Honing Vs. Boring

[Neil Jones]

Boring gives you a straight hole. Honing gives you a nice surface finish.

Question-Is honing without boring capable of accurately correcting an out of round hole, a bell mouthed hole, a tapered hole, a hole that is barreled or a misaligned hole?

[Carld]

Answer is, NO. If an existing hole is out in any plane as you described then reboring and posibly honing is the only way to correct it.

If boring a new hole then the honing process is to remove tool marks and to correct and bore dimentions. That is, if the bore is true it will still have tool marks and diameter variations that need to be removed. Hense the reason for leaving a bore undersize and then honing to size.

If you hone an existing bore the out of round usually migrates around the bore as you hone it. Bell mouth will not disappear. A misaligned hole will stay misaligned and get larger.

Bore then hone.

[Mcgyver]

there's hones and then there's hones. the common spring loaded ones do nothing to correct bore errors, the expensive Sunnen ones will correct an out of round bore, but none of us have them at home

mostly boring gives you a straight hole, but not always. A hard spot, clamping pressure, stress pulling things into a new equilibrium after the cut or faults in the spindle bearings or bed can lead to a bore being not perfectly round and/or not straight. the homeshop solution is lapping which will get things very smooth, straight and round (if done properly)

[thebusdweller]

I agree with Mcgyver, a Sunnen machine will do the trick. I have an old unit, paid $200.00 for it. Tom

[IOWOLF]

A ball hone MAY do the trick.

[Neil Jones]

there's hones and then there's hones. the common spring loaded ones do nothing to correct bore errors, the expensive Sunnen ones will correct an out of round bore, but none of us have them at home

mostly boring gives you a straight hole, but not always. A hard spot, clamping pressure, stress pulling things into a new equilibrium after the cut or faults in the spindle bearings or bed can lead to a bore being not perfectly round and/or not straight. the homeshop solution is lapping which will get things very smooth, straight and round (if done properly)

The Sunnen hone will only take care of out of round and not the rest of the conditions I listed? For the other conditions it's as Carld stated you must bore then hone?

[lazlo]

the expensive Sunnen ones will correct an out of round bore, but none of us have them at home

What about those miniature cylinder hones that Sunnen and Lisle make? They have a micrometer adjust, and they look really darn nice:



They're $130 at Amazon (with free shipping). I've been tempted, but I haven't had a job for one yet:

http://www.amazon.com/Lisle-16000-Small-Cylinder-Hone/dp/B000P1802O

[Forrest Addy]

Here's what about boring and honing. First of all glaze breakers, brake cylinder homes and other units having spring-loaded stones do nothing to correct bore roundness or location. They can only selectively enlarge size and improve finish.

Boring locates and sets the geometry of the bore axis. A bored hole can be used as is unless there's a need for a superior finish or a finish texture a hole with feed marks cannot provide.

A rigid body hone as in Lazlo's photo and others of the Sunnen products, those made by Barnesdrill, etc cannot locate a bore's axis but it can straighten and round a bore to very close tolerances depending on the skill of the operator and the equipment available.

So Bored Hole gets you accurate bore axis location and geometry in relation to adjacent features

Rigid Body Honed Hole gets you refinement in bore diameter, finish and straightness

Spring Loaded Stone Honed Hole will enlarge a bore and correct for bellmouth or barrel shape.

All have their places and limitations.

For the record 0.003 to 0.005" is usual for honing stock in a bored hole.

We used to make steam chest throttle rods and bushings and hold the 1" dia nitrided rods so 0.0002" of a perfect cylinder in 20" or so and the nitrided bushings to 0.0001" of a perfect cylinder and 0.0007" clearance on the diameter with their rods. They were so accurately made, the rods in the bores would act as an air bearing if assembled perfectly dry and the rod spun with the fingers. It took a 20 step process to make them that way. These linked the throttle valves inside the steam turbine to the throttle operating linkage (think funny looking cam shaft and wierd looking lifters.

There was 1200 PSI steam at 1050F inside the steam chest and atmospheric outside. There was a gland exhaust that lead to a gland exhaust cooler whose discharge led to the condensate system. These rods and bushings ran 5 to 7 years usually 24/7 showing little wear in that time. They were routinely replaced as wearing parts at maor overhaul.

I can't believe I remembered all that from 40 years ago.

[Oldbrock]

brockley1

We had a steam turbine in North Wales and the valve mentioned last post stuck in the wide open position. the 12' dia rotor was doing 6000 when the room was vacated. Part of the casing stuck in the peak of the brick wall 30' up. I hone a lot of Harley cylinders, sometimes removing up to .030". With cast pistons it is not uncommon to shoot for 3/4 thou clearance, not much on a 3 1/3" piston but that what the customer wants. Never had a seize up. I have a Sunnen honing machine with coolant and use a A-600 honing head. I rough with GY25-J17 and finish with a GY25-J67. Yes, I use the keyway stone sets because I also hone a lot of two stroke cylinders and the regular set would hang up in the ports. Harley cast iron cylinders are the hardest cast iron bores I have run into. They must use a superior chilling process. With that setup I can get the bore perfectly round and parallel Peter Don't forget to use torque plates on Harley cylinders. It's a must. single on Pan Heads and two on Evolution.

[Oldbrock]

brockley1

Further to last post, you must use torque plate or plates on Harley cylinders, Pan head one plate evolution, two plates. I was going to add this to last post but it kept vanishing off the screen. Don't know what was up. Peter

[lazlo]

A rigid body hone as in Lazlo's photo and others of the Sunnen products, those made by Barnesdrill, etc cannot locate a bore's axis but it can straighten and round a bore to very close tolerances depending on the skill of the operator and the equipment available.

So Forrest, is that an endorsement? In other words, for $130 - $150, are those little hones a Poor-Man's (or HSM'er) Sunnen hone?

Or put another way, are they worth buying?

[mixdenny]

What about those miniature cylinder hones that Sunnen and Lisle make? They have a micrometer adjust, and they look really darn nice:

I have one and they work terrific. True story: I bought mine from a friend who had worked at a custom engine building shop. I had a water damaged BMW 6 cylinder engine in my 1971 2.8 liter Bavaria (crack in the head and the coolant rusted the pistons in place) and was trying to rebuild it myelf, including an overbore to the next size piston. He assured me this hone was what they often used.

So, I borrowed a cylinder bore gage and started honing with the coarse stones, checking with the bore gage often. I had a big 1/2" drill motor driving it, the hone comes with a hefty spring to hold it in the air and you bounce it up and down. S L O W L Y it honed the block out, 0.020" over I think. Man, it took me a couple of days, but I finally got it, no taper to the bores as far as I could measure. My arms were dead tired.

When I mentioned it to my friend later, he was astonished, and explained the hone was just for the final thousandth or so, it should have been bored to begin with!

That engine had 80,000 more miles on the rebuild when I sold it years later, it ran perfectly, used no oil. I also tig welded the cracked aluminum head, which had split right through a valve pocket, and had a new valve seat installed. One of my better fixes.

So yes, this type of hand hone can straighten out tapers and bellmouths. It operates on a parallel arm mechanism and has a micrometer adjustment.

Dennis

[lazlo]

Thanks Dennis and Forrest!

[tattoomike68]

Boring gives you a straight hole. Honing gives you a nice surface finish.

Question-Is honing without boring capable of accurately correcting an out of round hole, a bell mouthed hole, a tapered hole, a hole that is barreled or a misaligned hole?

I real quality honing shop can take some DOM tube and end up with a fairly strait and true bore. I used to make some big Hydraulic cylinders for grape harvesters that were 6" bore and 70" long. I would machine them with threads and O rings, we would weld about 150 LBS of mounts to one side then shipped them out to get honed. They would come bach with a strait and round hole when they were done after we turned them into a banana by welding on them.

There are shops that can hone some stuff super nice but a home shop guy might have a hell of a time.

I broke my ankle on the job once and was stuck sitting running a sunnen hone for a few weeks doing "light duty" and that job sucked. After 4,000 bronze bushings I never want to touch a hone machine again.