Breaking of Drills

[Pmedic828]

Has anyone experienced problems with drills breaking while drilling holes with a chuck in the tailstock drilling small holes. I am attempting to make a drill bit holder for 1/32 drill bits up to 7/64. I turned down some hot rolled steel that i had laying around to 1/2 inch decreasing to 3/8 inch . I wanted to drill a hole in this stock and place a set screw to hold these small bits.(my chuck will not hold anything smaller than 1/8 inch bits) I attempted and succeeded to drill and tap the set screw hole. next, i wanted to drill about 1/2 inch into the holder to set the small drills. using plenty of oil, i peck drilled and started the hole. The problems is when drilling deeper than about 1/4 inch, the bit either breaks off in the hole when advancing, or it breaks when extracting to apply more oil. I have broken at least 10 drills. I have the tail stock up next to the stock, the quill is not extended more than about 3/8 inch. these drills seem to unwrap or fracture into pieces. I would like to drill about 3/4 inch total depth 3/8 to set screw hole, and about 3/8 past set screw so bit can be shortened to prevent breaking off a long skinny drill bit. Anyone guide me on what i am doing wrong? Any suggestions?

 

[Terrywerm]

It sounds like you might be running into trouble when the bit is about to break through into the threaded set screw hole. You would probably have better luck if you drilled the smaller hole before you tap the threads in the set screw hole.

Another problem would tend to creep up when you attempt to drill past the set screw hole. The bit will tend to wander around on the far side of the hole and the hole it starts there will not be truly in line with the initial hole that you drilled. If it were me, I would drill the smallest hold first, namely the one that will hold the drill bit. After that I would drill the hole for the set screw, then tap it. You would probably have to chase the drill hole after tapping to clear out any burrs.

I also am having a bit of difficulty understanding how a single tool will hold all of the various sizes of bits that you might encounter in those small sizes, and still keep the bit on center.

Your best bet might be to look for something like this for your small bits:


If I remember right I found this one at my local hardware store for about $5 and it has been worth every penny. It will handle bits from about 1/8" down to about .015" or .020", or smaller than any drill bit that I have. It has a 1/4" hex shank that you can simply chuck up in any regular drill chuck.

ON EDIT: Just found one on eBay here: http://www.ebay.com/itm/140672135367?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 for $7.99 plus $3 shipping. I might just have to order one or two for myself just in case the one I have ever gets damaged or lost.

 

[Bill C.]

It sounds like you might be running into trouble when the bit is about to break through into the threaded set screw hole. You would probably have better luck if you drilled the smaller hole before you tap the threads in the set screw hole.

Another problem would tend to creep up when you attempt to drill past the set screw hole. The bit will tend to wander around on the far side of the hole and the hole it starts there will not be truly in line with the initial hole that you drilled. If it were me, I would drill the smallest hold first, namely the one that will hold the drill bit. After that I would drill the hole for the set screw, then tap it. You would probably have to chase the drill hole after tapping to clear out any burrs.

I also am having a bit of difficulty understanding how a single tool will hold all of the various sizes of bits that you might encounter in those small sizes, and still keep the bit on center.

Your best bet might be to look for something like this for your small bits:
View attachment 49992

If I remember right I found this one at my local hardware store for about $5 and it has been worth every penny. It will handle bits from about 1/8" down to about .015" or .020", or smaller than any drill bit that I have. It has a 1/4" hex shank that you can simply chuck up in any regular drill chuck.

ON EDIT: Just found one on eBay here: http://www.ebay.com/itm/140672135367?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649 for $7.99 plus $3 shipping. I might just have to order one or two for myself just in case the one I have ever gets damaged or lost.

Might try Lowes or Home Depot, look in the power drill section. Good luck

 

[Bill Gruby]

These are expensive but they will save you a lot of broken drill bits. http://www.royalprod.com/product.cfm?catID=16 I use one when drilling like you are. You have complete control of the drilling operation. ------ "Billy G"

 

[Tom Griffin]

You are likely running it too slow. A 1/8" drill should be run at 3200 rpm and ideally (not practically), a 1/32" drill should be run at over 12000 rpm in steel.

Tom

 

[george wilson]

I agree. You need to have a high RPM when drilling small holes. I have a Servo brand mini drill press that runs up to very high speeds,and is only used with very small drills. Years ago,a small motor with a taper shank on one end and a small drill chuck on the other was made for use in lathe tailstocks. I think it was called a "Drill Speeder". You might could make one out of a sewing machine motor and a small chuck. Fit a taper shank to fit your tailstock on the other end. You could use a foot operated speed control from a sewing machine,too.

Maybe you could cobble up a way to hold a Dremel tool in your tailstock?

 

[Ray C]

Are you starting the holes with a center drill first? One problem that can happen when you don't start the hole first, is that the bit flexes and starts the hole in the wrong place. Then, as you advance, it puts too much sideways pressure on the bit and it can snap.

Is there a possibility the bits are not sharpened properly? If one side cuts more than the other, you'll drill a crooked hole and in the case of small bits, that leads to the same problem as above. Does the swarf come out evenly from both flutes? That tells you if the sides are even.

Is there possibly something wrong with the tailstock RAM? Maybe it's not coming out straight.

Sound like you're doing most things properly though. Oil helps lube the flutes to clear swarf. Packed-up swarf is a sure-fire way of busting a bit. But that doen't sound to be the case here.

Ray