Thread: Drilling 30mm hole through 10mm plate

Good quality hole saw, lubricant, and correct speed. How many do you have to do?

Ray

Step drills are intended for sheet metal only.

I will not say your task is impossible, but I would suggest it is pretty close. I think it would be very difficult and expensive. The only option as far as I know would be a core drill. I don't think your drill press would have enough power to do this job.

It would be cheaper and easier to get somebody with the proper equipment to do it. The other option is to drill a circle of small holes then file to size.

Dean

Use a hole saw with very light feed. Withdawl regularly to remove swarf and liberal lubrication. I recently drilled a 32mm hole in medium carbon steel 30mm thick. Just took some time.

Simon

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Originally Posted by Stephen H

Hi everyone. What's the best method for drilling a 30mm hole through a 10mm thick piece of 250mmx200mm steel?

While researching the problem I discovered the existence of step drills (and there's one that goes to 30mm!), but I suspect they're only for sheet metal.

What do you guys think? Would a step drill work, or is there a better way?

(Difficulty level: Cheapo Bunnings bench drill)


Stephen.

How close to 30mm do you need?

Simplest solution for you is probably to bring the piece of plate to me down the Channel or find an engineering shop up town. My Arboga drill could do it in one pass but I don't think I have a 30mm drill bit. 1.25" maybe.

Doing it on a Bunnings drill press - not going to work. Even if you buy all the bits that drill press won't go slow enough or have enough torque to get the job done.

As Ray said, good quality hole saw is your other best option. Lots of lubrication. Slow speed.

PDW

PDW

Build a nice little dam around the hole with blu-tak or similar and fill it with lubricant.

Hole saws can get really nasty. Experimenting a few weeks ago I had one release my Jacobs Taper on two different chucks. Slow speed is absolutely key (as the others mentioned). I drilled (using a Sutton reduced shank drill) some 24mm holes a few weeks back in mild steel to a depth of 80mm. Was not bad at all with coolant and running a slow speed. The chips came out beautifully. The key is the speed and coolant.. I then used a boring head to take the hole out to the finish diameter. I know you are limited to a drill press, but a hole saw will give you a nasty and likely oversize hole. You could possibly investigate a Rotabroach drill/cutter but I have no experience with them. Some swear by them for larger diameter holes.

My vote is for you to take it to PDW..

IMG_5607.JPG

Edit: The more I think about it I am not sure a Bunnings drill press will have the torque needed to turn a large reduced shank drill. Hole saw may well be the only option..

What Variant22 said, go meet PDW, with a suitable drill bit. That could be expensive, check eBay et al and a bit made by a reputable manufacturer, even if old and in need of sharpening could be much better than some no name drills made from who knows what, but new in a box. Pete knows how to sharpen drills!
Rob.

another alternative but they have gotten a bit expensive since i bought mine http://www.practool.com/super-drill.html

That super drill looks awesome......

The 'superdrill' is exactly what I was going to suggest. I've nearly worn mine out...
hey should not be that difficult to make.
I think on the strength of this thread, I'll take measurements tonight and make a sketch. I think everyone should have at least one size of these.
They are actually a two-step piloted adjustable boring bar, not a drill at all. They work extremely well in a drill press.
Until later on - right here.

Originally Posted by jhovel

The 'superdrill' is exactly what I was going to suggest. I've nearly worn mine out...
hey should not be that difficult to make.
I think on the strength of this thread, I'll take measurements tonight and make a sketch. I think everyone should have at least one size of these.
They are actually a two-step piloted adjustable boring bar, not a drill at all. They work extremely well in a drill press.
Until later on - right here.

These "Super drills make good sense, They seem to be a simple but good alternative for drilling large holes.
regards
Bruce
ps Like Joe mentioned should be easy to make.

Wow, some great advice.

I'm thinking my Bunnings cheapo bench drill isn't going to like a hole saw, so it look to me that my choice comes down to having someone else do it (thanks PWD - and to answer your question 1.25" would work fine), or investing $99 in one of those suspiciously magical Superdrills.

I gather from the Superdrill website that 1/2hp at 300RPM is preferred, but my Bunnings cheapo seems to be just under half HP at 0.47, and minimum RPM is 580. Anyone think that's close enough?

My preference is to do it myself (oh, and accumulate another tool in the process...), but I'm not going to be stupid about it - if I've got to take it to a shop, then so be it.

Originally Posted by Stephen H

Wow, some great advice.

I'm thinking my Bunnings cheapo bench drill isn't going to like a hole saw, so it look to me that my choice comes down to having someone else do it (thanks PWD - and to answer your question 1.25" would work fine), or investing $99 in one of those suspiciously magical Superdrills.

I gather from the Superdrill website that 1/2hp at 300RPM is preferred, but my Bunnings cheapo seems to be just under half HP at 0.47, and minimum RPM is 580. Anyone think that's close enough?

HP wise that is OK but I personally think 300 RPM is a bit fast, (I would use 200) but that is just . At 600 RPM wise you might just end up blunting the cutters..

Here it is - as close as I can make it to mine.
The Hex shaft is a mod - based on the shocking wear on mine. Cutting bigger holes is a struggle for a 1/2" chuck to hold this thing. I you can, make it hex. My original tool is mild steel. A better tool steel one would last longer. Case hardening would be even better.

I'm going to have a go at making a new one as well now. I intend to drill the two tool steel holes 6.35dia and then make a crude broach out of some 6.35 square tool steel (turning one end to 6.35 in a 4-jaw chuck and turning a taper from there to maybe 10mm from the other end. Then use my T&G grinder to make some teeth on all 4 sides along the taper). Then push the broach through the hole in my little press with cutting fluid.

By the way, I think the bottom cutter would be better at 4.8 or 5mm square - I have had the grub screw let go because the thread is a bit too short. Both cutters should be HSS.

In use, you drill a 12.7mm hole on the drill press, then swap for this tool and adjust the stick-out of the bottom cutter to the required radius between 12.7 and 25.4. If a bigger hole is required, then set to 12.7 radius and bore through. Then adjust top cutter to required radius.
Put moly grease on the piloting section and use cutting fluid for the cutter. Feed slowly. When you get a continuously curling swarf coming out of the hole, you have hit the 'sweet spot'.

The kit was/is available with bushes/spacers for larger holes still, but in my view the drive spindle diameter is too small for holes over 50mm and a 1/2" drill press not powerful enough.
If you find this useful for bigger sizes, make a bigger one for your mill!