger than this will end quickly in frustration. This applies to annular cutters.

Another way of determining the largest hole would be to find the largest size Morse Taper standard drill that will fit your spindle taper. Anytime the drill size gets above 1 1/2 times the shank diameter things start to get sketchy.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
The drill point web takes a lot of pressure so a pre-drill and drilling in incremental diameters can help.
Taking too much is tough to do out of a drill chuck or with a belt drive machine..

Running at a slow speed is best for larger drills, and can provide more torque in a gear machine but in a belt machine, the belt slippage and chuck holding capacity can limit the torque.

Your DP looks heavy-duty and gets down to 65 RPM, still, a tang drill likely would be better for large-size drilling.
 

DDoug

Diamond
Joined
Oct 18, 2005
Location
NW Pa
I am brand new to this forum, retired and have a woodworking and metal working shop for my own use. I am at best an amateur hack. My question that I posed to different people seems to get different answers so I'm just trying to sort it out. Specifically I want to drill 1 to 1.5 inch holes in steel plates using drill bits with reduced 1/2 inch shanks. I have a Jet 2HP 20 inch variable speed drill press. My question is about the chuck. If I use a Jacob's 20N Super Ball Bearing Chuck, the maximum drill capacity is 1 in. But can I use a 1.5 inch drill bit diameter with 1/2 inch shank in such Chuck? Or will I get slippage because of the excess torque exceeding the capacity of the chuck? Also I asked a supposed expert at MSCDirect this question and he said run it at a slower speed so the torque would be less which makes no sense to me as I thought torque increases at lower speed. Your feedback would be greatly appreciated.
When you remove the chuck, what do you see ?
 

rogertoolmaker

Cast Iron
Joined
Jan 3, 2016
I have a cheap 1" drill bit with a 1/2" shank. It will drill steel plate just fine, but 1.5" may be too much for a 1/2" shank. I would also recommend an annular cutter, or a MT shank drill. What is the lowest speed on your drill press?

If your determined, first drill smaller holes to reduce the force required. Your always matching the job with your equipment in the shop. Even so 1/2" shank is skimpy with a 1 1/2" drill. Expect the drill to slip in the chuck. If your OK with that, go for it! The drill should run about 160 RPM for 1 1/2" dia. and the 240 RPM for the 1" dia.

Roger
 

Superbowl

Cast Iron
Joined
Feb 12, 2020
Put the bit in an indexer and use a carbide mill to make the shank triangular. That won't slip in the chuck.
 

PeteM

Diamond
Joined
Jan 15, 2002
Location
West Coast, USA
As others have said, use an annular cutter. Cleaner cuts, lower HP required, and far less chance of grabbing your workpiece or vibrating the drill holder out of its (I presume for most Jet 20s DP's) 3MT shank holder.

Use cutting oil - black sulfurized pipe threading oil from Home Depot etc. is fine for steel and readily available.

If your drill press has a 3MT shank, you might invest in a cheap 3MT to ER32 collet adapter. Most annular cutters have a 3/4" holding portion that will fit in a 3/4" ER32 collet. You could also try your 1" Albrecht chuck, but it's not as good a solution IMO.

Next thing to consider is how to pilot the annular cutter. Either drill a small pilot hole for the standard annular cutter pilot (which you might want to spring load) or make an outside guide - even plywood with a 2" or so hole (whatever you're doing) can work. You can also easily make up a pilot that will serve as a knockout for the center bit. Remove cutter from collet, punch out the center bit, put cutter and pilot back in the collet and drill another hole.

While you're at it, make sure you have a good way to secure your work.
 

woodchuckNJ

Cast Iron
Joined
Jun 7, 2014
Location
NJ
since this is a machinist forum you are hearing about using an annular cutter, which is good advice.

But how accurate a hole do you need? If you are just punching holes, even a bimetal hole saw will produce an easier, quicker hole than a twist drill. and your drill press won't complain.

But the hole is not perfect. Neither is the annular compared to a boring head. But it's like a volkswagen to a mercedes, to a ferarri.

if the hole just needs to be a good hole, a bimetal hole saw will do. Just put a piece of wood under the metal.
 








 
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