Lantern Pinions

I’m having difficulty drilling a lantern pinion. The 0.030” diameter drill does have a tendency to wander.
Any thoughts on how to control it would be much appreciated.

David

You can break most of the twist off and regrind what is left. Niko.

What is the provenance of the drill? I have a couple of those "microboxes" and one of them when you look at the drills many of the points are very poorly centred.

any chance given the style of lantern pinion you are trying to make to do all the drilling on two plates soldered together as a stack, then separate them and cut them to final round shape?

I've used this method many times when trying to make plates or discs with identical hole locations. I usually drill an extra smaller dia hole to act as a reference for aligning the finished assy and get the holes assy'd in the same order they were drilled.

For the drilling itself, I'm assuming you used a centredrill first, and are using good quality twist drills?

Thanks Niko but I don't think that I'm up to sharpening a drill that small. Having said that, I could give it a go.

David

Thanks John,

I'll check them.

David

Thanks Jeff,

I've not tried that but it's certainly worth a shot.

I did attempt a centre drill and also a spot drill but the indentation left by them was larger than the hole I am drilling so the benefit of a centre drill was lost.

David

Drills that small can be held in the drill chuck almost to their end. You only need 2 or 3 mm protruding. This makes the drill very stiff and it will not whip. I don't know how you are drilling. I do mine by dividing the lathe headstock with the pinion blank in the chuck/collet and the drill in an auxilliary spindle on the cross slide running as fast as I can get it. It is also possible to get very small centre drills if you really get stuck. They go down to 00 which have a 25 though pilot.

regards Martin

There is an interesting You Tube video that I tripped over a few days ago that shows the making of a lantern pinion. He makes a spade drill from the pivot wire to drill the trunions.

DIY Cycloidal Gear Cutter: Part 4 Making the Lantern Pinion - YouTube

Might be an idea - the spade drill is probably a lot stiffer than a twist drill at that size

Edited By speelwerk on 06/11/2021 17:44:07

Spade drill is the way to go for that sort of size.
If you can make them from carbide so much the better - it’s stiffer.

PCB drills are another option that works well

edit to add photo, Lego man for scale:

Dave

Edited By Dave S on 06/11/2021 18:13:29

I concur with some of the above. Use quality drills, and carbide drills are stiffer. Make sure that the setup is rigid and that the work is firmly clamped. For small drills spotting with a centre drill first is a waste of time; they leave a poorly defined indent that invites the following drill to wander. I find that letting the drill just "touch" the surface before applying cutting pressure allows the drill to form its own dimple. Here are two 0.8mm holes drilled 8mm deep in tungsten alloy, on the Bridgeport, using the above techniques:

Andrew

I agree with you Andrew on the comment on spotting with a centre drill but the OP wants a 30 though hole and 00 centre drill have a 25 though pilot so it's perfectly possible to obtain aa accurate pilot hole with the correct tiny lead for following up with the 30 thou drill.

regards Martin

Thank you all, I'm happy that it's not only my incompetence that's the problem

There are some great ideas here for me to try.

Thanks again, David

My experience of small centre drills is that you look at them, and ping the pilot snaps.

Andrew

Well you are more geared to to the heavier end of the spectrum

Martin

Edited By Martin Kyte on 07/11/2021 08:20:57

Thanks for the link Peter,

I noticed that he drilled the first side of the pinion with a twist drill and then carried on through the other side with a spade drill. What would this be for?

David

If I understand him correctly ( at about 4:40-4:50 in) he drills the first side undersize with the carbide drill, and then uses the spade drill - which is made from the same pivot wire as will be used for the trundles - as a reamer for the front holes to get them to exact size. Then he uses those holes to support and control the shaft of the spade drill while he makes the rear holes.

His carbide drill doesn't look long enough to drill all the way to the back in any case.

It just looked like a neat and fairly simple way of getting the holes to exactly the size of the pivot wire.

Another tip when making lantern pinions. When making the bobbin, leave a thin section in the middle so that this will act as a guide for the drill as it bridges the gap. After all the holes are drilled this section can be removed.

Thanks Peter, that makes sense.

David