milling radius without rotary table free sample

I disagree with blanik (although I haven"t watched that video) and I think it can be done with manual feeding, but you need to be set up correctly and take extreme care. A nice fitting pin has to be used for the centre of the arc/circle to pivot on and ideally it needs to have a cap or nut on top to stop the part being able to climb off it. You also need to have hard stops at the limits of the arc/circle so the part cannot free spin if it does get grabbed by the cutter. Finally, only take shallow cuts and only convential milling so that if the cutter does grab it takes the part away from your fingers and don"t have a "death grip" on the part so that if it does grab it will come out of your hand and you can"t be dragged into the cutter. I"ve successfully machined radii on many conrods and similar parts with this method and it"s reasonably safe if done correctly and carefully. On the other hand, without hard stops, etc, you are just asking for trouble if/when the cutter grabs on you. Take care!

You say you have a rotary table. Use it. Make a setup similar to the photos in RichR"s post. Do conventional milling, which we would find in that last photo where the end mill rotates to the right, and the table would be rotated in a counter clockwise direction, so that the cutter and work are moving in opposite directions. For a plate 3/8 thick I suggest going with a four flute end mill. It will give a fine finish and have less chip load per tooth than a two flute.

Thread milling uses a standard G02 or G03 move to create the circular move in X-Y, then adds a Z move on the same block to create the thread pitch. This generates one turn of the thread;

Outside Diameter (O.D.) Thread MillingO.D. Thread Milling Example, 2.0 diameter post x 16 TPI: [1] Tool Path [2] Rapid Positioning, Turn on and off cutter compensation, [3] Start Position, [4] Arc with Z.

For many applications, (approximately 99.735% of the time, actually) you can simply allow for a radius to be in the corner. Typically this isn’t a big deal, so unless there is a very specific reason as to why having a normal radius is impossible, just go this route.

Ok, so let’s say that simply putting a radius on the inside corners won’t work for you. Maybe there’s a mating part that’s square and it needs to fit in that pocket that we were using as an example above.

Now in these examples, there is no clearance. If the mating part has a broken edge, this isn’t a problem. If it’s a sharp edge, I like to add a bit of clearance on that corner undercut to make sure it will always cut cleanly. Something like 0.010″ on a 0.25″ radius undercut usually works perfectly fine.

Here’s a pro tip: If you’re wanting something CNC machined, make the radius slightly oversized from the intended tool diameter. What this does is reduce the contact area of the cutter against the finished part geometry, and will result in a better surface finish.

My favorite way of designing this is to add the radius to match the exact cutter diameter, then offset the surface by the 0.010″ or 0.015″ – that way you get both your smooth, chatter-free surface finish and the extra corner clearance to make it work every time.

What’s basically going on here is that the practical radius of the inside corner is heavily related to the length of the tool required to cut it. So if you need a deep pocket cut, you’ll need a long tool.

Rotary broaching is really cool – it’s a way of making internal polygon geometry, and it can be done extremely quickly in a CNC mill or lathe. It can also be done for making external geometry, such as splines and hexes.

The downside to rotary broaching is that the units themselves are very expensive, so they’re typically only practical for medium or high-volume production.

Technically, you won’t get true square corners – you’ll get a tiny radius that’s equal to the radius of the wire (plus a little extra for something called a spark gap). Typically this will be in the neighborhood of 0.005″-0.006″, although it can be smaller.

You still won’t have perfect square corners, since the laser has a diameter and the kerf is a little larger than the laser, but usually this radius is so small that it’s negligible.

A traditional, 3-axis milling machine can cost several hundred dollars or more. The milling machine you see here uses a rotary tool to power the tool bit. The precision comes from two sliding tables that move the workpiece in the X (left-right) and Y (front-back) directions. A platform moves the tool up or down in the Z direction. This milling machine is a handy tool to have in the workshop and the perfect solution for machining in miniature.

T-slots can be very useful where it is necessary for two parts of a mechanical system to rotate relative to each other but can be clamped securely together at any angle. It is not possible to use this if the two parts have to rotate whilst a large force is being applied to them. In this case a circular dovetail is probably more suitable. One common example of the use of a circular T-slot is that used for mounting the top slide of a lathe onto the cross-slide. It can, however, be used in many other situations where two parts have to be able to rotate and then be clamped rigidly together.

It is then parted off. If the finish of the surface is not good enough from parting off, the workpiece can be turned round in the chuck and the parted surface turned flat. It is now ready to have the T-slot milled on the milling machine.

If the part is small enough it can be held using a three jaw chuck mounted on a rotary table. The chuck is mounted on a backing plate. This is wider than the chuck and has slots on opposite side that are used to clamp it to the rotary table as can be seen in Fig. 4.

The only other alignment problem is the distance of the center of the chuck from the axis of the spindle. This will determine the radius of the T-slot.

In many cases this can be measured with a ruler. If it is important that this is accurate then the chuck can be aligned with the spindle as follows. The rotary table/chuck pair is sitting loose on the milling table. A spigot is fitted in the milling chuck. The rotary table/chuck are moved so the other end of the spigot can be tightened up in the chuck. The milling table is moved so the rotary table/chuck can be clamped to the milling table. At this point the rotary table/chuck pair is aligned with the spindle. The milling table is locked in the y direction. The chuck is loosened. The spigot in the milling chuck is removed. The milling table is moved in the x direction by the radius required for the center of the T-slot. The milling table is now locked in the x direction.

For the cutting of the actual T-slot the x and y positions do not change. However a note should be made of them since is necessary to make some slight movements of the table as will be seen later.

Alternatively the workpiece can be mounted on a rotary table. It needs to be accurately centered. Since the workpiece already has a hole in its center this can best be done using another spigot. One end of this fits the hole in the rotary table. The other end fits the hole in the workpiece. It can then be clamped in this position

What might seem to be a T-slot cutter but which has a curved shank is not a T-slot cutter. It is a cutter for cutting keyways for woodruff keys. These are totally unsuitable for cutting T-slots.

If the angle through which the two parts rotate is small enough then it is possible to cut a hole in the middle of the T-slot to take the T-slot cutter. An example of this can occur on a milling machine where the milling table rotates, but by not much more than 45° in either direction. An example of this is shown in Fig. 8.

Figure 8 shows the top surface of the knee assembly of the milling machine. The milling table has been lifted up above and the bottom of it can just be seen at the top of the Fig 8.

At this point only the slot for the shank of the T has been cut and it is facing upwards. The workpiece is taken out of the chuck and put back in but the other way up (the “right” way up – the way it would be on the lathe). A hole is cut using a slot drill centered on the slot on what is now the top side. The hole is centered with the center line of the T-slot. This slot has to be big enough to take the wide part of the T-slot cutter. But the width of the T-slot cutter could well be bigger than any available slot drill. The hole cannot be bored because there is not enough height for a boring head in this case because of the height of the rotary table/chuck. The hole can be “enlarged” just by moving the workpiece around and using almost any size slot drill.. (This is where the table might need to be moved around by a small amount as mentioned earlier). This hole does not need to be perfectly round or accurately positioned. After having done this the table is moved back to the original x and y positions.

The slot drill is removed from the milling chuck. The collet in the milling chuck is changed for the one needed to hold the T-slot cutter. The workpiece is taken out of the chuck. The narrow part of the T-slot above the hole is slightly widened using a file so it is just wide enough to take the wide part of the shank of the T-slot cutter. Any swarf is cleared off the workpiece and the chuck etc.

T-slot cutter is put shank first into the big hole and then through the widened part of the T-slot so it comes out on the other side. It is then screwed into, or just fitted to, the collet in the milling chuck. The work piece is then fitted into the chuck on the rotary table and this is tightened up. It should fit without having to move the milling table at all.

The T-slot cutter is tightened up as well as possible with the fingers and then with a open ended spanner or failing that a mole wrench. (The usual spanner might not be useable because the workpiece is in the way.) The height of the milling table will have to be set so that the bottom of the cutter touches the bottom of the T-slot at the same time as the bottom of the workpiece sits on the jaws of the chuck properly.

If necessary, the rotary table can be moved slightly so that the shaft, i.e. the narrow part, of the T-slot cutter is just clear of either side of the slot.

When the cutting is complete, the chuck is loosened so the workpiece is free and the milling table lowered. The workpiece is now floating and is being held simply by the T-slot cutter. This has to be removed to free the workpiece.