PDA

View Full Version : Counter-sink size



Fasttrack
03-31-2007, 11:01 PM
Hey guys i got a quick question for you all:
What size countersink do i need for a 1/4" 20tpi flat head socket cap screw?
Evidently it takes an 82* countersink but no idea what size i should buy; mcmaster gives the head diameter as .531. The countersinks from enco just give a size and a shank size, i assume that the size is the body size...? So i reckon i would need 9/16 or larger, right?

thanks

lane
03-31-2007, 11:06 PM
Get one with a body, size of around " and a single flute weldon style.They work better.

PolskiFran
03-31-2007, 11:18 PM
Size is the body size (head of the screw). While Weldon type countersinks are probably the best, I usually use single flute regular type as opposed to the multi flute countersinks. My single flute countersinks usually perform double duty as sheetmetal drills. No out-of-round holes.

Frank

Fasttrack
03-31-2007, 11:35 PM
Alright cool! Thanks for the quick replies.

I'll add a single-flute countersink to my shopping list.

Uncle O
04-01-2007, 08:23 AM
I like the "Zero Flute" style myself.....very smooth cutting action.
Singles if no Zero available

Swarf&Sparks
04-01-2007, 08:34 AM
I'll go along with that, Uncle O.
If by no flute, you mean through drilled type.
Best/easiest countersink I've used.
Acetal or 316 SS, no prob.

Uncle O
04-01-2007, 09:13 AM
I'll go along with that, Uncle O.
If by no flute, you mean through drilled type.
Best/easiest countersink I've used.
Acetal or 316 SS, no prob.


Yes Sir , that is what I am talking about....

DR
04-01-2007, 09:44 AM
Flute-less, Weldon type, fish-eye.....these names usually all refer to the same type.

Yes, they work well. We use them in all materials from plastics to 316 stainless. I even have the special fixture for sharpening them.

Funny thing, after all these years of swearing by them, recommending them to anyone who asked....recently I found out Weldon recommends them only for soft materials because or the relatively fragile cutting edge.

Swarf&Sparks
04-01-2007, 09:50 AM
"the relatively fragile cutting edge."
Damn, I wasn't aware of that. In my ignorance, I just keep bashing holes in 316 and the odd piece of inconel and hastelloy!
:D

Great tool.

BobWarfield
04-01-2007, 11:29 AM
I will agree that the zero flutes work extremely nicely. Enco has Zeo zero flutes on sale pretty often, perhaps even now.

I heard a trick from a machinist that I really liked. He countersinks with the spot drill and just does the countersink at the beginning instead of the end. Saves a toolchange.

You can buy 82 degree spot drills, but the 90's will work almost as well for most jobs. Run your spot drill down to 1/2 the head diameter as that's what works with 90 degrees. Here is a little table I made up of the depth to cut as well as the error of 90 vs 82 for various sizes of hardware:

http://www.thewarfields.com/cnccookbook/img/CNCCookbook/CounterSinkDepths.jpg

Best,

BW

wierdscience
04-01-2007, 11:47 AM
If your using them in the mill combinded drill and countersinks work well too and don't require a second operation.

While we are on the subject,who decided that screw heads would be 82*instead of 90*?

And why are six flute countersinks called "chatterless" when that's all they do is chatter?:D

DR
04-01-2007, 12:11 PM
I will agree that the zero flutes work extremely nicely. Enco has Zeo zero flutes on sale pretty often, perhaps even now.

I heard a trick from a machinist that I really liked. He countersinks with the spot drill and just does the countersink at the beginning instead of the end. Saves a toolchange.

You can buy 82 degree spot drills, but the 90's will work almost as well for most jobs. Run your spot drill down to 1/2 the head diameter as that's what works with 90 degrees. Here is a little table I made up of the depth to cut as well as the error of 90 vs 82 for various sizes of hardware:

http://www.thewarfields.com/cnccookbook/img/CNCCookbook/CounterSinkDepths.jpg

Best,

BW


Yep, spotting drills.

One of the mysteries of machining to me is why they aren't used more.

I still roll my eyes when I hear of guys using center drills where a spotting drill is the best and most correct tool to use.

Now that you've brought up the subject, I can almost bet someone will respond saying they've used center drills for years to spot and countersink holes.

IMO, it's a ridiculous thing to do. Look in any book of shop hints and you'll find methods of removing broken off tips of center drills, but never a mention of removing the tip of a spotting drill (because they don't break off in the work).


Use the spotting drill to establish the hole location and countersink. Use the zero flute on the back side of the part to clear burrs.

on edit: there is one problem with using spotting drills to pre-countsink....they don't come with reduced shanks so the max diameter countersink on a 1/2" capacity chuck machine is 1/2".

gundog
04-01-2007, 12:43 PM
I use countersinks to make some parts for my small business. I stumbled onto these by accident they are designed for aircraft. They have saved me a lot of time. My use for them is not high precission work. I have some .250 5052 aluminum parts that I have cut on a water jet and the water jet makes the holes then I have to countersink 12 holes on each part. I use these micro-stop countersinks I don not hold the aluminum down only by hand and rotate the part through countersinking all of the holes by hand the pilot on the cutter centers up and the cage is adjustable for depth of cut. I can move right through all holes very fast and they all come out with exactly the same depth. This is one company you can get them through but there are others ATI is one they are owned by Snap-On. I bought the first ones on ebay and have since ordered new ones and new cutters. Depending on your use and how many holes you need to do these might be worth the money.
Mike

http://www.aircraftspruce.com/catalog/topages/microstopcountersink.php

http://www.aircraftspruce.com/catalog/topages/microstop.php

Evan
04-01-2007, 01:23 PM
I use six flute countersinks. They cut faster and don't chatter. It's important to use cutting lube with a countersink. I do a LOT of countersinking.

Carld
04-01-2007, 02:05 PM
I like and use the M.A. Ford brand of single flute countersinks. I use one slightly larger than the head of the bolt to be countersunk. The single flute cutter gives a better finish when you learn how to use it.

DR
04-01-2007, 02:09 PM
......
And why are six flute countersinks called "chatterless" when that's all they do is chatter?:D

Are you using quality countersinks?

The Severance brand chatterle$$ are good, they don't chatter ever.

Fasttrack
04-01-2007, 02:47 PM
I still roll my eyes when I hear of guys using center drills where a spotting drill is the best and most correct tool to use.

Now that you've brought up the subject, I can almost bet someone will respond saying they've used center drills for years to spot and countersink holes.

IMO, it's a ridiculous thing to do. Look in any book of shop hints and you'll find methods of removing broken off tips of center drills, but never a mention of removing the tip of a spotting drill (because they don't break off in the work).


:D I thought i was the only one who did that. I didn't have a spotting drill so i'd been using a center drill. Of course mine are 60* so i figured i'd need a real counter sink for these screws, but just the other day i broke the tip off of a center drill. :o I decided right then and there that i'd have to buy a spotting drill next time i ordered something from enco, so along with the cap screws, countersink, layout dye, a few endmills, and some TCMT inserts, i've got a spotting drill :D

Marc M
04-01-2007, 02:59 PM
I've used multi-flute countersinks all my life. A few things are required for good result.

First and most important, your setup needs to be ridgid. On my old Craftsman benchtop drillpress I had a difficult time controlling chatter. The table was elastic and the spindle bearing (yes, it only had 1 at the bottom) was junk. When I got the Solberga, I discovered it cuts like butter and I no longer worry about chatter.

Next, it needs to be decent quality and sharp. If it's dull you'll have nothing but problems no matter what you do. Run it slow and use the appropriate cutting fluid.

I tried single flute versions but I was never able to get a very good finish. I tried a no flute design (import) which did eliminate chatter, but it was slow and dulled fairly quickly.

Lew Hartswick
04-01-2007, 04:03 PM
And why are six flute countersinks called "chatterless" when that's all they do is chatter?:D

I think one of the bigest problems with a countersink chattering is WAY to fast
speed. Too may people just leave the drill at the same speed they were
drilling at. (is that sentence on of those "up with which I will not put"?) :-)
...lew...