PM Research #7 It Begins

[Lo-Fi]

My thoughts on approaching this setup:

What matters is getting the bore "true" to the outside of the casting, not the core hole which could be shifted quite badly. It's only there to save valuable material and some machining, after all.

Indicate off equally off the three jaws holding the round part, get nice and central, bore initially with an end mill so it doesn't follow the off centre hole. Face true. Bore to size. Should get in the ballpark, if I'm not missing a quirk of the casting geometry...

Look forward to seeing what you come up with!

Ian

 

[Janderso]

I have success.
The method I used to center the cylinder worked extremely well.
I was able to bore both cylinders using this method and verified the accuracy as best as I could.
The three points on the dial, 9:00- 12:00 - and 3:00 wall thickness varies by .002”
The bore is concentric as well on both. The length of each is within .002”

 

[Jim Dobson]

Enjoying this thread, please keep the pics coming.

 

[Janderso]

That seems like a perfectly fine way to do it. Just make sure you don't use a drill-bit, use a boring bar there, otherwise the bit will be drilling off center and will drift (or worse, catch and remove the part from the chuck)!

Is the back of the cylinder 'flat'? You likely want to make sure that is the case so you can square up both sides at the same time (unless you're going to flatten the other side on the mill).

Thinking about using the mill to flatten the back side is probably easier than resetting it up in the four jaw.
Oh well, it’s done and it worked out well.
I’ll tell you one thing, you can’t be in a hurry doing this.
My goal is to build my skills, that I am doing!

 

[Janderso]

Ok, done for today. I got to the point where I need a 3/16-40 model tap and die.
This is of course after I drilled for the 3/16-40.
It’s a taper thread.
You won’t find this at the local hardware store, well not at my local store.
When I called I asked for hardware. Ha, remember back when you had smart people that dedicated their day to helping customers and had the experience to know what a tap is.
I’m showing the fit between the cylinders with a .500” gauge pin.
Tapped for 5-40, .125” deep.
I must say, drilling through the length and finding a centered hole on the other end was satisfying.
Measure twice, cut once.

 

[EricB]

PMR has all the taps and dies you would need. Their pipe thread tools are kind of pricey, but I haven't found them elsewhere.

Eric

 

[Janderso]

Boy howdy, they have them and I ordered what I need.
Well, I’ll take good care of them as I hope to build again

 

[Alcap]

When I started reading some of the model engine builds I thought " I would like to try that " then I realized my skills are not there yet lol Your doing a wonderful job , Al

 

[macardoso]

Need help!
I really don’t want to screw up another cylinder.
I have the cylinder centered in the four jaw as shown.
Is there a better way?
The cylinder at 90- 180 and 270 degrees is centered this way.
Thanks

That's exactly how I did the cylinder for my #6

 

[Janderso]

That's exactly how I did the cylinder for my #6

View attachment 337801

View attachment 337800

That's either a large cylinder or a small lathe/chuck.
My 10" 4 jaw makes the little cylinder look even smaller.