That's what they are for, slot drills for end cutting as in sinking to a depth and then traversing to cut a slot, but end mills cannot drill as by definition the teeth form does not cut on centre point (although just to confuse issues some 3 flutes do – but these I consider more of an upmarket slot drill.

Martin

A lot depends on the length of the cut, that is the thickness of the brass. Using the flutes close to the plain shank if possible makes the cutter stiffer and stronger for its diameter compared to using the tip. You will have to look at the cutting edges on the sides to see the point at which they run out. Its common practice to keep a cutter that is blunt or badly chipped at the end for cutting with the less used sides to get a bit more life out of it.

It would be risky to, for instance, for a 6mm cutter to be used to make a sideways cut in 12mm thick metal all at once, the forces might be too much even for brass.

Edited By old mart on 18/03/2021 21:00:09

I would hold the base flat and then use the side of a cutter to mill the vertical edges of the "U" shapes to the 7/16" width (actually make to fit the extrusion.

You can then mount the casting on its side and make a series of plunge cuts moving further towards the bottom of the "U" until you are at the required depth.

No need for end cutting mills even 4-flute ones as most of the pockets is cast so just needs a clean up of the cast iron.

Have a look at some of DrG's early posts as the same part was covered there

Edited By JasonB on 18/03/2021 21:04:17

Also pays, if the job permits it, to cut with the top of the flutes rather than the end. For example, when squaring off the edge of a plate. It reduces wear on the base and lower part of the flutes, which normally do most of the work.

Dave

Yes, either dress it up on a suitable HSS grind stone or if carbide a green stone or a diamond impreg wheel. Failing that an angle grinder could be used but be careful not to overheat – this applies to all grinding operations.

If I have a chipped cutter I usually do not bother to 'clean it up' I just mark them with a red ink marker pen around the chip area and continue to use it if not too restrictive. I leave these 'red' cutters in a bin, when enough are accumulated they next go on the Clarkson for the full works!

Martin

Be aware that when using a 4 flute milling cutter to form a slot that a say 10mm 4 flute cutter will not cut an accurate 10mm slot from start to finish.

You will need either a 2 flute cutter, sometimes called a slot drill, of the diameter of the slot you want or a smaller 4 flute and cut each side seperately.

Jim

Or just get a ctr cutting 4-flute cutter

Though they do tend to move about a bit more than a 3-flute in a light machine when plunged straight in.

Edited By JasonB on 19/03/2021 07:27:09

Fingers crossed I haven't broken a cutter yet when climb milling, even when the cutter does grab the table. The X axis on my mill has about 0.6mm backlash, so it's pretty obvious when the cutter grabs.

A rule of thumb when climb milling is to make the width of cut less than one third of the cutter diameter, or more than two thirds. Cutting at around 50% of cutter diameter creates high shock loads on the teeth as they enter the cut. When cutting at more than two thirds of cutter diameter the initial cut trajectory is away from the direction of table movement. So there is no grabbing. For small widths of cut I usually climb mill with a maximum width of cut of 10% of cutter diameter. Chip thinning means that the actual chip load is less than the feedrate implies. So even if the cutter grabs it isn't going to break.

For small cutters, say less than 6mm, which are most likely to break the cutting forces simply are not large enough to grab the table on my mill, even when climb milling. With larger cutters if grabbing becomes an annoyance I tweak the table lock to add a little drag.

Andrew