Countersink vs center reamer?

[bw77]

Would like to know - what is the difference between a countersink
and a center reamer?

Center reamer

http://www.grainger.com/Grainger/KEO-Center-Reamer-3P386

Countersink

http://www.grainger.com/Grainger/KEO-Countersink-3P419

Thanks.

 

[Trucky]

They're practically the same. No real discernible difference.

Both styles can vary in the number of flutes, material, length, angle, coating, etc.

 

[garboui]

my best guess is that the countersink will have a cut angle the same as a screw head and is made to take out material. the reamer is probably a 90deg cut as well as not having an aggressive cut so that it will be easier to leave a small chamfer after breaking/deburring the edge.

 

[Linh]

There both 82 degrees which are made for screw heads. You will get less chatter compared to a single flute.

 

[Kevin54]

There is no difference at all except for the number of flutes. Using a drill press, you may be better going with the 6 flute as it keeps itself centered better than the single flute. In a mill where you know you are on direct center, I like the single flute. Also, depending on the brand name of the countersinks, the 6 flute is often called a "no-chat" meaning that it will not produce chatter. Don't believe it. The 6 flute will produce quite a bit of chatter, especially with a drill press.

As far as cutting angles, you can get either in a wide array of angles. Depending again on the manufacturer and where you order them from, the angles can be a little deceiving. Some will list an 82 degree countersink as a 41 degree countersink. The 41 degrees is per side whereas the 82 degrees is included degrees.

 

[Trucky]

There is no difference at all except for the number of flutes. Using a drill press, you may be better going with the 6 flute as it keeps itself centered better than the single flute. In a mill where you know you are on direct center, I like the single flute. Also, depending on the brand name of the countersinks, the 6 flute is often called a "no-chat" meaning that it will not produce chatter. Don't believe it. The 6 flute will produce quite a bit of chatter, especially with a drill press.

I've found that even when using a drill press, an odd number of "flutes" helps to reduce chatter the most, thus most of our countersinks are of the 3-flute variety. We really only use more flutes when material removal is a concern, such as a big chamfer (And by big, think .100-.200 across).

 

[bw77]

As far as cutting angles, you can get either in a wide array of angles. Depending again on the manufacturer and where you order them from, the angles can be a little deceiving. Some will list an 82 degree countersink as a 41 degree countersink. The 41 degrees is per side whereas the 82 degrees is included degrees.

Several angles available - 60,82,90,100,110,120.

What are the guidelines for selecting the angle?
Which angle would you choose for deburring?
What is 60 degree used for?

Thanks again.

 

[t100]

general industrial and automotive are 82* countersink, aviation is 100*.

90* is normally used as chamfering tool.

 

[Trucky]

Several angles available - 60,82,90,100,110,120.

1. What are the guidelines for selecting the angle?

2. Which angle would you choose for deburring?

3. What is 60 degree used for?

Thanks again.

1. Purpose. For general deburring, I would use a 90* included countersink, maybe 6 flute to speed it up a wee bit. (Not literally the rpm) Single flute countersinks should be used when multi-flute countersinks might chatter a lot or the hole is too small for a multi-flute countersink to enter.

82 degree Contersinks are used for countersinking flathead screws.
90 degree Countersinks are used for chamfering and deburring.
100 degree Countersinks are used to make screw and rivet holes.

general guidelines:
ISO Metric use 90°
Imperial BA, BSF, etc. use 90°
UNC, UNF use 82°
Aviation fasteners use 100°

As for 60* specifically, I know we have a few at the shop, but I venture to say we haven't used them much at all yet. Perhaps for a hole made for a pin or something pressed in. Heck if I know.

2. Like I said, 90* or even 82* will work in most all cases for deburring. I prefer 90* because of the even material removal from both "lands" (If you know what I mean..)

As for material, HSS will do you fine unless you're doing production work which in that case I recommend carbide as a minimum, and be careful with those things. If it's a huge burr, take it off with pliers and clean up the rest with the CS.

There are also "through-hole/zero-flute" countersinks designed specifically to prevent almost all chatter. Google will help you out here

3. Mimicking the angle used by center drills in some applications, possibly.

 

[A_Pmech]

I'm solidly in the one-flute and zero-flute c-sink camp.

I hate multi-flute c-sinks. If I need to butcher a job I'll just use an axe.



*6-flutes work great in a hand chuck for deburring.

As for 60* specifically, I know we have a few at the shop, but I venture to say we haven't used them much at all yet. Perhaps for a hole made for a pin or something pressed in. Heck if I know.

Reaming centers, maybe?

 

[Trucky]

Reaming centers, maybe?

Only the new guys have to make centers... and we send the good centers out to actual professionals

 

[Nader]

If you're chamfering:
Standard flat head screws are 82 degrees
Metric flat heads are 90 degrees

 

[Kevin54]

Not all flat head screws are 90 degrees. And flat head allen screws are 82 degrees.

It really pays to have a few different sizes and angles on hand if you do or plan to do any countersinking at all.