How do you drill cross holes in small cylinders (brass or steel). The cylinders are 3/8 - 1/2" in diameter and often less than 1" in length. The hole is 1/4"
I am having all sorts of problems with this: The clamping is limited as the clamps often interfere with the drill, especially centre drill. I find it impossible to clamp both ends of the cylinder for the same reason. I tried drill press vise, v-blocks, side-ways chucks, you name it.
What usually happens is that the part tends to flex somewhat and even if it does not there is horrible chatter.
Some sort of sacrificial v-block? But the part still has to be held in it somehow.
One for the drill (you'd fuss with drill bushings if making lots of holes).
One for the part - snuggish fit.
Clamping - you can slit to the hole for the part, then clamp the slit closed. Or you can add a few more cross holes and some setscrews to clamp it. Choose a faster method if making a lot of parts (some sort of air powered clamp, perhaps).
I do this periodically. I take a block of steel and drill a hole to hold the piece and drill a hole for a guide to drill the cross hole. If I am doing a bunch of them or want to do it nice I use a drill bushing for the cross hole. I clamp the block of steel with whatever.
Are these solid cylinders, or hollow ones like pipe or tubing? That can make a big difference.
The flex is why I wondered about whether it was hollow.
What I would do, assuming that the workpiece is solid, is to first part off a piece of the same diameter stock in the lathe after center drilling it and drilling it to just pass the 1/4" drill bit. This piece should be perhaps 1/4" to 1/2" long.
Then put the workpiece in the vise parallel to the jaws, place the drilled piece on top of it with the hole vertical, clamp the vise, and drill through the workpiece using the hole in the part which you made to guide the drill bit square into the centerline of the workpiece.
You won't need the center drill -- but if you get the drill bits with split points, you will probably drill more easily.
If you're going to be doing a lot of this, make the guide from mild steel, and case harden it so the drill bit does not enlarge the hole as it is used.
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If the part is hollow, what I would be tempted to do is to make up a special jaw for the vise which has a pin which matches the ID of the workpiece hole. This pin would stick straight out from the fixed jaw, and you would slide the workpiece over it, and then clamp it in place with the vise's movable jaw. Mount the vise to the drill press table so the hole goes right where you want it -- and be *sure* to use split point drill bits for this, as you don't have a guide to keep the bit from walking, and normal chisel-point bits *love* to walk on rounded surfaces.
If you want to be a bit more stable, make two jaws with short pins to hold the workpiece properly from both ends.
If the two diameters of workpiece have different through hole diameters, make two sets of pins on the vise jaws -- one for each size.
It probably would not hurt, if you have a lot of these to make over time, to make up a separate vise with the modified jaws so you don't have to be swapping jaws frequently.
Hmm ... you *could* also mill pockets just the right diameter i the opposing jaws.
Note that I'm assuming that the ends are parted off in a lathe so they are not at an angle. If you are using a hacksaw, you should at least pop them in the lathe to clean up the ends before drilling.
I didn't see where the OP wrote anything about "intersecting" holes, did I miss something? I always thought a "cross hole" defined just one hole through a part.
A little drill press vise I've had for over 40 years came with a jaw block which can securely clamp small round parts. It has "V" openings to clear drills:
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Maybe something like that could help the OP.
That vise also came with another jaw block which can clamp tapered parts, and if used with the first block can let me clamp tapered shafts, It has a stub on its lower side which fits in the vise slot and keeps it from ssliding out sideways:
Solid. Sometimes there is a much smaller axial hole (1/8") as well. The purposes vary. Most frequently they are used to attach gnomons to the sundial armature.
I think it is a function of a short piece being held in a v-groove of a drill press by its end and bending under pressure (that has been the only way to get near it with a centre drill).
Right. I can see myself making a jig along those lines. I have just seen a nice one on YouTube also. I think the frequency of doing this will justify it.
No doubt the time will come I shall be drilling hollow cylinders and this will be very useful.
A perennial project in The Model Engineer magazine was the cross- drilling jig. Most consisted of an upside down "V" with some manner of drill bushing and a clamping mechanism for the part. If you want to spend some bucks, Heinrich makes them and MSC catalogs them. You need the drill bushing for accuracy, just going at it on a curved surface leads to wandering and breakage. I have used a crotch center in the lathe tailstock to do cross-drilling. I had a Jacobs headstock chuck to hold the bit, I used a center bit to start with and progressed from there. The work was long enough to hand-hold. Drilled the hole first, then cut and faced to length and hole position. It was low-accuracy, but got the job done. Crotch centers seem to have vanished from the catalogs, I got mine from Sears waaay back. Basically a round v-block on a Morse taper shank. One could be made up easily enough.
A perennial project in The Model Engineer magazine was the cross- drilling jig. Most consisted of an upside down "V" with some manner of drill bushing and a clamping mechanism for the part. If you want to spend some bucks, Heinrich makes them and MSC catalogs them. You need the drill bushing for accuracy, just going at it on a curved surface leads to wandering and breakage. I have used a crotch center in the lathe tailstock to do cross-drilling. I had a Jacobs headstock chuck to hold the bit, I used a center bit to start with and progressed from there. The work was long enough to hand-hold. Drilled the hole first, then cut and faced to length and hole position. It was low-accuracy, but got the job done. Crotch centers seem to have vanished from the catalogs, I got mine from Sears waaay back. Basically a round v-block on a Morse taper shank. One could be made up easily enough.
Those Heinrich cross drilling jigs look very neat.
If you are doing only a few, what I do is to mill a small flat, and then spot drill and then through drill with a screw-machine length bit, all without removing the workpiece from the mill vice. With the milled flat, it's easy to find the center of the flat, which is where the hole is drilled. I've used this method to drill diametrical holes in spherical parts.
If you are making a lot of parts, I'd make something like the intersecting-holes jig that others have discussed.
A small, motorized, cross drilling spindle that fits the QCTP and is automatically located on the lathe centre line is an ideal tool for second operations such as described in the foregoing posts.
You apparently are cutting short lengths and then drilling cross holes; it might be better to drill first and then cut. That is, you could drill all the cross-holes in the long piece of stock, before cutting short pieces to length, on the basis that work holding for the drill step is more demanding than for the end-finishing step.
Clamp the part in the mill vise with a parallel under it; pick the height parallel so the top of the cylinder is slightly below the top of the jaws. Pull the parallel out. Use an edgefinder on the jaws to center the part under the spindle. Spot with a center or spotting drill. (Double check to make sure you removed the parallel. ) Drill to size.
If you're doing this on a drillpress, in place of using an edgfinder, chuck a piece of the same diameter as the workpiece and lower it between the jaws to center things up before clamping the vise.
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