Drilling a 3/4" hole

[allinon72]

I'm probably going to get flamed for this...

Why can't I find a 3/4" drill bit for metal? I need to enlarge an existing hole. All I can find is wood spade bits and masonry bits.

 

[Strouty]

Google is your friend, also any welding supply store should have bits that large. Check local grainger, look on the interweb for them. Go to www.mcmaster.com

 

[IndyGarage]

Most homeowner style drills are low on power for a 3/4 drill bit - andyou need a reduced shank drill bit to fit in most drill presses or handheld drills.

Look on a metalworking website - go to www.enco.com and you'll find what you are looking for.

 

[Kevin54]

Have you tried Fastenal if you have one around. I would also think an ACE Hardware would have on.

 

[mike7]

If you can't find a drill bit, you could always use a bi-metal hole saw.

 

[sberry]

Show a picture of hole? Several ways to do it but a 3/4 bit is common. Here is a dandy,,, added 2 bolts to each side of loader,,, battery drill, 3/4 holesaw, tap water and about 20-30 minutes, ha

 

[Strouty]

you could also go to home depot and get a 3/4 inch step bit (or unibit). They say they are good to 1/8" but I have and still do use them for much thicker (1" plate). Just keep them oiled so they stay cool. I actually used WD-40 once.

Linky:

http://www.homedepot.com/h_d1/N-5yc...angId=-1&keyword=step+drill+bit&storeId=10051

 

[Charliekilo]

Have you tried Fastenal if you have one around. I would also think an ACE Hardware would have on.

Fastenal is a wholesaler and are quick to tell you .
Buy in bulk or buy it somewhere else.

 

[BD1]

How thick is material ? Is this a hole through flat steel ?

Unibit will be fine and may give you more for the money. Hole saws are great too, depends on circumstances .

 

[allinon72]

I need to get thru about an inch of material. Hole saw will not work because it won't stay centered in the existing hole.

 

[sberry]

So many ways to enlarge a hole. My neighbor brought me a couple unibits from HF, really good especially at the price, so cheap everyone should have a couple. I use some hole saws, drilling in place on machine, takes a couple minutes but set up is so fast, limited tool cost, good finish. I do use oil most times. rapid tap, tap magic and about 3 or 4 drops per 1/8 or so of material with decent saw,,, which on some level I consider a consumable.

Battery drills and some modern bits are some of the most productive tools I own. Would be at a stone loss without it.

 

[Tim Kennedy]

Charliekilo: Around here [W. PA] Fastenal has several stores -- all are retail/wholesale --
they're actually nice stores & knowledgeable help.

 

[Charliekilo]

Charliekilo: Around here [W. PA] Fastenal has several stores -- all are retail/wholesale --
they're actually nice stores & knowledgeable help.

Must be a west coast attitude?

 

[gorilla]

Reduced shank drills are called silver+demming drills, Enco, MSC, McMaster-Carr all have them. I think even Harbor Freight sell a set. You will need a drill motor that runs slow about 300-500 rpm.

 

[chappys4life]

Charliekilo: Around here [W. PA] Fastenal has several stores -- all are retail/wholesale --
they're actually nice stores & knowledgeable help.

In Virginia they are the same way I have ordered 2-5 bolts many of times with no issues.

 

[Charliekilo]

How thick is material ? Is this a hole through flat steel ?

Unibit will be fine and may give you more for the money. Hole saws are great too, depends on circumstances .

How do you center a uni bit in an existing hole ?
If I could I would "patch" the existing hole with a thinner material braze or tack weld and use it as a guide.
Depending on portability it probably be easier to take it to someone and have them drill it.

 

[diggerrick]

I need to get thru about an inch of material. Hole saw will not work because it won't stay centered in the existing hole.

If the hole isn't too far from an edge, can you clamp a piece with a pilot hole centered under the existing hole? You could center it by eye fairly close, or use a hole saw the same size as the existing hole to center the pilot.

 

[xtremek]

How do you center a uni bit in an existing hole ?
If I could I would "patch" the existing hole with a thinner material braze or tack weld and use it as a guide.
Depending on portability it probably be easier to take it to someone and have them drill it.

Because of the taper, uni-bits usually center themselves. They're great for opening up existing holes. Just remember to keep it lubed, cause no one likes to get drilled dry.

 

[cj7jeep81]

i've got the silver and demming bit from harbor freight. had i think 1/2" up to 1", in 1/2" drive. have used them many times, and they work really well.

 

[csp]

How do you center a uni bit in an existing hole?

Every step in a uni-bit is another existing hole. They center themselves.

 

[NUTTSGT]

I bought a couple of large bits at Sears a few years ago. Since you are enlarging a hole, I would try a unibit. I've used a carbide bit more than once,it may not be pretty but it'llget the job done.

 

[buening]

Keep in mind a Unibit is intended for thinner material due to the depth of "steps" on the bit. A unibit won't work on enlarging a 1" thick steel plate unless the overall diameter of the unibit is exactly the size of hole you need. Something to keep in mind.

 

[NUTTSGT]

Keep in mind a Unibit is intended for thinner material due to the depth of "steps" on the bit. A unibit won't work on enlarging a 1" thick steel plate unless the overall diameter of the unibit is exactly the size of hole you need. Something to keep in mind.

You're right, I missed the going through 1" of material.

 

[buening]

Also, the hole saw won't work even with a backer plate with a centered hole unless you replace the stock center drill bit on the hole saw with a longer one. Typically the hole saw drill bit sticks past the hole saw 1/2" or so. You pretty much just need a 3/4" drill bit, sourced from a local Grainger, Fastenal, or industrial supply. If you have time, buy a set online from Enco or others that have been mentioned. Even the Harbor Freight kit mentioned would get you by if you have one local. I assume this will likely be a one time use instance and not a frequent use. No sense in going with a high priced/quality bit if you use it once every few years.

 

[Jim B]

In Virginia they are the same way I have ordered 2-5 bolts many of times with no issues.

The Fastenal near my house here in Northern Calif. sells retail also. Or maybe they just do to me to get me to leave the store.

 

[nutjob]

To use a holesaw drill the 3/4" hole in a piece of wood. Center this over the smaller hole and clamp in place. The wood will guide the holesaw, no pilot bit needed. Of course this depends on having room to clamp a piece of something over the smaller hole.

Also, you can get a special arbor that allows you to mount 2 hole saws on it. The smaller one on the inside of the larger one and it sticks past the larger holesaw. The smaller one will center the larger one.

Kevin

 

[theoldwizard1]

I bought 3/4" "standard" drill bit turned down to 1/2" at a local surplus store (Kitts, Farmington, MI). I think it was actually less than $10 !

Keep the speed down and use lube.

 

[signcrafter]

Harbor freight 3/4" unibit. 90 day warranty so you can drill till it wears out and exchange it or jsut buy a couple at 6 bucks a piece and be done.

 

[xtremek]

I wouldn't buy HF hole saws. I tried to cut through 1/4" strap steel and couldn't get 1/8" before they were dull.

 

[Zeke]

I wouldn't buy HF hole saws. I tried to cut through 1/4" strap steel and couldn't get 1/8" before they were dull.

What is 1/4" strap steel? If it's the same stuff that crate strapping is, no wonder you couldn't drill it.

 

[Highbeam]

Buy and use the 3/4" bit. It is the right tool for the job. Be ready to hold on to that drill for dear life or to let go and stay clear because when a bit that large digs in hard it will spin the drill in a hurry. Lot's of busted knockles have happened.

Hole saws are fine when you don't have an existing hole.

 

[Charles (in GA)]

Fastenal is a wholesaler and are quick to tell you .
Buy in bulk or buy it somewhere else.

I've had good experiences with Fastenal and never been told to hit the street because I wasn't a contractor or business. If they have it, they will sell it to you. With something as large as 3/4 inch, the bits probably are packaged individually. Smaller sizes are packed as many as a dozen to the pack, and yes, you gotta buy it they way they have it packaged, but thats never been an issue for me.

Charles

 

[1948]

few things i can tell you if you dont already know. im not sure what size hole youre starting out with, but most hardware stores sell single drill bits in the bigger sizes, at least around here. but anyway, once you get the 3/4 you need to buy some other ones too. lets say the hole you have now is 1/2 inch hole, you would want to drill the hole out again with a 5/8 before the 3/4 it will cut a lot faster and smoother. also, when i use a hand drill with anything over 1/2 inch i dont use the chuck key, i just tighten them by hand. because when they catch you can really hurt yourself. (i myself have a pretty powerful hand drill and have hurt myself pretty badly) letting the drill bit slip a little in the chuck will save you a lot of hurt. as others mentioned, if you can, use oil too and dont go balls out fast with it.

 

[Zeke]

It always catches when punching through. That's the beauty of a drill press.

We should all have a hole-hawg angle drill for the big holes. You can get hurt with any hand held tool, but that one takes some practice before you can let it hurt. More often the work will break loose.

 

[1500hd]

Fastenal is a wholesaler and are quick to tell you .
Buy in bulk or buy it somewhere else.

Michigan Fastenals are also retail. I've purchased individual nuts and bolts from Fastenal if they had an open package of them. You could use a cutting torch if the hole does not need to be perfect.

 

[Sureshot]

Just wrap the pilot bit with tape or find a bushing at an autoparts store if you want to use a hole saw but getting a bit sounds a whole lot easier for that thickness.

 

[BD1]

Only one hole ? Might be better off to take to a shop and have it done if precise center is required. Wouldn't hurt to find out. Just a thought.

 

[Charliekilo]

Michigan Fastenals are also retail. I've purchased individual nuts and bolts from Fastenal if they had an open package of them. You could use a cutting torch if the hole does not need to be perfect.

The Fastenal near me brought out a package of 50 set screws of the size I only needed a few of. When I said I only needed five I was told that is how they come. Then was pointed to a sign saying they sell only wholesale. I also was asked for the name on my account.
I figured they all were like that.

 

[xtremek]

What is 1/4" strap steel? If it's the same stuff that crate strapping is, no wonder you couldn't drill it.

Just stuff like you'd buy at TSC. Flat stock, Strap steel, whatever. I think it was cold roll 1/4"x 3". Back to the issue, they're right, have a good grip on the drill, and if you go the route of a regular style drill, the stepping up is the best way to go.

 

[jonzer12]

Go in any decent auto parts store and pony up for a regular 3/4 twist drill. Don't waste your money on a hole saw if you are drilling metal. You won't like the price of any decent hole saw that will survive any real use on metal. Last time I used mine was to drill shackle holes in 1" plate on my Jeep bumper. Cut just fine.