Help with Countersinks

G

gudspelr

Joined
Jul 1, 2013
Messages
451
So, I feel kind of like an idiot... I'm making a liner lock and hoping I can get it to be my first successful solo build for a folder. But, I need some help with my countersinks. I need to use one to help deburr drilled holes and have run into some "challenges". I had a 1/4" diameter, single flute, carbide countersink already on hand. But, that single flute ends up making the liner move around and around and around.... Plus, it seems like the smaller diameter can end up giving me some issues as I start running out of cutting flute, if that makes sense.

SO, I decided to get online and ordered a 6 flute, 1/2" diameter, carbide countersink. I was all excited because it finally came today and immediately went into the garage to give it a go. I grabbed a scrap piece of liner (from past failures...) and it became apparent very quickly that things weren't going to work out. The point of the countersink is, well, not there. This particular countersink is flattened off at the point instead of going all the way to a point. So, my smaller screw holes can't get chamfered. I even tried it on my 3/32" holes and those holes are just a fuzz too small for the flutes to get in there. Needless to say, I was pretty frustrated that I didn't realize that problem before ordering.

I borrowed a cheaper HSS one from my dad and gave it a whirl. It countersinks the Ti liners, but actually leaves a small burr on the top that I can catch my fingernail on. I feel like it cuts in some of the countersink, but just isn't sharp enough to not leave a burr that I'll still have to take to my granite plate and sandpaper....

Soooo, what do you guys use? Am I missing something with the single flute one? I feel like that wobbling actually opens the hole up just a tad. Should I just find another 6 flute carbide one with a point instead of that flat? What do you use and how do you like it? Thanks for any suggestions.

Jeremy

First time posting pics from imgur….hoping it works right...




 
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You use countersinks that are the size of the hole drilled. 1/2" countersinks are best for 1/4" to 1/2"holes, etc. Get one for the size range of holes you drilled in the liners.
 
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A 3/8" or 1/2" single flute M.A. Ford HSS 82 degree countersink will do everything you want. From deburring to counter sinking for 0-80 flat heads. Skip carbide counter sinks, I've never had one that didn't chatter in manual use.
 
I cant stand using single flute countersinks unless it's in a mill and the set up hasn't moved since drilling the hole, or I can go back to location with a DRO.
I prefer using 3 flutes ran at less than 200 rpm and 6 flutes if the machine will run less than 100.
The only way I know to get rid of most of the burr is to have a depth stop set to hold the quill in position while the cut finishes.
 
Thanks for the advice, I appreciate it. Most of the holes are for 2-56 screws, both pre tapped and clearance. Also, some for 1/16” pins, then there’s the 3/16” pivots and 3/32” stop pin holes. I first got an 1/8” countersink, but found that just didn’t have the necessary diameter to cut the required countersink for the flat head screws, so that’s what made me double to 1/4”.
For you that like single flute, are you running them in a mill with everything locked down? I’m trying to figure out what I’m doing wrong that makes the material want to wobble as the one cutting edge makes contact. The only way I can think of to keep that from happening is to have the material locked down, but that would make the whole process of simply deburring a hole a lot longer.

Jeremy
 
I've found lighter pressure to be important. If I try to push too hard, it chatters. I use enough pressure to get chips started then back off a little and let it cut. Then a little more pressure to move the cut deeper and let it cut.......and so on.
 
I use a 4 flute .187" M.A. Ford 82 degree counters sink for deburring and counter sinking(imagine that:p)2-56 screw holes in my titanium liners. I mostly use a .375" 6 flute for the .187" pivot holes.
Turning fairly slowly. No chatter issues.
 
If the work piece is bouncing around with the single flute cutter it's either because your hole isn't round (as the csink makes the chamfer round, it's taking greater depth of cut in one portion of the hole than the other) or the csink is poorly ground. If your CS is raising a burr, it's dull or not very free cutting geometry.

With the single flute M.A. Fords, it doesn't matter what size you use. All of them 1/2" and under come down to a sharp point with good cutting geometry. Their 6 flutes are marketed as "chatterless" and in my experience are, but do not cut down to a 0 diameter.

It's carbide countersinks with their odd grind geometry that all suck IMO. Whether it's a $5 chinese one or a $100 OSG.

M.A. Ford 3/8" single flute
M.A. Ford 1/4" single flute Sometimes it's nice to have a smaller uniform diameter CS to get into tight spots, for example a hole near a integral bolster that a 3/8" cutter may not clear.

I only buy 82 degrees because I don't care if my chamfers are exactly 90 and 82 degree countersinks are for matching flat head screws.
 
I really appreciate all the feedback-I may grab some scrap and drill some more holes and try a few different setups and see what I can come up with.

Jeremy
 
I just wanted to add one more post with some results. I tried a few different things with the countersinks I had and got so-so results. I needed to make an order for some taps and drill bits so I added the MA Ford 3/8” HSS one that Kuraki linked to above in the cart, as well. I just put it in the drill press and gave it a whirl. WOW. Huuuuge difference. I don’t have the knowledge base to understand why the single flute carbide one makes my material wobble around and this one doesn’t, but this HSS one is fantastic. It leaves a great finish, no wobble, and goes down to a point so I can easily de-burr my small holes, too.

Thanks to everyone who helped and Kuraki for that link.

Jeremy
 
When I see him recommending a helix cutter for alum or a spiral tap to someone, I just pony up and buy it.( I have been lurking on his advice to others ;) and what a difference the quality cutting tools make.
 
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