"drill" a Square Hole




This is a short vid showing how to make a quick and dirty broaching tool to make square holes.

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    46 Discussions


    5 years ago on Introduction

    having been thoroughly bored but impressed by the statistical analysis of static and dynamic material loads and strengths during my grad degree in physics...I would recommend that anyone unfamiliar to what can occur under extreme dynamic loads (since you slipped over some of the tedious of the 'heavy' work), should familiarize themselves by talking to someone with experience or at least reading about it. I've had my forehead sliced cleanly open by a shattering shard of tool grade steel that I was hoping to press into a brass plate but in retrospect might have misjudged the size of hole required by a few ten thousandths.... But if you live through it, (and don't get so scarred that you can never be gainfully employed...but that's a DIFFERENT story!...), then you will learn a new skill and go on to self betterment.

    I would have loved to seen the entire 'boring' process (forgive the shop humor). But it would give better understanding of just what the stresses are and if a person wants to risk it in their own shop at their current experience level.

    -scarred and impressed... Thanks.

    1 reply

    4 years ago on Introduction

    I've been on intructables for a while now, and I'm getting pretty tired of self-proclaimed experts nit-picking every instructable they read. I read this one and found it interesting.

    I too noticed the speed of the drill, but so f$%king what?

    If you have a compliment, great. A legitimate question, great. But rather than tell an author how wrong they are, via the comments section, send them a private message, or even better, write your own instructable!

    So my question is....

    What do the grooves in the broach tool do for you. What happens if you don't cut them in?

    1 reply

    Good Question!

    It's like the hex hole instructables, the broach just mashes through the steel and it makes the hole nasty. If you cut nice sharp grooves then each groove takes a little cut out of the steel and leaves a nice crisp hole. Sort of like tiny nibbles instead of a big old bite...

    Also, if the material is thicker, you'd never get the tool through because you are trying to remove too much material in one go.

    Hi Rick,

    To file a square, slide fit 3/8" hole would take considerable, practice, care and patience. I'd like to see you do it, as a comparison. Please post a vid if you do.



    5 years ago on Introduction

    Notes to all. I have 30 years experience as a job shop and ship yard machinist. The drill speed was actually about right for drilling mild steel with a coolant medium. The chips come when the speed and feed is right and you get long curly shavings when it is wrong. I knew immediately that he had used a coolant...steel on steel does not smoke!

    If this sort of thing breaks your little hobbie vice then you need to upgrade to better tools. I use my steel vice as a press all the time and did so in the shops as well. The deep socket was a great use. I guess he COULD chuck up a piece of 4140 heat treat in a lathe and make something to do that job but if you are only doing this once or twice a socket is great. Good steel and generally hardened and tempered.

    I have actually done this and made my own broaches the only difference being that I made my broach and then hardened it and tempered it. I ground it on a die grinding machine and it was perfectly sized to + or - .001" and used for making broached holes on a drilling rig.

    You can broach a hole in hardwood but it needs to be made with a more aggressive bite. Look at the difference between a hack saw and a wood saw. The only safety thing that I would add to this is to make SURE that you wear good safety glasses. I never saw his face and assume that he was so GREAT ibble!

    1 reply

    5 years ago on Introduction

    arduinoversusevil, I'm glad you showed us the overall process, but I think there are a couple points you might consider.
    1: Explain the options a person has a little more. For example, you can actually drill a square hole with an oscillating 3 fluted tool like:
    2: If you're going to point out the fab of a square broach, you might point out the key considerations a person should have, such as taper angle, material, jugs for grinding etc.
    3: If you want to make sure that your broach goes in straight, you need a collet. A square broach makes it more difficult, but you can make one out of 2 pieces of stepped aluminum that hold just the top.

    But otherwise, I congratulate you on solving a problem that most would throw their hands up in the air over.

    5 replies

    Reply 5 years ago on Introduction

    Thanks! I wish it was mine. But I can't take credit.
    I found this a while ago. I have a Bridgeport Series 1 and it would be nice to have this adapter for making switch panels for square bodied switches.

    Hi PK,

    You'll note that it is a cartoon. Not real.

    It would work in your BP, but never in a million years with a hand drill.


    5 years ago on Introduction

    No, drill speed too fast, no flood coolant, or even a shot of lubricant during the procedure.


    5 years ago on Introduction

    You forgot to SHOW how to make the broach. Once you have the broach the rest follows.

    Thanx Much, Dutch


    5 years ago on Introduction

    I always wondered how that was done. Now do a video on making the broach! Thanks to the poster who mentioned the drill bit-chisel for wood. Learned something there, too! Thanx!


    5 years ago on Introduction

    The perfect example of how to ruin the thread on a vice. They are intended for work holding, not crushing!

    2 replies

    Hi Smelter,

    Indeed, rules is rules? You're aware that there is a shear pin retaining the nut that is designed to fail if the designed clamping force is exceeded?

    Yes I am aware of that pin. I have also met in my working life, a number of vices that have the thread worn out just in one spot!