Drilling one inch holes

[Pooh_Bear]

I need to drill some one inch holes. Quite a few of them.
Should I drill a small pilot hole then drill the one inch hole,
Or should I drill a small hole, then a bigger hole, then a bigger hole, up to one inch.

I have one hole that I need to drill at 3/4 inch to accept a 3/4 axle temporarily,
then I need to go back and drill the hole out to one inch.
Is this gonna give me problems.

I have one one inch drill bit. I don't want to have to buy another.
For the cost of two of these bits I could have a machine shop do all the drilling.

Thanks.

Pooh Bear

 

[Egon]

Have you considered a metal cutting hole saw. They may be just what you are looking for.

 

[RedRocker]

I'd step it out, maybe start with a 1/4, then 1/2 then 3/4 then your inch.
Bigger you go, the slower you go.

 

[RonMar]

Well if you already have the drill bit, then yes, drill a pilot hole first as the broad tip of the 1" bit will not cut very well and that is where a lot of friction will be generated. For 1" I would drill a 1/4" or 3/8" pilot hole. You shouldn't have any problem drilling out the 3/4" hole to 1" providing that you secure things firmly on the drill press. With a 3/4' hole, the cutting edge will dig in to the sharp edge of the existing hole deeply at first and tend to move the workpiece. If clamped firmly and you ease into it slowly, you should not have any problems. Since the larget bits are so expensive, for most things over 1/2" I use a bi-metalic hole saw. The only place I would use a bit was if I was having to bore thru more than about 3/4"-1" thick as that is about the limit of the hole saw. Since they use a pilot drill in the blade holder, I can place the hole pretty precisely using a center punch divot to get the pilot drill started.

 

[mbrule]

Assuming that you are drilling steel and it is not real thick, get yourself a 1"
Unibit, or step drill. I will work great for what you need.

Matt

 

[3RRL]

Couple of question first...sounds like you already bought the drills too?
What kind of material are you drilling? Mild steel I presume?
How thick is it?
What machine are you drilling this on? Mill, drill press, by Hand drill?

Generally, I try to push the largest drill through I can with the least amount of steps. This obviously saves time if your machine can handle it. So let the "toughness" of drilling be your guide. Also, when drilling through thin material, if your step holes are too close (in size) to the next size drill, often the larger drill will "grab" like crazy. This is a bad thing when hand drilling, so try to make the difference in steps large enough so the next size drill does not do that, but small enough to push through without killing yourself. If you're doing it in a drill press or milling machine, you need only a Ø3/8" or Ø1/2" pilot hole than go to the Ø3/4 drill (or reamer drill if the hole has to be reamed to size for a perfect fit). You can go right to the Ø1" hole after that and use cutting oil on the larger sizes.

Good advice on going slower rpm on the larger drills if your machine allows it. Another tip I use to drill thinner material (and harder material) is to sharpen the tip at a lessor angle (less pointed than standard 118° inclusive angle) and less relief. I find it does not grab quite as much as standard.

 

[Pooh_Bear]

The material is plain 3/8 plate steel. Also some 4x4x.25 square tube.
Drill press is an old cheap Ohio Forge (old home depot) brand.
Lowest speed is 240 RPM.

Where can I get a hole saw for metal.
I got my drill bit set from Harbor Freight.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=527

What can I expect to pay for a 3/4 and 1 inch hole saw.

Total for the project is at least eleven 3/4 inch holes and 14 one inch holes.

I could reduce the number of 3/4 holes to 2 if I could find someone local
that has a plasma cutter or O/A torch and works cheap.

Any of ya'll within an hour or so of me?
http://web.infoave.net/~poohbear2767/whereilive.htm

Thanks.

Pooh Bear

 

[3RRL]

I've heard a lot of good things from guys using those hole saws...especially on thinner material and for non-critical holes. Harbor freight sells them as does Lowe's and Home Depot. Probably local hardware stores too, of course.

 

[deerhunterf350]

I bought a set of RIGID Bi-metallic hole saws 7/8" through 2" for 40.00 at HOME DEPOT. Then used a 1/2 or 3/4 HP OLD, OLD , OLD Drill motor that weighs probably 15 or 20 LBS. It is threaded for a Length of 3/4 Pipe for leverage. Me and a Friend can punch a 7/8" hole through 1/2" plate, using some cutting oil in about a minute and a half. Cut 10 holes and the Hole saw still was cutting like the steel was hot butter. I did let the Hole Saw cool for a couple of minutes between each hole.

 

[deerhunterf350]

I have one hole that I need to drill at 3/4 inch to accept a 3/4 axle temporarily,
then I need to go back and drill the hole out to one inch.
Is this gonna give me problems.

Pooh Bear

Drill the Hole at 1" , then find a piece of Pipe , that can be used as a bushing. Temp. Tack weld the bushing to reduce the 1" hole to 3/4" , then grind tacks off, knock bushing out, and you are back to 1" hole again.