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Old 09-06-2014, 09:10 PM
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Default Using a solid carbide bit

I have this HF crescent wrench that I want to drill a couple a couple of holes in the jaws to make an adjustable spanner wrench.

The first wrench I made the Jaws drilled with a high speed drill. This Jaws on this wrench is harder and will not drill with a HS drill.

So I am going to do something I have never done. I am going to use a solid carbide drill.

I have the wrench set up in the mill but I am not sure how fast the drill should be turned fast/slow. I will use cutting oil. My guess the drill should be turned at a slow speed.
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Old 09-06-2014, 09:15 PM
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Quote:
Originally Posted by Charlie C View Post
I have this HF crescent wrench that I want to drill a couple a couple of holes in the jaws to make an adjustable spanner wrench.

The first wrench I made the Jaws drilled with a high speed drill. This Jaws on this wrench is harder and will not drill with a HS drill.

So I am going to do something I have never done. I am going to use a solid carbide drill.

I have the wrench set up in the mill but I am not sure how fast the drill should be turned fast/slow. I will use cutting oil. My guess the drill should be turned at a slow speed.
Nope generally double the speed of HSS, going slow will just kill the carbide.
What is the diameter of the drill?
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Old 09-06-2014, 09:21 PM
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My Machining Data Handbook for C-2 carbide recommends 100 sfpm for 52-54 Rockwell C and 75 sfpm for 54-56 Rockwell C.

I would run with the 75 sfpm.
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Old 09-06-2014, 09:35 PM
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My Machining Data Handbook for C-2 carbide recommends 100 sfpm for 52-54 Rockwell C and 75 sfpm for 54-56 Rockwell C.

I would run with the 75 sfpm.

............. (75) x (12)
RPM = ------------------ .
........... (dia.) x (3.14)
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Old 09-06-2014, 09:42 PM
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We have this thread, depending on what the point looks like on the drill and size, may grind a starting spot with a Dremel but it would have to be concentric or you may break the bit.

http://www.shopfloortalk.com/forums/...ad.php?t=14206
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Old 09-06-2014, 10:01 PM
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Dumb question are you thinking of using a drill press or a mill? I really would
not recommend a drill press, they generally lack the rigidity or the tolerances
needed for running solid carbide tools.
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Old 09-06-2014, 10:57 PM
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yes,I forgot the dia. it is .125. And I will use the bridgeport type mill that I have.

I don't have any idea what the rockwell hardness is, the wrench being a HF special.
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Old 09-06-2014, 11:46 PM
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Quote:
Originally Posted by Charlie C View Post
yes,I forgot the dia. it is .125. And I will use the bridgeport type mill that I have.

I don't have any idea what the rockwell hardness is, the wrench being a HF special.
HHS drills are generally 58-62 Rc; 4140 full hard is 56. You said that a HSS
drill will not cut. So your wrench must be close to the drill hardness. Cheap
tools are often hardened but not tempered properly, leaving them brittle so
they break easier. I am guessing that you wrench is in the mid fifties.

So I come up with 2290 rpm for 1/8" drill that does not surprise me for solid
carbide. Since my Bridgport is a step pulley head I would like cut that speed
in half and run my ~1100 rpm speed, my choices about that is ~1700 and
~2700.

When setting up the part make sure the part cannot move and the surface you
are drilling into is as close to perpendicular as you can make it. Lock both the
x and y axes. You have to make sure the part will not move, solid carbide
tooling is not forgiving. I have grenade more than one SC end mill. Wear at
a minimum safety glasses. A full face shield would not be overkill and a shop
apron is not a bad idea either.
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Old 09-07-2014, 12:35 AM
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You will need a center spot for that small a bit.
if the bit skates it will snap.

use a larger carbide drill bit just to get a spot started then use the 1/8"
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  #10  
Old 09-07-2014, 09:40 AM
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Quote:
Originally Posted by Shade Tree Welder View Post
............. (75) x (12)
RPM = ------------------ .
........... (dia.) x (3.14)

Damn!! Math!! I never could paid attention, Linda Lanzsaratti, sat in front of me with skin-tite low-rise pants, I couldn't concentrate ....................
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