Push broaches for square holes

I have several ¼ inch square holes to make in components, to fit shafts, and would like to use a broach for this. The only supplier I can find is MSC who charge north of £100. Does anyone know of any suppliers at more reasonable costs. I doubt I can justify £100 plus, and before anyone suggests filing, the holes are deepish and my filing, I don't think, is up to it.

It's certainly possibe to make your own broaches from silver steel especially that sort of size.

Clickspring did a reasonable video to get the idea.

**LINK**

regards Martin

Possibly a rotary broach as an alternative?

Also mrpete222 recently showed how to make a square hole without a broach.🙂

Clickspring’s video is typical of his skills. He makes it look easy, of course.

I've got a 1/4 sq push broach, and you're right they do cost north of £100 a kick. BUt if you would like to PM me with details of what you want done I'll consider doing same for a small fee to charity.

Quantity, material, length of hole, any orientation requirement, any thing else relevant. Can't remember the size of pilot hole offhand but approx 6.5 mm - it's slightly larger than the across flats dimension of the square hole. Broach cuts dead to size 0.250 across flats IIRR.

Where are you - I'm in W Glos UK. Forgive me if we don't meet up, present restictions as you know, but if you can post me the bits I'll make the hole and post 'em back

Best rgds Simon

A broach (push or rotary) is the best way to make square holes but the cost to purchase or time to make one could depend on how often it will be used. (different if you have deep pocket or plenty of spare time).

An option for just 1 or 2 holes is to drill a hole and file square. But my hand filing skills are not that good. Using a filing guide is an option to keep the file sqaure to the work (another one of those projects to do when i get round tu it)

You can also hold a file in the chuck of a mill or drill press to keep it vertical and use the quillt to move up and down.

Similar to this Youtube video by Joe Pie but an a bigger size: Square Hole

Paul

I have bought broaches from Steelman, in the past, they don't seem to have online ordering anymore but worth an e-mail they were cheaper than the DuMont ones from MSC

You are concerned that £100 is an excessive price. Examine carefully the item you would receive for that money and ask yourself if you could make something of equal utility for the same price. DuMont's site in the US is a good place to start to gen up on broach technology.

In addition, it may simplify your work, open up tooling options and ease the path of any tooling you do use if you can critically examine the 'deepish' nature of the holes. Consider what depth the actual square portion needs to be and any part that does not need to be square see if it could perhaps be made circular of a diameter equal to the across-corners measurement of the square.

Many years ago when I was an apprentice I had a job which required a square hole. This was achieved by drilling a pilot hole just undersize followed by marking out each side with the square shape. Corners were removed by careful filing and the the final square was achieved by using a 1/4 in square HSS tool bit as a broach. The "broach" being pushed through the hole using an arbor press.

And the material you need the holes in is ... ?

Tim

Edited By Tim Stevens on 08/02/2021 10:16:40

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Thanks to all those who have replied for their suggestions. I am surprised by the number of those who have taken the time. I need to make holes up to .75 inches deep in cast iron and steel. Clickspring's video is excellent, but I already have one piece of tooling to construct and don't want more I'm afraid. I want to concentrate on my project while I am still not too old to enjoy the finished article.

I will try the Steelman route, but suspect I will finish up with MSC and Dumont broaches.

Thanks again.

Martin

I've not used a broach but have looked at obtaining and using small ones, but only in steel. I think I would be very wary of using a 1/4 inch push broach in cast iron, I would imagine that there is a danger of fracturing a corner at the outgoing end.

I stand ready to be educated by those with experience.

Jim

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Quote from Simon Williams 3 - "Can't remember the size of pilot hole offhand but approx 6.5 mm - it's slightly larger than the across flats dimension of the square hole. Broach cuts dead to size 0.250 across flats IIRR."

Just checked my DuMont 1/4" square broach and the pilot hole size is inscribed '17/64"' (or 6.74mm). For preventing 'break out' damage on CI I have in the past used a sacrificial plate of aluminium. You do need a good arbor press with these broaches - using a vice or anything which is 'flexible' is guaranteed to break the broach.

Martin

You do need a good arbor press with these broaches

I use a hydrauic press for jobs such as this. Just a much easier alternative to the typical arbor press. I expect a ‘nominal’ sized hole would suffice for metals that are more easily machined than steel?

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That is true. When i was maintenance Electrician in a large Engineering works. They had Broaching machines. Pretty huge pieces of kit. Very robust. They all dragged the workpiece through the broach.

Steve.

Try the used tool and machinery dealers,or give Tracy tools phone call. I have cut a lot of keyways in cast iron gears and pulleys,no trouble with break out.I use a hydraulic press,cut cast iron dry,

You don't mention what machinery you have but consider looking for a slotting head for your mill if you have one. Will be way more than £100 for a broach but you will be future proof for any other sizes (and potentially shapes other than square going forward! It's a sad fact of life that time has to be expended either in making specialised tooling or setting up to use it - it's all part of the process

Paul

If you can keep the spindle of the mill from rotating you can use it as a slotter by chucking up an appropriate shaped cutter. The cutter needs a degree or so back clearance. Typical feed is a thou or two per stroke. Cut out one quadrant at a time. I used half a drill blank ground square at the end and having 1* back taper. Avoid making the cutting tool too large or you will have trouble pushing it through the work. My tool was about 3/16" square.