Reaming out holes in thick steel?

[FatTire]

I want to enlarge four 13/16" holes in 1/2" thick steel to accept 7/8" pins. This on a piece of equipment so I have to use a hand drill. I happened to have a 15/16" black oxide bit, not too surprisingly that doesn't work at all. In 10 minutes I only penetrated about 1/8" in one hole. So I need to decide between buying an $80 construction reamer (high speed steel, manufacturer says it is OK for stainless) or pick up a 29/32" cobalt drill for under $50. I'm guessing the reamer would work better even though it is softer. Is that correct?

 

[jmc]

Cobalt drills are harder than high speed steel, but brittle, and tend to chip if setups are shaky, like with hand held drilling. HSS reamer might work better, if you're not taking too much out. I'd finish the hole you started on last, in case it's been work hardened.

Did you resharpen your 15/16?

 

[mrmikey]

Reamer would be lot better, using a bitt you're going to either break it, break your wrist, burn out your drill or jamb your fingers. Get a three flute tapered reamer. If you're not fussy about being perfectly true, use a carbide burr..........Mike

 

[FatTire]

Thanks. The 15/16 was basically new, I used it for one project drilling some thin aluminum, just a couple of holes.

 

[5030]

Did you resharpen your 15/16?

The question is...do you know how to correctly sharpen it?

 

[FatTire]

Reamer would be lot better, using a bitt you're going to either break it, break your wrist, burn out your drill or jamb your fingers. Get a three flute tapered reamer. If you're not fussy about being perfectly true, use a carbide burr..........Mike

On my first attempt I thought my wrist would be wrecked a few seconds before the drill burned out.

 

[workinonit]

That's a tricky thing to do when you can't vise it down in a drill press. Any chance you can use bushings instead? I'm not sure of your application but I think I know what you are trying to do.

 

[workinonit]

On my first attempt I thought my wrist would be wrecked a few seconds before the drill burned out.

Are you using an AC drill or battery powered?

 

[zzvyb6]

I'd use my fire wrench with a washer template on both sides. If these are for lift link pins, don't they have a shoulder on them to hide your artwork ?

 

[workinonit]

It's amazing what a good cut I can get with my plasma cutter with a guide template. Problem is, you have to have a plasma machine.

 

[5030]

If it was me, I'd use a right angle die grinder and an abrasive stone to enlarge the holes. Lots safer and easier on your wrists.

 

[5030]

I'd use my fire wrench

ya mean a Gas Axe? That could be ugly, very ugly.

 

[workinonit]

A die grinder is a good option. You don't have a lot of material to remove. And it is only 1/2" thick.

 

[TMGT]

I want to enlarge four 13/16" holes in 1/2" thick steel to accept 7/8" pins. This on a piece of equipment so I have to use a hand drill. I happened to have a 15/16" black oxide bit, not too surprisingly that doesn't work at all. In 10 minutes I only penetrated about 1/8" in one hole. So I need to decide between buying an $80 construction reamer (high speed steel, manufacturer says it is OK for stainless) or pick up a 29/32" cobalt drill for under $50. I'm guessing the reamer would work better even though it is softer. Is that correct?

What rpm were you using? Most hand drills have a hard time running slow enough and still power a bit that size. You should be running around 350rpm for a 15/16" in mild steel (which I'd assume it is).

A good sharp HSS bit shouldn't have a problem opening up a hole in 1/2" unless its hardened or an abrasion resistant steel. If thr original hole was plasma cut you might want to slow down the bit a little more also.

 

[WranglerX]

Best solution for big holes I have found are "tapered bridge reamers" and a 1/2 inch corded drill you can hold if reamer gets stuck....

Bridge/Construction Reamers | DrillsandCutters.com

Bridge/Construction Reamers. Drillsandcutters.com stocks Bridge Reamers & a large selection of other drills & cutting tools.

drillsandcutters.com

 

[zzvyb6]

ya mean a Gas Axe? That could be ugly, very ugly.

Ugly is a relative term. Some of my relatives ARE ugly, but i get the job done. Die grinder can work. Fire Axe is more satisfying. Its a 2 minute job for 4 holes. Cover with pretty washers. Options for adjustments if your high tech CNC math didn't quite work out.

 

[fried1765]

I want to enlarge four 13/16" holes in 1/2" thick steel to accept 7/8" pins. This on a piece of equipment so I have to use a hand drill. I happened to have a 15/16" black oxide bit, not too surprisingly that doesn't work at all. In 10 minutes I only penetrated about 1/8" in one hole. So I need to decide between buying an $80 construction reamer (high speed steel, manufacturer says it is OK for stainless) or pick up a 29/32" cobalt drill for under $50. I'm guessing the reamer would work better even though it is softer. Is that correct?

I just did this in some 1/2" A36 steel.
I up sized 13/16" holes to fit 7/8" pins.
You can buy a 3/4" "drum sander kit" from ACE hdwr.
ACE item # 2495083.

An even better option is to buy the little drum discs from McMaster Carr.
Their little drum discs are much higher quality than ACE, last twice as long, and are not very expensive.
I bought 10 from them for about $12, still have 6 left.

The McMaster Car package description is: "Spiral No-Lap Band"
I bought 80 grit.
If you go to their website, you will find virtually every size and type you could possibly want.

 

[BlueBerryFarmer]

I had a service tech (with a mag drill, Hougen bits) do something similar.

I'd luv having that setup (pretty darn expensive) --- not in my budget presently.

 

[dieselscout80]

I would try a step drill bit before a standard drill bit.

Amazon.com: IRWIN Step Drill Bit, 3/16-Inch to 7/8-Inch, 3/8-Inch Shank (10234): Home Improvement

Buy IRWIN Step Drill Bit, 3/16-Inch to 7/8-Inch, 3/8-Inch Shank (10234): Step Drill Bits - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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[cqaigy2]

I've not found the right angle with abrasive to be very satisfying. But the four fluted reamer, or step bit i've been more successful with.

Most hand held drills have a hard time going slow enough for that sized bit. I've got an old corded makita hand held that can turn pretty slow and maintain the torque needed to that and it will twist your hand off at the wrist if you don't let go when the bit gets stuck.