FreeCAD 3D design for a HSS tool bit

All,

I'm trying to learn FreeCAD. After getting to grips with the basics, I wanted to create a HSS right hand turning bit. I can't find any good examples to learn from and I'm struggling to create the multi angle surfaces.

Does anyone have an FreeCAD of an HSS tool bit I can learn from?

Many thanks.

I never used FreeCad. from my experience with other platforms I would say you need to establish new auxillary planes from which to make your cuts. Send me a PM and I will detail the steps you need to get it done.

Dave, one of the moderators, had a "Making a Start in FreeCAD" thread, I assume you have read that. The thread doesn't use a tool-bit as example but may give you some ideas. There are a few examples in Steves-Workshop.

Thor

I had previously read that thread and it get me a little further. I guess I need to plough on!

What exactly did you envisage? A picture of a freecad drawn part? An stl or step file (which can't be posted on here)? a video of it being done?

You video suggest would be the best so I can see how the design is created using FreeCAD. If not, a FreeCAD doc of a tool bit I can look at to see how the surfaces are created.

PM'd e-mail address and send a Freecad file to the OP would be best then he can see how it was constructed.

I could help you out with an Alibre file but not a lot of use to you.

Easiest way is to draw an angled line on the side or top of the tool then add two more lines to make a triangle and extrude cut with an added draft angle.

GingerLathe's object is trickier than most to 3D model because it has a number of faces that aren't at right angles to each other. As most models are developed at right angles, FreeCAD (and other software) defaults to this, and it's necessary for the modeller to adapt. Jason mentions Alibre's extrude tool can be told to cut at a draft angle, but FreeCAD's equivalent doesn't support that convenience. Instead it's necessary to define planes and cut from them.

This 2D drawing illustrates a knife tool. (Some angles are exaggerated):

The tool is ground to present a sharp edge to the work. Metal is removed to provide clearance to stop the tool rubbing, and more metal is removed 'rake' to sharpen the wedge and improve the cutting action. Rake depends on the material, up to 40° for softer metals like Aluminium, and down to 8° for a high-carbon steel. Mild-steel is in the middle - about 27°. As removing metal to improve cutting action weakens the tool, the angles and amount of metal taken off are carefully controlled in industry to balance cutting rate against tool life. For amateur purposes I see little value in that and just grind roughly to the shape recommended for mild-steel. Approximately!

From top to bottom, GingerLathe's knife tool might be ground by first grinding the Front clearance to create a wedge. My drawing is an exaggeration - 8° is more realistic than 17°!

Next, the top rake : 27° rather than my 6°. As swarf flows over this face, one of my books recommends grinding in the direction swarf travels and then polishing the surface. The lip can be developed or moved forward to act as a chip breaker - useful to stop long ribbons forming.

Finally, front clearance and side rake. These don't seen to be critical other than the angle at the point should be nearly 90° for strength.

I modelling this in FreeCAD by drawing a rectangular blank, defining tilted planes relative to the blank, sketching on the plane and then removing metal along planes with the pocket tool:

The button used to create planes in circled in red. Planes can be rotated (Yaw, Pitch, and Roll) and Moved in X,Y and Z. Modelling the tool needs 3 planes, none of which are at a right angle to the tool blank or to each other. Bit fiddly to set up, but gets easier with practice.

Hope that helps.

Dave

Edited By SillyOldDuffer on 09/02/2021 12:05:52

Many thanks Dave. I'll have a go at this approach. Would you be able to send me the FreeCAD file if I PM you my email address?

Thanks

Spencer

Another way to do it in Alibre is to make the top-down profile, then create planes along the angle edges at the relief angles and use these to extrude cuts that finish the shape.

No problem at all. Here is it on Dropbox, otherwise PM me and I'll email it.

Dave

The willingness to help others never ceases to amaze me on this form. Many thanks Dave. This exactly what I need. Really appreciate your time.

Spencer