View Full Version : Mills and Drills Is a unibit good for drilling 3/16" steel?

Brian Elfert
01-29-2013, 12:03 AM
Is a Unibit a good idea for drilling holes in 3/16" steel, or am I better off buying the correct size twist bit? The holes are 3/4" diameter. I have used my Unibit to make a fairly large hole in steel before, but it was only 1/16" thick.

phil harold
01-29-2013, 1:58 AM
the maximum would be 1/8"
Step Thickness 1/8 in

Craig Coney
01-29-2013, 9:53 AM
Depends on how many you are planning on making. I've used them before on steel up to 1/4" thick. If the material is thicker than the step you need to drill from both sides of the material to the center.

Keith Outten
01-29-2013, 10:06 AM
Take a look at the cheap step drills from Harbor Freight, with the three piece set each drill has more steps which provide for deeper drilling in thicker material. I recently drilled over a hundred 1/2" diameter holes in 3/8" steel plate for a pulverizer I was building for my tractor. Today I am using the same drill bit to drill 1/2" holes in 6" heavy wall steel pipe making new supports for my work shop.


The trick is to find the right size unibit for the job but even if you have to drill from both sides they sure save time.

Brian Elfert
01-29-2013, 11:54 AM
Why do Unibits save time? Is it because they have the steps and don't drill the full hole size at once? My only reason for using a Unibit is because I already have one and I would like to avoid the cost of 3/4" drill bit if I can. I need to drill 8 holes.

George Carlson
01-31-2013, 10:15 AM
You didn't mention if you were hand drilling or using a press. One nice thing about unibits is that they make a round hole, even in thin sheet metal. Normal two flute drill bits tend to make triangular holes when done by hand. At 3/4" even 3/16 steel can behave like thin sheet metal.

James Rambo
02-01-2013, 7:30 PM
remember not to let the unibit get too hot. I just used a 1 3/8" unibit to cut a 1" hole in seven peices of 1/2" steel for a rock rake for my tractor. The last hole was a bear to cut because I did not wait for the bit to cool between holes. But it worked quickly and did not have to use several drill bits.