old-cat
Fir Man
If you have a minimum of 5 cutters, precision sharpened it MIGHT work. BUT a single cutter will follow the surface that's already there.
cut the base on my 385xp on the bridgeport mill!
- Thread starter Mattyo
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That's better. I happen to know the individual I believe. And if its who I think it is, the guy is about designing solutions to both the improbable and impossible. An amazing story actually.
Thanks for stepping up for me Walt, I appreciate the vote of confidence.
A little over the top though, don’t want to have to live up to those lofty expectations, lol.
Well, maybe You can’t, but I don’t seem to have an issue with it…
I’ve had little problem getting the deck to squish band within a couple thou, if I thought it required greater accuracy than that I could spend a bit more time to do it but fail to see the need.
You do have a valid point though, it’s not dial-a-thousandth, a hamfisted bonehead could certainly make a mess of a cylinder with this thing. I remember one of tree monkey’s photos where he cut clean through the top of a cylinder to demonstrate the relative ‘effectiveness’ of such a tool.
Takes a bit of common sense to use, a small amount of skill even.
Requires a bit of time and determination to really let it ‘get away from you’ though, whereas doing it under power on a lathe/mill takes but a twitch and a fraction of a second for things to go very wrong.
Properly set up, there's no chance for the cutter to contact the cylinder wall plating, even if you tried.
And actually it doesn’t tend to follow the original surface, I spent some time trying to make it do so as that makes things somewhat easier, when (as it usually is) the starting surface is already acceptable. It can be optionally set to cut to a certain depth only, or go ‘freehand’ and then how aggressively the cutter is angled starts to come into play there.
Have tried it with multiple cutters and found no advantage there, also things like staggering the cutter positions, leading, trailing, other various cambers/castors and angles of attack. No magic bullets discovered, turns out simple/obvious is quite good enough, for me anyway...
A little over the top though, don’t want to have to live up to those lofty expectations, lol.
Well, maybe You can’t, but I don’t seem to have an issue with it…
I’ve had little problem getting the deck to squish band within a couple thou, if I thought it required greater accuracy than that I could spend a bit more time to do it but fail to see the need.
You do have a valid point though, it’s not dial-a-thousandth, a hamfisted bonehead could certainly make a mess of a cylinder with this thing. I remember one of tree monkey’s photos where he cut clean through the top of a cylinder to demonstrate the relative ‘effectiveness’ of such a tool.
Takes a bit of common sense to use, a small amount of skill even.
Requires a bit of time and determination to really let it ‘get away from you’ though, whereas doing it under power on a lathe/mill takes but a twitch and a fraction of a second for things to go very wrong.
Properly set up, there's no chance for the cutter to contact the cylinder wall plating, even if you tried.
And actually it doesn’t tend to follow the original surface, I spent some time trying to make it do so as that makes things somewhat easier, when (as it usually is) the starting surface is already acceptable. It can be optionally set to cut to a certain depth only, or go ‘freehand’ and then how aggressively the cutter is angled starts to come into play there.
Have tried it with multiple cutters and found no advantage there, also things like staggering the cutter positions, leading, trailing, other various cambers/castors and angles of attack. No magic bullets discovered, turns out simple/obvious is quite good enough, for me anyway...
old-cat
Fir Man
For anyone who wants to have the squish clearance in the .020" range, I totally agree with what you are doing. I am a little more radical that most saw builders, with my own saws, .015" is my MAXIMUM. I'm just in a learning curve, so I might have to alter my ways!
I'll always be on the learning curve...
On smaller bores I'll go to .015 but stick to .020 on the bigger stuff and mostly stay under 200psi on the large ones anyway. For the small difference in comp that 3-5 thousandths makes I'd rather stay on the safer side, plus if you really want that much additional comp it's usually just a matter of taking the squish band that much deeper.
Also depends on whether I consider the saw more of a gtg toy or a daily cutter...
On smaller bores I'll go to .015 but stick to .020 on the bigger stuff and mostly stay under 200psi on the large ones anyway. For the small difference in comp that 3-5 thousandths makes I'd rather stay on the safer side, plus if you really want that much additional comp it's usually just a matter of taking the squish band that much deeper.
Also depends on whether I consider the saw more of a gtg toy or a daily cutter...
For me it's (The cutter) an interesting concept because it allows the typical enthusiast to move further into the realm of performance enhanced hobby/work saws without the investment of a machine shop... next is a clever tool to take some material off cylinder bases with cylinder flanges, like Husqvarna 372's. 
Any idea's short of a lathe setup?
Any idea's short of a lathe setup?
I typically stay in .020 range on all the saws. There is a point of diminishing returns.. not just in power, but also in "user friendliness". I guess my confession is I've been.. prudent, boring, un-inspired... trying to stay within boundary's ... 185lbs or .020 which ever comes first.... on the "for real work" saws. Does it really matter?? Probably not, but it makes me feel .... responsible. Think if I wanted more compression I would rather "shrink" the combustion chamber (decking/squish band mods or popup), but right now I'm happy with how the saws perform and most of all the reliability to this point in time.
Think if I wanted more compression I would rather "shrink" the combustion chamber (decking/squish band mods or popup), but right now I'm happy with how the saws perform and most of all the reliability to this point in time.
I occasionally/randomly have issues with 'tool chatter', leaving small striations that look worse than they measure out to, maybe only a few tenths.
Sometimes I take a couple minutes to sand them out, only because it annoys me to look at 'em.
Been thinking of adding a spot on the mandrel for a cutter to put the transition radius on the edge between the squish band and dome.
Probably not worth the bother, presently I just go around it with a burr or big ball stone and then sand a bit to blend.
old-cat
Fir Man
The reason I set my squish tight is primarily to reduce octane requirement and make the gas burn faster. Higher compression is just a bonus.
Sorry, I have a lathe and cutting the base is quick/easy/low risk, so not much incentive to mess with alternative methods.
You could likely do something that would effectively be the inverse of the mandrel squish cutter but making it adjustable for different cylinders would be challenging.
And of course it would be absolutely impossible to keep the base perpendicular to the bore, only traditional methods can accomplish that...
??
You are going to need to convince me that higher compression requires less octane......
Octane is about controlling volatility & stability in a fuel so you can infact push the mechanical boundaries such as compression and ignition timing.
Sorry, I have a lathe and cutting the base is quick/easy/low risk, so not much incentive to mess with alternative methods.
You could likely do something that would effectively be the inverse of the mandrel squish cutter but making it adjustable for different cylinders would be challenging.
And of course it would be absolutely impossible to keep the base perpendicular to the bore, only traditional methods can accomplish that...
Oh well... I tried...
(Some day over a beer I'll tell you the story of the dreaded plate, (a plate with a hole cut in it...still have it) & Big Bore KTM's)
old-cat
Fir Man
You are twisting what I said. I didn't learn what I stated above on my own, it came from R&D engineers and I built an engine to verify. I found out that what they said is TRUE!
Now I'm all confused.... un twist the statement and theory. I can begin to buy into the concept if its about combustion chamber shape.... but its a tough sell if its about compression.
But higher octane gas burns slower...
And I've yet to have detonation related issues with 87 pump gas...
I'm at near sea level. Maybe an altitude related issue?
Actually, forget I said all that, not a conversation I want to pursue...
old-cat
Fir Man
Just re-read what I said first.
The one that was giving me trouble with that was a 7300 cylinder. It has a very wide band and small chamber to start with.
Dammit Walt, now you have me thinking
.A mandrel fit to the bore with a flange on top, a groove in that flange to hold a cutter that clears the cylinder skirt and extends down to the base.
Measure/trim skirt to be sure it's paralleled to base.
Set the height of the cutter so the flange has a gap to the skirt equivalent to the desired depth of cut, spin with downward pressure until flange hits skirt.
Done.
And I think it could be made to be adjustable to different bore sizes in much the same way as I do it with the squish cutter....
It's unfortunate that anyone who would have the equipment capable of producing one of these, doesn't need it
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