Engine BORING & HONING

[chase78]

I'm think about taking up hone and boring engine as sid income with a CNC... AS anybody body have any tips for me to get a true center on a cylinder?

How much work would it take to 'SLEEVE A HONDA ENGINE"?

[One of Many]

Check out some of the equipment used to do it the professional way. Not that the equipment is within reach, but it does show the work holding methods and some of the rigidity decent buck can buy.

Rottler Mfg.

I hear these are work horse machines, but I know little to nothing more about them after the factory tour.

The smell of Polane and fresh cut cast iron is called aroma therapy!

DC

[Mcgyver]

finding the centre is readily done to a thou with an centre finder or better with an indicator, or am i misunderstanding the question? saw a neat set up the other day for lapping large cylinders using a surface grinder and milling machine. cylinder was mounted on a large surface grinder table that provided that back to and fro motion while hone was turned at an appropriate speed by a horizontal mill in sitting next to it

[keebler303]

Originally Posted by Mcgyver finding the centre is readily done to a thou with an centre finder or better with an indicator, or am i misunderstanding the question? saw a neat set up the other day for lapping large cylinders using a surface grinder and milling machine. cylinder was mounted on a large surface grinder table that provided that back to and fro motion while hone was turned at an appropriate speed by a horizontal mill in sitting next to it

you could just use the quill of a vertical if the cylinder is not too big.

Matt

[Bill Johns]

Your safe bet, if you don't know how to center and locate properly, would be to just use the existing cylinders center. You will find they are plenty close enough.

[NC Cams]

Depends what kind of engines you're going to work on....

I-4, I-6, V-6 or V-8 all have different issues.

Finding center of bore is done 2 ways:

1. indicating off the crank C/L (Sunnen provides their customers with tooling and V-blocks to help do/find it, Rotter, BHJ and others do as well).

2. indicate off the existing center of the given bore and then bore on the established C/L axis. Adequate for simple rebuilds, marginal for H/P use, lame for all out racing.

Keep in mind that as you bore the cylinder, the quill is extending further and further thus the spindle is getting less and less rigid - holding C/L and creating a non-tapered bore of proper size becomes much more difficult in a boring machine/mill that is NOT specifically designed to bore blocks larger than a go-kart block.

Even in pro shops that are well equipped with CNC's, a true dedicated boring bar (Rottler, Sunnen, Tobin Arp or the like) are THE boring bars to use. Some guys power hone oversize with a CK-10 or the like but this merely works off the centerline that is there and that the hone creates for itself.

In set-up's alone, if you use a vertical mill, you'll go broke. Punching the hole is easy with a mill - getting it where it should be and to the proper size is the hard part.

THink very seriously about kluging up a boring bar. It doesn't pay if/when you screw up a bore because you botched a set-up and ruined a block.

Sleeving is easy - if you know how to bore, hone and do size fit calculations. The how-to is not something that is easily conveyed in 50 or even 500 words on a M/B. Proper guidance and training is MANDATORY.

Still want to DIY???

Start obtaining boring bar info from Rotter, Quik-Way, Sunnen or whomever else makes them anymore. Once you see the way they function, reality can set in and you can make a better choice/decision.

[One of Many]

I didn't get to ask this question of the folks at Rottler.

Primarily for racing...but. How would they set these machines up to do tapered bore consistantly? I'd think a dwell setting to spend more time in the bottom of the bore, but this kind of work could be more operator intensive than pure machine work. I do not know if they actually bore to a taper or what.

From what I recall, the boring bars were very short, rigid and used a carbide insert.

DC

[NC Cams]

FIrst of all, most guys don't want to bore a tapered hole.

Want it tapered, first of all, how much?

If it is only a few thou, you can easily hone it that way with uneven stone pressure in concert with selective dwelling of the stones at top or bottom of bore. if you have a CK-10, all you do is push the "dwell" button and it stays there until you release it.

Yes, it does require operator finesse - the bores do NOT cut equally nor do they all cut the same. Thankfully for GOOD machinists, things work out that way. If it were easy, everybody could/would do it.

Shorter stones will more easily facilitate a tapered hone - stone ovelap results in "double cutting". Thus, it can be easy to generate a barrel shaped (bulged middle) bore as opposed to a conical taper.

Yes, short and rigid boring bar spindle is what you want in order to bore a round, straight, (relatively) untapered hole.

[One of Many]

I suppose how much taper would depend on the block material? Years ago, I heard some guys boasting of .008-.013. Tighter at the top of course.

Then there was some other parts of the conversation that mentioned torquing a head or some kind of head that would put the block in a condition closer to what it will be in use, prior to honing. Whether they go as far as heating the block, rather than an educated guess is another minute detail to get every sliver of perfection, sounds like it could be over the top.

I have read a few articles about lapping model airplane cylinders this way, but those were non-ringed pistons too.

My reasoning for posting the Rottler link was to show the fixturing and how a block should be set to keep the bores on location and in line to the associated surfaces. I could not imagine doing a V8 block on a Bridgeport series 1 size machine. A 4 cylinder, maybe!

DC

[NC Cams]

All kinds of tricks have been used over the years in an attempt to gain a performance advantage - tapered bores are probably one of them.

In actuality, rings seal at both the face and on the sides. Depending on the ring configuration, the rings' side sealing capability/potential is enhanced by chamfers and bevels - these cause the rings to "twist" in the groove when they get squeezed into position.

THus, when you combine piston tilt due to clearance, there is travel potential that can occur between the rings and grooves. Lots of wear or movement potential can atually cause the rings to friction weld to the grooves - this can really compromise real sealing potential.

Granted one could experiment with tapered bores BUT the downside risk(s) is/are NOT one that I'd try to encourage in any way, shape or form.

THe last thing you need is for a MORE difficult environment of ring-to-groove sealing potential - a tapered bore would surely be detrimental to side sealing potential all things considered. The extra wear potential from additional ring movement as it tries to conform to a tapered bore would surely NOT help the ring-to-groove relationship.

As far as I know, round smooth untapered bores still offer the best sealing potential than avante garde alternatives.

The tricks with deck plates, block heating and/or bolting bell housings, motor mounts, etc to the engine have CLEARLY demonstrated positive effects with regard to bore sealing potential. Any shop that does NOT use at least a deck plate is almost asking for a comeback due to poor oil control and/or ring sealing.

I know of a case where a stripped block measured round and then went 0.008" out of round when the main caps, heads and other crap was bolted into place. Real hard for any ring to seal in that environment whether the bore is either a straight or tapered bore.

As long as I"ve been involved in racing (since 1965), guys always seem to look for magic when it comes to bore preparation. However, good, sound basics (which some guys lack or short cut) really need to be followed, actually mastered, FIRST before you start trying exotic non-traditional bore finishing techniques.

[RICHARD ZASTROW]

Amen

[Geof]

I thought getting tapered bores was easy ... just run the engine for 150,000 miles or so.