cut the base on my 385xp on the bridgeport mill!

[weimedog]

I have a lathe. In fact, it might even be possible to put the cylinder on the lathe. I wanted to see if this was possible. I know you guys think its easier on a lathe, but I'm not so sure. I've seen it done, and ideally you need a long rod ...same diameter as the piston and then a live center up against the head. Off hand, I don't have any material big enough to make a mandrel like that. a block of wood maybe?

so I figured I'd try this. took about and hour and a half to get it level with shims in a vice that was BARELY big enough to grab it...

it also seemed to me that it was less risky to mess up a case than an oem cylinder .... I can just find another case.... new oem jug... I dunno.

so thats what I was thinkin, wagnerwerks is right, I worked with what I had. actually, I think this is quite pretty... though one day I'll get a cylinder on the lathe and play w/ that.

Falls into "If your a hammer, everything looks like a nail" category. Also with a decent CNC mill & renshaw probe setup, you can do pretty much the same things to a cylinder as typically done with a lathe. Cutting the base, even cutting the squish band with the right tooling. But a lathe can't do what a mill can. SO being an old manufacturing engineer/ CAD/CAM/CNC type, I hope to be seeing more guys exploring that route. I plan too. Tough to get "circular interpolation" with a manual mill though, although with a rotary table and clever fixturing you can do some similar thngs. CNC means bucks..... and a Lathe can be much cheaper & certainly a practical way to trim cylinders & pistons....

Remember those old "Tree" brand mills with the interactive graphic controllers?? Hummm... they go for around 10k used....

 

[Mattyo]

I actually have more experience with a lathe than I do on the mill....and if I had had a piece of nylon that'd make a good mandrel I would have used that....but I'm glad I did this on the mill...neat project for a beginner like me...

Weimedog... r u afleetcommand....on youtube? Love the video and it'd be great to meet u sometime.....if u are ever in ct I owe u a beer....or lunch....or something!

 

[psuiewalsh]

http://www.ebay.com/itm/12-TROYKE-M...131003132420&rk=3&rkt=6&sd=151522794870&rt=nc

 

[Red97]

A boring/facing head would be a lot easier than a rotary table. IMO, but a new kit is very pricy 1500$ plus. But they are very nice and hold close tolerance. The good thing about the boring/facing is you only have to set the cyl up once.

 

[Chris-PA]

The only cylinder I have cut yet was done on a lathe without any insert. I was able to clamp it on the cylinder base ridge from the inside with a 3-jaw. I put a thick washer or nut over the point of the tail support so I could tap the cylinder around and get it square. I used an old lathe at work. It has a gear reduction so I could go very slow.

Of course, it was a 38cc Earthquake cylinder that was, shall we say, indifferently cast and machined to begin with. In particular it has an as-cast domed piston, and the combustion chamber had evidently gotten a little slumpy in casting, and I had to do a little grinding in two spots under the spark plug boss. So I didn't really have much to go on for a reference. I decided that the squish measurements had been pretty close all the way around and so I used the existing base machining.

In the end I got it right on side-to-side, but a little off front to back - I decided to go with it as it offset the crank centerline just like Zenoah is doing with the new GZ4300/543XP.

 

[LegDeLimber]

If you can lay hands on some pipe or any sort of suitable solid stock that's close to size, but a bit under,
build it up with some good old JB weld or some equivalent and turn to size.
edit: and ditto on checking the spigot into the cases for interference now.

I'll just assume you have a test indicator, since you were able to mill the cases.
You said someting about not knowing if the head was squared with the table?
shoot, grab about a foot of appropriate sized rod or your test rigging and
chuck it up and get sweeping and dial that head in!
If you're ever going to bore the chamber and face the base of a jug, you'll absolutely
have to have that test indicator to get get the bore lined up with the spindle.

Man do I miss being in the second shop i worked for. equipment was all well kept
and t hey had recently bought a new lathe and the 4 jaw with it
was able to handle my 500cc Yamaha cyl.

 

[Mattyo]

Next time I try something like this i'll take everyone advice and get some nylon round stock and use it to mandrel up a cylinder on the lathe.... just to prove to everyone I can

Unfortunately, I don't spend a lot of time at my folks house where the machine shop is... and the equipment is old to begin with, but reasonably functional. For what I'm doing, the tolerances will be fine.... not trying to be Randy or anything

 

[weimedog]

Next time I try something like this i'll take everyone advice and get some nylon round stock and use it to mandrel up a cylinder on the lathe.... just to prove to everyone I can

Unfortunately, I don't spend a lot of time at my folks house where the machine shop is... and the equipment is old to begin with, but reasonably functional. For what I'm doing, the tolerances will be fine.... not trying to be Randy or anything

I wouldn't worry too much about what other folks think... fact is you are growing a skill set and having fun. I happen to appreciate those who take what they have and adapt them to a situation as you are doing. Bottom line, the mill concept is a sound one. Next thing we know you will be doing things like adapting larger carburetors to those cylinders with milled manifolds and innovative things like that with that mill! Your fortunate to have access to that kind of equipment and even more fortunate to have a personality willing to create... Hope more pictures follow.....

 

[Mattyo]

workin on video .... but I'm also workin on my car that I recently wrecked... everyone's ok but this is keepin me from my saw

today is too nice to not be outside workin on the car... got it fairly well apart...

 

[old-cat]

I wouldn't worry too much about what other folks think... fact is you are growing a skill set and having fun. I happen to appreciate those who take what they have and adapt them to a situation as you are doing. Bottom line, the mill concept is a sound one. Next thing we know you will be doing things like adapting larger carburetors to those cylinders with milled manifolds and innovative things like that with that mill! Your fortunate to have access to that kind of equipment and even more fortunate to have a personality willing to create... Hope more pictures follow.....

He also puts up with a lot of flack from people like me!

 

[wcorey]

I see little reason you can't use a piece of hard wood for a cylinder mandrel, I use about anything I can find that's big enough.
On a nice piece of stock I'll cut in a few steps to accommodate different sizes and also use both ends, really doesn't have to go very deep into the cyl bore.

I've cut squish bands using the lathe/boring bar and the mill/boring head, I found it takes about the same time either way.
The cut is quick and easy (a bit easier on the lathe), the setup is a time consuming pain.
Finally got around to making an adjustable mandrel that holds a bit to do the squish cut manually, only takes about ten minutes total to do one now.

Stating the obvious for most but... The big advantage of cutting the case is that usually a replacement standard p&c can be used, just like cutting squish allows for an un-modded replacement piston (as opposed to a popup).

 

[old-cat]

I see little reason you can't use a piece of hard wood for a cylinder mandrel, I use about anything I can find that's big enough.
On a nice piece of stock I'll cut in a few steps to accommodate different sizes and also use both ends, really doesn't have to go very deep into the cyl bore.

I've cut squish bands using the lathe/boring bar and the mill/boring head, I found it takes about the same time either way.
The cut is quick and easy (a bit easier on the lathe), the setup is a time consuming pain.
Finally got around to making an adjustable mandrel that holds a bit to do the squish cut manually, only takes about ten minutes total to do one now.

Stating the obvious for most but... The big advantage of cutting the case is that usually a replacement standard p&c can be used, just like cutting squish allows for an un-modded replacement piston (as opposed to a popup).

Could you please go into a little more detail. Are you talking about a shaper bit to scrape out the squish band?

 

[LegDeLimber]

I've heard of some folks using a piston and putting self-adhesive sandpaper on the dome
then doing the chamber work with it.

edit: But DON'T foeget to take off the ring first. They would seriously scratch the cylinder wall when twisting the piston around

 

[mdavlee]

I cut squish manually myself.

 

[Jim Timber]

I wouldn't do it on my CNC either. Too much fussing for a one-off.

 

[wcorey]

Could you please go into a little more detail. Are you talking about a shaper bit to scrape out the squish band?

Yes, you could use a shaper bit, and I guess it could be termed as 'scraping' it. However, how you hold it in the cylinder is the key aspect. I think using this method has been around for a very long time, I first became aware of it through a tree monkey post.

Not simple to explain the adjustable part without pics but the basic mandrel is easy. Just a big round bar of something (aluminum, nylon, wood...) that fits the cylinder closely and holds some sort of cutting bit in a slot, parallel to the squish band and just off the cylinder wall. I usually angle the cutter to give a couple degrees taper to the band up/in toward the chamber.
Cutter is just a flat blade made from tool steel or carbide, like a lathe bit or a piece of planer/shaper blade, I use a typical triangle carbide lathe insert. Tool steel would likely give a better cut on the aluminum but sometimes there's a good bit of nikasil to get through first so I opted for carbide.

To use, insert mandrel into bore and rotate while applying downward pressure. I seem to get better control by having the mandrel stationary and rotating the cylinder. The chips can be pretty thick and look like little roll pins...

One problem, as with the cylinder holding mandrel for base cutting, is that you need one for each size cylinder. In my case that's a couple dozen or so and since I'm not doing a large number of any one size, it's almost easier to just machine each cylinder than to make the cutting mandrel.
So, you make One that's adjustable to cover all sizes, I started giving it serious thought while using an old Lisle ridge reamer utilizing a ramp and roller type setup. Many ways to skin a cat there, the options are seemingly endless. I put my emphasis on finding something simple and quick to make, rather than elegant and complex...

One of these days I'll get around to doing a write up on it, have showed it to a number of people at GTG's over the past year or so, not proprietary or anything.

 

[weimedog]

Yes, you could use a shaper bit, and I guess it could be termed as 'scraping' it. However, how you hold it in the cylinder is the key aspect. I think using this method has been around for a very long time, I first became aware of it through a tree monkey post.

Not simple to explain the adjustable part without pics but the basic mandrel is easy. Just a big round bar of something (aluminum, nylon, wood...) that fits the cylinder closely and holds some sort of cutting bit in a slot, parallel to the squish band and just off the cylinder wall. I usually angle the cutter to give a couple degrees taper to the band up/in toward the chamber.
Cutter is just a flat blade made from tool steel or carbide, like a lathe bit or a piece of planer/shaper blade, I use a typical triangle carbide lathe insert. Tool steel would likely give a better cut on the aluminum but sometimes there's a good bit of nikasil to get through first so I opted for carbide.

To use, insert mandrel into bore and rotate while applying downward pressure. I seem to get better control by having the mandrel stationary and rotating the cylinder. The chips can be pretty thick and look like little roll pins...

One problem, as with the cylinder holding mandrel for base cutting, is that you need one for each size cylinder. In my case that's a couple dozen or so and since I'm not doing a large number of any one size, it's almost easier to just machine each cylinder than to make the cutting mandrel.
So, you make One that's adjustable to cover all sizes, I started giving it serious thought while using an old Lisle ridge reamer utilizing a ramp and roller type setup. Many ways to skin a cat there, the options are seemingly endless. I put my emphasis on finding something simple and quick to make, rather than elegant and complex...

One of these days I'll get around to doing a write up on it, have showed it to a number of people at GTG's over the past year or so, not proprietary or anything.

Think we saw it over at the Cutting Edge GTG... a very creative and capable individual too BTW. One of those deals where he's a bit ahead of the curve. And it takes the "experts" a bit of time to catch up.... trust me on that assessment..

 

[LegDeLimber]

http://www.ebay.com/itm/12-TROYKE-M...131003132420&rk=3&rkt=6&sd=151522794870&rt=nc
As long as it isn't so worn that it shifts .020 or so, when you tighten the clamping screw.
If I bought a used one, i would lightly snug the clamp screw and spin the table to look for any tight or loose areas.
Some tables may get used in a repetitive job and could have a worn spot while the rest of the table feels ok to just a quick, cursory little spin of the feed screw.

When running a universal mill, I used to mill a slight angle on a lot of flat stock
that might be a third of the table travel.
So what i would do is just grab the Dykem and paint a little spot on the table to keep track of the last travel zone used and then (if length permitted) I would try to shift the next batch over to the next area of travel.
Just worked my way back & forth over the mill table.
I was trying to evenly spread the wear and tapering off the ways.

 

[old-cat]

Yes, you could use a shaper bit, and I guess it could be termed as 'scraping' it. However, how you hold it in the cylinder is the key aspect. I think using this method has been around for a very long time, I first became aware of it through a tree monkey post.

Not simple to explain the adjustable part without pics but the basic mandrel is easy. Just a big round bar of something (aluminum, nylon, wood...) that fits the cylinder closely and holds some sort of cutting bit in a slot, parallel to the squish band and just off the cylinder wall. I usually angle the cutter to give a couple degrees taper to the band up/in toward the chamber.
Cutter is just a flat blade made from tool steel or carbide, like a lathe bit or a piece of planer/shaper blade, I use a typical triangle carbide lathe insert. Tool steel would likely give a better cut on the aluminum but sometimes there's a good bit of nikasil to get through first so I opted for carbide.

To use, insert mandrel into bore and rotate while applying downward pressure. I seem to get better control by having the mandrel stationary and rotating the cylinder. The chips can be pretty thick and look like little roll pins...

One problem, as with the cylinder holding mandrel for base cutting, is that you need one for each size cylinder. In my case that's a couple dozen or so and since I'm not doing a large number of any one size, it's almost easier to just machine each cylinder than to make the cutting mandrel.
So, you make One that's adjustable to cover all sizes, I started giving it serious thought while using an old Lisle ridge reamer utilizing a ramp and roller type setup. Many ways to skin a cat there, the options are seemingly endless. I put my emphasis on finding something simple and quick to make, rather than elegant and complex...

One of these days I'll get around to doing a write up on it, have showed it to a number of people at GTG's over the past year or so, not proprietary or anything.

I am a retired engine machinist. I'm very familiar with the cutter you described and I will never allow a tool like that on one of my cylinders.
You CAN NOT make the squish band square with the cylinder with that tool! The ONLY way is with a single point cutter in a lathe, the way Randy does it.

 

[weimedog]

I am a retired engine machinist. I'm very familiar with the cutter you described and I will never allow a tool like that on one of my cylinders.
You CAN NOT make the squish band square with the cylinder with that tool! The ONLY way is with a single point cutter in a lathe, the way Randy does it.

Wow. If I counted all the times I was told what was possible and impossible.... The difference between those who create and those who re-create.

Now if the line was along the lines of what's probable & improbable.... lol! I would react differently.

(My first task as an Manufacturing engineer was to convert a shop full of Warner-Swazy 2AC's & New Briton chuckers with CNC lathes.... Gang tooling & form tools to carbide inserts, and it couldn't be done if the experts in and around that shop were asked.... I had to do all the programming, fixturing (chuck & jaw designs), and teach an unwilling audience how to run the new systems. What I lost on cycle time I made up on setup time for the typical lot sizes they did...AND let them expand into more custom work for military contract types. by the time I was done, ALL the machine tools with form tooling and gang tooling were gone. And those who said it couldn't be done as well. Rough story, but true)