Replies

1. 
   ErnieConover | Nov 08, 2007 03:36pm | #1

   Drills, in general, tend to center better when the work is spinning and the drill is stationary--as in the lathe. Gun drills, as the name implies, were originally developed for drilling gun barrels where a straight hole is vital to accuracy. Any hole deeper than three times the diameter is considered a deep hole.

   Modern gun drills for cutting metal are carbide tipped and have a hole through the body to deliver coolant (sometimes compressed air) at the tip. The coolant cools the cutting edge, improves the cutting action and carries the chips up and out through a groove in the shaft.

   The simplest of gun drills is what is called a D drill and can be shop made. I can make you a sketch if you need one. D drills require a starting hole so a starting hole about three diameters deep would be first made with a twist drill. The gun drill is then chucked in the tailstock and you drill through.

   No matter what drill you use, constant clearing is necessary. You must withdraw the drill entirely from the work and clear all chips from the flutes about every diameter of depth.

   What I am unsure of here is whether you are simply trying to get a straight hole which you will then ream conical or you will work with a constant diameter hole. Most woodwinds have conical bores I believe. Maybe your flute is an exception?

   It is possible to regrind a standard twist drill "barefaced" and have it drill very straight. Long twist drills are available from industrial suppliers. (You want to ask for an "aircraft") drill. Let me know some sizes involved here and I will try to help some more. I can sketch how to regrind barefaced.

   With best regards,
   Ernie Conover

1. 
   saschafer | Nov 08, 2007 06:59pm | #2

   "Most woodwinds have conical bores I believe."

   It depends on the instrument. Flutes and clarinets are cylindrical, while oboes and saxophones are conical, for example. It's also the primary difference between modern trumpets (cylindrical) and cornets (conical).

   -Steve

    

   Edited 11/8/2007 10:59 am ET by saschafer

1. 
   ErnieConover | Nov 08, 2007 08:43pm | #3

   Yes, but what hole size do you want to bore and do you need a sketch of the drills I mentioned?ERC

1. 
   saschafer | Nov 08, 2007 09:35pm | #4

   Sorry, I'm not the original poster--just adding my two cents.

   -Steve

    

2. 
   Weller | Nov 09, 2007 03:09am | #5

   Bore size required is 3/4 inch so I'm thinking twist drills, at least any I've encountered, won't be an option. I'm interested to learn a little more about the "D-drill" you refer to... given the $100 + price tag attached to the gun drill I figure I'd need, your "shop-made" comment has a nice ring to it. If possible, the sketch you refer to would be appreciated.

   Re the cylindrical vs. conical debate, my reading seems to indicate that modern instrumemnts of this type are conically bored, the barrel section anyway... that's to be the challenge for prototype no.2.

   Thanks for your time,

   Bob

    

1. 
   ErnieConover | Nov 09, 2007 03:02pm | #6

   I will make a sketch over the weekend.ERC

2. 
   ErnieConover | Nov 14, 2007 05:00pm | #7

   I did some research on gun drills. I was under the impression that you just wanted a 3/8" hole and not as large as 3'4". The former could be made from a 20" section of rod you could grab with a Jacobs chuck. A 3/4" drill will have to be made in two pieces. I have attached a sketch but it would require some metalworking. You could drill the blind hole for brazing the shaft to the slug that will form the actual drill in a wood lathe. Just keep the speed slow. You will have to drill a pilot hole about three diameters deep (2-1/4") with a twist drill before inserting the gun drill. The home made gun drill will require constant clearing, perhaps more often than each one diameter of depth. A steady rest to hold the end of the work your are drilling may be necessary.With best regards,
   Ernie Conover.

   
3. 
   Weller | Nov 15, 2007 03:46pm | #8

   Thanks very much for your input Ernie... appreciate it.

   All best,

   Bob 

2. 
   [email protected] | Dec 10, 2013 09:22am | #9

   Compressed air supply tool holders are available here these will allow you to drill wood with a gun drill.

   http://www.hammco.com