|Steve Withnell||19/04/2019 09:43:28|
796 forum posts
I need to make two holes in copper sheet, nominally 22mm. Nominally, because I want the hole to be a push fit for a selected piece of 22mm copper waterpipe.
One sheet is 1.5mm thick and 55mm diameter overall and the other 3mm thick and 105mm diameter. (If you read the same magazine that I do, you will know what this is for )
My plan was to sandwich each sheet between two pieces of 18mm ply and clamp it down onto the mill table, then drill out to 19mm. Then use a boring tool to creep up to the push fit diameter.
The questions - is this the best way of achieving the goal? What do I need to manage to ensure a nice clean hole and what spindle speed should I run the boring tool at?
|John Olsen||19/04/2019 10:49:55|
|1028 forum posts|
I would probably use a hole saw for the initial hole, still using the bits of ply as you intend. Ordinary drills are not always very good on sheet metal. Otherwise a step drill or a conecut would make a better job on sheet metal than a normal drill, but they can be a bit expensive if you don't already have one.. Using a boring tool, either a boring head in the mill if you have one, or boring in the lathe should be a good way to get the final size. Take it gently with all the work, copper can be a bit grabby at times.
|Don Cox||19/04/2019 10:55:12|
|48 forum posts|
A search of eBay "Holesaws" turns up loads of suitable 22mm cutters for about £3, use the clamped ply idea to keep it all flat and try a nice slow speed to start off with.
|vintage engineer||19/04/2019 11:09:35|
247 forum posts
Q Max punch will give you the neatest holes.
|not done it yet||19/04/2019 11:15:26|
|4497 forum posts|
Adjustable tank cutter? Or Qmax type (may not be rated for 3mm and the ‘nominal’ size may not be quite as ‘nominal’ as you might want) Nominal size of 22mm pipe may not be quite 22mm exactly, but could be swaged to fit? I clearly don’t read the same mag as you, so no idea how far you might want to push this pipe through the hole.
The methods suggested above but I think I might cut into something more robust under the sheet.
|Paul Lousick||19/04/2019 11:38:52|
|1373 forum posts|
Step drills are designed for making holes in sheet metal. Available is a range of sizes. Drill to nearest hole size and finish by hand with a round file if necessary. (Hole size can also be enlarged with a taperred reamer).
Edited By Paul Lousick on 19/04/2019 11:46:36
4402 forum posts
Clamp it to the faceplate in the lathe and trepan it with a parting-tool-like trepanning tool then finish to size with a boring bar? Or avoid trepanning by drilling a small hole in the middle and facing outwards with successive cuts to near the finished size then bore to finish.
Spindle speed? 400rpm or so should do the job.
Edited By Hopper on 19/04/2019 11:45:38
|Steve Withnell||19/04/2019 13:18:03|
796 forum posts
Thanks folks. I've so much going on I'd forgotten I had a set of step drills, if they won't go all the way, I can use a boring bar to get to a push fit with the pipe. The pipe is very short (it's not a plumbing job) around 20mm and needs to be a precise fit, which is why I thought about teasing out to size with a boring bar.
|Neil Wyatt||19/04/2019 14:22:30|
17714 forum posts
Step drills are ideal for this sort of job and much under-rated. As thyey have no rake they are less likely to grab, but do secure the work.
|Guy Lamb||19/04/2019 17:31:19|
|85 forum posts|
I too would use a tank cutter, perhaps sandwiching the work piece in between a couple of scrap copper to minimize
any burring. Hole saws tend to 'rag' when cutting copper I've found.
|Jon Lawes||19/04/2019 20:20:48|
370 forum posts
Q max would be my vote too, even home made.
|Phil Whitley||19/04/2019 21:05:10|
1147 forum posts
may not be suitable for your purpose, but if you drill a smaller hole for a length of threaded rod, and the select a couple of sockets from a socket set, the smaller having the external diameter of the hole you want, and able to fit inside the larger with a reasonable ammount of clearance, assemble them onto the threaded rod with one socket on either side, and tighten the nuts thus forcing the smaller socket through the sheet and into the inside of the larger one, you will find you can form a very usable socket into a flat sheet. I have done this in steel, aluminium and copper. Anneal it first! you could even turn up a couple of dies on the lathe, but I have found that sockets work just as well, provided you can find the correct diameters.
|John Reese||20/04/2019 03:19:05|
|836 forum posts|
I have a set of these:
They work really well on sheet metal. For brass I had to dub the points. They will probably work as is for copper. Expect the holes to be a bit oversized due to runout of the cutter.
|Boiler Bri||20/04/2019 08:59:15|
832 forum posts
I use rotabroaches. They quite cheap on fleabay. You have to have a 3/4" collet though. They cut very accurate holes.
Edited By Boiler Bri on 20/04/2019 09:00:30
|Michael Gilligan||20/04/2019 09:14:00|
15470 forum posts
Interesting to note that they also do 'Mini Cutters'
|Former Member||20/04/2019 09:34:09|
[This posting has been removed]
17841 forum posts
Step Drill for me, think the one at the back in this photo was 16mm, if you need a really accurate fit then do the last step with the boring head - sharp tool sped as you would if turning 18mm dia in teh lathe but may have to be less if the head is off balance.
|Nigel Graham 2||21/04/2019 21:21:18|
|585 forum posts|
Steve's question shows the hole has to be quite accurate.
Whilst a hole-saw will rough out the bulk of the metal, even the rigid-bodied type will NOT give an accurate hole! They are not designed to do that, they leave a rough-walled hole, and tend to run eccentrically. Also, most of the readily available ones are sized for standard water-pipe and electrical conduit material in applications not needed a close push fit.
The older type of hole-saw, consisting of a ring of bandsaw-blade clipped into in a groove in the face of a large bush, is even less accurate.
Do use hole-saws, but be aware of their limitations, and use one generously under-size to leave accurate finishing by the various techniques described above.
A step-drill in a decent machine-tool may give the fit you need for the particular work-piece: try on an off-cut first.
A cone-drill can be used with care to give a tight fit, but obviously the hole will be tapered and diameter control is difficult. The significance of the taper will be controlled by the material thickness and the fit required.
Step-drills and cone-drills are not desperately costly from places like Screwfix and Toolstation (which also sell hole-saws), and very useful tools indeed. Assuming appropriately matching diameters of work and tool and the fit requirements, they can leave a finished-size hole needing no more than as the drawings say, removal of burrs and sharp edges.
I use all of the above for various tasks, obviously depending on material and purpose, and have even roughed out holes through thick plastic with a hole-saw, though that was somewhat fraught process as the tool is really intended for thinner and slightly harder materials than an inch of soft thermoplastic (PVC)! I did that 'cos I wanted to keep the central slug as bound to come in handy one day...
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