Wednesday, January 31, 2018

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

Sunday, April 24, 2016

Indexing tool for watchmakers lathe

Hello friends
Today I completed the indexing tool for the watchmakers lathe. I've had on my wish list making some very fine rope knurl wheels and in order to do this I needed to be able to very accurately index the chuck. Having recently completed the new stands for the lathe with the accessory mounting t-slots, it seemed a perfect opportunity to design the indexing set up around just that. Below are the results
Watchmakers lathe indexing tool mounted and adjusted

I had used the indexing pin and holes that come stock on the back of the headstock phenolic pulley. It's very hard to get light into there to insure a visual confirmation of inserting the pin into the right hole. I designed this new unit to put the pin on the back of the indexing plate and I put the pin support arm out far enough for good light and good visual line of sight.

I designed and 3D modeled the mounting tabs that use a 1/4-20 bolt to slide into the T-slots. You can see the mounting here.
T-slot mounting for Watchmakers indexing tool

I also developed the indexing pin as a spring loaded assembly. The inside of the very end of the hollow tip is tapered so that when the pin slides home it locks in place with no play at all. The pin is shaped to fit exactly into the index holes in the spindle mounted plate. The back of the pin is also tapered to leave no play at all.
Withdrawing spring loaded indexing pin

indexing pin assembly

Indexing pin guide tip

Indexing Pin

Indexing pin parts

The arm of the assembly is quite robust to eliminate any flex. I slotted the head to be able to clamp down the pin assembly. very handy as I can leave it loose and position the arm angle correctly first, then slide the pin assembly into close contact and tighten it down.
Indexing tool swing arm

Indexing pin arm clamping head

I designed and shaped the levered nut for comfort and ease of repositioning.
Indexing tool with custom clamping nut

I'm happy with the whole assembly and especially happy that it now works as part of the new accessory mounting system.
Cheers, Kevin

Wednesday, April 30, 2014

Step #1: Imagining the WW lathe Steady rest

After weeks of creating temporary solutions for holding longer pieces of stock and after an equal number of weeks searching online for a micro-adjustable steady rest (ebay included), I came to the conclusion that the vast majority of what was available for my beautiful little WW lathe were steady rests with much more basic functionality. Additionally, the vintage steady rests were regularly selling for astronomical numbers on Ebay. I resolved to design exactly what I wanted and make it! (Below is the completed result of what began as this wish to have something better than what was available).
It is now working so well, I decided to do more than post the fun of making it. I'll be offering the main parts as a kit for anyone who is interested and I'll do my best in this blog to detail all the specific process insights I learned while making this wonderful tool .
The completed Mowrer WW lathe steady rest
All purchased and fabricated parts for the Mowrer WW lathe steady rest
It is now working so well, I decided to do more than post the fun of making it. I'll be offering the main parts on ebay as a kit for anyone who is interested.
Detailed drawings for fabricating the additional parts are included with the parts you see above.

Step #2: Designing and Modeling the Steady Rest

Preliminary design layout for Mowrer WW Steady Rest
I have a lot of experience in going from concept to prototype as I am inventor with an industrial design degree and am fully trained in drafting and modeling my designs in a 3D program, and have had many of them rapid prototyped using today's cutting edge services available online.
I had also been experimenting with making parts from bronze infused stainless steel from shapeways rapid prototyping service and had been extremely impressed with how detailed, dimensionally accurate and functionally strong the parts made from this material and process were.
Preliminary 3D design

Diving in, I developed a micro-adjuster system that was low profile and could be adjusted with finger pressure yet lock down rock solid once dialed in. I also wanted the steady rest to pivot open like on the big boy lathes for the ability to perform multiple machining operations on a part and replace it into the lathe with extreme accuracy. It's also great for multiple parts in small runs.

It was also important to me to make the design easy to finish. I love doing detail work but I don't love arduous process to get to a beautiful result. I think you'll see more of how I've developed these parts to facilitate easy lapping, filing and minimal machining with maximum accuracy as the steps proceed.

Step #3: Establishing the first surfaces on the Steady Rest frame halves

Well, Christmas in September arrived! The upper and lower parts for the frame were the first to arrive from Shapeways. As you can see, the finish resembles casting even though there is no casting involved. A big difference is that there is no differential cooling shrinkage and warping happening like you get in traditional casting. This means I didn't have to design an overly thick part to remain material safe and that in turn has huge benefits like:
  1. All critical surfaces are very close to final dimensions and can be brought to final dimension with a file and lapping, or you can machine them as well, your choice. I used both.
  2. I am able to include very accurately located guide holes for drilling out screw and pivot locations without having to blue and scribe or spend hours doing centering and numerical set up on a mill.
The raw bronze-infused stainless steel frame parts

Raw lower frame part showing guide holes on the back

Raw upper frame part
The very first surface to fit are the sides of the two little alignment nibs on the top surface of the lower frame half. This can be done with an edge file (only the edge has teeth), or by milling a very small amount of material off the mating surfaces of the top flat and the sides of the alignment nibs. Be sure to check frequently and take pains to make these surfaces generally perpendicular to the front face of the steady rest (the face without the clamp tightening screws). It's not hyper critical as the true reference surface (the front) will be lapped with both parts held together insuring alignement.
frame mating surface fitting

Step #4: Lapping the front faces on the Steady Rest frame

I was careful to keep a slight interference fit on the alignment nibs in their housing slots on the top half of the frame. I can now push them together and easily hold them in place with one hand. This is important because the next step is to lap the "front" face of both parts simultaneously on a flat surface using increasingly finer grits of sandpaper from 80 grit to 600 grit. I designed the frame to work this way on both the front and back. As I lapped, I was careful to keep changing up how I held them and keep doing circles and figure 8's on the abrasive paper so as not to lap more metal off of one side and lose parallel from front to back. This didn't take more than 20 minutes to bring up a great surface that just looks terrific. I stopped at 600 until the whole unit is built because of the scratches I'll undoubtedly get from some of the other work.
Top and Bottom frame parts lapped held together to 600 grit

Step #5: Lapping the back faces on the Steady Rest frame

Rinse and repeat for the back using a feeler gauge to keep testing that you are staying absolutely parallel to the front face. Of course, you can also use a mill to do the same now that you have a good flat front surface to set face down. As with the front, just take off enough to get to a smooth surface. I've designed it so that the front to back thickness is not critical (but parallel is key).

You'll notice I added two brass strips to the saddle surface of the bottom of the frame. You can choose not to but I've just carefully lapped a 15 inch lathe bed that took hours and hours and I want a softer metal touching it wherever I can. There's plenty of material on the raw part to tune the center height to fit any of the WW style lathes.
Back of top and bottom frames lapped

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...