Ideas for sanding (cutting) the base, no lathe.

[TreeWorks]

That's what I mean by bearing bores,I've just changed one case and sometimes it's not even close to the other one.
The crank not sitting square with the bore is the problem I see. If the cylinder is leaning forward or back a few thousandths I can't see what that would hurt, side pressure would be the killer.

I was thinking the same thing but as much side to side movement as there is between piston and rod I think a thou or two would be fine. the cases and cylinder flange are machined surfaces not ground I bet it's more forgiving than one might think. Maybe my ideas of close tolerances Is skewed as I'm stuck out in the .0001 wastelands 8 hrs a day. I guess if ya ham fist it and end up say .005 out side to side that be around .010 - .015 movement side to side as it reciprocates. Maybe it would cause some premature wear. Doubt it would make a grenade but I could see loss of power
.... you would also see it when you check squish if your doing the crushed solder thing. So why dosent someone do it to a 30$ chinese cylinder and see what happens heck make it .006 out side to side ??

 

[A.E.E.llc]

That's what I mean by bearing bores,I've just changed one case and sometimes it's not even close to the other one.
The crank not sitting square with the bore is the problem I see. If the cylinder is leaning forward or back a few thousandths I can't see what that would hurt, side pressure would be the killer.

So how do you know your bases are perpendicular to the bore when using a belt sander? 288 pistons in a 066/660 cylinders require a substantial amount of material removed.

 

[jmssaws]

So how do you know your bases are perpendicular to the bore when using a belt sander? 288 pistons in a 066/660 cylinders require a substantial amount of material removed.

I'll cut them on a lathe if I'm worried about it not being flat.
I don't use a 288 piston anymore because of the bearing.
I cut .100 off a 394 cylinder today but not with a sander.
If I only need 030 0r 040 off a stihl cylinder I'll just sand it off.
I can cut 040 off in a minute or less and it be no different than it was.
If you measure all 4 corners before then you know what it should be after.
I think we're trying to build a Ferrari out of a pacer worrying about if the bore is 0001 out of square. No possible way the factory can get it any better than we can.
The 066/660 cylinders is cast same as the case and there ain't 2 alike,squish and timing vary on everyone so I can't believe every saw made has a perfectly square bore.

 

[A.E.E.llc]

 

[ANewSawyer]

Not the engineer but I would think that if clearances were that fine, cylinder swaps wouldn't work. And definitely case halve swap would be a no go. Remember, none of these manufacturers are in the game to build the greatest saw but to make a buck. They want to keep expensive process, and waste from them, to a minimum.

 

[A.E.E.llc]

Not the engineer but I would think that if clearances were that fine, cylinder swaps wouldn't work. And definitely case halve swap would be a no go. Remember, none of these manufacturers are in the game to build the greatest saw but to make a buck. They want to keep expensive process, and waste from them, to a minimum.

Tight tolerances are the reason why swaps work.

 

[ANewSawyer]

I will stop talking about stuff I know nothing about now.

 

[t4driller]

On mine I measured all 4 corners and just made sure that they were all the same except .047 thinner. I think til I was done the one corner was .001 off.

 

[Definitive Dave]

Hmmm. Anybody work the math on that? The distance across the cylinder extension flanges on the 346NE is 1.925", which we can round to 2". The height of the cylinder is, roughly anyway, 6". So then, at the top of the stroke, the piston is off its perfect theoretical path by .003". Your mileage may vary....

I am *s-wordty at math and know next to nothing about the intricacy of a machine shop but did you just round off two numbers to get the basis for a theoretical answer to the equation ?
lols

 

[dbittle]

Exactly. (Or approximately, anyway). Yes, or mostly. Its a 90% solution, for horse shoes, hand grenades, grade point averages and government work.

 

[jmssaws]

Get a big box of case halves and try to find 2 that match at the cylinder base.

 

[ANewSawyer]

Simple solution for a complicated problem. Wooden dowel on a flat wooden baseplate. Turn the dowel to the same size as the cylinder. Dowel keeps the cylinder from tipping, apply sand paper to the base and go to work. If you wanted to, add a piece of metal over the wood baseplate, to keep the wood from wearing down. Then apply sandpaper to the metal.

If it is a flanged cylinder, use the appropriate size hole saw, just make the base deeper than the flange.

 

[jmssaws]

I only have 500$ for my lathe,gave 200 for the one before that. I have far more money in burrs and hand peices.

A cc right angle is almost that much.

The sander I have cost more than the lathe. If you look they can be had cheap.

 

[A.E.E.llc]

Please let this thread die. Lol

 

[ANewSawyer]

Yes, but you don't always have space for the lathe. I like thinking outside of the box. I am stuck in a box so much that it feels nice to think outside it. Sometimes the thought is the most enjoyable part of the idea.

 

[Metals406]

Please let this thread die. Lol

Bump. [emoji6]

 

[drf256]

Get a big box of case halves and try to find 2 that match at the cylinder base.

Do we know how the factory does it?

I assume the cases halves are mated and then the cylinder base area is decked for final clearance. That area looks machined and not cast to me.

I'm on the side of believing that incredibly accurate tolerances are at play here. That's how these saws last for millions and millions of rpm. Not necessarily port height or squish, but bore squareness and concentricity.

 

[stihl_head1982]

I only have 500$ for my lathe,gave 200 for the one before that. I have far more money in burrs and hand peices.

A cc right angle is almost that much.

The sander I have cost more than the lathe. If you look they can be had cheap.

post a picture of the sander please. Me likey the idear!

 

[Tor R]

On Husky 545/550 I would defently go for milling the cases instead of cutting the base.

 

[Jswanson]

How many saws after two threads in one?