Gallery, Projects and General > How do I??

How do I machine a square hole?

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Mogas:
Ok Madmodders
Thanks again for the welcome.
This is my first information seeking post so please excuse my ignorance!
Attached (hope I get that right) is a crude and unprofessional drawing of a locking tail-wheel for our kitplanes.
The standard tailwheel steering block does not break away and castor. I devised a cunning plan to modify it so that it will disconnect from the rudder and castor when deflected more than 30 degrees from centre.
This works very well but here is the problem: Everybody wants one!
I would like to do as much of this modification as possible with my lathe, the best I can do at the moment is drill the 5mm hole in the 16mm spindle but then have to file it square by hand, this is the time consuming part! particularly when I have about 10 to make  ::)
First prize for me would be if I could machine this square hole blind and not even have to weld and re-turn it.
I hope that this makes sense.
Tools I have are an ordinary lathe and drill press. I hope to have a small milling machine soon.
Any help would be greatly appreciated.
Mogas

sbwhart:
Hi Mogas

Now this may sound a bit rough arse,  :whip: but one way you could do it is.

1:- Make a 5mm sqaure tool bit by modifying a bit of HSS, or file  one up from silver steel heat it to cherry red quench in water temper back to straw colour quench again.

2:- Drill your 5mm hole.

3:- Mount your 5mm square bit of steel in your drill chuck or tool post.

4:- Make shure everything is clamped up tight, and force the 5mm bit of square into the hole, this will cut a square for you.

I've used this method in bits of plate.

Have a few trial runs on scrap before you do it for real, try experimenting by putting slight releafe on the tool, or using your vice to squess the square into the work etc.

You didn't say what the material was you were trying to cut if its ally it should work like a dream steel a bit more dificult

Good luck

And have fun
 :wave:
Stew

PS There is nothing wrong with the drawing it communicated the mesage 1st class,  :thumbup: you should see some of our Crap O cads we post.

Stew

bogstandard:
Hi Mogas,

Just a little note to let everyone know that this isn't a site where anyone can get free development time.

This site is run for hobbyists, and as such is not into bulk production problems.

But just in case you are a hobbyist just trying to solve a problem, this might help a little.

Why the square pin?

If the nose is shaped correctly on a round pin, and the spring pressure is correct, it should automatically keep itself in an upright position whilst swinging the nose thru an arc. The problems arise if the recess it is fitting in has any straight sides, then the nose can tilt over, in which case you would require side guidance of the pin to keep it upright.

If you would require the pin to stay upright with the hole providing guidance, then the sketch below might be a possible solution for you. It can all be carried out with a drill press and lathe, plus a bit of filing on the pin nose.

You can easily develop it using a bit of scrap material, and once you have the correct sizes for the side holes (they shouldn't need to be very big), then it is just a matter of transferring it over to the original items.

P.S. the stabilising pin thru the main pin should be the same diameter as the small side holes, and the ends rounded over by hand to fit the small side grooves formed. Also, you wouldn't need to drill all the way thru, then weld it up, as you won't need to file the hole square

Hope this helps

John

Mogas:
Thanks bogstandard and sbwhart
John, I do produce these things for a profit and I certainly was not trying to pull the wool over anyone's eyes! I suppose you could call this free development time but in my defence your Honour I have to point out that I am sharing my ideas at the same time. 
In all seriousness I will stop this right here with this post if the Moderators so desire.
That would be a great pity as I have already seen a partial solution to this problem in your post John and would like to take it to bits a little further.
Watching with interest
Mogas

Bernd:
Mogas,

John has just given you a gentle nudge as to the purpose of this site.

That being said please continue.

Regards,
Bernd

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