Back Yard Mechanic needs to Drill 7/8" Hole

[jmc]

Cheaper, yes. $36.99 plus shipping

I have been using a set of these for a couple of years. They are holding up just fine but I don't drill big holes very often.

8 Piece Silver and Deming Drill Bit Set
Top quality M2 high speed steel bits
Black industrial finish
Precision ground
Includes handsome fitted wooden storage case. Shank: 1/2"; Sizes: 9/16", 5/8", 11/16", 3/4", 13/16", 7/8", 15/16", 1"
$36.99

Like Oasis, I've had good luck with my set of S & D twist drills. Sounds like the same set except my wooden case is anything but handsome! Anyway, 700RPM is about 50% too fast for drilling 7/8" in mild steel. Once they overheat, they'll lose there hardness so don't push them too hard for too long.

 

[Egon]

Try a machine shop.

 

[Gordon Gould]

Thanks for all the feed back. I never thought of a hole saw.
I was mostly concerned about the 700 rpm on my drill press.
It seems a little fast to me for a 1/2" hole so I was worried
about a 7/8" but I sounds like I should be OK.
If the hole isn't perfect nobody will notice - I cut all the steel
plate with a Sawzall. I clamped a couple of angles back to back
on either side of the cut line to use as a blade guide. Actually it came out
pretty good. Think I'll look for some cheap drill sets.
Thanks alot.

 

[2manyrocks]

What are the advantages of using windshield washer fluid as a lubricant? I've heard of using ATF, but this is the first time I remember anyone suggesting washer fluid.

I've not had good luck with large, cheapo drill bits. Seems like I ruin them pretty quickly.

 

[Window Geek]

Whenever we've had to cut holes in machine tabletops, we've used the Lenox hole saws too. Portable, way less tailings and easy to spot. The windshield wash takes the heat away and keeps the metal from sticking (melting) to the saw teeth. I've used water with a little dish detergent in a tank sprayer with great results too. We've cut through 1 1/4" steel plate with a hand drill in about 10 minutes. It's great for big bolts and hose passages.

 

[captaincrab55]

Carbide tip hole saw and some cutting oil.

I use the cutting wax... I've drilled hundreds of 7/8" with the same carbide tip hole saw with cutting wax in heavy duty commercial grade panels...

Don't take it the wrong way, cutting oil will work too.

 

[PILOON]

Recently I needed a fairly close tolerance 3/4" hole.

While hole saws cut well when lubed, they end up in a loose fit. SO, I ground off the outside staggered teeth to be flush with the drum (bell).
Was surprised to find
A -cutting was excellent, in fact better than with staggered teeth.
B -no binding and cleaner cut
C -teeth no duller, perhaps even better.

Staggerd teeth are much better for wood in that wood binds due to sawdust while metal does not swell like wood.

I lubed with what I had on hand; WD40.

I have even bored 3" holes in 1/2" plate with a quality hole saw on my press drill. Worked fine!

 

[BHD]

if one has a cutting torch one can cut a rough hole and then weld in a bushing or a shaft collar,

 

[cowsrus]

I always thought those hole saws were strictly for wood, just by looking at the teeth on them. I never dreamed that you could drill holes in thick steel until i read this. I can't wait to try it out.