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Square peg in a square hole

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Wolfie03/02/2011 23:20:58
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502 forum posts
Ok heres one. How the hell do I drill a square hole??
 
A blind one too. OK I could see the method of putting a file through a round hole and filing it square but that ain't gonna work for a blind hole.
Gray6203/02/2011 23:37:45
1058 forum posts
16 photos
I think the best way to go for this is with an EDM machine. There are many designs out there ranging from the simple to the ludicrously complex.
 
Another solution is to use a slotting device in your lathe, Hemingway do a kit for such a device and with a little ingenuilty one could be produced without castings.
Nicholas Farr04/02/2011 00:01:54
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3988 forum posts
1799 photos
Hi Wolfe, there was an artical in ME issue 4285 vol 197 which you can view on the digital archives if you are a subscriber.
 
Regards Nick.
NJH04/02/2011 00:25:57
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2314 forum posts
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Hi Wolfie
 
Go to All topics at the top of the page and enter "Square Hole" in the" keyword box" of the Search for: strip. You will find this subject has been discussed exhaustively!
 
Cheers
 
Norman

Edited By NJH on 04/02/2011 00:26:45

chris stephens04/02/2011 00:31:36
1049 forum posts
1 photos
Hi Wolfie,
First of, what do you need a square hole for? There is an easy method using inserts but it depends on the final use as to whether it will work for you.
chriStephens
John Olsen04/02/2011 06:16:21
1294 forum posts
108 photos
1 articles
Depends partly how big the hole is too. For nice small ones, you may be able to get away with drilling a round hole, then driving in a square cutter, made from a piece of HSS. Just grind the end a bit so that the corners stick out a little, then line it up and drive it down the hole. This should be OK up to about a quarter inch square. There will of course be a bit of a daggy bit left in the corners.
 
There is a technique with a sort of triangular drill guided by a square plate.The drill has to be in a floating holder so it can get into the corners. It can't actually produce a perfect square but is close enough for practical purposes. I haven't tried that one myself, but it has been in hte ME more than once over the years.
 
Then you can make a square hole that goes right through a round piece by filing, then braze the whole piece into a round hole in the job.
 
regards
John
Wolfie04/02/2011 08:03:56
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502 forum posts
I need to make something to wind a clock thats lost its key, so quite small.
 
Actually on reflection I don't suppose it has to be blind... Mind you I don't have any files that small.

Edited By Wolfie on 04/02/2011 08:05:10

Andrew Johnston04/02/2011 08:46:54
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7061 forum posts
719 photos
If the part can be mounted in a lathe (which I guess a clock key could be) try a rotary broach:
 
 
Caveat: Never used them myself!
 
Regards,
 
Andrew
Michael Cox 104/02/2011 08:59:38
555 forum posts
27 photos
If you want to make a clock key then I think you could easily form it. For example, if the key is 2 mm square it has a circumference of 8 mm. Take a piece of thin wall tube with about the same internal circumference = 8mm/PI =2.5 mm. Tap a piece od 2 mm square bar into the tube and it should deform the tube to a square shape. It will be a tight fit and to remove it then gently hammer the external faces of the tube and the 2 mm bar should come out. Then braze or solder a handle on the square tube. You may have to anneal the tube during the forming operation to prevent it splitting.
I have made hexagonal steel sockets by this means - see:
Hope this helps
Mike
NJH04/02/2011 09:52:06
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2314 forum posts
139 photos
Ah Wolfie
 
I know it may go against the grain of this forum but for a clock key I wouldn't consider making one. They are readily available in pretty much any size you may need and certainly for much less than you would pay for any specialised "square hole cutting tool"
 
Try here :-http://www.m-p.co.uk/
 
Regards
 
Norman
DMB04/02/2011 11:03:52
1585 forum posts
1 photos
SMEE stand @ an XBN. possibly within last couple of years, they were demonstrating a method of making square holes in round bar. I think it involved milling out a `trench` down one side, deep enough to end up central in bar then filling in outer edge with a piece silver soldered in, leaving a square hole in the middle. This would `do` for larger jobs requiring strength. Just mentioning this for future ref if anyone needs a strong job, but above method with deformed tube should be sufficient for clock winding.
chris stephens04/02/2011 11:31:16
1049 forum posts
1 photos
Hi John,
That would be my little display that you saw.
 
Wolfie, have to agree with NJH, although easily made there are occasions when it is better to buy, unless you need an excuse to "play". If you are going to play, as Clock keys are often made from Brass, drilling deep and filing would work well enough.
chriStephens
 
Richard Parsons04/02/2011 12:06:37
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645 forum posts
33 photos
The problem with drilling square holes is that the holes are not truely square. They have round corners'
Ian S C05/02/2011 10:50:16
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7468 forum posts
230 photos
A good many years ago I made a device for winding clocks that involved a quite large reduction ratio, and just today I was visiting the son of the chap I made it for, so I had a look to see how I had done it, and found that I had used the method advocated by chriStephens, the slot was either 5/32" or 3/16" can\t remember which, does\nt matter now, but it worked well, the old boy had quite a number of clocks. He was an electrition, should have collected electric clocks, would have saved the winding.  Ian S C

Edited By Ian S C on 05/02/2011 10:51:52

Polygon07/02/2011 16:27:37
2 forum posts
Wolfie, what size is your hole?
 
At Polygon Solutions Inc. we make a rotary broaching system which will create square holes with sharp corners in metal parts up to about 1" diameter in through or blind holes. The tools work on lathes and mills, but will realistically only broach to a depth about 1-1/2 times the diameter.
 
Learn more at http://www.polygonsolutions.com or see our video:
 
 

Edited By Polygon on 07/02/2011 16:31:20

NJH07/02/2011 16:57:07
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2314 forum posts
139 photos
 Very interesting Polygon - but not a very cost effective solution  to produce just  one clock key!

Edited By NJH on 07/02/2011 16:57:44

Edited By NJH on 07/02/2011 16:58:05

Polygon07/02/2011 17:06:48
2 forum posts
Great point! I tend to lean towards high production mentality. Some machinists have used the broaches by themselves as more of a punch or shaper. This gives you a precision form, but saves on the larger cost of buying the toolholder. I guess if you do small projects like this regularly the cost of the toolholder would make more sense.

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