Is There A Good Way To Make Oversized/taprered Drill Bits Common Jacobs Chuck?

[jere m]

Maybe this is a foolhardy or hopeless question but I am looking for the best solution I can find.

I bought a bag of used assorted drill bits for $20 from Craigslist. I have a very limited income so I was happy to get them. the problem I am running into is many of the bits don't fit my 1/2 inch jacobs chucks. some of the bits were turned or ground down with a rough finish to fit by a previous owner. I have a small 8x12 hft lathe but I don't dare put the twist end of the drill bit in the 3 jaw lathe Chuck.
I know there are larger jacobs chucks and fittings for tapered drill bits but they are as good as unobtainable for the time being.

so my question is how does one go about turning down the shank of a drill bit or making an adaptor?

 

[Round in circles]

Jere,
How big is you lathe chuck and does it have a hollow cross shaft , in other words will the drills actually fit in your lathe?

Here are one or two way's of skinning your cat that I have used :-
Most drill shanks are fantastic material for turning in the lathe you can get a real good finish using tungsten tipped tooling .

If you have say a 1/4 " end that has been turned down on a bigger drill & you want to remove it grind it off keeping the tang quenched so it does not harden, then face it off square in the chuck & put a tiny rounded edge on the faced off end to stop you cutting your fingers as they can be very very sharp. .

Slit some copper water pipe along its length use it to wrap around the drills where they will fit in the chuck jaws save for the bit you're wanting to remove. Cutting the strip to ensure it is circular all round the drill ( no gaps or over wraps )
Centralize the work in the chuck with a DTI if you have one or with the back end of a rounded cutting tool in the tool post ( you grind it if you have a grinding stone )

Another way if you don't have a grinder or DTI is for you to thread & counter bore a round bar so that it can hold a 1/4 " diameter steel ball bearing ( cutting the head off big bolts can be useful here ) Then make a coned cap to hold it in place either by threading the cone or using some epoxy resin to hold the ball in the counter bored hole ensuring that some of the ball bearing is poking out the coned cap to be able to touch the work piece.

I dare say the simply counter boring the end of a square or round bar and using super glue or epoxy will be OK to make the indicator tool.
To use the tool you use your eye to see the distance gap and adjust accordingly
another way is to use feeler blades to measure the run out and again adjust things till it minimized , checking several times that is is true all the way round . .


If you can hold some of the shank wrapped in copper in the chuck so much the better .
I've turned down all manner of drills over 1/2 " like that as well as taper drills .


Here in Great Britain drills with the shank of a smaller diameter than the body are called Blacksmith Drills..
Using that term you might find a You Tube clip showing you how others do it .
One some of the morse tapers drills I've managed to turn the half inch shank and still had a workable morse taper to play with.
On one or two of the longer bigger morse taper drills I had to grind off an inch or more with the angle grinder then resharpen the drill so that they would fit in my little drill press.

For one 8 mm morse taper drill that I wanted to keep as a morse I turned down a # 2 morse adapter sleeve to a 1/2 " at the tang end .... there was just enough metal to do it without wrecking things. It enabled me to do the job .
Morse tapers are very cheap on eBay to buy so I've gone & purchased another two .

 

[jere m]

Jere,
Slit some copper water pipe along its length use it to wrap around the drills save for the bit you're wanting to remove.

If you can hold some of the shank wrapped in copper in the chuck so much the better .
I've turned down all manner of drills over 1/2 " like that as well as taper drills .


Here in Great Britain drills with the shank of a smaller diameter than the body are called Blacksmith Drills..
Using that term you might find a You Tube clip showing you how others do it .
One some of the morse tapers drills I've managed to turn the half inch shank and still had a workable morse taper to play with.
On one or two of the longer bigger morse taper drills I had to grind off an inch or more with the angle grinder then resharpen th drill so that they would fit in my drill press.

For one 8 mm morse taper drill that I wanted to keep as a morse I turned down the # 2 morse adapter sleeve to a 1/2 " at the tang end there was just enough metal to do it without wrecking things. It enabled me to do the job . As morse tapers are very cheap on eBay to buy I've purchased another two .

Thanks the copper tube should do the trick for most of the bits!

there are a few approaching 29mm I might just have to give up on those. I don't think I can fit enough length in the lathes chuck

 

[Wreck™Wreck]

Put them in the chuck and turn the shanks, most twist drills have soft shanks that turn easily, a full hard drill is difficult to hold in a drill chuck. Don't worry about holding them in a 3Jaw chuck it will not hurt them.
Twist drills have back taper by design, the pointy end of a new drill is close to nominal diameter, the diameter gets smaller as it approaches the shank by a few .001's.

In the USA reduced shank drills are known as "reduced shank drills", also Silver and Demming drills.

 

[T Bredehoft]

Put the twist end in the chuck far enough into the chuck that you clamp on the round part, just below the flutes. Turn them down to 1/2, or anything smaller than 1/2, but be sure you then tighten the tailstock chuck very tightly when using them to drill, you will have removed the hard skin on the drill and it won't be as easy to hold, will want to spin.

 

[Round in circles]

Thanks the copper tube should do the trick for most of the bits!

there are a few approaching 29mm I might just have to give up on those. I don't think I can fit enough length in the lathes chuck

Ever thought of turning those biggies between the chuck ( again with a copper wrap ) and have the tang end in a live centre at the tail stock then turn them down at the tail stock end ( most of the big morse tapers should have an accurate counter sunk center in the end of the tangs ) .

 

[bill stupak]

How about milling hex flats on them? That would reduce the size and make them twist resistant in the drill chuck.

Bill

 

[Wreck™Wreck]

Put the twist end in the chuck far enough into the chuck that you clamp on the round part, just below the flutes. Turn them down to 1/2, or anything smaller than 1/2, but be sure you then tighten the tailstock chuck very tightly when using them to drill, you will have removed the hard skin on the drill and it won't be as easy to hold, will want to spin.

Actually twist drills are hard all the way through and not cased hence they may be sharpened, the shanks are not hard so that they may be more easily held in a drill chuck, the harder the shank is the harder it will be to hold in a drill chuck. I am sure that you have noticed that twist drills that have been spun in a chuck often have deep grooves and ridges from the chuck jaws, center drills and taps have full hard bodies and shanks respectively which makes them difficult to hold securely in a typical drill chuck and are not grooved when spun. The soft twist drill shank is actually slightly deformed by the jaws allowing them to be held more securely.

Do this test, use a file and run the sharp corner over the shank of a quality twist drill, PTD, Chicago Latrobe or Guhring say, then over the cutting part of the drill and let us know the results, then try it on the shank of an endmill or the body of a center drill. Chucking reamers also have soft shanks suitable for easy turning.

It may seem counterintuitive but the harder the shank the more difficult the tool is to hold in a chuck.

 

[jpfabricator]

What is the taper of your drill press quill? You may be better off finding some morse taper collets that match your quill taper

Sent from somewhere in east Texas!

 

[brino]

Jere,

A silly question.......but are you certain that your drill press does not use a Morse taper to hold the stub that the drill chuck is on?

I was offered a bunch of taper shank bits because the owner jokingly said that "my chuck won't hold them!".
What he missed was that his drill press did use a Morse taper, like the middle row in this picture (from wikipedia):
https://en.wikipedia.org/wiki/Machine_taper#Morse



It is driven out using tapered wedge thru a slot in the spindle.
Here's a good reference.
http://www.ereplacementparts.com/article/3425/How_to_Remove_and_Reinstall_a_Drill_Press_Chuck.html

Have a look, this may save some effort.

-brino

EDIT: The above was written because I saw a morse taper bit above. Perhaps I mis-understood and you are asking about holding cylindrical shank drill bits.