Group Project: Dividing Head - The Build

[rwm]

I finished my method of retaining the spindle. It turns very smoothly. Its basically a big washer with an Oillite bushing.


I worked on the worm mount today. Used the rotary table to trepan a hole then used the boring head.



There is damn little material between the holes. I am wondering if I should thin out the material around the 1" hole so it can flex more there to prevent flexing concentrated at that thin web?
This part really needs to be made of steel, but I had a hard enough time getting a 3" hole in 6061! If you make this use steel. Maybe worth your time to get a hole plasma/laser cut?

 

[rwm]

Final decision:


and here we are!

 

[rwm]

Drilling the holes in the trunnion for the index pin.

I decided to do every 15 deg instead of 10 deg. I feel like the angles of 30, 60, 45 will be the most common. I screwed up one hole. Fortunately it is 15 deg so I doubt it will ever be in play.





I thought of a neat trick! to get a hex socket on the end of the pin I shaved down a 4-40 screw and put in into a hole with red loctite. I am not optimistic it will stay in but I wanted to experiment.

The hole is not threaded. I was not going near stainless with a 4-40 tap!

I had a lot of silly mistakes today. Nothing terrible but annoying that I can screw up some of the simplest things. That dowel pin above is the 3rd try! I had to pull the first two because they were bent. One trunnion hole was somehow drilled slightly off angle. I still don't know what happened.

 

[extropic]

How did you set the angles for drilling the trunnion? Angle blocks? Digital angle finder? Other?

 

[rwm]

Angle blocks. For 15° I had to combine the 10 and the 5. I must have *****d it up somehow.

 

[rwm]

FYI- the loctite hex head to the pin works great. I will be using this trick again. This would work super well for a 4-40 screw threaded into a 1/4" pin. You might even be able to use a #6.

 

[rwm]

Who wants an update?


Here it is in use cutting the first part. I am using it to make parts for itself. Cutting the slots in the knob for the trunnion index. 304 stainless. 1/4" endmill. Using the device in direct indexing mode with 12 slots.



And here we are:


I put some paint on the unmachined parts of the base. I finished the spindle lock screw.

 

[rwm]

I am now done with everything not related to the index plate.
I do not have CNC and I do not intend to manually drill all those holes! I am open to suggestions about index plates. I can buy new for $60 but I would have to modify those plates to fit this bolt hole pattern. I note a common index plate has a center hole of 21 mm and a bolt hole circle that does not match these plans. I was hoping someone with a CNC mill would want to tackle this?

For the index plunger assembly I am considering going off script again. I am very happy with the design and function of the trunnion lock so I am thinking about duplicating this (different pin of course) for the index plunger. It would have a longer knob but use the same concept of a dowel pin dropping in a hole in the bushing.

I am looking at these plates:

I can make a bushing to go over the shaft. That would be useful to retain the shaft anyway using a set screw in the bushing. I'm sure the bolt circle is metric but I could drill 3 new holes at 1.125" dia. I'll probably make my own index pin assembly anyway and not use that cheap one.

 

[Flyinfool]

Sorry I just spent another week out of commission with heart issues so have not been keeping up.
I think we will need to get together with all the mods so that I can get them all incorporated into the drawing set.

YES I am following this all closely. It looks wonderful so far.

You mentioned the sectors above. I do have the first set of sectors near finished. I made a fixture for the rotary table to cut the inside and outside outlines. I made another left and right 3D printed fixture to make that last tapered cut. As simple as they look it took a lot of noodle scratching (at least for me) to figure out how to actually make these.
I also have a sheet of black delrin big enough to make all of the sets with a couple leftover for setup oppies.

 

[rwm]

@Flyinfool - Glad you are following! Delrin; interesting choice. I'll bet that will work well.
So far the device works great. It will be convenient to use for direct indexing which I do a fair amount. Beats a collet block.
I am re-thinking my decision to not use a plate to lock the outboard end of the trunnion. The more rigidity the better. I will likely add this but note that to lock, the hub has to be made shorter (as drawn it is .255 while the aux base is .250 thick). There would then be 8 screws to lock the trunnion. Since you only do this one time per use this is not too onerous? Perhaps we should have gone with 3 screws at each end?
I am also wondering about some kind of chip shield for the worm?

Edit: the problem with making this end cap lock is that the end cap is hidden by the main index plate. You can't get to the screws. Unless I go with the 100mm ebay plates. Then you could get to a single center hole screw.