Machining base without a lathe*

[jb-chainsaws]

I'd say that case looks almost as if it's been assembled from two separate saws, as I know at least with Stihl the case is machined after being closed, so that gap would worry me some?

 

[Al Smith]

When I cut bases on a lathe I pick a corner to measure and use that one for the thickness taken off.

To be honest several times I failed to do that ,forgot which corner. However as a result of same I became very adept at making gaskets so as not to have a head knocker.Chit happens .

 

[mdavlee]

To be honest several times I failed to do that ,forgot which corner. However as a result of same I became very adept at making gaskets so as not to have a head knocker.Chit happens .

I always do an intake side corner near the clutch side. Saves the hassle of remembering now

 

[Al Smith]

When I did the cylinder on a 200T I failed to realize there isn't enough room to get a set of micrometers over the flange lip nor a set of calipers .Got creative and used a set of telescope gauges and measured off the face of the collett closure .--still had the make a freakin gasket .Not much room for error on those little rascals.If I recall they only have about 35 thou clearance to start with .

 

[jmssaws]

I can take a fine point sharpie and scribe a line all the way around the base at 010 or 020 or whatever.
Make a mark and measure till it's right then use your finger as a stop and trace the edge.
Carpenters do it all the time

 

[jmssaws]

Having a squish target is good but if your shooting for 020 and get 017 or 023 I can assure you it won't be any different at either.
This is why you always cut the base first when cutting the chamber by hand so you can sand to desired squish and you won't over cut the chamber.

 

[jmssaws]

Unless your using plastiguage your squish measurement will probably be off more than your machine work.

Check a few with solder then with plastiguage, your 020 can become 010

 

[mdavlee]

Unless your using plastiguage your squish measurement will probably be off more than your machine work.

Check a few with solder then with plastiguage, your 020 can become 010

Very true. Anything under .015" with the small solder will read a lot thinner with plastigauge.

 

[jmssaws]

Very true. Anything under .015" with the small solder will read a lot thinner with plastigauge.

You have to use very small solder like 030 or less for it to be close.

 

[mdavlee]

You have to use very small solder like 030 or less for it to be close.

Even with that there's a difference. I've tried 3 different solder and the yellow plastigauge. Around .018-25 they read about the same.

 

[jmssaws]

I'll spend my time grinding and making power not fretting if my squish is 003 to big,it's a chainsaw not a pocket watch.
What we do to them makes every part have tighter tolerances.

There's a few cylinders like a poor timed 660 cylinder that I'll only cut on the sander. There's a method to the madness.

Same with timing,if I finish grinding and check it and instead of 100 122 80 like I had laid out its 100.5 123 79.5 there's no way in hell I'll change it,there's so much more to it than a number,hell what I call 100 might be your 98 or 101.

I've probably built who knows how many 066 and 064 and if there's 2 alike it's a accident, I let the cylinder tell me what to do,same with machine work.

 

[paragonbuilder]

I can take a fine point sharpie and scribe a line all the way around the base at 010 or 020 or whatever.
Make a mark and measure till it's right then use your finger as a stop and trace the edge.
Carpenters do it all the time

Yup. Amazing how accurate you can be with a little practice.


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[jmssaws]

Yup. Amazing how accurate you can be with a little practice.


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Friend of mine can draw a line in the middle of 2x4 that's better than a chalk line and faster.

Mess with this stuff 50+ hours a week for years and you get a good eye for thousands.

 

[mdavlee]

I let squish go if it's over 17. Under that with solder I'll open it up. I usually get within .001" on my calipers cutting squish by hand. I figure that's better than it started.

 

[cease232]

I'd say that case looks almost as if it's been assembled from two separate saws, as I know at least with Stihl the case is machined after being closed, so that gap would worry me some?

It highly unlikely that this case was ever split and reassembled. This saw is not super common.
I don't know for sure but I doubt stihl machines the case after assembly. What would stop shavings from entering the case? Someone correct me if I'm wrong.
Considering this saw is as old as I am I'd say the gap isn't a problem.


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[cease232]

Friend of mine can draw a line in the middle of 2x4 that's better than a chalk line and faster.

Mess with this stuff 50+ hours a week for years and you get a good eye for thousands.

People are always amazed you can scribe a line without a chalk line. When I was framing my chalk line was only used for angled marks.
Not that I do finer woodworking I still use my finger and a pencil to scribe many things. As you said it's amazing how accurate you can see and feel thousandths with some practice.


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[Moparmyway]

I've measured with a caliper from the squish to the base, on 4 corners ............. the factory has ALOT more tolerance than I do.

Ragarding using solder for squish : If you keep rolling the piston back and forth over the solder untill you can barely feel it hitting, you'll get the same reading as plastigauge

 

[Red97]

I've measured with a caliper from the squish to the base, on 4 corners ............. the factory has ALOT more tolerance than I do.

Ragarding using solder for squish : If you keep rolling the piston back and forth over the solder untill you can barely feel it hitting, you'll get the same reading as plastigauge

This^

Last couple I have been using a piece of .015 pre squished solder.

That way I don't have to bolt the jug everytime. Just keep cutting/sanding the band until you can just feel it touch. Then check with fresh solder.

 

[paragonbuilder]

This^

Last couple I have been using a piece of .015 pre squished solder.

That way I don't have to bolt the jug everytime. Just keep cutting/sanding the band until you can just feel it touch. Then check with fresh solder.

That's a good idea Joe!


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[drf256]

I just did the squish on an 026 jug. Same area read .022 with .032 solder and .018 with .023 solder.

That was measured with a micrometer and not a caliper.

Just goes to show that you need the closest solder possible to your intended goal.