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Step Drills?

CalG

Diamond
Joined
Dec 30, 2008
Location
Vt USA
Here is a question that has troubled me over the years.

What is the advantage to hole production when using a step drill over a single diameter tool?

I have many (not hundreds, but close) step drills from size #10 to 3/8" from my aviation days. They do make nice holes.
Much like a drill ream "dreamer" combination.

Why is that grind not a standard item?
 
Here is a question that has troubled me over the years.

What is the advantage to hole production when using a step drill over a single diameter tool?

I have many (not hundreds, but close) step drills from size #10 to 3/8" from my aviation days. They do make nice holes.
Much like a drill ream "dreamer" combination.

Why is that grind not a standard item?

Because you’ve stockpiled all available step drills, nobody else has been able to experience them and see the light? :-)

More expensive than conventional drills, since more grinding work and a lot more material?
I thought step drills are primarily for use on sheet metal and thinner stock.
 
When I first started to acquire step drills I considered them as sort of a novelty. I have found that on many occasions they are by far the best drill for sheet metal especially when enlarging an existing hole. They don't tend to grab and cut a good clean hole. This is aside from the fact that you get to start out with a pilot hole and work your way up to the limits of the drill without having to swap drills. Because of their design they are dirt simple to sharpen. This is one of those things that I would suggest if you have never used one then try it.
 
Come to think on it, I've got a couple step drill that have been undercut during the re-sharp. I hate those things in thin stock! Rattle around like rocks in a coffee can.
 
Aviation may be a pilot drill instead.

We picked some up at a ask shop near castle AFB in Atwater and the pilot starts on center then cuts the final.

Sharp and cut well.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
Last edited:
Aviation may be a pilot drill instead.

We picked some up at a ask shop near castle AFB in Atwater and the pilot starts on center then cuudes the final.

Sharp and cut well.

Sent from my SAMSUNG-SM-G930A using Tapatalk


Tony help me!

What word is intended where cuudes appears? ;-)

In this age of CNC tool grinding, Drills made from snoth blanks of HSS, cost and complexity can not amount to squat in regard to producing a step drill.

I will say this, step drill produce round holes in thin stock instead of those three lobe epitrochoids. ;-)
 
I am confused I guess. Are we talking a step drill like 1/4" to 5/16" making a hole an c'bore? Or the step drills for sheet metal that go from 1/8" to 3/4" or such, but each diameter is only .10" or so long? IMO, the latter are worthless for anything BUT sheet metal, don't see how they would functional for anything else....

But OP mentions a specific grind, so...?
 
I am confused I guess. Are we talking a step drill like 1/4" to 5/16" making a hole an c'bore? Or the step drills for sheet metal that go from 1/8" to 3/4" or such, but each diameter is only .10" or so long? IMO, the latter are worthless for anything BUT sheet metal, don't see how they would functional for anything else....

But OP mentions a specific grind, so...?

I was thinking the same thing.
We use some step drills that we get special ground for specific applications on production parts where we have multiple diameters in one hole location with multiple corner breaks etc...They work decent to speed up a cycle time by 15 or 20 seconds per hole at times which makes a big difference when doing multiple holes / parts. The down side is we dont do much tool sharpening in-house so there is the expense of getting them sharpened (which really isnt that much) but the biggest down side is when crap happens and for whatever reason you are sitting there without sharpened tools on hand when you need them. I would like to say that never happens....but regardless what system gets put in place it will eventually bite you in the butt.
 
Seems to me that they do make "step" drills in single diameters. I believe they call them gun drills. And they have their uses, but general purpose drilling is not one of them.
 
Seems to me that they do make "step" drills in single diameters. I believe they call them gun drills. And they have their uses, but general purpose drilling is not one of them.

Huh? How is a gundrill in any way a stepdrill?
 
Not familiar? I use step drills all the time for sheet metal work.

I did say "in single diameters". If you look at the tip of a step drill and the tip of a gun drill, they will be very similar. And gun drills will have a full diameter for at least 180 degrees around their axis. This full diameter helps to guide them. Step drills have a full diameter for around 270 degrees around their axis and again this helps guide them.

Seems to me that they are very similar except for that multi-diameter thing.



LoL! Apparently he is not familiar....
 
Yeah, there are step drills that look like Christmas trees, which are OK for some sheet metal work, and there are step drills that look like a regular jobber style drill bit, except they have a small pilot section that is still a drill.

I pulled a couple pounds of them, all sub-3/8", out of a surplus place years ago and still have some.

Sorta like the center drills for drilling a center divot on a lathe, except, well, regular length, normal looking drills, except with a stepped initial point.

The ones I got were almost all split point, and sharp, so they start a treat on the spot you touch them down to.

In a perfect world, they would grind something like that either as a machine reamer behind the point, or with a different number of flutes, to clean up those odd holes that seem to want to lobe out triangular, from the two flute tip in thin stock!
Would make drilling a couple thousand rivet holes a real treat!:ack2:
 
There seems to be a question as to just what you are referring to.

How about posting a photo of one or more of the bits you are talking about. Larger ones would be best.



Here is a question that has troubled me over the years.

What is the advantage to hole production when using a step drill over a single diameter tool?

I have many (not hundreds, but close) step drills from size #10 to 3/8" from my aviation days. They do make nice holes.
Much like a drill ream "dreamer" combination.

Why is that grind not a standard item?
 
In production it's pretty handy to have tap drill, body clearance and c'bore in one operation with one tool. The presumption being all details are pretty much concentric, co-linear and in the right relationship to one another.
 
I recently discovered step-drills with a lot of tools I purchased. I tried them on a job where I was drilling 3/8" holes by hand. Wow what a difference it made in both ease of drilling and time it took to drill to 3/8" in 3/32" material. Night and day.

Best Regards,
Bob
 








 
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