clamshell lapping

[metallic]

I'm working on a Homelite 240. It's a 39cc homeowner saw with a reed valve inake and a split base (clamshell) design. I needed to smooth the two surfaces of the crankcase before reassembly, so I found an old piece of tile and spray-glued some 400 grit sand paper to it. Seems to work pretty well.

 

[Mastermind]

Excellent idea.

 

[idiotwithasaw]

I like the tile idea. Got a stack of marble in the barn leftover from my parents kitchen remodel. Definitely gonna keep this in mind.

 

[jakethesnake]

Smooth idea man dales pale ale eh? Never heard of nor saw round here anywhere close to a rolling rock lol

 

[TJ the Chainsaw Mechanic]

Cool!

 

[Terry Syd]

I use a sheet of glass to stick the sandpaper on (contact cement works well, you can remove and replace the sandpaper easily). I don't push or pull the object to be 'milled' as it tends to trim the edges too much. I tend to 'twist' the object as I move it across the abrasive.

 

[metallic]

Smooth idea man dales pale ale eh? Never heard of nor saw round here anywhere close to a rolling rock lol

Dale's Pale Ale from Brevard NC, yet they sell it all the way up here in MA. Good stuff if you like hoppy beer. I grew up drinking Rolling Rock and it's not like ole "33" at all.

I use a sheet of glass to stick the sandpaper on (contact cement works well, you can remove and replace the sandpaper easily). I don't push or pull the object to be 'milled' as it tends to trim the edges too much. I tend to 'twist' the object as I move it across the abrasive.

I recall seeing this done on dirt bike engines and indeed they use a twisting motion with the piece. Also, some folks say to switch from left hand to right hand and from clockwise to counter-clockwise so that you don't preferentially mill down one area due to differences in arm strength or whatever. Try to mix it up as much as possible all while keeping the case flat on the sandpaper.