Recommendations for a good step drill (uni-bit)

[evintho]

I'm using a step drill at work to drill holes (7/8") in electical boxes so I can install Greenlee knockout punches. I love the step drill! I'm old skool and have always used drill bits. The wife asked me what I wanted for Xmas. I want a good quality step drill! I'm using an Irwin at work. I see Greenlee makes a nice one. Anyone have any good recommendations? Cobalt or HSS steel? School me on step drills!

 

[cheechi]

i got the Irwin 2 piece set from HD at the recommendation of another member here & the 3 piece HF set on sale at the recommendation of a guy at work. both are nice & go through thin sheet without issue. haven't used them for anything else.

 

[Chadwilliam1]

my boss usually bought me Irwin or greenLee and never had a complaint.

 

[Roots]

Hilti.

 

[mrpizza]

I have used the harbor freight one to punch dozens of holes in sheet metal and in stainless steel kegs. However for long term use I would go with th greenlee one or the Irwin unibit.

 

[oldmerc]

I have worn out quite a few Irwin , Milwaukee , Greenlee , Viking .
all seem to last about the same length of time / number of holes . Irwin seems to be the best value .IMHO

 

[Mickey O]

Any decent brand will work (I bought a pile of Swiss made ones for a few bucks a piece at a garage sale, probably should have bought all of them), get the shorter/fatter ones as the skinny/longer ones break easier (even though some of the skinny/longer go up to 7/8" which seems ideal). Get yourself some of these:

To get the start perfect then use the unibit to go to the size of the threads on the knockout punch and you won't have to use the hash marks on the punch to center it.

Now after typing this I'm thinking why would you be buying drill bits to use at work, the employer would be providing those, so I'm guessing you want one/some for personal use? From looking at flea bay they're quite expensive, I'd wait for a deal unless you really need them for something specific. I've got several and don't use them all that much, mostly just when I'm using knock out punches. For the money I'd probably use a starter bit and a regular drill bit.



.

 

[Provincial]

I used a Harbor Freight bit to punch clearance holes for 1/2" and 3.4" conduit through hardened steel girts on my metal building. It was the largest bit they offer, and I ran it with a Milwaukee 1/2" variable speed drill at pretty slow speeds and used cutting oil. I drilled over 100 holes with that bit and it still works like new! This material was so hard that I quit trying to use knockout punches on it after about 5 holes, and the plumber stripped the threads on a Greenlee 4" punch after two holes. On mild steel boxes, the bit should last forever if not run too fast.

The drawback to the HF bit is that you need to drill about a 3/16" pilot hole because it doesn't start a hole well by itself. But, as Mickey O points out, the pilot hole locates the knockout punch properly.

 

[paranoid56]

sadly, i would say HF over the irwin one. i have tried a few different ones (not the greenlee ones) but my irwin one lasted less then one of my HF ones. and my HF ones are still going strong. and not to mention you can get the 3 pack for like 5 bucks lol

 

[RCStocker]

I just have one question for you and your hole drilling.
Is this new construction or remodeling old instulations.

If this is all new work I would take the boxes and drill all the holes on a drill press with the box held in a good boldted down vice. I know you don't alway know which side but if you are an electrical contractor you can pre drill boxs and just keep them on hand. If they are large boxes and you are installing another line you can't do that. Most small bxes don't have a right side up.

I have pre drilled many holes on the drill press or milling machine. I have even used a roter table to mill the proper size whole when I did not have a bunch.

Does Vermont American make them. They did years ago. I had good luck with those also.
My bet is that all the step drills are made in China these days and it really does not matter what brand you buy. They are all about the same quality. The do make expensive ones but they will break the bank.

 

[RCStocker]

You can get a bench top dril press and put it on a rolling cart and move it around the building you are working in. That way you can drill the whole on the spot to match your needs. Less time involved in drilling holes and much easier. Do the lay out drill the box then attch the box.

 

[fivespdcat]

I would check ebay for some NOS Irwin Cobalts. They go for a good price and are top quality. I can't vouch for any of the new asian made ones.

 

[AZ_Catskinner]

My "front line" unibits are Greenlees, but I have been starting to buy the Harbor Freight ones to keep "in stock". The HF's cut really well, last about as long as the "non-electrical specialty" brands, and are cheap enough to toss when they start losing their edge.

Somewhere in my bit drawer is an old Klein that my Granddad bought 20 or so years ago that has been at it for years and still has a good edge on it.

 

[Monte]

Ruko

http://chadstoolbox.com/search.aspx?find=ruko+step+drill

 

[A_Pmech]

Ruko

http://chadstoolbox.com/search.aspx?find=ruko+step+drill

Those look interesting... A bit harder to sharpen, but the positive rake angle will reduce feed pressure pretty substantially.

Everybody IS sharpening their Unibits, right?

 

[Monte]

Everybody IS sharpening their Unibits, right?

sharpening is there a drill doctor for step drill bits ?

 

[JASTECH]

I read Ruko are top notch too. I've used Uni-Bit doing electrical and they last.
>
>
I did'nt know you could sharpen them, how is this done?

 

[bw77]

Lenox vari-bit, good quality, made in USA. But not cheap.

http://www.lenoxtools.com/pages/Product.aspx?productId=VaribitStepDrillBits

 

[A_Pmech]

sharpening is there a drill doctor for step drill bits ?

A drill doctor for stop drills?

Oh dear...

 

[JASTECH]

I read Ruko are top notch too. I've used Uni-Bit doing electrical and they last.
>
>
I did'nt know you could sharpen them, how is this done?

 

[A_Pmech]

I did'nt know you could sharpen them, how is this done?

Very easily!

It depends on the way the Unibit was made. If it's a true Unibit, the flute is cut with a radiused milling cutter on a chordal path to provide a back rake angle to the cutting edge. To sharpen it, dress a 1/4" or 3/8" wide type 1 grinding wheel to a radius roughly equal to that of the flute. Holding the Unibit to the wheel, grind the radius to undercut the flute face on the cutting edge side. Keep grinding lightly until the tool sharpens up, being careful to maintain the positive back rake of the flute. It should only require a few quick applications to the wheel to bring it back unless it's totally trashed.

For many other brands, such as Milwaukee, use a type 1 wheel dressed to a wedge face or a type 11 or 12 cup wheel. Grind away a little bit of the cutting edge face until it sharpens up.

The true Unibits with radiused flutes can be sharpened a substantial number of times if you keep them sharp so the corners don't break down. The other types can be sharpened a few times, but they're a much cheaper design and don't have a lot of extra metal to allow for sharpening

 

[JASTECH]

A Pmech, Thanks for learning me a touch. What about the Ruko design? I need to setup a grinder just for sharpening. But it seems like I would need a bunch of stones dressed differently? Is there a simple way or setup one just for drill bits with different stones?

 

[A_Pmech]

A Pmech, Thanks for learning me a touch. What about the Ruko design? I need to setup a grinder just for sharpening. But it seems like I would need a bunch of stones dressed differently? Is there a simple way or setup one just for drill bits with different stones?

The Ruko design with a helical flute does not lend itself to offhand sharpening. While it could possibly be done offhand, a tool and cutter grinder would make the job easy.

For twist drills you only need one wheel, a 38A60KVBE (although an "I" or "J" hardness works too). Dress the face flat with a 21 grit silicon carbide dressing stick and keep it flat!

You'll need a bushing to adapt the 1-1/4" arbor of the wheel to fit your bench grinder unless you order wheels with a smaller arbor size, which are fairly difficult to find.