Tool Grinding attachment for watchmakers lathe

Hi friends. So I've gotten terribly tired of dull bits and tools. If you're doing any work at all, you end up buying and endless sea of drills to replace the dull or broken ones and the same is true of milling bits of all sorts. To compound the troubles, no one grinds tools and bits for brass so the all-purpose grind is grabby and even dangerous at times.

Tool grinding attachment for watchmakers lathe

Net/net, I started looking at getting a used tool grinder and quickly came to the conclusion that they were incredibly expensive, even used.

Well, after thinking through making one and all the various axis I'd need to be able to accurately pivot or advance the tool along, it dawned on me that the cross slide for the watchmakers lathe with the milling attachment already did most all of that! All the whole setup needed was a way to accurately index the bit held in the standard collets!!

 I had already made a custom collet to hold the grinding wheel so off I went to design and make the additional bits to convert the milling attachment to an indexing tool. Here's the sum total of all the parts I needed to make.

elements of tool grinding attachment

Completed parts for tool grinding attachment for watchmakers lathe

And what the assembly looks like mounted on the machining spindle.

Mounted tool grinding attachment

To get started I needed to make the body shell that would fit over the spindle frame. This would have to include a spring loaded drop pin for indexing the spindle as well as a spindle lock

Facing the round stock held in steady rest

center drill the round stock to start the drilling and boring

Drilling the bore

Opening up the detente end of the casing

Next would come the indexing collar. I made this from an internal bit of 12L14 steel I had leftover from another project and a bit of brass round stock. I machined the inner steel wear collar to size and press fit it into the brass collar after using my indexing wheel and the aux machining spindle to put 4 evenly spaced recesses in the collar for the drop pin to locate on.

drilling indexing detentes into spindle collar

The outer brass collar would carry the indexing marks which I cut into the brass using a sideways V-ground cutting bit held in the cross slide. Using a travel stop I was able to very accurately engrave the little lines in the collar by keeping the bit super sharp and advancing the cut 5 thousands into the surface per pass. There's just something beautiful about indexing marks on a good tool.

Engraving indexing lines on the watchmakers lathe

After making the drop pin and the spindle lock lever I could hardly wait to get sharpening. Apologies, I forgot to take photos of this part but it's fairly straight forward. A lever with a screw and a spring loaded pin just like the one I made for the indexing tool elsewhere on this blog.

As an aside, the black knob on the draw bar was designed and 3D printed and pressed onto the draw bar. I love the feel of it and it's absolutely concentric.

My most pressing need was to sharpen my milling bits both dovetail and standard. I mounted the works and started on the dovetail. It all went smashingly well!

Set up for grinding a dovetail cutter

Proper angle for grinding a dovetail cutter

Grinding a dovetail cutter on the watchmakers lathe

That is until I discovered just a small amount of play in the fit of the dovetail into the collet! After measuring the sharpened bit I decided that the small bit of off center grind this imparted was not acceptable. I needed to make my own collet to hold the tools so I decided on brass because the pressures are extremely low with virtually no chance of sudden impact.

Shaping the collet blank

After shaping the collet I used the threading attachment I made (coming next on a post) to cut the proper threads. This was by far the most satisfying part of the project. no wobble, no flexing, just incredibly sharp and accurate threads!!

Using threading attachment for brass custom collet

I then drilled and tapped the holes for 4 set screws even though the fit was very snug. Taking no chances and wanted complete adjustability. I even chucked up each bit in the collet and used a dial indicator to insure perfect concentricity before grinding.

threading brass custom collet

drilling set screw holes in collet

adjusting cutter to perfect center in collet

A half a day of sharpening 2 dozen dull bits later and I could not be more pleased!!

Grinding a four flute mill cutter

Grinding a jewelers number drill

It works stunningly well on putting a four facet point on the tiniest of drills as well. Boy I had to study up a lot on angles and drill theory. Still quite the newbie but the drills are working well and now I'm setting aside a day to grind an entire number drill set to just do Brass and one for Ferrous metals. Sharp tools!!

Four face grind on small drill

Enjoy, Kevin