You asked how spiral coolant holes through solid carbide drills are
manufactured.

I talked to our company's in house tool grinder who used to work for a
well known tool maker.

He explained that the solid carbide twist drills with coolant holes are
added when the carbide is in a "play dough state" (his words not mine).
The holes are formed with round plastic string, similar to 'weed wacker'
string.

While in the 'play dough state' the string is fed in a spiral pattern
inside the carbide while being extruded through a nozzle to make a drill
blank. The string is removed before hardening of the carbide takes place.

The spiral pattern has a controlled predefined lead. In fact when
purchasing the blanks he must know the lead or risk cutting into the
coolant holes when grinding the flutes.

As an example:

http://pdf.directindustry.com/pdf/wa...602-97823.html


He also said that at a time before the above process was perfected a
fluted drill blank was inserted into a tube and then sintered to form
coolant channels while fusing the two pieces together. He didn't go into
much detail here as this is evidently an outdated process.

HTH
John

On Thu, 08 Dec 2011 19:18:55 -0500, John wrote:

You asked how spiral coolant holes through solid carbide drills are
manufactured.

I talked to our company's in house tool grinder who used to work for a
well known tool maker.

He explained that the solid carbide twist drills with coolant holes are
added when the carbide is in a "play dough state" (his words not mine).
The holes are formed with round plastic string, similar to 'weed wacker'
string.

While in the 'play dough state' the string is fed in a spiral pattern
inside the carbide while being extruded through a nozzle to make a drill
blank. The string is removed before hardening of the carbide takes place.

The spiral pattern has a controlled predefined lead. In fact when
purchasing the blanks he must know the lead or risk cutting into the
coolant holes when grinding the flutes.

As an example:

http://pdf.directindustry.com/pdf/wa...602-97823.html


He also said that at a time before the above process was perfected a
fluted drill blank was inserted into a tube and then sintered to form
coolant channels while fusing the two pieces together. He didn't go into
much detail here as this is evidently an outdated process.

HTH
John

Right. You not only have to know the lead, you also have to know where
at least one of the strings is located.

They indicate that with a little detent in the extrusion die, which
shows the radial position of one of the strings on the extrusion, and
it stays true in relation to the string after it's sintered.

--
Ed Huntress

Top posted because it's more efficient...

Thank you for the info. Always neat to learn this stuff.

Regards,
Joe Agro, Jr.
(800) 871-5022 x113
01.908.542.0244
Flagship Site: http://www.Drill-HQ.com
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com
Production Tapping: http://www.Drill-HQ.com/?page_id=226
VIDEOS: http://www.youtube.com/user/AutoDrill
FACEBOOK: http://www.facebook.com/AutoDrill
TWITTER: http://twitter.com/AutoDrill


V8013-R


"John" wrote in message
...
You asked how spiral coolant holes through solid carbide drills are
manufactured.

I talked to our company's in house tool grinder who used to work for a
well known tool maker.

He explained that the solid carbide twist drills with coolant holes are
added when the carbide is in a "play dough state" (his words not mine).
The holes are formed with round plastic string, similar to 'weed wacker'
string.

While in the 'play dough state' the string is fed in a spiral pattern
inside the carbide while being extruded through a nozzle to make a drill
blank. The string is removed before hardening of the carbide takes place.

The spiral pattern has a controlled predefined lead. In fact when
purchasing the blanks he must know the lead or risk cutting into the
coolant holes when grinding the flutes.

As an example:

http://pdf.directindustry.com/pdf/wa...602-97823.html


He also said that at a time before the above process was perfected a
fluted drill blank was inserted into a tube and then sintered to form
coolant channels while fusing the two pieces together. He didn't go into
much detail here as this is evidently an outdated process.

HTH
John

On 12/8/2011 5:18 PM, John wrote:
You asked how spiral coolant holes through solid carbide drills are
manufactured.

I talked to our company's in house tool grinder who used to work for a
well known tool maker.

He explained that the solid carbide twist drills with coolant holes are
added when the carbide is in a "play dough state" (his words not mine).
The holes are formed with round plastic string, similar to 'weed wacker'
string.

While in the 'play dough state' the string is fed in a spiral pattern
inside the carbide while being extruded through a nozzle to make a drill
blank. The string is removed before hardening of the carbide takes place.

The spiral pattern has a controlled predefined lead. In fact when
purchasing the blanks he must know the lead or risk cutting into the
coolant holes when grinding the flutes.

As an example:

http://pdf.directindustry.com/pdf/wa...602-97823.html



He also said that at a time before the above process was perfected a
fluted drill blank was inserted into a tube and then sintered to form
coolant channels while fusing the two pieces together. He didn't go into
much detail here as this is evidently an outdated process.

HTH
John

interesting. i use weedwacker string to form channels in clay. i leave
it there when firing the clay (around 2300F), and it just disappears.
wouldn't removing the string distort the carbide before it was sintered?


..

On 12/9/2011 10:45 AM, chaniarts wrote:
On 12/8/2011 5:18 PM, John wrote:
You asked how spiral coolant holes through solid carbide drills are
manufactured.

I talked to our company's in house tool grinder who used to work for a
well known tool maker.

He explained that the solid carbide twist drills with coolant holes are
added when the carbide is in a "play dough state" (his words not mine).
The holes are formed with round plastic string, similar to 'weed wacker'
string.

While in the 'play dough state' the string is fed in a spiral pattern
inside the carbide while being extruded through a nozzle to make a drill
blank. The string is removed before hardening of the carbide takes place.

The spiral pattern has a controlled predefined lead. In fact when
purchasing the blanks he must know the lead or risk cutting into the
coolant holes when grinding the flutes.

As an example:

http://pdf.directindustry.com/pdf/wa...602-97823.html




He also said that at a time before the above process was perfected a
fluted drill blank was inserted into a tube and then sintered to form
coolant channels while fusing the two pieces together. He didn't go into
much detail here as this is evidently an outdated process.

HTH
John

interesting. i use weedwacker string to form channels in clay. i leave
it there when firing the clay (around 2300F), and it just disappears.
wouldn't removing the string distort the carbide before it was sintered?


I am just relaying what I was told by someone who was once 'hands on' in
the process, anything I say personally would just be ill-informed
opinion. I could have misunderstood I suppose but I don't think so.

John