How does one go about boring a cylinder?

[Apples]

Considering a milling machine. How hard is it for a novice to bore a cylinder block of a small mower engine or an air compressor etc?

Just thinking of what I could do with a milling machine.

My large twin cylinder A/C is a bit dodgy I think, takes a long time to pump up.

Assuming a rebore and hone and new piston is the problem.

How hard or is it possible to bore the a/c block on a knee mill?
How do I get the boring head centred in the block?
How do I get the cylinder 90degrees and dead straight with the boring bar?

I would have to get it straight forwards, backwards, left and right. And then get it centered....

Peter

[Stepper Monkey]

Unless you REALLY screwed the bores (i.e. deep gouges in the walls from fragments of shattered piston, etc.), you don't need to go to the trouble of a true rebore like you are thinking. Not unless you are boring it out far enough to resleeve or something truly and utterly drastic. If its normal wear and sloppiness you can just use a hone to take it up to next available oversize unless you have some truly epic egg-shaped bores.
The hones I own have what looks to be three pivoting sharpening stones on each of three spring loaded arms attached to a mandrel to fit a chuck. They are self-centering and handle angular misalignment just fine - you can use them with a freaking hand drill and still get quite respectably round bores. They only cost like twenty bucks or less at any auto parts store. There are hones sized for bores from brake cylinder to diesel truck piston sized, so that isn't an issue either.
Finding new oversize rings or pistons, now that may be an issue depending on the age and model of compressor.

Honing is really easy, and as you've figured out, boring it is nigh impossible to do yourself. If it does have to be bored you might not want to do it at home, specialty engine shops have the setup to do it fast and pretty cheaply.

[Eurisko]

The best way to do a re-bore is to use a dial test indicator to tram the cylinder. You'll have to sweep the cylinder with the indicator to get it dead on. The block may have to be shimmed to make sure that the boring bar is perfectly parallel and centered on the cylinder.

Not impossible, but honing would be my first choice.

If the cylinder diameter is too small to use an indicator, honing may be the only choice.

[BobWarfield]

Can be done!

http://industrialhobbies.com/images/460bb1.jpg

More details here:

http://www.cnczone.com/forums/showthread.php?t=46983

Best,

BW

[Apples]

Yeah thats the go......
Will look at the v8 bore article after this .

=-----------------------------------------------
I'm surprised that you say you can just use a hone. I have one.

How much can a hone take off?. Well really how long do you want to keep honing it for???

I was under the assumption that I would need to go to the next sized piston an rings, thus requiring a re bore.

They say you need to make up a tank an keep pumping hining fluid in. Which I think is just oil?


Peter

[sluggo]

I don't know how the cylinder could be to small to use an indicator? but he is right about tramming it in with a best test.

[Apples]

Just read an article where you use a dial indicator with a long arm on it that rides on the ID of the bore, hole, pipe that you want to cut.

Turn the rpm on to the lowerst setting eg 100rpm, and the long arm thin spins around in the collet or chuck oe what ever it is. The needle will be jumoing around up and down etc. Then you just wind the x y handles untill the dial test indicator needle is the most stable.

Done!

Assuming the bore that you are cutting is going to be 90degrees to the deck, then you could make up bit of flat plate to bolt the deck to, cut a hold where the bore is. Then support each end and that should keep it square to the boring bar.

That, I reckon would work.

Thoughts?

[Kiwi]

In my experience the spring type hone is only for de-glazing.
To hone you need a Ammco type:
http://www.etoolcart.com/index.asp?P...OD&ProdID=1076

[greg b]

I do this for a job on motorcycles,we use boring bars, cnc mills and lathes to do the job and believe me as simple as it sounds its not,just getting the thing straight is one thing in a mill stopping chatter is another if its a cast iron liner unless you have a special heavy duty boring bar that will go right down the full stroke and the mill with the right taper to do it, forget it.As far as honing with a toy 3 prong deglazer its not going to happen unless your prepared to stand there for a long time,you have to use a qualitiy hone like a sunnen ,with the right stones the machine we made can pull up to 1mm out if we need to ,but thats only if the cylinder is straight to start with and its to much of a hassel to set up.If you have the gear go for it, if you dont,for what it cost dont stuff it up it takes to long to fix it.regards greg

[cam1]

Hi:
This is why automotive machine shops were invented.The cost of having a cylinder bored & honed is quite minimal, and the equipment automotive shops use are designed to produce on size circular x hatched bores perpendicular to the crankshaft axis. Not trying to dicourage home machining, just trying to provide a cost effective reliable alternative.

regards

[Mcgyver]

Originally Posted by Apples Just read an article where you use a dial indicator with a long arm on it that rides on the ID of the bore, hole, pipe that you want to cut. Turn the rpm on to the lowerst setting eg 100rpm, and the long arm thin spins around in the collet or chuck oe what ever it is. The needle will be jumoing around up and down etc. Then you just wind the x y handles untill the dial test indicator needle is the most stable.

wow, running the machine with the indicator in it is nuts, i view indicators as precision instruments and only use quality ones....i would not do that under any circumstances. Also, I usually use a tenths indicator, not that i'm working to a tenth, but it gives the resolution neccisary to do a decent job setting up. that approach would chew up an indicator in no time. sounds a bit like the advice of an auto guy with limited machining knowledge. Also, unless it was a coax, how would you even be able to see the dial? You need to move from side to side to read it from one side of the cylinder to another.

Why wouldn't you just do it regularly, set the indicator up, spindle in neutral and rotate by hand adjusting until the reading is the same all around. you'll get a more accurate result and the indicator will live to indicate another day

you don't need a plate with a hole in it, just set up on some parrellels and strap clamp it firmly but gently.

[Geof]

Originally Posted by Apples Just read an article where you use a dial indicator with a long arm on it that rides on the ID of the bore, hole, pipe that you want to cut. Turn the rpm on to the lowerst setting eg 100rpm, and the long arm thin spins around in the collet or chuck oe what ever it is. The needle will be jumoing around up and down etc. Then you just wind the x y handles untill the dial test indicator needle is the most stable....Thoughts?

Originally Posted by Mcgyver wow, running the machine with the indicator in it is nuts, i view indicators as precision instruments and only use quality ones....i would not do that under any circumstances.

No not nuts. I think just a not-completely-exlanatory description of a Co-Axial Indicator,

Have a look at:

http://www.blakemanufacturing.com/pages/aboutus.html

A very, very nifty device, I use it frequently.

And here is a blatant plug for Blake manufacturing!!!! Buys theirs not the cheaper imported knock-offs which are useless in my experience.