How I cut the squish band with a mill

[Pincher]

Disclaimer- this is just how I cut a squish band, not how everyone should cut a squish band.

When looking for parts for a Jonsered saw I ran across a MS361 with scored piston at the Husqvarna dealer. For $75 it had to come home with me.

After using the mastermind method of cylinder cleanup I checked squish with a new piston.

It came in at .014 without .017 thick base gasket. .031 squish is probably fine, but why not try to get .020 without gasket. Time to set up cylinder in mill.

Turns out the cooling fins on the LH side are relatively perpendicular to base.

 

[Pincher]

Time to check if square.

A little tapping and shimming to get the run-out under .001.

Now to find center.

Its good to check run-out near the to and the bottom of cylinder to verify.

Next step, grab boring head.

A trick I learned from a professional, use a piece of paper when touching off on a part to prevent damage.

 

[Pincher]

Time to find the squish band.


I bring up the knee while rotating by hand until I hear it touch.

Set my zero. Since I am only removing a few thousandths, Manually turning boring head going one at a time worked for me.

I took seven.

 

[Pincher]

Blow the chips out and rinse with isopropyl.

Time to check the work.

Should have been .021, may have a little slop in milling head but good enough for who its for (me). For the people who care, the timing numbers with no porting.
exhaust, transfers, intake.

 

[Pincher]

Now a rant on Stihl prices that do not make sense to me..

brand new piston can be had for under $50.

A foam buffer is almost $10. WTF?

 

[Spladle160]

I think you've just touched the tip of the stihl pricing iceberg. What's a 261 vs p&c run?

 

[Pincher]

The 361 piston is reasonable compared to quality aftermarket. The foam piece is a ripoff.

 

[Deets066]

Boring head does work, I like the rotary table better

 

[Pincher]

Closest thing I have to a rotary table is my brothers milltronics CNC mill. He would have to program it though.

 

[Deets066]

 

[Pincher]

Thats a good way to do the base! Haven't used the boring head to trim the base yet.

 

[Deets066]

Thats a good way to do the base! Haven't used the boring head to trim the base yet.

Doing it like this, it’s easier to clamp the jug in a squared vise with the base flat. Then touch off all sides of the fins square

 

[Pincher]

I didn't touch the fins on this one, turned out they were square with the base already. Using wood to clamp it in the vice allows a little forgiveness if fins are not perfect.

Your shops cleaner.

 

[BlacknTan]

View attachment 225062 View attachment 225063

Professionally done..

Very nice! I made my living crankin handles for 45 years, and that setup looks better than many guys who called themselves journeymen.

 

[Deets066]

Professionally done..

Very nice! I made my living crankin handles for 45 years, and that setup looks better than many guys who called themselves journeymen.

Took a bit of work before hand to get there.

 

[Deets066]

When setting up the rotary table, adaptor plate, and chuck. I’ve gotten in the habit of stoning everything when setting up.

 

[Agent Smith]

Thanks for sharing. I like to see different ways to skin a cat

 

[MarcS]

Nice work! Always enjoy the machining threads on this forum and seeing everyone’s methods and shop equipment.

Are you a CVTC graduate by chance? I’ve got a set of parallels identical to yours.

 

[Pincher]

Im not a CVTC. My college years were spent at NDSCS. They had JD ag tech. The parallel you saw was my brothers who attended Dunwoody.

 

[Mattyo]

What always amazes me about machining....there's always someone with a different approach to a problem. Interesting. Thanks !