Milled my first cylinder tonight!!!!!

[parrisw]

Sorry, I read every post and I still don't understand how your mandrel works. Let me try - the cylinder slides on but gets tighter when the squish band meets the mandrel? What does the tailstock do besides keeping it more rigid?

If your mandrel had a hole through it and 3 or 4 slits along the length, and a taper to match your live center, then tailstock pressure would expand the mandrel. Then if cylinders varied a few thousandths in diameter you could grip a wider range.

I am NOT criticizing your work! You did it and I didn't! And it looks good. I'm just trying to understand better.

The idea is to have it fit one bore size, just small enough that it slides on, and you face the end square! Then the tail stock adds pressure to hold it without slipping, the end of the mandrel butts up to the squish band holding it square.

 

[Saw Dr.]

Sorry, I read every post and I still don't understand how your mandrel works. Let me try - the cylinder slides on but gets tighter when the squish band meets the mandrel? What does the tailstock do besides keeping it more rigid?

If your mandrel had a hole through it and 3 or 4 slits along the length, and a taper to match your live center, then tailstock pressure would expand the mandrel. Then if cylinders varied a few thousandths in diameter you could grip a wider range.

I am NOT criticizing your work! You did it and I didn't! And it looks good. I'm just trying to understand better.

The friction is between the end of the custom mandrel (which is finished square on the end) and the combustion chamber in the cylinder. The tail stock adds enough pressure to create the friction, which keeps the mandrel from spinning inside the cylinder.

 

[volks-man]

hey parris,

good work.
i was looking at a mini precision lathe @ 'horrible freight' recently. i had this very thing in mind.


i am wondering if you can mill down a flat-based cylinder in a sanding disc with any real success?
though i haven't tried to install it yet,
i have fooled around with a poulan piston on the sander. i took nearly 2mm off. i measured with a digital caliper from the squish band to the bolting flange. i got the four corners as close to perfect (measured from the squish band) as they were before i started. placed on the sander table the base had no daylight showing anywhere.
how close does a saw cyl need to be?

 

[parrisw]

hey parris,

good work.
i was looking at a mini precision lathe @ 'horrible freight' recently. i had this very thing in mind.


i am wondering if you can mill down a flat-based cylinder in a sanding disc with any real success?
though i haven't tried to install it yet,
i have fooled around with a poulan piston on the sander. i took nearly 2mm off. i measured with a digital caliper from the squish band to the bolting flange. i got the four corners as close to perfect (measured from the squish band) as they were before i started. placed on the sander table the base had no daylight showing anywhere.
how close does a saw cyl need to be?

For me, I'd want to be no more then .003" runout. I wouldn't sand it, not to say that hasn't been done. The mini lathe would be useless for this, the cylinder I did, just barely fit on mine, which is a 9"

 

[volks-man]

For me, I'd want to be no more then .003" runout. I wouldn't sand it, not to say that hasn't been done. The mini lathe would be useless for this, the cylinder I did, just barely fit on mine, which is a 9"

this is what i was thinking of.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93799

wouldn't work?

how long before you start turning custom pistons from scratch?

 

[Feez]

OH! I get it now!

The main ingredient that escaped me was the one piece cylinder / head. I've worked on bunches of two stroke motorcycles back in the day and I forgot chainsaw heads didn't come off. When you referred to squish, I thought you meant the top area of the cylinder where the rings don't touch. I knew what 'we' called squish, but I thought how could squish help when it's in a cardboard box with all the other parts. :blush:
Thanks, now I like the idea even more - and I have a lathe!

 

[parrisw]

this is what i was thinking of.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93799

wouldn't work?

how long before you start turning custom pistons from scratch?

I can't say for sure, but you wont be turning any bigger saw cylinders. Like I said my lathe is a 9" and this cylinder barely fit. See if you can find out what the swing over cross slide is, that'll tell ya how big a piece you can turn.

Custom pistons eh. Not likely.

 

[parrisw]

The main ingredient that escaped me was the one piece cylinder / head. I've worked on bunches of two stroke motorcycles back in the day and I forgot chainsaw heads didn't come off. When you referred to squish, I thought you meant the top area of the cylinder where the rings don't touch. I knew what 'we' called squish, but I thought how could squish help when it's in a cardboard box with all the other parts. :blush:
Thanks, now I like the idea even more - and I have a lathe!

Good to hear you got it now.