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How To Countersink Brass W/O Chatter

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RicoWarner

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Hi all -

Did read other threads, very helpful, posted a reply to one--but it is a few years old--thought would also post specific question here. Lots of good tips on selecting 0-flute or single-flute countersink, giving lots of feed, low speed.

Specifically what I am wondering is if the material the countersink is made of makes much difference...? See all sorts of materials for the CS itself, and wondering if some might chatter less than others with brass?

Have 60 holes to countersink and took tons of work to get the parts to where they are. Five holes per part. Really want to succeed with all the holes, first time. Any help appreciated. Tried one test hole and it was total trash! Wow, who knew countersinking brass would require this much finesse? Thanks!
 

stupoty

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The single flute cutters don't have the problem of creating a geometric pattern due to bouncing in their own pattern (like bumps on a road getting worse from the bounce of tires in the ripples) I have the most success with a single flute countersink or sometimes doing it free hand with a hand held drill.

Drill press or mill is easier to get the same depth though, I guess it depends upon the required look and precision.

I have a two flute counter sink that is the next size up that I have to use on bigger stuff that is also nearly as reliable.

It is almost as bad as braking a tap on a final operation doing the counter sinks wrong. (I once counter sank about 8 holes perfectly on the wrong side of a thin part , massive palm face :oops2: )

Stu
 

Bob Korves

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There are lots of different types of brass, different alloys with differing hardness. Some are pretty easy to machine, others often cause problems. I find that fewer flutes, slower speeds, and more pressure on the tool for heavier feeds helps me most often. Don't dwell, be either cutting or withdrawing the tool. Make real chips.
 

benmychree

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The material that the countersink is made of should make no difference in its cutting ability; single flute is likely the best choice, and the tool should be sharp, brass does not like dull tools.
 

Jeffers

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Watch Robin Renzetti’s excellent form tool YouTube video. He takes the last cuts by turning the chuck by hand for the final cut, I am sure this would work in your application with a single flute countersink alternatively grind a d bit and use a boring head with a depth stop?


Sent from my iPhone using Tapatalk
 

projectnut

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I've used MA Ford Uniflute countersinks almost exclusively since the 1980's.

They do an excellent job on any material I've ever used them on. Over the years I've done extensive work in stainless, aluminum, cast iron, brass, and dozens of other materials. They don't jump around like the multiflute styles, and hold an edge far longer. Several years ago I purchased a fixture to sharpen them. In nearly 30 years of ownership I've only had to sharpen them a couple times.


At the time it cost about $50.00. As you can see from the link they have gone up considerably over the years.

IMG_0571.JPGIMG_0572.JPGIMG_0573.JPG

Keep in mind countersinks come in several different angles. 82* is most common for SAE threads, 90* for most metrics, and 100* for aircraft fasteners. I also have 45*, 55* and 60* for specialty fasteners
 

projectnut

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I forgot to mention in my previous post that 90+% of the time my countersinking process was done on either a vertical mill or a drill press.
 

macardoso

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I use HSS 5 flute countersinks. I can easily place a small chamfer in any material without chatter, but the deeper I cut the worse the chatter gets.

I suspect that unlike a drill which needs constant pressure through the length of cut, a chamfer cutter has an increasing chip size as it moves through the cut. Because of this, the deeper you cut, the more force must be applied to fully form a chip. Once you let it begin to chatter, there really isn't much hope to clean it up using the same tool.
 

RJSakowski

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As Mike said, countersinking before drilling the hole, fairly well eliminates chatter. Slowing the rpm also helps. In some cases, I have actually turned the spindle by hand. I have seen countersinks where the flutes are not equally spaced which will tend to eliminate the harmonics that cause chatter but I haven't actually tried one as yet.
 

RicoWarner

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Ok! And wow! Rhanks to everyone for the excellent tips. Will try the MA Ford Uniflute and the many tips on same test material. Will let you know how it goes.
 
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