Drilling/boring an angled hole through a cylinder

[andyf]

I'd welcome ideas on how to set up a cylinder (OD 20mm, 40mm long) to drill and bore a 15mm hole through its length. The awkward part is that the axis of the hole is at an angle of about 5^o to the axis of the cylinder; see C-o-C below, showing the thing in longitudinal section and an end view. All I can think of is to put the cylinder in the 4-jaw, with packing of the same thickness at the outer end of jaw 1 and the inner end of jaw 3, before drilling the hole.

No great accuracy is needed; I'm helping a friend with who is fitting new double gates. The pins on the "crooks" (L-shaped things) mortared into his gateposts are several mms smaller than the gate hinges which drop over them, so sleeves are needed. One crook is bent 5^o off vertical, and the skewed sleeve will help. He doesn't want to risk loosening the mortar fixing or damaging the (stone) gatepost by trying to straighten the crook, which would need some heat and force.



Thanks in advance,
Andy

[DMIOM]

Andy,

If you're making these from solid, then you should be OK drilling; if you're opening up an existing sleeeve then I would worry about a drill grabbing and would be inclined to bore rather than drill.

Holding it - assuming you have a mill, if you don't have a tilting vice, I would pop it between a couple of small V-blocks in the ordinary vice and then just kick it off to the left or right to get your pintle's 5 degree angle. What you will have to do is carefully mark the centre you need to start drilling / boring from though!

Dave

[Lew_Merrick_PE]

Andy,

From your statement, "put the cylinder in the 4-jaw, I would assume you are trying to do this on a lathe.  That sound "problematic" to me.  It would be better to use a mill or drill press.  As the cylinder is ø20 mm X 40 mm, you have the advantage of 5° being approximately 1.75 mm rise in 20 mm of length.  A 1.75 mm shim placed under the outside edge of the cylinder gives you a close-to-5° angle.  Similarly, moving (in the appropriate direction, of course) 1.75 mm off-center on the cylinder gives you your start point for drilling or boring.  Thus, if you have something to use as a (90°) angle plate for your mill or drill press, the only "challenge" is to find a good way to clamp it in position at the 5° angle against your angle plate.  A couple of pieces of plate bored to ø20 mm and then dressed down to (say) 18 mm depth ought to do the trick.  (The ø20 mm hole is drilled/bored very near the edge of the plate or bar.  The edge is cut back leaving a nearly complete circle at one edge.  Cross-drilling a couple of screw holes to clamp the part to the angle plate completes it.)  If you work with a "1-2-3" block as the base for this, the bottom of your cylinder will be (about) 25 mm off your table to clear your drilling/boring tools.

???

[AdeV]

You would ideally want some way of fixing the sleeve to the crook - if the sleeve bound to the gate hinge & rotated, with that taper it might rip the crook apart...

[andyf]

Thanks for the suggestions, guys.

After careful consideration I realised (a) there's no point being too precise about the thing unless I take very careful and difficult measurements of the exact degree of bend on the offending pin, and exactly which bit of it has a centre which lines up with the other pin above it, and (b) they aren't my damn gates anyway, and I won't get paid more than a couple of  .

So I've made a sleeve with plenty of clearance and a tapered bore to fill up the gap between the oversize hinge and the pin, so the two of them can make their own minds up as to how they fit together.

To make this and another five sleeves (my pal has double gates at the front, and a small one on a side boundary), I used a part painted, part rusted piece of what looks an upright from some school railings. Dreadful stuff to turn/drill/bore.

Andy