Using the side of an end mill

[Nick WelburnParticipant @nickwelburn]

I’ve got my new sx2! It seems very nice and I’m up for doing some work on it. One job I have to do is On my 10v to mill out the space for the brass bearing carrier to slide into. I have an appropriate sized end mill (the one I broke with the z slide) can I use the side of the end mill to make the slot and the semicircular end?

[Nick WelburnParticipant @nickwelburn]

[Oily RagParticipant @oilyrag]

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

[Nick WelburnParticipant @nickwelburn]

Cool, I suspected as much as the flutes run up. Just wanted to check before sticking a load of lateral load through something not designed for it!

[old martParticipant @oldmart]

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

[Nick WelburnParticipant @nickwelburn]

Love this place. You ask a question and some one guides you along. I’ve learnt an extraordinary amount. Many thanks again!

[JasonBModerator @jasonb]

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

[Anonymous]

Despite the name end mills are intended to be used on the side flutes. So the larger the depth of cut the more use you get for the money. Here's an example:

Central is a 10mm carbide endmill – material is hot rolled steel, depth of cut is 20mm and width of cut was 1mm conventional milling and 0.5mm climb milling. One is paying for the flutes so one might as well use them.

Andrew

[SillyOldDufferModerator @sillyoldduffer]

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

[Nick WelburnParticipant @nickwelburn]

As a slide aside, the end mill in question I’ve broken the tip off. Can it be recut? If I just flatten the tip with something TBC.

[Oily RagParticipant @oilyrag]

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

[Anonymous]

Not accurately without some form of tool and cutter grinder. But if the damage isn't too severe one modification is to hand grind a chamfer on each tip. Of course the endmill can't then be used to create internal right angles, but the finish when facing should be better. Larger secondhand cutters for sale often have the tips modified to be chamfered or rounded. One can buy new endmills with radii on the tips, albeit at a fair premium over a square endmill.

Andrew

[Jim NicParticipant @jimnic]

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

[not done it yetParticipant @notdoneityet]

Posted by Oily Rag on 18/03/2021 20:44:04:

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

Not helpful for this thread, but as an aside, an end mill can be used to make holes, generally to a more precise size/shape, than an ordinary twist drill. It simply requires a pilot hole to be made first – of adequate size to avoid that non-centre cutting area.

[JasonBModerator @jasonb]

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

[Howard LewisParticipant @howardlewis46836]

For most purposes, unless backlash prevention devices are employed, climb milling should be avoided. Although it can produce a better surface finish, it is likely to pull the cutter and job into each other, causing damage to both.

So, the direction of feed should be so that the workpiece approaches the cutting edge head on, from the opposite direction.

Howard

[Anonymous]

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

[Howard LewisParticipant @howardlewis46836]

Like Andrew, when climb milling cannot be avoided, I nip the table locks to prevent the cutter trying to drag the table..

One or two end mills that have suffered on the end are still used n, cutting on the flutes, to clean up the ends of jobs in the milling vice.

Too much trouble to grind the end flat (especially with carbide and a diamond wheel )

Howard

[Author]

Posts