How do I drill square holes ?

Parts of my Pansy require square holes, the usual suppliers don't have square drills so apart from using a square file and hoping for a good outcome is there a better way of doing it ?

Phil,

Sorry, I will have to make this quick ... [off to the Dentist ]

look at Broaching, and at the various Slotting Attachments.

... or invest in a Shaping Machine.

Many ways to skin a cat.

MichaelG.

.

P.S. ... Filing out a round hole is a very honourable way of doing the job. [Watchmakers have been doing it that way for centuries.]  ... But do not try using a square file; or you will never succeed.

Edited By Michael Gilligan on 22/10/2014 09:22:45

Phil I wouldn't consider a square file use a triangular one to get into the corners

I seem to remember an article in the distant past on drilling square holes

Roy

Roy,

This youtube video maybe of interest to you.

https://www.youtube.com/watch?v=rjckF0-VeGI

Martin P

Phil, unless you are going into mass production, you would be best with the triangular file, or you could make a suitable broach from either silver steel (harden and temper), or grind one up from HSS, and use the lathe as a shaper.

Ian S C

Hi

One method you could use is Wobble or Rotary Broaching which will cut a variety of shapes. Mike's workshop shows a relatively easily constructed system for the lathe and the principle is shown in this wikipedia article under rotary broaching. I believe that this has been covered in the past in this forum and had a feeling that there may have been an article in MEW but that may be my grey matter confusing things.

Cheers

Martin

Could you explain how to use the lathe as a shaper, in this respect, Ian please?

Hi Jack

I suspect that Ian is suggesting that you mount the item on ( say) the faceplate and lock the spindle, fit an appropriate tool in the toolpost and rack the saddle back and forth applying the cut with the crosslide. OK method for light cuts ( and infrequent use as it is a bit tedious!).

Regards

Norman

Phil,

What sizes are the holes, and what thickness of what metal are they in? Are they through-holes or blind?

I made a lever arrangement to rack the top-slide, to save wear on the saddle gearing. The second photo shows it in use cutting a test keyway in what would be a pulley. There are many versions of this accessory, mine was made up from the scrap box.

For a square hole, I think I would mount a cutting tool with a square corner pointing to the lathe centre height and index the work. Taking light cuts should get the job done. If you mounted the work in a 4 jaw you could use the jaws to index the work.

Is a complete square necessary? or could just enough metal be removed to locate a square shaft by its corners in a larger hole.

CotswoldsPhil

Stan Bray used to champion a very simple way to get started. Mark out the square with its diagonals. Drill holes about 1/5 of the full size of the square accurately in each corner. Now drill a central hole of diameter that of the full square. This will just cut into the smaller holes, so take it easy. You can make the drills slightly undersize for a less stressful life.

This will remove most of the metal and make finish filing or broaching much easier than just a central hole.

The diagram shows the small holes as 1/5 of the larger one, I'd probably use a bit smaller.

Neil

Neil - thanks for that tip. This is where we are going down hill rapidly, a wealth of information held by a relatively few people which isn't being passed down, or there is no way to easily pass it down. We will soon no longer be model engineers but instead be shaman !

Some good stuff here thanks. The square hole is 5/32 square by 3/16 deep and goes through - not blind. Which technique would be favourite ?

.

Very philosophical, Fizzy ... and all too true !!

This forum should be a good way to easily pass some of it down [if only we could get some better "system" into the idexing of posts].

Here is my slight embellishment to Stan Bray's wisdom [and Neil's illustration]:

Assuming that it doesn't matter for other reasons ... it's worth moving those small holes outward a little, so that they provide relief at the corners of the square. It makes the filing job much easier.

MichaelG.

Hi Phil,
Some time ago there was this thread on making an hexagonal hole. some of the suggestions there may help you. On the 7/7/14 I made a suggestion on that thread which may solve your problem. You could make the tool out of silver steel and heat treat it.

Les.

.

Phil,

I don't think you have yet told us how many, and in what material, but; it looks like an ideal job for broaching.

Here is a good description of broaching square holes, using the Watcmakers Staking Tool. ... You could, of course, use any reasonable makeshift approximation of the staking tool.

MichaelG.

I am looking at 1 hole in steel. I like the 5 hole approach for bigger square holes but I think for me the corner holes, at under 1mm, are too small for success. At the moment I am thinking of a tool made from silver steel which I push through a central 5/32 hole with my vice. Appearance doesn't have to be perfect as this bit is on the regulator buried inside the (huge) dome, the regulator rod, with a square end, from the cab engages in it

First drill a 5/32 round hole. Then, from a piece of 5/32 square silver steel turn up something like this on your lathe. Harden and temper it, and push it through the drilled hole.

Edited By Gary Wooding on 23/10/2014 08:16:44

Edited By jason udall on 23/10/2014 09:10:10

Phil,

Gary's excellent sketch shows a suitable tool very nicely.

I would, if I may, just add a couple of points of clarification.

1. You will see that it is turned with a slight "countersink" ... this is especially worthwhile when cutting steel, because it gives some positive rake to the cutting edges.
2. You may have a problem with the chips building-up and jamming ... because there is negligible clerance between pilot and hole.

Definitely worth a try, although I suspect that a slight variation may be required because of (2)

MichaelG.

.

Edit: note that the Staking Tool avoids the need for a  pilot.

Edited By Michael Gilligan on 23/10/2014 09:40:21