Countersink bits, does more flutes mean less chatter?

[BaronJ]

Hi Guys,

I made repairs to my Weldon countersink sharpening jig today.

This is how it looks now. I've replaced the sized plastic nut with one made from mild steel.
I've also recovered the 2MT chuck spindle and dispensed with the 1" inch tool sleeve that it fit into.

This is the new nut that I made today, replacing the plastic one. I've used the same three M5 grub screws to secure the 1/2" diameter chromed
steel rod. It turns easily, and took a 3/8" by 24 tpi thread for the chuck fitting without issue.

This is a close up of the new nut. Single point threaded at about 200 rpm. Running the lathe in reverse and cutting away from the chuck.
I used a carbide full form threading insert to cut these threads.

These are the two items that were used originally on this jig. Incidentally the chuck used was a 1/2" inch German Rohm one
That I bought complete with this arbor. The one inch machine socket I picked up in the local scrap yard.

 

[benmychree]

Here is a fixture sold by M.A.Ford for sharpening their countersinks, the large sleeve has a cam form on both of its faces for different sizes of countersinks, the smaller cylinder fits snugly inside and has a 1/2" bore with a sleeve to reduce to 1/4" for smaller countersinks; the disc has a ball bearing set in its back face that rides against the cam face. The large sleeve has a flat ground on it that orients it when clamped in a vise on the grinding machine; one simply mounts the tool being sharpened in the bore of the spindle, clamps it in place with a setscrew with the tool's flute lined up with a notch in the disc and rotates it with the disc while maintaining inward pressure to hold the ball follower against the cam face.
I have another fixture, much more sophisticated made by Weldon that has interchangeable cams and a crank to rotate it, it shares it's main body with the Weldon end mill sharpening attachment.

 

[pontiac428]

O-flute countersink sharpened easy enough. I just took a blind stab at it with the tool post grinder and got good (enough) results.

(from mobile)

 

[BaronJ]

Hi Pontiac,

The one major flaw in your set up is that it will remove the relief behind the cutting edge.
If you go up a few posts there is a video that explains what needs to happen to sharpen any countersink properly.

Indeed if you look at my pictures you will see that the threaded screw rotates and moves the countersink forward by 30 thou per rotation to maintain the relief spiral behind the cutting edge.

 

[pontiac428]

Are you saying that O-flute c'sinks are ground eccentric? I thought the O provided the lead angle, and chip evacuation was through the flute. I could be wrong. I just set it up and ground it, haven't tested it yet. It's the wrong angle for my project, I need a larger 82 deg anyway. I'll come back and report on whether it cuts or not when I find a hole to chamfer with it.

 

[BaronJ]

Oh it will cut, but not very well !
Yes I am saying that the cone is tapered.
Go look at the video, hang on I'll get the post number for you, here you go Post 21.
That video explains all.

The inside of the hole provides the cutting edge and the tapered cone provides the relief. A bit like the relief on a drill.

 

[ezduzit]

...I've used the same three M5 grub screws...and took a 3/8" by 24 tpi thread...

Why have you mixed metric and SAE threads?

 

[BaronJ]

Hi Ezduzit,

Thank you for reading my post.
Normally they would all have been metric, however the chuck body is threaded 3/8" X 24 tpi.

 

[jdedmon91]

Hi all.
I need to get a countersink bit with a body diameter of minimum .775" for the M8 screws that I'm planning to use in aluminum and mild steel.
The 3/4" bit will be too small so I've been searching online for a good 7/8" or 1" countersink bit,
I have never owned a zero flute bit, all I've used have been single flute and a couple of 6 flutes, which all performed equally well ,what's confusing is what 's called "chatterless" countersink bits ,it seem to suggest the more flutes a bit has the less chatter it'll produce but on the other hand I have read posts here praising the zero flute countersink bit as the better performer , so here's my question: do I stick with a single flute bit since I know what to expect or do I get the zero flute and hope it'll cut a smooth CS ?
I looked around ebay and amazon, there's a lot of cheap bits for sale and almost all claim to cut metal but one item I found that sounds good is KEO brand :
https://www.amazon.com/gp/product/B00947BU22/ref=ox_sc_act_title_1?smid=ATVPDKIKX0DER&psc=1
View attachment 275522
Please let me know what you think.

To me they are the bests ones


Sent from my iPhone using Tapatalk

 

[MSD0]

The speed was likely my issue. Thanks guys. I will try slower.
R

Going slow with heavy feed has always worked best for me. I usually get the best results if done in one shot, so a depth stop will help.