What size (3mm shank) ball endmill should buy?

**John S** · 02-06-2009

One think I noticed with those is they are 4 flute, now 4 flute can be centre cutting or can't depending on how they are ground.
The ad doesn't say centre cutting so it's anyones guess, if one flute doesn't cross over centre then they won't plunge cut.

Can you post after you have received them ?

**HankMcSpank** · 04-06-2009

Just as a footnote, the Chinese seller (who's English is very good), has reported that these 4 flute endmills do bore dowanwards as well as cut sideways.

As predicted Jenny from the block hasn't answered my email, so her wares are only available to peruse in person - Bristol could be a suitable contender? ;-)

**John S** · 04-06-2009

Good, Most modern stuff is but you never know.

**HankMcSpank** · 07-06-2009

Just thought I better post a follow up to this - I think I've screwed up here! Basically, the ones he sells on Ebay are 4mm shaft (Dremels take 3mm end mills)...I emailed him to ask if he did 3mm shaft - he does, but stupidly, a couple of days later I only went & bought the ones he's selling online forgetting that those are in fact 4mm shafts! doh.

So in short....don't buy off that link that I gave above - email the seller to ask for 3mm shaft prices.

I'll get me coat.....

**HankMcSpank** · 07-06-2009

Just out of interest... what type of router are end mills with 4mm shafts used with?

I'm figuring those routers with 1/4" capability, but with a collet to shrink it down a litt?

As it goes I do have a larger 1/4" router (but it makes way too much noise)...I shall probably hang onto them for after when I get my acoustic shroud built!

**John S** · 07-06-2009

Hank,
It's the way things are changing, all the old engineering books like Chapman etc are totally out of date as regards tooling. For one thing what we knew as cutter descriptions have changed out of all context and even the manufacturers come up with their own descriptions.

At one time we had slot drills and end mills, slot drills are two flute with one flute going over centre so it can plunge and hey ho cut a slot.
Ends mills were 4 flute and had a hole in the centre for the grinding wheel to run out into and for that reason they couldn't plunge cut, you had to start off the work and move in hey ho hence 'end' of the work.

However modern CNC grinding techniques mean we can get 2, 3, 4, 5 or even 6 flute with or without centre cutting. Confused :question: well you will be.
The manufacturers haven't helped in that they call some cutters 4 flute end mills but they can plunge cut and on the same page they call a similar cutter a 4 flute slot drill.

So basically they have thrown the book out the window and it's a free for all. The old standards and terminology have gone forever. Don't believe me look in J&L book, or Cromwell, or WNT

Now the next bit is shanks, we had 4 sizes in metric and imperial.
6,10, 12 and 16 or 1/4", 3/8", 1/2" and 5/8" with 1/8" or 3mm for the tiny sub spindles. Many were threaded to fit the Clarkson type chucks.

With the advent of Carbide it was harder to grind the thread and the Clarkson fell out of favour for the straight collet chucks such as the ER series.
Because the ER series has no gaps in the range unlike a 1/2" Clarkson which can only hold 1/2" it then became viable to make the cutter size out of the blank size so we get things like a 7mm cutter ground from a piece of 7mm stock, add to this it can have 2, 3 or 4 flutes and still be centre cutting and you can see how we have moved on.

Hope that answers your question.

.