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1st March 2014, 03:23 PM #1Member
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Drilling 30mm hole through 10mm plate
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.
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1st March 2014, 03:39 PM #2
Good quality hole saw, lubricant, and correct speed. How many do you have to do?
Ray
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1st March 2014, 03:43 PM #3
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
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1st March 2014, 04:10 PM #4GOLD MEMBER
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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
Sent from my GT-I9195T using TapatalkGirl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.
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1st March 2014, 04:13 PM #5SENIOR MEMBER
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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
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1st March 2014, 05:01 PM #6Tool addict
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Build a nice little dam around the hole with blu-tak or similar and fill it with lubricant.
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1st March 2014, 08:13 PM #7SENIOR MEMBER
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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..
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1st March 2014, 08:43 PM #8SENIOR MEMBER
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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.
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1st March 2014, 08:47 PM #9SENIOR MEMBER
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another alternative but they have gotten a bit expensive since i bought mine http://www.practool.com/super-drill.html
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1st March 2014, 09:05 PM #10Senior Member
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That super drill looks awesome......
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1st March 2014, 09:28 PM #11
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.Cheers,
Joe
9"thicknesser/planer, 12" bench saw, 2Hp Dusty, 5/8" Drill press, 10" Makita drop saw, 2Hp Makita outer, the usual power tools and carpentry hand tools...
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1st March 2014, 10:15 PM #12GOLD MEMBER
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1st March 2014, 11:44 PM #13Member
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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.
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2nd March 2014, 12:13 AM #14.
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2nd March 2014, 12:52 AM #15
Superdrill Drawing
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!Cheers,
Joe
9"thicknesser/planer, 12" bench saw, 2Hp Dusty, 5/8" Drill press, 10" Makita drop saw, 2Hp Makita outer, the usual power tools and carpentry hand tools...
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