End Mill and Drilling Questions (Milling Bits)

Quote:

The company is the world’s best Carbide Roughing End Mills supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

Originally Posted by johnwalkeasy

Oh, and also, You say that a center cut end mill is not as effecient as a drill. What do you mean by that. What I,m doing is drilling 3 holes in 1/2 steel hot roll. 2 will be 7/8" and one will be 3/4". I,m making a set of rockers for a springer on a chopper. the 3/4 hole is for the axcle. I have a 7/8" drill and a 3/4 drill. And I can use a milling machine to drill holes. But I need for holes to be true and clean. And I was thinking a end mill would do a better job. Also they need to be the same so the wheel will be dead center. Thanks, John.

They are not designed to drill holes so if you are drilling from a blank (no predrilled hole) the force needed to penetrate the steel is very high even with a center cutting end mill, (a no center cutting will not pentrate very far at all.) By predrilling the hole you remove the majority of the axial force needed and are cutting with the edges of the flutes as the tool is designed to cut.

How to tell the difference, question do you know what a center drill is and how you use it on the lathe? Then you know what "turning on centers" is well a non-center cutting endmill has what looks like a center drilled in the end of it. A center cutting end mill has one of the cutting flutes come to the center of the endmill and the others do not. This makes for a lateral thrust when plunging with the end mill. By predrilling the hole you eliminate this lateral thrust and make a more accurate hole.

However if hole size, finish and straightness is needed you best under drill the holes by a 1/64 - 1/32 and finish them with a reamer. It is an expensive way to go on the tooling end. But if you will be doing more of it down the road it is the best way to go...

You should be able to plunge cut all three holes. I will suggest that you pre drill all three holes with a 1/2" drill first. Then finish them with the end mills. The hole will be close to a reamed holes for straightness and finish.They are not designed to drill holes so if you are drilling from a blank (no predrilled hole) the force needed to penetrate the steel is very high even with a center cutting end mill, (a no center cutting will not pentrate very far at all.) By predrilling the hole you remove the majority of the axial force needed and are cutting with the edges of the flutes as the tool is designed to cut.How to tell the difference, question do you know what a center drill is and how you use it on the lathe? Then you know what "turning on centers" is well a non-center cutting endmill has what looks like a center drilled in the end of it. A center cutting end mill has one of the cutting flutes come to the center of the endmill and the others do not. This makes for a lateral thrust when plunging with the end mill. By predrilling the hole you eliminate this lateral thrust and make a more accurate hole.However if hole size, finish and straightness is needed you best under drill the holes by a 1/64 - 1/32 and finish them with a reamer. It is an expensive way to go on the tooling end. But if you will be doing more of it down the road it is the best way to go...

__________________
Shade

"Prepare to defend yourselves."
-- Sergeant Major Basil L. Plumley, Ia Drang Valley

II. Key characteristics of an end mill

The main features used to describe an end mill are illustrated below.

On top of these geometric features, end mills are characterised by their type, number of flutes, material (and coating). Thus, in a classical catalogue, the end mill above would be described as:

• Type: flat end
• Number of flutes: 4
• Material: solid carbide
• Shank diameter: 6mm
• Cutter diameter: 6mm
• Overall length: 50mm
• Flute length: 22mm
• Helix angle: 45°

Each of these features has a direct influence on how the end mill will behave during a machining operation and on the cutting possibilities in terms of performance and shapes.

What size of end mill should I use?

Imagine you want to mill a very deep pocket inside a high part. You will need a long tool to be able to machine the bottom without colliding your spindle mandrel with the stock of the material. Hence, the length of your end mill will be determined by how deep it must penetrate into the material. The associated concept with this observation is called &#;stickout&#;. It is defined by the distance from the end of the tool holder to the tip of the end mill.

Also, keep in mind that the cutting depth should never exceed the flute length of your end mill. If cutting deeper than the length of the flutes, chips won&#;t clear properly, heat will build up and you risk to damage your tool.

At this point, it might seem smart to buy end mills that are as long as possible to have the flexibility to use them in more situations, right? It&#;s actually not the case, because the more stickout, the less rigid a tool is. If it sticks out too far and you work it too demanding, the cutting forces will make it bend, which is what is called &#;tool deflection.&#;

Tool deflection can actually be very problematic since it induces:

1. chatter, which are vibrations caused by the relative movement between the workpiece and the cutting tool;
2. bad surface finish with ripples, mostly induced by the chatter;
3. inaccurate tolerances on the machined part;
4. reduced tool life resulting from bending fatigue.
   

In short, shorter end mills are more rigid and less expensive. So save the extra-long ones for operations where they are really needed

Shank & cutter diameter

The diameter of your tool will have a direct incidence on the profiles you can cut. Let&#;s say you want to make a box and assemble it using 90° interlocking joints.

Additional reading:
10 Questions You Should Know about Diamond Flush Grind Blades
How Post Tension Anchor Services Work Efficiently
5-Axis CNC Milling Services: Direct Comparison for Precision Results

Contact us to discuss your requirements of Tg Vs Er Collets. Our experienced sales team can help you identify the options that best suit your needs.

Since your tool is a cylinder with a certain radius, it won&#;t be possible to do it as such. Indeed, the tool will leave a circular profile in every internal corner, with a radius equal to half its diameter. The larger your end mill diameter, the bigger the radius of this circular profile. In order to overcome this problem, CNC operators use what is called &#;dogbones&#;. Dog bone corners describe the shape of a corner that is extended outside the cut area to create a perfect 90º corner.

On the other hand, increasing the diameter of your tool offer two main advantages.

First, it makes your tool more rigid, which will allow you to make deeper cuts while minimizing tool deflection. A lot more rigid actually, since increasing diameter by 2x will increase its rigidity by a factor of 16x.

Secondly, it improves your MMR (Material Removal Rate) since the end mill can remove more material per unit of time when it is moving inside the material, allowing you to optimise certain operations and do the same job faster.

How many flutes should I choose?

Flutes are the deep spiral grooves that allow chip formation and evacuation. They are the part of the end mill anatomy that create those sharp cutting edges (sometimes referred to as &#;teeth&#;).

The number of flutes on your end mill is a crucial parameter that depends mostly on the material you want to cut and on the capabilities of your machine. Indeed, the number of flutes on your end mill will impact:

1. the feed rate of your machine,
2. the surface finish of your piece, and
   
3. the ability of the tool to clear chips.

Feed rate is indeed directly linked to the number of flutes of your end mill: if you add flutes, you will have to increase the feed rate, or decrease the rotational speed of your spindle, to keep a constant chip load. So depending on the speed capabilities of your CNC machine and of your spindle, you might have to choose an end mill with less/more flutes.

If you are not familiar with those concepts, we recommend you to have a look at our article on feeds and speeds.

Secondly, having more flutes on a tool creates smoother cuts, but it also leaves less space for chips to evacuate. This can be somehow overlooked if you are cutting soft materials, but not at all if you are cutting aluminium for instance. The reason is that aluminium produces very large chips compared to other materials. So when the end mill is cutting down in a hole or a slot, its flutes provide a crucial path for chips to escape. That explains why it is recommended to use 2 or 3 flutes end mills with aluminium since they have more chip clearance than with a 4-flutes one, where the chips will jam progressively, overlapping the cutting edges of your tool and making it break eventually.

To sum up, fewer flutes are best at chip clearing, while more flutes create a smoother surface finish.

Should my helix angle be higher or lower?

General-purpose end mills typically have helix angles around 30°. Increasing the helix angle will reduce the cutting forces and the amount of heat and vibration generated during the milling process. Hence, end mills with a higher helix angle tend to produce a better surface finish on the workpiece.

It comes with a trade-off, unfortunately. The end mill will be weaker and won't sustain heavy depths of cut with high feed rates. So lower helix angle cutters are stronger, but they give a less smooth surface finish.

If you are looking for more details, kindly visit Tool Holder Definition.