How to Make a Clean Hole with 1 1/8" Dill Bit?

[swwrobotics]

Hey everyone, so for our practice bot, our team was having trouble drilling the 2014 KOP chassis with a 1 1/8" bit, similar to the one shown here: http://drillsandcutters.com/dwdrsd1-...hlOgode FEA_A. We need to fit bearings into four holes we drill so they need to be precise.

When we tried drilling a practice hole in the 2014 chassis, the drill bit jumped around a lot, got stuck every once in a while, and in the end we ended up with a piece with a very jagged hole in it. Is there a way to fix this problem? Like squirt a bunch of lube on the piece while drilling it? Or buy another type of bit? Any advice would be appreciated.

Also keep in mind we're just using a normal cheapo drill press and none of that fancy CNC machine stuff (which I wish we had). Thanks!

[pfreivald]

Originally Posted by swwrobotics

Also keep in mind we're just using a normal cheapo drill press and none of that fancy CNC machine stuff (which I wish we had). Thanks!

In that situation, I'd use an appropriately-sized hole saw, lube, and sufficient patience. (Heating can be a problem when trying to precision-drill holes on a less-than-stellar drill press. Consider taking more time than you want to!)

[mrnoble]

We have used step drills, such as the Irwin Unibit. Grainger has an assortment of them, with some going up to 1-1/8" and larger. Harbor Freight has a set for cheap, but they don't last and are a bit dull.


http://www.irwin.com/tools/browse/dr...it-step-drills


http://m.harborfreight.com/catalogse...obile_redirect

[pfreivald]

Originally Posted by mrnoble

We have used step drills, such as the Irwin Unibit. Grainger has an assortment of them, with some going up to 1-1/8" and larger. Harbor Freight has a set for cheap, but they don't last and are a bit dull.


http://www.irwin.com/tools/browse/dr...it-step-drills


http://m.harborfreight.com/catalogse...obile_redirect

Yes, I absolutely meant a step drill and not a hole saw. Hole saws are notorious for their inaccuracy. Step drills (with a properly punched, piloted hole) are much better, and we've used them for bearings for years.

[mrnoble]

Originally Posted by pfreivald

Yes, I absolutely meant a step drill and not a hole saw. Hole saws are notorious for their inaccuracy. Step drills (with a properly punched, piloted hole) are much better, and we've used them for bearings for years.

I wondered.

[pfreivald]

Originally Posted by mrnoble

I wondered.

In the future, please don't be shy about calling me out for something that's O.o-worthy! My brain thought one thing, my mouth said something else. (And I use Voice Recognition to type, so that's not a typo!)

[mrnoble]

Originally Posted by pfreivald

In the future, please don't be shy about calling me out for something that's O.o-worthy! My brain thought one thing, my mouth said something else. (And I use Voice Recognition to type, so that's not a typo!)

[Oblarg]

Use a step bit to get up to 1 inch or so, finish it off with the 1-1/8'' bit.

You can, of course, use the step bit for the whole thing but I've always found they don't leave the nicest finish on the hole (lots of burrs, and if you go too far you end up widening one end).

Edit: As for general drilling practice, you should always have a bottle of cutting oil handy when you're using a drill press. It almost always gives you better results. It's not always necessary on aluminum (I tend to skip it for the 1/4'' or 3/16'' holes we drill loads of to save time), but it's an absolute must for getting good results on steel and it really does help for larger holes on aluminum as well. I went a long period of time not knowing this, to my detriment.

[DonRotolo]

Originally Posted by cgmv123

Start by using a center punch to accurately place the center of the hole. Then drill through with a bit like 1/8". Then use the 1 1/8" bit. Remember to properly align the workpiece under the drill press each time. Cutting oil will help too.

Good advice, except for the part about going from 1/8" to 1-1/8" directly. You absolutely need to work your way up to 1.125 as others have noted. PM me if you want to know why.

You cannot hand-hold a drill to make such a hole. This is dangerous. A drill press is the only safe way to make that hole with a drill bit. Your jagged hole is from the human inability to keep the drill perfectly centered on the pilot hole. As the bit bounces off the walls of the hole, you get chunks taken out instead of slivers.

[EricH]

Originally Posted by DonRotolo

You cannot hand-hold a drill to make such a hole. This is dangerous. A drill press is the only safe way to make that hole with a drill bit. Your jagged hole is from the human inability to keep the drill perfectly centered on the pilot hole.

I'm going to disagree on that, Don. I'm willing to bet that with the right extra equipment, I could nail a 1.125" diameter hole with a hand drill, or two. I've done something similar before, though with a smaller hole. (I've hand-drilled one using a step drill, too. That was "fun".)

I'd be using some core drills, an egg cup or two, a drill block and clamps, and a bunch of bushings, ending with a reamer. For the larger holes, I'd use a much slower drill. It's definitely possible, but it'll take time. (I tried to hunt stuff like that up on McMaster yesterday, but no dice. Might have to try another source.)

[George C]

We've had great success this year starting with a centre drill, then 1/8 or so, then 1" (largest drill we have) then reaming to 1 1/8. As said previously, a 1 1/8 reamer has a very large shank and is very long. We cut it off just long enough so that when we chucked it up in a lathe with the teeth behind the chuck we didn't damage the teeth. We then turned the shank down to 1/2. We do as much of the reaming as possible in a vertical mill because it's more rigid, we can secure the work better and we can cut the rpm way down. Has worked really well.

[DonRotolo]

Originally Posted by EricH

I'm going to disagree on that, Don. I'm willing to bet that with the right extra equipment, I could nail a 1.125" diameter hole with a hand drill, or two. I've done something similar before, though with a smaller hole. (I've hand-drilled one using a step drill, too. That was "fun".)

I'd be using some core drills, an egg cup or two, a drill block and clamps, and a bunch of bushings, ending with a reamer. For the larger holes, I'd use a much slower drill. It's definitely possible, but it'll take time. (I tried to hunt stuff like that up on McMaster yesterday, but no dice. Might have to try another source.)

Eric, I have no doubt you could DO it. My point was that it's not SAFE to use a hand-held drill for such a large hole using the OP's twist drill setup. Core drills react differently to snags than twist drills.

That also doesn't mean I have never done it. But I know the dangers and addressed them. Case in point: I still have all my limbs, and in proper working order.

[cgmv123]

Start by using a center punch to accurately place the center of the hole. Then drill through with a bit like 1/8". Then use the 1 1/8" bit. Remember to properly align the workpiece under the drill press each time. Cutting oil will help too.

[swwrobotics]

Originally Posted by cgmv123

Start by using a center punch to accurately place the center of the hole. Then drill through with a bit like 1/8". Then use the 1 1/8" bit. Remember to properly align the workpiece under the drill press each time. Cutting oil will help too.

Oh thanks. I'm actually not sure if we'll be able to center punch the piece though since the area we're drilling already has a bunch of holes around it (I know, its a bad idea) but we'll give it a go.

Originally Posted by mrnoble

We have used step drills, such as the Irwin Unibit. Grainger has an assortment of them, with some going up to 1-1/8" and larger. Harbor Freight has a set for cheap, but they don't last and are a bit dull.


http://www.irwin.com/tools/browse/dr...it-step-drills


http://m.harborfreight.com/catalogse...obile_redirect

Also, thanks! We'll definitely look into these.

[JesseK]

Qty 1: Silver & Demming 1-1/16" Drill Bit
Qty 1: 1-1/8" Reamer, exactly 1.125"

Haven't had a bad hole since.