DIY case boring... tips/tricks?

[Nitori]

This is sort of a continuation of my tomfoolery with a CL100 engine. I have a 125cc jug for it now, but the case needs to be bored out by the tiniest margin. I need to remove roughly .04 inch around the diameter, probably more like .05 to get a reasonable non-interference fit.

I have 2 cases, so I figured I'd test out my idea on the crappy one first. Started with one half just to experiment.

Used a Dremel with one of these carbide cutter bits:

It went through the case like nobody's business, but left a lot to be desired in the control department. Sort of a wavy cut even though I was moving it smoothly.

So I cleaned up the ripples with a flap wheel, and this is how it turned out:

Not bad for a homegrown, half-assed free hand job. Problem is it's not perfectly concentric. Also I would still need to take off more material to fit the jug.


My plan for the "real deal" is to line up the halves of the case, bolt & clamp the buggers together solid, and do what I did before but stop & test fit often.

My good case's spigot:

It doesn't really even look all that precise in stock form...

So my questions are this:
- Any tips or tricks on how to indicate to the center of the spigot better and make a smoother initial cut?
- I should be fine even if it isn't perfectly concentric, right?

I'm basically only going to have to take off enough material to remove that bevel from the spigot's edge, so it's not an extreme bore-out by any means.

 

[teazer]

That's not as neat as say a Bridgeport, but a damn site nicer than the set I did with an air die grinder. That thing made waves you could surf on. All hyperbole aside, you will be fine with the way you are doing it. Take your time and check often.

 

[hillsy]

As long as there is enough base left to seal the base gasket it doesn't really matter how tidy (or untidy) the milling is.


I agree with Teazer - that pretty neat work for a hand job (so to speak.... )

 

[Saturnicus]

You probably have discovered already that the cutting tool will dig in to to material if you cut from left to right as the teeth will want to grab material. It can easily cut gouges going this way.
For more control cut from right to left in small touches at a time. Kind of touch, lift, touch lift manner.
Taking time and care you'll probably do a very good job of it.

 

[J-Rod10]

My advice: Make sure you wear gloves. You get one of those splinters of metal in your finger, good luck getting it out without a microscope and a razorblade.

 

[Nitori]

I hear you on the gloves. 8)
It turned out pretty well!

Here's how I clamped it all together:

(plus face shield)

Running the cutting tool very carefully & test fitting often, I followed the same procedure as before except I kept flipping the assembly side to side to access & see what I was working on more easily.

A lot of patience, some flap wheel cleanup, and a quick zap of 320 grit sandpaper later:

My only concern is when I test fit everything with studs and dowels installed, I had to gently mallet the jug to mate with the dowels, and there was a tiny bit of gap around the gasket:

I'm assuming this will go away when I torque down the head studs- does it look out of the ordinary to anyone?
I'm gonna get the case cleaned out in an aluminum safe hot tank & blast every last flake of aluminum shaving out, so I'd rather figure it out now as opposed to having to remove more material and re-clean! ;D

 

[hillsy]

You should probably work out if the sleeve is rubbing anywhere on the freshly milled cases and upsetting where the cylinder goes over the locating dowels. A smear of bearing blue around the sleeve should reveal if you need some more machining on the cases.


Looks pretty tidy, though.

 

[Erskine]

I'm planning on boring out some cases in the future so very interested in seeing how you progress doing it by hand.

 

[Nitori]

You should probably work out if the sleeve is rubbing anywhere on the freshly milled cases and upsetting where the cylinder goes over the locating dowels. A smear of bearing blue around the sleeve should reveal if you need some more machining on the cases.


Looks pretty tidy, though.

Thanks for that, it was one of those smack myself in the forehead "oh DUH!" moments. That was exactly the reason for the gap.

Ghetto garage tip: Don't have bearing blue/machinists blue/dykem/whatever? Dig around and find a blue sharpie marker, it works just as well! ;D

I found some small areas of interference, and I'm carefully (slowly) knocking them down by hand with some squares of 100 grit sandpaper.

Before:

After I got it mostly done:

I gave up for the time being to go grab a bite to eat, and figured I'd pick it up again tomorrow since I have it almost kicked.

 

[xb33bsa]

for future reference a large single cut 1" diameter works very well awood cutting bit carbide is not heeded as long as it is a hs good qaulity
you regulate the air/speed a bit and that ==kinda deal will cut like butter use lots of oil or beezwax