Down on the Farm, Boy

[sshire]

A consensus.
Seriously, if I could make tools as elegantly as Don, I'd probably give it a try.

[Roger B]

Looking excellent    Still following along   

[Graham G]

Yup I'm still here too 
Top work there Stan.
cheers
Graham

[fumopuc]

Hi Stan, I like the chuck and good progress.

[sshire]

Down on the Farm, Boy
Episode 9

A Tale of Two Pistons

Moving on from the cylinder to the piston, I started with a 6061 round and turned it down to .998.
Since this will use o-rings instead of cast iron rings, I’m just going with the drawing dimensions.
I also modeled it in Inventor to have a better idea how it should look.







Then the o-ring groove. I kept widening the groove until a .105 gauge pin just fit.



The piston ahead of the groove is a few thou smaller in diameter.



First is a .235 deep, .500 diameter flat bottom hole. After drilling,, I finished with a .500 end mill.





Then a counter-bore.



Next, a slot is cut at the mill. When I changed from the angle vise back to the Kurt, I was probably thinking about the next op and I should have had the vise bolts more than finger-tight.





So, back to the lathe to start on piston #2. This time, after turning to diameter (and after torquing down the Kurt) I decided to do the rest of the ops at the Bridgeport. The part stayed in the 5C collet.



At least it’s straight



Drill a .375 hole



Then the .500 end mill.



Next up a .75 end mill to start the counterbore



Finally, bored to .850



Now the .505 wide slot. I made sure to note the Y-axis start and stop points where I couldn’t miss seeing them.



No moving vises here.



Drill and tap two 4-40 holes. These are for set screws to retain the wrist pin.



Now the collet block is on its side for drilling and reaming the wrist pin holes.



Then rotated 90 degrees to drill and ream the oil port.



It looks like the 3D render, so it’s probably OK.



Wrist Pin

The wrist pin starts as a .25 diameter W-1 drill rod. The part is to be hardened and tempered.
It’s turned to .245 diameter and then drilled thru .125.



It’s to look like this.



After scribing the critical dimension marks, the collet, in the collet block, moves to the mill.





Then back to the lathe for deburring and parting to length.



The finished wrist pin.



Tomorrow I’ll harden and temper.

[mklotz]

A note to future novice readers...

As Stan has so cleverly shown, it's a really good idea to check your setup before beginning to machine.  With complicated setups, even simple ones, I grab the workpiece with one or both hands and, using everything I've got, try to pull it loose, shake it, twist it, etc..  One will be amazed at how frequently something shifts.

[sshire]

Marv
It's absolutely something I should have checked. If for no other reason than safety. Without the mass of the Kurt, the end mill could have easily caught, cracked, etc. I had torqued down on the vise handle and nothing moved. I usually do your grab it and pull technique. Spinning cutters and loose parts can end badly. Lucky this time.

[b.lindsey]

Sorry about the mishap with the vise, but round 2 sure looks good Stan.

Bill

[mklotz]

Marv
It's absolutely something I should have checked. If for no other reason than safety. Without the mass of the Kurt, the end mill could have easily caught, cracked, etc. I had torqued down on the vise handle and nothing moved. I usually do your grab it and pull technique. Spinning cutters and loose parts can end badly. Lucky this time.

I wasn't trying to pick on you.  Seriously.  I like to think that a part of our fun here should include conveying some of the less obvious lessons to novices who might read us in the future, if there is one.

BTW, loved the wrist pin sight gag.

[Don1966]

Stan mishap happen to remind us to stay vigilant when using machines.  Hopeful in a good way and not by injury.  I like the second round on the piston using the mill for the majority of the work. Nice work all the way around bud and love the wrist pin also. 

 
Don

[sshire]

Marv and all
It is critical that we either comment on, or show, anything that is not safe.
Not only for new machinists, but also for those with years of practice. A Sherline or a Bridgeport is capable of very serious injuries or worse.
Anytime I do something unsafe, I feel compelled to report it here in the hope that it will prevent someone else from doing that.
Let's all keep each other safe.

[sshire]

Down on the Farm, Boy
Episode 10

Back from an 80 degree Thanksgiving in Florida and back in the shop.

The wrist pin is to be hardened and tempered.

Threaded a stainless steel wire through the wrist pin (W-1 drill rod) and pre-heated the Walmart Special Oven that I got for powder coating. The temperature dial is next to useless (well, it is within 50 degrees F.) so the thermocouple came out of hiding.





Heat and magnet check then a dunk in water.





Followed by a brass brush cleanup. I checked the hardness with a jeweler’s saw which skated nicely over the surface with nary a scratch.



Then, into the oven for 2 hours at 400 degrees F. After the time was up, I unpluggged the oven and let the part cool to room temp.



While that was cooling, I turned the brass wrist pin bushing to diameter and drilled and reamed it. And, here’s the obligatory reamer shot.





Nice sliding fit, so parting off commenced and the bushing is done and in place.








Connecting Rod



A piece of 6061, cut to a bit over the required length, was squared up and milled to size.



Some marking out followed.



Drilled and reamed before removing the vise and hauling the rotary table to the mill. I swear the rotab has gotten heavier since I bought it a few years ago.



After indicating the rotary table, I turned and threaded a piece of drill rod to screw into the table’s center. Before I began rounding the end, the stop positions were marked with a Sharpie. This way I know when I’m close. I’ve done way too many parts that were overcut.





That end is finished and close enough to .500” (note 2nd obligatory Starrett ½” micrometer shot)



More layout for the taper.



With the taper lines vertical, I set stops on the “mini-pallet.”





So, pivot part against a stop and mill edge.





Unclamp the center hold-down and pivot the part against the other stop.



Then the center recess, again using both stops.



Flip the part over. Rinse and repeat for the recess.



Followed by files, various grades of Cratex and abrasive sticks.



And we end up here. Still some excess width at the big end to even out.



My plan (which can change on a whim) is to begin the valve cages, valves and other parts that belong to the head.

Stay tuned.

[AussieJimG]

So THAT'S how it's done. Thank you Stan, I am following this thread with great interest and lots of pleasure.

Jim

[b.lindsey]

Nice work Stan and I don't even mind the obligatory mic shots now that I can go fondle mine whenever I wish...   Hope you had a good trip to sunny FL. Nice to see you back on the project though too.

Bill

[Don1966]

Now that's what I call some fine work Stan, your just to cool buddy. I am with Bill on the mic since I have one also.

Don