Re: What is the difference between Center Cutting vs Non-Center Cutting End Mills?

--- In CAD_CAM_EDM_DRO@y..., "James Owens" <wotisname@l...> wrote:

> I believe in the States they call all these things End Mills. Over
>here a
> centre cutting end mill is called a Slot Drill or Mill and it does
>what it
> says, cuts slots. This can either be from the edge of the material
>or if the
> end cutting action is over centre it can be used to plunge and then
>machine
> a slot. An End Mill on the other hand is used only to machine from
>the edge
> of the material as it has no end cutting action and usually has
>more teeth
> than an Slot Drill.
>
> Terry

Unfortunately there is no longer a definative description of slot
drills, end mills and the like. Technology is to blame for this.
In engineering course books in the UK and the US these were always
clearly defined. Any departure from this meant marks knocked off,
period.
In the UK we called ours slot drill and end mills. Slot drills were
two flute cutters with an over centre lip that allowed you to plunge
and cut slots, hence the name. End mills were usualy 4 flute with a
centre clearance hole for the grinding wheel to run into. Because of
this hole they cannot plunge and are used to cut from the open end or
side of the work, hence end mill.
The US have different terms but basically the cutters are the same.
Then about 15 years ago the cutter industry threw the standards books
away in the search for better products / more profit.
First thing to go was the shank standards. Up until this point there
were 4 shank sizes 1/4", 3/8", 1/2" and 5/8", we won't bother going
bigger. In metric these were 6mm,10mm,12mm and 16mm.
The manufacturers found that a 1/8" cutter was always on a 1/4" shank.
which cost money to grind down, so they addopted 1/8" shanks, then
they adopted 3/16" shanks and in the end they said damn it shank size
is cutter size. A few years ago a 5/16" collet was very rare, now
they are included in the sets.
I have recently bought some 7mm and 9mm cutters. These are on 7 and
9mm shanks.
Then they moved onto cutter geometry.
Three flute cutters have always existed in larger sizes but the
advent of CNC cutter grinding in 5 axis meant that small 3 flute was
viable. It was also then viable to produve ANY type of cutter with an
over centre cutting edge making these able to plunge.
Now this is where the confusion started and is still with us today.
In fact I personally don't think it will ever go away or be clarified.
The confusion started because the manufactures didn't know what to
call these new products.
Were they called slot drills?, centre cutting slot drills?,end
mills?, centre cutting end mills? they compromised by calling them
ALL of these.
Pick any catalogue up and look. I have the J&L one in front of me. In
two pages, three manufactures call them all of these, some
manufactures list their imperial products as 4 flute slot drills and
the metric product as 4 flute end mills !!
Catalogues are produced by office staff who haven't a clue what the
ptoduct is. I'm afraid the rot has set in and will stay.
What you have to look for is whether the cutter is centre cutting. In
time I don't think this will matter as all the recent cutters I have
bought have all been centre cutting, thanks to the advent of the CNC
grinders.
Where the confusion still occurs is because people are still working
out of old text books they have a fixed definition of what is what
depending on how or what they were taught.
Until people accept that the standards have been lost or an
explanation similar to the one above is included in new books this
argument will always arise from time to time.

John S.