Pocher Ducati 1/4 - two nuts

[Roy vd M.]

To my surprise @silver911 asked me to machine two parts for his Pocher build. The surprise was twofold: 1) I haven't been using the lathe / mill for that long; and 2) Silver's work is astonishing. See here his topic. But as he doesn't have these machines at his disposal he couldn't make these parts convincingly himself. 

 

In the end I accepted the challenge.

1. I received the parts two days ago.



2. This is what the lower part on the previous photo should look like.



3. Ron asked me to use the dimensions of the kit parts as a basis. Improving them would not be too difficult, but getting them perfect... another thing. The plan was to make each nut in three parts: the lower ring, the 'toothing' and then the crown holding 16 grooves. 

 

I started on the middle part, because I reckoned that was the hardest. It sure was... 

 

If there are any questions on this drawing or anything else in this short topic, let me know and I'll gladly elaborate. 

4. First I turned an axle to be able to easily check whether the part will fit. Here the Pocher part is mounted.  



5. After preparations the first milling action is made.  



6. Each of twelve teeth now has one side: 





7. Next the other sides and a lot of correctional work because the drawing wasn't completely accurate (or the mill, or...). Eventually I would make another one because it didn't like this part. Then I thought I liked the new part, until I made another one which was better. So then I didn't like the second part anymore and I machined a fourth. The third and fourth cost me considerably less time because the milling machine was finally set up right after the second specimen. 

 

The part slightly slopes at the face. This is modeled by using an indexable cutting tool. 



8. Drilling a hole.



9. And then, slowly, increasing the bore, just large enough to fit the axle shown under 4.



10. Cutting off the part (photo taken while making specimen #1)... checking and measuring until the desired width (2,42mm.) is attained. 



11. The result of this part after sanding. Still a bit dirty. If you look closely you can see what I didn't like: the teeth do not (recessedly) join perfectly. 





12. So yesterday I tried again. A lot of testing and adjusting... finally I thought I had figured it out. See here specimens #1 (left) and #2 (right). 



Neither specimen will eventually be used in Ron's build. After these I machined two new ones that I liked much better. 

 

13. After finalizing the 'tooth parts'... plus two ring parts, plus two 'larger ring' parts just in case those are needed. As said, it was sometimes difficult to establish what the real part would look like dimension-wise, trying to replicate that as well as I could but still holding on to Ron's wish to use the basic kit dimensions (the most important of which: the inner diameter). That's why I added a larger ring and an even larger ring. If the two small rings (which resemble the real deal best) for some reason do not look right, there are these larger rings. Hopefully they won't have to be used. 



14. What a shame... making the 'crown parts' and not thinking for one second... the milling machine is merciless. It's not difficult to see the mistake: 

 

(by the way, to the left is the Pocher part) 



So the crown part will have to be done anew. 

 

15. Turning: you can see that the chuck does not touch the cutting tool... but only just. 



16. This is the work drawing for the crown part.   



17. How to make one of sixteen grooves: 
 

 

20. Final check to see whether the new parts would fit the Pocher axle.





21. The last part is a center axle for one nut. Done! 






 

 
I hope Ron will like these parts and I can't wait to see them in place. 

[silver911]

Well...one things for sure Roy.....you have no concerns about Ron liking them....I love them....and couldn't have wished for better.

 

I am truly grateful that you accepted the commission to make these for me and.....I now have the opportunity to raise the level of detail another notch....thanks to your skills.

 

I am so looking forward to receiving them....and can't wait to use them

 

Much respect Roy.

 

Ron

[Codger]

A brilliant alliance between two meticulous craftsmen!

 

Roy, the depth and skill of your work are outdone only by your time commitment and ethic.

 

Ron, yet another visual feast for what has become your tour-de-force Ducati. The detail layers are becoming indistinguishable from something on the Ducati factory floor.

[Pouln]

Looking very nice, Roy. well done. 

I think you are becoming a real machinist.

[Roy vd M.]

@Codger and @Pouln I'm grateful for your compliments. 

 

Here the end result of the parts in place can be seen. 

 

 

22. I forgot to explain why I decided to make three parts (left hand side) resp. four parts (right hand side) rather than simply one. The reasons:

 

- More detailing is possible this way, for example the recesses of the 16 slots. 

- The parts can be finished in an easier way. Mainly sanding the center part (with the 12 'teeth') can be done way easier in a standalone part of course.

- Separating the ring part enables a very smooth surface finish of that ring. It's possible to mill the 'teeth' while leaving the 'ring' but annoying sanding will have to be done. Also, the teeth will not have a sharp 'inside' angle because the mill bit is positioned differently. And a smaller mill bit would have to be used or else the 'inside' angle would not be sharp enough.

- It is also a matter of risk management. Making one mistake (such as I did on one of the 16 slots) will not force me to start all over. 

 

Not a reason but an extra bonus is that the parts can be sanded to become thinner as Ron desired. For example the ring part I turned to a thickness as indicated by Pocher, but I hoped the model would allow that ring to be thinned slightly. Fortunately Ron told me it did. 

 

Aluminium can be glued using brown Gator Glue. If anyone plans to use it, send me a PM and I'll provide some tips on how I use this 'wonder glue'. 

 

23. The most difficult parts to machine are of course the crown parts and the 'teeth' parts. Step plan for the crown parts: 

 

 

 

1. Make bore of 9,8mm with drill and bore cutter, on lathe. 

2. Turn outside diameter 13,25mm. 

3. Face part and set hand wheels to 0. 

4. Turn a groove of 0,40 wide, 0,40 deep (on drawing: 0,30). 

5. Turn diameter to 12,05 except for a bit of 0,53mm. Keep checking until 0,53mm. remains. 

6. Using the mill, cut 16 grooves of 1,0mm. wide and 1,6mm. deep. 

7. Cut off at 2,1mm. 

 

24. Step plan for the teeth part, using a drawing I had not yet shared:

 

 

 

I have no idea what that all means, but what matters most is this:

 

 

 

Here the step plan (see the previous pictures as a guide):

 

1) Pick a piece of aluminium rod of 6,11mm. in diameter. Mount it in a collet chuck (or regular chuck) and mount that on the dividing head of the mill. Dividing head should be vertical.

2) Fasten dividing head, fasten mill lever.

3) position the mill head all the way down and then search the zero point of the Y slide: where the mill bit would 'kiss' the part on its side. Set Y slide handwheel to zero.

4) position the mill head all the way up and search the vertical zero point: where the mill bit would 'kiss' the part on its top. Set Z handwheel to zero.

5) Move the X slide to the left so that there is clearance between part and drill bit. 

6) Move Y slide 2,1mm. forwards. Move Z slide 6,1mm. downwards. Make the first cut, using the X handwheel. 

7) Unfasten dividing head, rotate 1/12th (see manual of your dividing head how many rotations that is) and repeat 6). 

8) After all 12 right hand cuts are made, it's time for the left hand cuts. I had to turn the dividing head 4,75 turns (40 turns=360 degrees). Fasten dividing head. 

9) Set Y and Z back to zero. Then choose 5,7mm. for the X-slide and 2,06mm. for the Z-slide. Make the first cut, using the X handwheel.

10) Make the 11 other cuts and you're done on the mill. 

11) Make bore and recess for the crown part, on the lathe. Not sure of the exact measurements here, they are somewhere on the drawing as seen above. Otherwise this should not be too hard to figure out.

12) Cut off the part. 

 

Good luck

[Codger]

Brilliant! Having been an art student and definitely NOT a math major, I would never be able to make parts such as these.

 

Edited May 27, 2017 by Codger

[Roy vd M.]

@Codger It was not easy to find out some of the numbers as described above, especially the four key numbers after the arrows in the last drawing. The computer-drawn image didn't appear to perfectly 'work' in practice so I had to correct, set, correct... until I had screwed up the part. Once more... it was mainly a matter of trial and error rather than mathematics. I am probably the least worthy of the term 'mathematician' of all people on this forum. I dropped maths when I was 16 years old (that would not be possible under current school regulations) and decided I'd go for 6 languages and history class. But as is often the case, when you're having fun and when you're really interested in something you'll understand so much better what it's all about. That's what has often helped me in modeling: I cannot swim beautifully but I'll reach the other side if I really put everything to it.  

 

 

To come back on the Everbuild-Gator-Glue-explanation-and-tips-offer: I started a topic about that here. 

[Roy vd M.]

I received a request to make another one of these. Unfortunately time doesn't permit that, I'd love to start the Delage measuring preparations... least I can do though is make better photos of the drawings, as these may be used for 3D printing or so. 

 

 

 

 

The third one I think I didn't upload before, I think it was the first sketch / step plan. If anyone has a question about writings / numbers etc., just let me know and I'll try to decipher. 

[sharknose156]

Roy,

 

Extra-ordinary work and skill at design and lathe engineering ! 

i don t know how this thread has escaped me. 

 

This augurs extremely well for the Delage work.

if i had the time i would volunteer as your assistant to take the measurements of the Delage.