Drilling precision holes

[Charles L. Cotton]

I'd like to build this brass sorter, but I have no idea how to drill the precise holes that would be needed. Not counting .45ACP and .40 S&W, here are the the holes I'm worried about: .380 ACP (.374"), 9mm (.391") and 38 Super (.406").

Is it possible to drill these holes within a 0.002 - 0.005 using a drill press?
Chas.

[flowrie]

Those are "machined" tolerances, not "fabrication" tolerances.
I would recommend a machine shop with CNC machinery.
Drill press probably not viable, you may spend more money redoing it several times.

[jason812]

Those are "machined" tolerances, not "fabrication" tolerances.
I would recommend a machine shop with CNC machinery.
Drill press probably not viable, you may spend more money redoing it several times.

This...

Short answer no.

Long answer possibly. Drill bits don't make round holes. With these tolerances you will need to ream them. Drill 1/64th under size then without moving the part, install reamer and ream hole. Then change to drill bit, move to next hole and repeat. It might be able to be done but it will not be fun.

[karatedad]

The typical at home type drill press will not have the spindle stability to hold close tolerances. This would be better accomplished on a small vertical mill. Depending on the material used for the plate you can hold tolerances within .005" by stepping the hole and using a new drill for the final size. Had your maximum been .002" I would have said drill and ream or drill and bore depending on material and available tooling.

And yes, I do this for a living and can easily hold .005" with a drill if necessary. However, our company doesn't allow us to do "government work" so I am not in a position to offer to do it for you and you certainly don't want to pay our rates to have this done. A small local shop would be your best bet.

[Wag2323]

Do you really need the hole tolerance to be that tight? Looks to me the sorting is all done with cameras so the hole size on the disc doesn't need that tight of a tolerance.

[txsmiley kf5wre]

Call me

[Jusme]

Do you really need the hole tolerance to be that tight? Looks to me the sorting is all done with cameras so the hole size on the disc doesn't need that tight of a tolerance.

I thought the same thing the proximity switches open a (door?) underneath based on the height of the brass, rather than the diameter. The first one is set highest, the second lower in height, and the third one the lowest. I am not a machinist and I don't play one on TV so my assessment may be all wrong.

[Wag2323]

Do you really need the hole tolerance to be that tight? Looks to me the sorting is all done with cameras so the hole size on the disc doesn't need that tight of a tolerance.

I thought the same thing the proximity switches open a (door?) underneath based on the height of the brass, rather than the diameter. The first one is set highest, the second lower in height, and the third one the lowest. I am not a machinist and I don't play one on TV so my assessment may be all wrong.

I don't know much about brass height but if you could sort by height then I would probably try something completely mechanical. I would change the holes in the disc to slots that are cut toward the center and are angled backwards as they go toward the center. I would set some blade type blocks at the height of the case type and try to make it so the blade pushes the correct brass toward the center of the disc along the slot. if the brass is pushed farther in there would be a hole it could drop into.

Rather simple idea but would take some work in making it so the brass would not slide along the slot unless forced to by the blades and that the brass doesn't tip out because of the blade instead of sliding along the slot. The blade angle and slot angle probably take some trial and error and I would make it out of wood for testing.

[Charles L. Cotton]

Thanks guys, you confirmed pretty much what I suspected. I process several thousand rounds of brass annually, but not enough after any range session to be worth a lot of work or expense. I can just use the Shell Shorter with the extra 38 Super and .380ACP plates.

The comment about cameras has me thinking about an Arduino-controlled sorter, but again, that's too much work for the application.

Thanks,
Chas.

[lfinsr]

You don't need to hold the tolerance you're suggesting. The hole only needs to be between the intended sizes. Using your example you could drill the first hole anywhere between .374" and .390", a fairly wide range. The next hole would be between .391" and .405", etc.

If I were building this I'd probably use slots since it would jam up if the casing didn't fall right away. I suspect if you could dissect the machine you linked to that is exactly what was done. Since creating a slot is times more difficult than drilling a hole I'm guessing the easiest solution is to farm it out to a local machine shop.

My 2 cents worth.

[mr1337]

I'd like to build this brass sorter, but I have no idea how to drill the precise holes that would be needed. Not counting .45ACP and .40 S&W, here are the the holes I'm worried about: .380 ACP (.374"), 9mm (.391") and 38 Super (.406").

Is it possible to drill these holes within a 0.002 - 0.005 using a drill press?
Chas.

The brass sorter in the video doesn't rely on precise holes. Those devices on the side are optical sensors (laser?) that are measuring the diameter [edit: or height] of the casing. If the diameter [edit: or height] matches the desired diameter, it operates a servo that opens a door to let the casing fall through.

[edit:] Reading the other responses (especially Justme's) as well as there being 3 optical sensors instead of just 1 that would be needed if they were just measuring diameter makes me agree with Justme's height assumption, not diameter. However, with enough precision on the spinning motion, the same could be done with a laser measuring the diameter. In fact, probably the best implementation would measure both diameter and height in order to sort more types of ammunition that share similar diameters but have differing heights.

[jmorris]

I agree. The holes are all the same size, it's detecting the height of the case. Mechanically I'd try something like a rock sorter.

Actually I just remembered having seen a bowl - like sorter that fits into a 5 - gallon bucket. Slots in the bottom of the proper size. Shake it and the proper size falls through. The move up to the next size.

[E.Marquez]

Is it possible to drill these holes within a 0.002 - 0.005 using a drill press?
Chas.

No sir, that is a machining operation. That kind of tolerance is well beyond even a high end drill press and twist drill.
You wold drill the hole undersized and then ream to final size

[lfinsr]

You guys are absolutely correct. I didn't watch the video close enough the first time. With the volume up you can hear the solenoids actuating the mechanism allowing the cases to drop.