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Independent Tool Review
by Peter Brett - November 2005
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01444 440188
G and J Hall's Powerbor Stepdrill
Several Steps in the RIGHT Direction
One of the difficulties with trying out specialized equipment is that I have to find people and situations that I can ask to help me with facilities and scenarios that will provide an accurate reflection of whatever tool I am reviewing. I was therefore very pleased to accept the invitation from G and J Hall to visit their factory in Sheffield and try out their new range of step drills in their testing facility. They were very careful to leave me alone to try out the products, but most of all I was pleased to be left with some large sheets of 25mm and 12mm thick steel in which to drill as many holes as I wanted. I was also given the free use of one of their renowned POWERBOR Electromagnetic drilling machines to treat as hard as I liked.
The stepdrill is not really a new idea. It has been used in various guises for a while now. Most independent electricians and plumbers probably have one in their toolkit for enlarging holes in thin sheet material. Most recently, the technology has been tried for steel erectors, people who need to drill biggish holes in substantial steel structures. G and J Hall’s take on this was to enlarge the smaller step drill used by plumbers and electricians and modify it with some unique, patent pending, features to enable it to work in really demanding drilling applications of the type that steel erectors would encounter. The result is a really successful tool that is easy to use, does not demand anything than simply buying the correct drill (No extra expensive technology to buy), and brings a versatility and convenience when drilling steel plate.
The POWERBOR step drills are available in a wide range of sizes that will cover all current applications and provide for a whole lot of newer ones.
For drilling a maximum of 12mm thickness the sizes range from 8mm to 48mm. Each drill has 5 steps on it, so the buyer can go from 8mm, 10mm, 12mm, 14mm and 16mm in the smallest size drill to 40mm, 42mm, 44mm, 46mm and 48mm in the largest, follow on, size. The drills in between cover the rest of the diameters in 2mm steps.
For thicker 25mm steel the steps have to be further apart and therefore there are only three steps per drill. Nevertheless, the range still covers all the hole sizes from 10mm to 50mm in 2mm steps, but there are a few more drills to choose from.
For users who still need Imperial sizes, roughly the equivalent range of sizes is available, but the steps are in 1/16 of an inch instead of 2mm. Some of the drills are “starters” in that they have pointed ends that will indeed start a hole and drill it through the steps. As the holes get bigger it is clearly not a good idea to start a hole using a step drill with a point. It is far more efficient to use a normal annular cutter and then use a “follow on” cutter with a blunt end to find the centre and then drill out the hole to the required diameter.
I admit that I showed the drills of all types no mercy. In the time I had available to me I drilled constantly, pausing only to change the bits when I needed to try out different tools. First of all I was amazed at the sheer efficiency and controllability of the POWERBOR step drills. Virtually the only hard part when you start with a pointed drill is getting through the first step. This usually takes about 3/4s of the time of to drill, the rest of the steps are literally completed in seconds. For example, drilling 12mm steel starting at 10mm diameter, it took about 45 seconds to drill the first hole. Then, in just 15 seconds the hole could be enlarged to 18mm. I only needed to use finger pressure to achieve this feat. The POWERBOR bits are coated with a special blue coating which gives the tool a long life even when the use of lubrication is not possible. For users suspended from a high steel frame this is particularly time and irritation saving. I noticed a small difference in time and ease when using drilling lubricant, but at the end of the test, there was no significant sign of wear on the drills, and the cutting edges felt ready for drilling a lot more holes.
I had a similar result using a “follow on” drill. I started from scratch drilling a 30mm hole with an annular cutter, I then changed the cutter for a 30 to 38mm step drill and enlarged the hole to the maximum 38mm. The whole operation, including changing the bit, recentreing and finding the grubscrew I dropped when changing the bit, took only a shade over two and a half minutes. This very large diameter hole was also achieved using only the standard POWERBOR PB32 electromagnetic drill, showing that end users may not need to invest in more powerful kit, because step drills don’t need as much “oomph” as ordinary cutters.
Clearly there are some other advantages to these step drills. Just like their smaller counterparts they can be used to rectify holes that are out of line for some reason. They are also much more rigid than standard shape twist drills, and can be used supported in an electromagnetic drill. This means that they have the support needed to drill accurately. Held in a chuck, a twist drill may not achieve such good results or may indeed break.
Drilling through stacked plates is also a complete doddle using the POWERBOR step drills.
In my mind I have rather unfairly associated G and J Hall with making only annular cutters. In truth, their product range is much wider and covers the requirements of many trades. All the drills are made in Sheffield and it is clear that they pride themselves on the quality of their manufacture. So, if you are thinking drilling, think of G and J Hall cutters. You could find some useful solutions in their range of products.
Independent Review by Peter Brett
Airstream Communications