• We want to wish everyone a healthy, happy New Year, full of joy and success. God bless you, and thank you for supporting The Hobby-Machinist.

[4]

Type of Drill

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

ddickey

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Apr 21, 2016
Messages
1,884
Likes
934
#1
What would be the particular use for a drill like this? It an NTM 3069c55-001.
 

Attachments

RJSakowski

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Feb 1, 2015
Messages
3,681
Likes
4,286
#2
They can be used for various purposes. For some, the reduced diameter provides for reduced drilling pressure and better final hole finish. They can also be ground with an flat or angled secondary cutting edge for simultaneously creating a through hole and counterbore or countersink.
 

Jimsehr

Active User
H-M Supporter - Silver Member ($10)
Joined
Apr 23, 2013
Messages
419
Likes
335
#3
Often used in production. You can drill a hole for a socket head cap screw where the screw goes thru plus the cap screw head can be countersunk at the same time.
Or you can drill and chamfer parts at one time. Time is money in production work. I have used hundreds of drills like that. There is a company in Downey Ca that is named Step Driils unlimited that grinds them to whatever size you need.
 

kd4gij

Active User
Registered
Joined
Feb 7, 2011
Messages
4,674
Likes
1,848
#4
That one looks like the the small is a tap drill and the large is clearance

Sent from my SM-G530T using Tapatalk
 

GoceKU

Brass
Registered
Joined
Jul 14, 2017
Messages
727
Likes
1,443
#5
I have couple of them, they are counterbore, often used for allen bolts.
 

ddickey

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Apr 21, 2016
Messages
1,884
Likes
934
#6
There are four steps. First is .375 & the last is .625. .521 & .578
 
[6]
[5] [7]
Top