Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

The basic approach to this is simple enough - mill away two sides, drill the hole for the pin. Then I chose to shape the end by hand - I'm not very good at that kind of hand work, but for this part it worked well enough. Then cut off with some stock left, into the lathe, face to length, turn the chamfer, drill and tap the hole. Here are a few pics en route. I had to use my standard approach of "make it at least twice" before it came out "well enough". It's about 0.01" too short, but I think it will work. The tang is spot on though, in terms of length, thickness and hole position.

















Made a few novice mistakes along the way, but recovered - didn't scrap the part.

Even managed to part it off, without too much drama.



Except for that blasted stub. But no matter, I left a little stock on the back face for some clean up, since I had a suspicion that parting off might not give me the final finish I want. I'll get there on that, but I know I can skim that face to a nice finish, so not too worried. Just trying to decide whether to make a little aluminum collar to hold it on the groove diameter, or just set it up in the mill and skim it there.




Can't remember for the life of me what project that resulted from, but it just needed a little boring out to size.



And when all was said and done, the backside cleaned up a treat.





Still needs a little deburring and chamfering on the inside of the lips, but you know - overall - satisfied with this part, plus tried my hand at some new things. Win!

So, finished up the eccentric hub this morning. I wanted to ACTUALLY finish it before moving on. So I did indeed chamfer the edges of the lips, which would have been a lot easier had I left the part on the stock bar a bit longer. No matter, the little collar worked well, and let me hold it securely without damaging the lips.

Then the last thing was the 5-40 hole for a grub screw.

Getting the orientation set up using a gauge pin:



Gauge pins are excellent tools to have. I bought a set a month ago, after seeing machinists at work establish locations using them, and then following up with an online tutorial from Joe Pie. I use these pins every time I am in the shoppe.

Then, drilling and tapping as has been seen and posted about a million billion times. Possibly more than that.





And there it is, hiding among the other parts, both finished, raw, part finished and of no use to anyone.





Next up is the eccentric follower.





All I did today was a little bit of clean up, and some measurements of the casting to understand how much stock I have. I'm trying to take a bit more time to get familiar with castings before actually setting them up, and try and figure out any "gotchas", and figure out what stock there is where, and therefore how to get machined surfaces located relative to surfaces that will be left raw, to make sure visual appeal is maintained. This is all part of making an attractive engine, I think.

I did get one side flat on the sanding belt. The casting started off approx 0.005" parallel between the two sides (crude measurement), and there is roughly .1" of stock to take off, so should be plenty.

I have clamped it in place ready for a skim of the other side. Only a minimum clean up right now - so that I can hold it for drilling bolt holes and cutting it in half. I'll go to final thickness after the two halves are bolted back together, so that I can make sure the center of the lobes is centered on the finished part. That's the plan anyway.



Centering the part in the 4 jaw was done crudely by aligning with a dead center. This seems to have worked well - I checked run out before boring - the inside was pretty true, the outside certainly had some visual run out, but it is not a perfectly concentric part. I decided to go with it as it was. The material removal on the ID was pretty consistent straight away, so I think this worked out well enough.



Setting up for the bosses.



I checked relative height of each side boss by touching off with the tool tip, and it was within 2 thou, as shown by the DRO in the pic after next.





Boss face clean up:





Getting ready to split. My prior set up was not thought through well enough, so I had to do a new set up to saw the part.



Obtaining center by using the saw, feeler gauge and DRO.







Clean up:



Ready for boring (probably what I'm doing to anyone looking at this thread)



Alignment:





After boring and facing:



And last but not least, the oiler hole:



I did a test fit on the eccentric hub, and annoyingly it is tight. However, I am suspicious of burrs on edges. I'm going to give both parts a deburr session and try again, but I may have to go back on the lathe and skim out a thou, which never works well. Hopefully deburring takes care of it.

Still, not a bad day. Cheers!