# Buying 90 or 82 zero flute counter sinks.



## COMachinist (Apr 7, 2021)

Went over to Amazon to look at a set zero flute counter sinks/deburring tools, found 60, 82 and 90 degree. I want to just to buy the most useful set for deburring holes. What do most of you use?
CH


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## macardoso (Apr 7, 2021)

82 degree fits flat head screws, 90 degrees is typical for deburring. 

Honestly, for small chamfers you'll never notice the difference between 82 and 90, making the 82 more versatile when you need to countersink a hole for a screw.


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## Winegrower (Apr 7, 2021)

I have seen it explained that metric screws are 90 degree, inch are 82.


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## macardoso (Apr 7, 2021)

Winegrower said:


> I have seen it explained that metric screws are 90 degree, inch are 82.


Ah, interesting, very possible


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## keeena (Apr 7, 2021)

Winegrower is right about the included angle for imperial (82*) vs. metric (90*) flat-head fasteners. You could buy the one which aligns with the system you use the most in case you ever have a need to sink a flat-head?

I use 90* for deburr/chamfer only because it results in an 'even' appearance (width and depth being the same).


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## shadetreedad (Apr 7, 2021)

Winegrower said:


> I have seen it explained that metric screws are 90 degree, inch are 82.


Correct, and 100 degree is aircraft.
mike


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## darkzero (Apr 7, 2021)

I use 90° for chamfers cause that'll give you a 45° chamfer. I also own 82° & 100° but for countersinking for flat screws.


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## Braeden P (Apr 7, 2021)

I have an aircraft countersink tool made by Martin aircraft tool really neat tool


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## Aukai (Apr 7, 2021)

Are the angles or live centers 60*?


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## darkzero (Apr 7, 2021)

Aukai said:


> Are the angles or live centers 60*?



Usually they are. But not for all bull centers & not sure about live centers with all the interchangeable tips. Regardless a countersink is not normally used to drill centers for use with a dead/live center. Countersinks need an existing hole in order to cut.


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## Aukai (Apr 7, 2021)

Thank you, I've needed to turn things with large bores, and the live center looses tension from the lip of the bore moving/wearing on the point of the live center. If that makes sense.


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## Flyinfool (Apr 7, 2021)

What Darkzero said
For a center a c'sink tool does not accurately follow the existing hole. You need a center to be accurate.

If the edge of the bore is wearing with a live center, then you are doing something wrong, there should be no movement between a live center and the work piece. If it is a large bore then at the time you are boring it you should cut the chamfer for your center at the same time, when you get to the bigger sizes not all centers are 60°. 
For smaller sizes you should use a center drill, some times called a combination drill / c'sink. This will give an accurate location, the correct 60° angle and clearance for the tip of the center.

I have all the angles of c'sinks, 60°, 82°, 90°, 100°, and 120° but then I have been accumulating tools for a half century. Start by getting what you need for the job at hand, It is not a good way to spend to just get things for the sake of getting them, although getting a set of something is the best way to get things you do not have an imediate need for, Like a set of drill bits, I am sure that there are still a few drill bits that have never been used by me. I got a set of c'sinks and have used all of them at one time or another. Same with the set of center drills.


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## darkzero (Apr 7, 2021)

Aukai said:


> Thank you, I've needed to turn things with large bores, and the live center looses tension from the lip of the bore moving/wearing on the point of the live center. If that makes sense.



As far as loosing tension, that could simply be the heating up & cooling of the part (and the center) causing that. When the part heats up, it will push the tailstock back (especially if you put too much tension), then when the part cools, not enough tension. If you are doing any considerable amount of turning supported by a center you should always check periodically for tension, especially when turning between centers. That's how I was taught.

As far as wear/scoring of the center's tip (if that's what you actually meant), even when I use a revolving center I always use lube on the tip & in the hole (I promise that was not meant to sound dirty!  ).

This is what I use. I buy it from Mcmaster or MSC. I've read that machinists used to use white lead back in the day but of course that stuff is not available anymore.


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## darkzero (Apr 7, 2021)

darkzero said:


> When the part heats up, it will push the tailstock back (especially if you put too much tension), then when the part cools, not enough tension.



BTW, the way I was taught, when using a revolving center, when sufficiently tensioned, you should still be able to turn the revolving tip by hand with the workpiece stationary, but not very freely, it should have a fair amount of resistance. If you apply so much force with the tailstock where you can't spin the center's tip at all, then that's too much. You're putting unecessary excessive load on the center's bearing(s) which will also cause excessive heat.


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## Aukai (Apr 7, 2021)

I am tightening it up too much, my issue is the material is deforming at the contact point of the live center, and losing dimensions during the operations.


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## darkzero (Apr 7, 2021)

Well Mike, if ya got lots of extra money to burn, you could always buy one of these!


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## Aukai (Apr 7, 2021)

You gonna co-sign


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## Alcap (Apr 8, 2021)

Braeden P said:


> I have an aircraft countersink tool made by Martin aircraft tool really neat tool


That’s a neat looking tool to keep the countersunk holes the same . Im sure it’s $$$$  Has anyone made something similar?


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## Braeden P (Apr 8, 2021)

they are only 40 bucks used heres one for 25 bucks









						Metalworking Countersinks for sale | eBay
					

Get the best deals on Metalworking Countersinks when you shop the largest online selection at eBay.com. Free shipping on many items | Browse your favorite brands | affordable prices.



					www.ebay.com


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## projectnut (Apr 8, 2021)

That’s a neat looking tool to keep the countersunk holes the same . Im sure it’s $$$$  Has anyone made something similar?

They come in many different sizes and can handle cutters to countersink holes anywhere from 1/8" diameter to over 2" in diameter.  There are several different manufacturers.  Most are surplus from aircraft manufacturers.  They work fine, but do have some drawbacks.  The cage limits how close you can come to an interfering corner or vertical member, and due to their length the are best used areas free of infringing obstacles.  They are generally used in quick change air powered hand tools, but they do work well in a hand drill or drill press.

The cutting tips are screwed into a threaded shaft built into the cage.  The smaller ones are 1/4-28 while the larger ones are up to 1/2".  There are 2 styles.  Either built in pilot or changeable pilot.  The ones with the built in pilot require a hole at least the size of the pilot to be used.  Those with a changeable pilot can be used either with or without the pilot.  The piloted cutters are difficult to sharpen without the proper equipment.  Those with the removable pilot can be sharpened on a surface grinder with a fixture.  In many cases it's less expensive to replace the piloted ones than to send them out for sharpening.

I have about a dozen different sizes and around 100 different cutters.  They come up on eBay for extremely reasonable prices every once in a while.  If you're looking I would do a search and save it.  You'll get notifications when new ones appear.  Just be sure to make the search broad enough that you don't eliminate some manufacturers.  Over the years they have been made by Magnavon, Zephyr, Briles, Wescon, Arvo Martin, ATI and many others.  MA Ford, Briles and others make replacement cutters.

Keep in mind the standard countersink angle on these tools is 100*.  Cutters are available in 45*, 60*, 82*, 90*, 100* and 120* as far as I know.  The 100* are by far the most popular and least expensive.


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## davidcarmichael (Apr 8, 2021)

Winegrower said:


> I have seen it explained that metric screws are 90 degree, inch are 82.


My experience has been that American screws are 82 degrees but all others on the planet are 90 and have been long before metric came along (e.g. UK fasteners). Never used an 82 while in the UK for 30 years (no metric).


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## Winegrower (Apr 8, 2021)

davidcarmichael said:


> but all others on the planet are 90 and have been long before metric came along


As noted above, aircraft hardware is a 100 degree countersink.    Since the Wright brothers, I suppose.


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## Aukai (Apr 8, 2021)

Somewhere in my mind Howard Hughes used flush rivets to smooth out air flow for better aerodynamics on planes. I wonder if he had a hand in this too?


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## COMachinist (Apr 15, 2021)

Well, looks like 82, and 90 would do. I don't work on, or any thing with aircraft.  I do use a metric screw once in a great while, but not often. My old multi flute counter sinks chatter like a flock of Magpies. 
Any way I did order both sets. 
Thank a lot for all the info and help.
CH


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## pontiac428 (Apr 15, 2021)

I may not work on (full-scale) aircraft, but I have to do sheet metal every now and again, such as race car aero.  I don't own a 100-degree countersink, so when I do countersunk rivets I grab what I have.  It works, but it's not as flush as airframe work.  Now I now why!


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## DavidR8 (Apr 15, 2021)

Go with the 100 deg sinks John, you'll pick up tenths/add top-end/increase fuel economy/look cooler


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## ddickey (Apr 15, 2021)

darkzero said:


> Well Mike, if ya got lots of extra money to burn, you could always buy one of these!
> 
> View attachment 361977


Rohm MT3 is less than $400


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