[Nitrous]

Hi folks,

I need some practical advice for drilling holes in brass rod. I have a milling machine but its been a long time since I've used a mill and never with such a small scale.

The brass rod is 0.093" diameter and the hole size is of the order .030 to 0.06"

I'm guessing this isn't as big a challenge as I'm finding, so I hope to get some practical advice.

Thanks
Nitrous

[fizzissist]

Depends how you're holding the rod.

In a collet block in a mill? clamp onto a piece of 3/32 drill rod or gage pin on one end in the collet block, then insert the other end of the clamped rod in the spindle collet... Then, clamp collet block onto the table without moving it side-to-side.

Release the spindle clamping, release the collet, put your rod in the collet block, put your drill in the spindle, and go to town! No indicating or anything... You're on center!

[txcncman]

Use soft jaws in a vise. Put a 0.015 shim between the jaws. Find the center and lock the table down. Use a 3/32" end mill to make an appropriately deep hole. Remove the shim and drop the brass rod into the hole and clamp it and drill away.

[Nitrous]

Use soft jaws in a vise. Put a 0.015 shim between the jaws. Find the center and lock the table down. Use a 3/32" end mill to make an appropriately deep hole. Remove the shim and drop the brass rod into the hole and clamp it and drill away.

My challenge started at the "find the centre" part of the procedure.
I'm able to put a flat in the rod to drill into. I was thinking of using a 1/32" end mill to actually cut the hole.

Thanks
Doug

[Nitrous]

Depends how you're holding the rod.

In a collet block in a mill? clamp onto a piece of 3/32 drill rod or gage pin on one end in the collet block, then insert the other end of the clamped rod in the spindle collet... Then, clamp collet block onto the table without moving it side-to-side.

Release the spindle clamping, release the collet, put your rod in the collet block, put your drill in the spindle, and go to town! No indicating or anything... You're on center!

I'm using a vertical mill, with an end mill in a speed collet. My problem is in getting the vertical translated into a horizontal "mid point".

I probably wasn't clear. I'm not tring to drill a hole "end on" but rather perpendicular to the long axis.

Doug

[txcncman]

I'm using a vertical mill, with an end mill in a speed collet. My problem is in getting the vertical translated into a horizontal "mid point".

I probably wasn't clear. I'm not tring to drill a hole "end on" but rather perpendicular to the long axis.

Doug

Yeah. Poor communication does that.

Cut a step in your fixed soft jaw about 0.080" wide and 0.080" deep. Edge find the step and then move back 0.0465" to be on center. Pretty simple really.

[fizzissist]

I'm using a vertical mill, with an end mill in a speed collet. My problem is in getting the vertical translated into a horizontal "mid point".

I probably wasn't clear. I'm not tring to drill a hole "end on" but rather perpendicular to the long axis.

Doug

Clamp the part by whatever means you can. Drill a hole thru, without concern for location. Take the part out of the clamping system.

Put a precise pin of a known dia thru the hole and rest the pin upon to matched gage blocks on a surface plate so that the part is horizontal, and perpendicular to the similarly horizontal pin. Take a height gage and measure across the top of the part, measure also across the top of the pin's dia.

Take the difference between the two measurements, add the radius of the pin, and that will tell you where the center of the hole is relative to the top of the part. Subtract that value from the measurement of the top of the part plus the radius value of the part to determine how much movement is needed to correctly place the cross hole in the part.

.... Or you could use an edgefinder, and add .100"

[Bob La Londe]

My issue with round stock has not been finding the center, but preventing a drill bit from flexing and walking off. Not always a big deal, but it can result in a substantially off center exit point. If good entry and exit are important I'll mill a slight flat on the round stock and, even center punch or spot drill it first. With .093, its going to be tricky and take some time and care no matter what you do.

[txcncman]

Always center drill or spot drill on small diameter drills if you want the finshed hole to be within 0.005" of desired location.

[JimBoyce]

A #0 combined drill and countersink (center drill) might work.

[elfrench]

I'm using a vertical mill, with an end mill in a speed collet. My problem is in getting the vertical translated into a horizontal "mid point".

I probably wasn't clear. I'm not tring to drill a hole "end on" but rather perpendicular to the long axis.

Doug

Does the end mill wander off center or are you having trouble locating the center? What tolerance is required for locating the hole on center?

I would build a jig with a drill guide to ensure the end mill/drill bit doesn't wander.