BLIND CYLINDER HONING

[bmuss51]

i am working on my fist engine which is a half scale new holland hit-n-miss. and i just got done boring the Cly.and tried to hone it. but i am having trouble honing to the bottom of the bore, which is blind. and the little i have honed was done with an Amoco Cly. hone. but i can't get to the bottom of the bore and i also am getting .002" taper from the open end to the bottom that i can measure. so at this point so far i have a good size at the open end but i can't get the piston all the way down the Cly. so could i get advise of how to continue?
the bore is 1.8755" at the open end and as far down as i can measure it is 1.8735. with my piston being 1.8745" and the rings are store bought for a 1.875" bore. and as of now when i stick the rings in i get .007" end clearance at the opening of the gap. so whats your thought on the end gap of the rings, like to much or about alright. and by the way there is 2 rings to fit on the piston. and the other thing is how much undersize should the piston be than the bore?

thanks in advance for your input!

 

[joeby]

It's very difficult to remove taper in a blind hole with a brake cylinder hone (spring loaded arms with the stones mounted on the ends of the arms and pivoting on pins), which is the type I'm assuming that you have. About the only way to correct taper with these is to dwell at the small end until the taper is removed, however, the stones are going to wear tapered also. Depending on where the piston crown will be at TDC, you might get by with doing this.

An automotive machine shop that has a Sunnen hone may be able to straighten it for you, and I think they can get pretty close to the bottom of a blind hole.

Some other things to consider would be setting up to bore the taper out, or using a shell reamer or hollowmill to get the taper out. I think I would take the time to set up and re-bore myself.

I would suppose you could lap it straight; but keep in mind .002 is a bunch to lap out.

If it were me, I would re-cut the bore until I had it straight and hone it again with good stones, not being concerned with nailing the print dimension. The engine won't care if it has a 1.880 bore. Apparently though, you have already made the piston, so it would probably need remade as well (dependent on how much oversize the bore ends up).

Kevin

 

[Maryak]

bmuss51,

I make my piston diameter 0.98 of bore diameter; 1.875 bore = 1.837 piston. The info came from Professor Craddock's writings on pistons, rings, bores etc.

Hope this helps ???

Best Regards
Bob

 

[bmuss51]

thanks for your ideas, but i found a idea that did work. and what i found was,to make a long story short.
i remembered that outboard motors, and some motorcycles use blind bores. so i asked a old friend that does bores for motorcycles.how he would do the hone, and his reply was an old experience from when he was growing up on a farm. he went to tell me he didn't have much money to rebuild when he was a kid , and used a piece of sand paper on a shaft which was spun by a drill. so i went on to expand on his idea and went to the local hardware store and bought a multi vaned sanding flapper which started out as a 2" . and boy was that hard to get in the 1.875" bore. but we got her in and the job is now done and measures as true as i can measure.
even when sliding in the rings i only get .001" end gap diff. from open end to the blind end. and the hole process only took 3 hrs including going to the hardware store and making a long shaft to adapt the flapper to my hand drill. and the hole size of 1.8755" is right in the ball park of what i wanted for a finish hone size.