Quick Tips

Last Update: 27-03-2017

This will be a collection of some simple tips and techniques that I have learned over the years and use regularly.

Quick way to make a radius grooving tool - 27-03-2017
Grinding external radius lathe tools - 20-03-2017
Regrinding carbide inserts for special operations - 03-02-2017
Using a ball bearing to hold rough and non parallel parts in a vice - 03-02-2017
Centering work on the rotary table - 03-02-2017

Quick way to make a radius grooving tool

Whenever I need a radius grooving tool for the lathe I try to find a piece of round Hss or Carbide with the right diameter that can be soldered on the end of a soft toolshank to form the radius cutting edge.
For the tool in this example I took a piece of unhardened toolsteel, machined a nose on the end, slightly narrower than the actual diameter of the Hss blank that gets soldered to it (I needed a 1,2mm radius on this tool, so I used a piece of 2,4mm diameter Hss and I machined the nose to 2,2mm with), then I machined a V-grove into the end of that nose to center the Hss blank. The toolblank was tilted by 5° to give the tool clearance without having to grind the actual clearance into it:

The finished toolshank with the 2,4mm Hss blank:

The Hss blank got hard silver soldered into the shank (Hss does not loose its hardness when silver soldered) and then ground sharp on the surface grinder (It could also done on the benchgrinder):

The 5° tilted round Hss blank alters the actual radius that the tool creates slightly, but in this case, the error is only 5/1000mm on the radius. It is quite easy to check this in a Cad program

The tool in use to machine a radius groove into titanium - The tool will only plungecut but not cut to the side, as there is no clearance to the side built into it:

Grinding external radius lathe tools

To grind a tool to turn concave radii, I rough out the radius on the benchgrinder using the edge of the grinding wheel. To finish the radius, I dress a grinding stone in my handheld rotary tool to the desired diameter and use it to finish the radius:

When doing this, I prefer to run the rotary tool quite slow to be able to press it tightly into the radius I want to form. Using a permanent marker on the surfaces to be ground shows you the progress.

Regrinding carbide inserts for special operations

In some cases it is benefitial to change the grind on an off the shelf carbide insert.
This part was such a case, it has to be turned down do a 3,9mm diameter, 17mm long. With a normal finishing insert it did not work very well, I could not hold any reasonable tolerance because oft the cutting pressure.

I did also not want to come back with a second tool for finishing, as I had to make a bunch of them.

I decided that a normal CCMT06 finishing insert with a 0,2mm nose radius is a good starting point, but I ground a substancial back- and side rake to the top of the insert.
That way I was able to rough and finish with two cuts - First cut took it down to 4mm in diameter, second cut finished it to 3,9mm +-0,01mm.

The way the insert was ground is very primitive: I grab them with a needle nose vice grip.
Then the the top face of the insert is held freehand against a diamond wheel, eyeballing the angles - I tipped the top surface about 5° back and to the right, to create a nice, positive cutting action with very little cutting pressure. As the insert has already a nose radius of 0,2mm, it is also a very durable tool.

Using a ball bearing to hold rough and non parallel parts in a vice

The purpose of the flat is to protect your vice.

Centering work on the rotary table

If your rotary table has a morsetaper socket in its center, a morsetaper collet and a pin can be a simple way to center a workpiece that has already a hole drilled in its center (Conrods for model steam engines are a good example where this technique works well.
The collet with the pin is just pushed by hand into the morsetaper of the rotary tabel and then the work is placed on parallels (to clear the collet) over the pin and clamped in place.