Honing cylinder throats vs. reaming cylinder throats

[DougGuy]

Reaming cylinder throats leaves the finish deeply scratched with tool marks and you have to go behind the reamer with abrasive to clean up the tool marks, now your throats gets bigger than what the reamer cut when you use the abrasives so it then becomes a guessing game, exactly what the finished diameter will be by the time the tool marks are gone.

The Sunnen hone is a precision automotive hone designed for fitting wrist pins and pistons to connecting rods allowing the user to achieve extremely precise fits with less than .0001" tolerance. Used with pistol diameter mandrels the way it locates itself in the cylinder throat keeps the tooling square and concentric with the centerline of the hole, it will round egg shaped holes, it will make barreled holes parallel, a lot of cylinders the metal gets flame hardened by the intense heat and then cooling from firing cycles and these throats will turn out belled like a funnel pointing outwards, Not only does the flame harden the area of the throat directly in the path of the flame, the repetitive thermal cycles can also cause the metal to contract over time, making the throat diameter smaller on the entrance than the exit. The Sunnen hone operator can make the hole parallel by riding only the tight portion with the hone, and keep it parallel during honing.

The number one main reason I switched to using the Sunnen hone exclusively is because the heat treatment in the long steel rods Ruger uses to make cylinders is all over the map. It changes hardness in a seemingly random fashion, I have encountered quite a number of Ruger 45 and 44 cylinders with 3 throats that cut easily with the throating reamer, then the 3 remaining throats the reamer will be excessively hard to turn, the reamer will squawk loudly when you turn it, and it will feel like you are about to twist the shank right off the reamer because the metal in this throat is a lot harder than the other throats on the other side of the SAME cylinder.

Other cylinders are much more consistent in temper and with these cylinders, throats will ream much more predictably and the throats will be more of a consistent diameter. The throats that are harder, will finish smaller diameter than the throats that cut normally, so now you have inconsistent finished diameters because the size of the bore the reamer cuts is totally dependent on the hardness of the metal you are cutting with it. Harder metal makes the reamed throat come out smaller than a cylinder with softer metal. Quite common with Ruger SA cylinders.

Enter the Sunnen precision automotive hone. It is a stepless system so there is no defined stops or notches or whatnot, and it will make all the throats the same diameter regardless of metallurgy of the parent metal. And it's nicely polished to 800grit when finished! A reamer just can't do what the Sunnen hone does, you don't have much control with a reamer, you are at the mercy of the temper of the steel in the cylinder. The Sunnen hone is not hampered by changes in temper. It will take longer to hone a harder cyinder throat, it slows the hone down but you would never know in the finished throat because they can be held within +-.0002" of each other, and in many cases +-.0001" throat to throat tolerance can be achieved given a bit more time and patience at the hone.

[contender1]

Great info here!

[DougGuy]

Great info here!

Thank you sir!

[Nueces]

I can testify that Doug's honing work is superb. It's a pleasure to observe a dead smooth finish on my cylinder throats.

[kerplode]

I can testify that Doug's honing work is superb. It's a pleasure to observe a dead smooth finish on my cylinder throats.

Agreed!

That reminds me...I have another cylinder I need to box up and send to him.

[Winger Ed.]

Moved to Wheelguns as per OP's request

[HWooldridge]

Yep. We used to have a Sunnen where I work and I used it to hone all of my revolver cylinder chambers. I checked final fit with .0005 incremental pin gages but we could get really precise and use an air gage (or the bore checker that Sunnen supplied) for a variable measurement. I think the hone is also faster than a reamer because you can hold the cylinder by hand rather than setting up a holder for the reamer. It's just better all the way around for that purpose.

[charlie b]

That's great news.

Does that mean nitrided barrels won't be such a hassle? That may get me off my butt to send a barrel to you (HK with poly rifling).

[challenger_i]

Doug, are you running the hone wet, or dry? If wet, what is your preferred fluid, and is it run in a constant flow or dribbled in during the process?

[HWooldridge]

Doug, are you running the hone wet, or dry? If wet, what is your preferred fluid, and is it run in a constant flow or dribbled in during the process?

I’m not Doug, but we ran our machine with flood coolant, which was a sulfur based oil we bought from Sunnen.

[M-Tecs]

Per Sunnen they claim many/most honing problems are caused by using the wrong oil. Different materials require different honing oil. In my shop I needed to keep three different honing oils on hand.

Honing of this type requires a flood of oil generally high sulfur and chlorine oils with various additives give the best performance. Soft materials like aluminum require a heavier flow. The high sulfur and chlorine oils can't be used in some airspace applications.

https://www.sunnen.com/Catalog/Cutti...-Honing-Fluids

This is an example of this type of process.

[castmiester]

Doug

the heat treatment in the long steel rods Ruger uses to make cylinders is all over the map. It changes hardness in a seemingly random fashion

from the beginning of it's production to date, or when did the QC start to go downhill?

[DougGuy]

Doug



from the beginning of it's production to date, or when did the QC start to go downhill?

It's not a QC issue. It's something that just comes with the territory. S&W doesn't have these random temper changes, their cylinders are much more uniform in metallurgical breakdown, as is Freedom Arms. If you want perfect cylinders with throats suited for cast boolits and blueprinted tensile strength and high quality alloys all the way through the cylinder, add another thousand to fifteen hundred to the price of a Ruger revolver. You think guns are expensive now, hold your breath, cause you ain't seen nothing.

Honing cylinder throats to suit, tailored to the half thou, sized half thou above boolit diameter is a pittance really, typically a one-time expense per gun. You spend more money on revolver grips than most cylinders cost to hone. Be THANKFUL gwasshoppa, that Ruger left us with tune-able cylinder throats, rather than one size fits all and who knows how big throats would be with that mindset?

[DougGuy]

Doug, are you running the hone wet, or dry? If wet, what is your preferred fluid, and is it run in a constant flow or dribbled in during the process?

I use the honing oil sold by Goodson. It's very close to Sunnen honing oil. I run it in a steady stream right on top of the mandrel.

That's great news.

Does that mean nitrided barrels won't be such a hassle? That may get me off my butt to send a barrel to you (HK with poly rifling).

I have not yet seen a viable path to honing a throat with a tapered leade in to the rifling. The Sunnen hone is meant and made for honing parallel bores like cylinder throats, connecting rods, pistons, etc..

I have dreamed about making an abrasive shaped like a boolit nose and with a live pilot to hold the stone centered in the bore, much like a Kwik-Way valve seat grinding machine uses a mandrel tightly fitted in the valve guide.

A segmented CBN stone shaped like a round nose/flat point/WFN boolit that will ride on the mandrel. Manson makes nice mandrels that fit in 9mm/357, 44 and 45 barrels and index off the lands. I have a friend who is in the abrasive business in China, I've gotten CBN (Boron) stones for Sunnen mandrels that are excellent quality and long lasting. I contacted him about this idea of a mounted abrasive, shaped like a boolit, with a hollow core that can ride the mandrel and have the CBN abrasive cemented onto it, he said I would probably have to have it plated on, but that's too thin, won't last so I haven't pursued it any farther than that.

[challenger_i]

Thank you, sir!

[charlie b]

Thanks Doug. I'll just stick with jacketed or plated bullets until I buy a new barrel for it.

[DougGuy]

Thanks Doug. I'll just stick with jacketed or plated bullets until I buy a new barrel for it.

I could have at least asked what caliber the gun?

[castmiester]

It's not a QC issue. It's something that just comes with the territory. S&W doesn't have these random temper changes, their cylinders are much more uniform in metallurgical breakdown, as is Freedom Arms. If you want perfect cylinders with throats suited for cast boolits and blueprinted tensile strength and high quality alloys all the way through the cylinder, add another thousand to fifteen hundred to the price of a Ruger revolver. You think guns are expensive now, hold your breath, cause you ain't seen nothing.

Honing cylinder throats to suit, tailored to the half thou, sized half thou above boolit diameter is a pittance really, typically a one-time expense per gun. You spend more money on revolver grips than most cylinders cost to hone. Be THANKFUL gwasshoppa, that Ruger left us with tune-able cylinder throats, rather than one size fits all and who knows how big throats would be with that mindset?

Freedom arms.... they look like Blackhawks. Guess everything about them are stellar. How do they shoot ?

[lightload]

Did I dream this--that Ruger New Vaqurero cylinders are a notch above the other ones in the Ruger line? I thought Doug had commented on the subject.

I make a point to read everything that Doug writes and wish to thank him for his contribution. Larry too. And Outpost. These guys are scientists.

[DougGuy]

Did I dream this--that Ruger New Vaqurero cylinders are a notch above the other ones in the Ruger line? I thought Doug had commented on the subject.

I make a point to read everything that Doug writes and wish to thank him for his contribution. Larry too. And Outpost. These guys are scientists.

The new models (3 digit prefix serial number, medium frame) that I have seen had an overall much better fitment, the barrels seem to be pretty much free of thread choke for the most part, and the cylinders are much more consistent in throat diameters, although they are still just a tad bit small for optimal cast boolit use, they are made better than the older 2 digit prefix guns. The Lipsey's limited edition guns are the pick of the litter.