Small-Bit Drilling of Brass

[Attuvian]

Folks,

Thinking of making a jig for forming grab irons out of piano wire.  Doing them by bending over the jaws of needle-nosed pliers is only my second preference.  In building a jig I'd prefer brass, but a block of aluminum would probably be easier to drill out and likely easier to acquire.  Question: Is drilling brass (or aluminum) feasible with, say, a #76 bit?

BTW, the grabs will be for HO.  Will likely use stock no greater than .015".

Thanks,

John 

[tstage]

John,

Brass and aluminum are considered "softer" metals and generally easier to drill into - even by hand.  Either one would work well for your situation.

Will you be drilling the holes by hand, or using a hand drill/drill press?  Also, how thick will your jig be that you drill your holes into?

In either case:

1. Make sure your pin vise or drill chuck holds the small drill bits FIRMLY w/o slipping
2. Make sure to choke up on the drill bit so that you minimize bending of the bit while you drill and avoid breakage.
3. It's your choice if you want to use cutting fluid (lubricant) or not.  Just be sure to drill and clear out the hole frequently if your holes are going to be deeper than 1/8".

Tom

[Attuvian]

tstage

John,

Will you be drilling the holes by hand, or using a hand drill/drill press?  Also, how thick will your jig be that you drill your holes into?

Tom

 

Thanks, Tom.

 

I can't see a need for legs on most all my grabs being any longer than 3/16".  I will experiment first with a mechanically steadied moto-tool and with multiple, lubricated passes.

 

John

[SeeYou190]

For me, te most touchy part or drilling through brass stock is when the drill bit just pierces the other side. That is where it sems to want to grab and snap.

.

Just go slow and be careful.

.

I have never drilled into alluminum stock that I can recall.

.

-Kevin

.

[RR_Mel]

I have tried all speeds from 20k to 180RPM and you are going to break bits no mater how you go about it.  I’ve had the best luck around 8K.  The tiny tips are going to break even in a pin vice.

 

I use .020” Phosphor Bronze wire for hand rails and grabs but go over size by .005” with #72 bit with a .025” hole.  I can normally get a half dozen holes per bit with the larger bit size.

 

I buy #72 & #76 in bulk

 

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=%2372+HSS+Wire+Gauge+Twist+Drill+Bits&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=%2376+HSS+Wire+Gauge+Twist+Drill+Bits

 

I’ve had the best luck using my Dremel Drill Press with the Dremel running at about 8000RPM, second notch on the speed setting.  I use cutting oil with as little pressure on the drill bit as possible and still cut.

 

I drilled 12 #72 holes in a Cary E7 cast metal body yesterday with a single bit, that’s one in a row!!  I found it really helps if you center punch the holes using a spring loaded punch.

 

 

Mel

 

 

 

My Model Railroad   

http://melvineperry.blogspot.com/

 

Bakersfield, California

 

I'm beginning to realize that aging is not for wimps.

 

[Attuvian]

Thanks, Mel. I'm big on spring-loaded center punches. Too bad I don't have one - yet. John

[Attuvian]

SeeYou190

For me, the most touchy part of drilling through brass stock is when the drill bit just pierces the other side. That is where it sems to want to . . . ..

-Kevin

 

. . . go into my finger - and I do the grabbing!

John

[doctorwayne]

Rather than using piano wire, I'd suggest phosphor-bronze wire.  I have a container of piano wire drop-type grabirons - an old Walthers product from the '50s, I think - and they're not all that well-formed.

The phosphor bronze is easier to form into sharp bends, and can be re-bent more easily than steel without work-hardening and the resultant breakage.

I make mine using a simple plastic jig and a small pair of smooth-jawed pliers and an X-Acto knife.

Wayne

[Attuvian]

tstage

Also, how thick will your jig be that you drill your holes into?

Tom

 

Tom,

 

I'm imagining getting hold of a piece of stock that's 3/8 to 1/2 inch thick, maybe 4 x 6 inches on the face.  I'd drill a series of holes inboard from the edge, for scale 12, 15, 18, 20, and 24 inch grabs.  One hole to account for each size.  Drop a wire in the hole, bend it against the face of the jig, then over the edge.  Lift it out of the jig, trim up the angles, and cut the longer leg to match the shorter.  Then have another bite of chocolate.

 

John

[ROBERT PETRICK]

I hesitate to reply, because my thoughts on this topic usually cause a lot of eye rolling and scoffing . . .

8000 RPM is way too fast for drilling. About 7990 of those RPMs are not cutting at all but rather skating and burnishing the bottom of the hole. The feed rate and the cutting rate have to match. A single, clean matched pair of helical swarfs should be educted through the flutes of the drill bit.

What the OP suggests would be better accomplished at about 30 RPM using a pin vise or a jeweler's hand drill. And I'd use a brass block instead of aluminum.

I'm not giving this as advice, I'm only saying what I'd do. Mileage and opinions vary.

Good luck.

Robert 

[gmpullman]

ROBERT PETRICK

The feed rate and the cutting rate have to match. A single, clean matched pair of helical swarfs should be educted through the flutes of the drill bit.

I used to drill a lot of brass at my former job. Most of the holes were one-inch and above but sometimes I'd get down to 1/8 or so. I had a set of drill bits that I custom ground just for drilling brass. I would knock off just a tiny bit of the leading edge so the drill wouldn't want to dig-in like a corkscrew into a wine bottle.

Brass will work-harden very quickly. Once this happens you will have a very difficult time to get through the hardened material. As Robert says, slower speeds and feeds are paramount.

https://en.wikipedia.org/wiki/Work_hardening

One of the handiest tools I've found for hand drilling small holes is this 100 RPM driver modified with a decent chuck*:

https://tinyurl.com/sdo3pkt

^{* it does not come with a chuck.}

motor-pin-vice by Edmund, on Flickr

Trying to drill through thick, brass castings can be very tiresome with a pin vice.

motor-pin-vice-chuck by Edmund, on Flickr

That's a #78 bit in the chuck.

Chuck_no78 by Edmund, on Flickr

Every machinist seemed to have their own preference for cutting fluid. Everything from lard to 1,1,1-tricloroethane and even MILK! I normally drill small holes in brass dry or using just a dab of kerosene on the bit. Sometimes I use a product called "Tap-Magic".

Good luck, Ed

[Attuvian]

gmpullman

 

One of the handiest tools I've found for hand drilling small holes is this 100 RPM driver modified with a decent chuck:

https://tinyurl.com/sdo3pkt

That's a #78 bit in the chuck.

Good luck, Ed

 

Thanks, Ed.  The tip on "work hardening" is a great alert.  Two questions: 1) what kind of battery drain do you get from drilling into metal at 100rpm drawing from three AAA cells?  And 2), can you provide more information on the chuck that you use with the pencil driver?  It seems that I saw a post from you in another thresad a couple of months ago where you spoke of this particular chuck but, of course, I'd likely never be able to find it.

 

John

[Attuvian]

doctorwayne

Rather than using piano wire, I'd suggest phosphor-bronze wire.  I have a container of piano wire drop-type grabirons - an old Walthers product from the '50s, I think - and they're not all that well-formed.

The phosphor bronze is easier to form into sharp bends, and can be re-bent more easily than steel without work-hardening and the resultant breakage.

I make mine using a simple plastic jig and a small pair of smooth-jawed pliers and an X-Acto knife.

Wayne

 

Thanks, Wayne.  Plastic might do.  As for phosphor-bronze, I have some .0125 on order through my LHS.  But I also have three long lengths of the .015 steel already on hand.  Granted, having paid a whopping 44 cents a stick for it I could dispense with that and make a second order of the Tichy 8 inchers in the same size.

 

Kinda thinking out loud here . . .

 

Cheers,

 

John 

[gmpullman]

Hi, John

The only available chuck that directly fits the General 500 hand driver is from MicroMark:

https://www.micromark.com/Drill-Chuck-For-Ultra-Tech-Precision-Power-Screwdriver

With shipping it gets pricey! I found a $10 chuck on Amazon but the adapter it comes with is bored to 8mm which means I had to make a bushing to fit the 7mm OD of the driver. I cheated and found that if I shrank a piece of heat-shrink tubing over the 7mm shaft it worked fine. I have a machinist friend working on a more permanent solution.

There is another option but it is a bit clunkier. You can find any power (low RPM) screw driver that uses a 1/4" hex bit adapter. There are dozens of small chucks (three jaw is best) that use the 1/4" hex mount.

I sometimes use this driver:

https://tinyurl.com/tmtvpoe

with this chuck mounted:

https://tinyurl.com/vrplyzj

There are dozens of similar chucks.

I still have the original, TWO, "cheapy" alkaline AAA batteries that came with my General driver. Probably have one hour of actual "drill-time" with it. I may use 1.2 V. NiMH rechargeables in it. It may run a little slower (better?) with 1.2V batteries.

[edit]  More photos:

Drill_chucks by Edmund, on Flickr

At the top is the "clunky" B&D power screw driver that accepts 1/4" hex bits (or a chuck, as shown) this turns at 180 RPM. I wouldn't use it for a drill size below, say, 1/16".

Next is the General 500. I actually use this one as a screw driver. There is a little slop in the output shaft, not so much rotational as axially. Still for under $15. I can live with it.

At the bottom is the General 500 that I used the heat shrink to adapt the chuck to. Again, I find it very useful for "powering through" many of the #60 to 80 holes I drill.

It does NOT replace a pin vice as there are still situations where I need that precice control. But for many drilling tasks it is ideal.

Chuck by Edmund, on Flickr

Many of the mini-micro chucks have a JTO (or I suppose they are saying JT (Jacobs Taper #0)

https://en.wikipedia.org/wiki/Machine_taper

My plan is to disassemble the General driver and have my machinist friend grind this taper directly on the output shaft. This would be ideal as the chuck would press on without any adapter.

Chuck_JT-0 by Edmund, on Flickr

Note the taper on the brass adapter in back. 

Hope that helps,

       Ed

[Attuvian]

Thanks, Ed. You have covered all the bases. I appreciate your being so thorough.

John

[tstage]

A less expensive alternative would be to place a pin vice into your drill press chuck and tighten down on the pin vise.  Just make sure your drill bit is centered in the pin vise.

I have two very good-quality pin vises (Starrett) and would have no qualms placing those into the chuck of a drill press.  The knurled shaft would hold up well.

To address Kevin's issue with blowout and broken bits: Placing piece of brass or aluminum on the backside of the block you are drilling through will help eliminate this issue.

Tom

[Attuvian]

More good ideas from Tom. You guys are all great contributors. Thanks again. Hope to track down a piece of stock today.