Cylinder boring

[cdyoung1985]

So a buddy just got his late grandfather's mill and lathe given to him, and none of us are machinists by any means. Welders, fabricators, general diy guys, but not machinists. I've got a klr250 dual sport I'm rebuilding, and the cylinder has been left out in the rain a few times. So before I order one, I'd like to try my hand boring. It has a torque plate on the lathe, and power everything. It's old, his grandpa passed in 84, and the stuff is older than that, but in emasculated shape. Looks like it belongs in a showroom floor.

This would be my first lathe project. Wondering what I need for the tooling? I know I need a boring bar, assuming I need it to be a bit longer than my stroke? What kind of material? If it goes at all well, I'll also be boring my Harley 883 instead of buying a kit.
Plan on tinkering with the lathe a bit before jumping into the bore, but don't think it'll be that bad.

 

[killswitch505]

I would attempt to bore a cylinder on the mill before doing it on the lathe using a boring head. I can get a pretty great finish with a boring head but I think you'll have to follow up with a honer.

 

[Aukai]

I have not seen it done on a lathe, but with the right fixtures, I guess it is possible. Now, cylinder wall finish, and ring selection can be very important here. Now days it is common to get a ring selected by the manufacturer for the application, and have a specific cylinder finish for that ring. They use profilometers to see the microscopic finish after honing. Piston to cylinder clearance is important also, I'm sure that it will still run well with the old fashion stone, and cross hatch, but check with the manufacturer you want to use for the right rings. Just my suggestion good luck.....

 

[GoceKU]

I've done couple of 49cc cylinders, i'm using an brazed carbide boring bar 30x30mm shank and i'm power feeding on the slowest feed my lathe has also im power feeding out of the bore, in some 2 stroke cylinders that have large ports in the bore is possible to get chatter in that case the cylinder is scrap, and always hone it to final size, for honing i use diesel fuel as a lubricant, best of luck and a rusty cylinder is a good thing to practice on.

 

[MarkM]

Before you attempt to bore it I would use a proper hone to clean up the rust. Get a proper measurement and you may find you may not need to bore it out. Diesel or Kerosene works well with hones. Make sure it is a spring loaded hone to keep concentricity.

 

[f350ca]

I rebuilt an old Wisconsin twin a while back. Boring it on the mill would have required using the knee as the cylinder was deeper than the quill stroke. Didn't relish all that cranking so set it up on the lathe. Made a heavy boring bar to compensate for the reach and all went well. Machined to a couple of thou oversize and used a Sunnen hone to take it to size.

Greg

 

[cdyoung1985]

Thank you all for your tips. I'd say one of the biggest reasons I'm planning on using the lathe is it's torque plate, rather than the mills clamps. Plus it's a single cylinder, and my Harley's cylinders are separate, so nothing like f350 posted.
I plan on using a hone to finish, thought it was required.
Biggest question right now is the boring bar. I think I want the liquid cooled one, unsure of diameter and length...

 

[tq60]

Before experimenting with creating scrap check into having it done.

Places that do this have correct everything to get it done correct and to spec.

Cost of tooling likely more than that of the job.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

 

[MarkM]

Your biggest enemy with boring the cylinder will be the boring bar flexing on you. Coolant isn t so critical. More of a luxury for this application. Use the biggest diameter bar you can and the least amount of stickout possible to do the job. I would stay away from carbide and use high speed with a very sharp edge. Carbide needs to get under the matarial and may cause you more grief with it wanting to rub and flex with the little amount of material you want to remove. Yes the hone is needed to give you the cross hatch pattern to help seat the rings.

 

[Groundhog]

Not sure how much the torque plate will help with a single cylinder bore, I guess that would depend on how badly you clamped it the mill. Torque plates, as I'm sure you know, are generally used (with questionable need) with multi cylinder heads to limit distortion. Can't hurt though!
I've bored cylinders on both lathes and mills with good results. Only bored cases (for big bore jugs) on a mill though.