Technical Tuesday, May 13, 2014: Cylinder Hones

[J-Mech]

In today's edition of "Technical Tuesday" we will be discussing cylinder hones.

It's that time of year. The tractors are coming out, and so are the motors. You might even be thinking of doing a rebuild yourself, and may be wondering about the tools needed to do the job. Well, lets take a look at cylinder hones.

(I want to state that the information I'm going to provide is not advocating doing a "rebuid" using only these tools, the purpose of this is to help understand specifics about the tools, so that an informed decision of what to use can be made.)


The Rigid Hone:

When you overhaul an engine correctly, the first thing your going to do is bore the block. Now, you'll probably take it to a machine shop for this, along with the piston and ring set, and let the shop fit the piston to the bore. When they get done with the rough bore, they have to fit the piston for it's running clearance, and bore "finish". The boring bar leaves the cylinder too rough to run, and the fine adjustment needed to fit the piston can't be precisely controlled with a boring bar. What do they use? Well, the Rigid Hone.

A rigid hone can be used in a drill, or like in the machine shops, in a machine that does the "arm work" of moving in and out of the bore automatically. The machine moves with a more fluid movement, and allows the honing process to be controlled so that not too much material is taken out, as can happen when doing it by hand with a drill. If you stop in one spot too long, or don't move from complete top, to complete bottom, you can remove too much material at one end or the other of the cylinder.

RIgid Hone.jpg

The rigid hone has a "screw" in the center that when turned, moves the two sets of stones, and the two guides, out together as a unit so that equal pressure is put out in 4 directions. This make the hone stay in a perfectly round shape no matter what the bore shape is. If there is a high spot in the bore, then the stones can't be set as tight because when it turns into it, the cylinder block, nor the hone will give way to the imperfection, thus "cutting down" the high spot, making a true and round cylinder. That makes this hone the perfect tool for finishing a bore job, or to clean up a cylinder for a new set of rings. The "rigid" construction will "bore" the cylinder straight and true because it cannot flex to fit the shape of an irregular bore. So, if your looking to put new rings in your engine, this is the tool you need. There are many different grades/grits of stones and guides for this style of hone. Just like with sandpaper, there are very coarse stones for taking out large amounts of material at a time, along with finer stones for a smoother finish. You can use these types of hones to "bore" an engine if you only need to go a few thousandths. (.005" or .010") However, I do not recommend it because using a boring bar is much more accurate, and takes far less time. Good as this hone is, it does have drawbacks. For one, they are mostly un-affordable for the do-it-yourselfer as the sticker price on these hones is in the $600 and up range. There are some cheaper ones out there but they still are well into the $400 category. Only other thing is, they leave the cylinder nice and straight, round and smooth, but do not put the crosshatch back into the cylinder. If you can rent or borrow one, then by all means, this is the tool to use. Also, because of the cutting ability of this hone, it needs to be lubricated. Either with honing/cooling fluid, or even WD-40 or soapy water if nothing else is available. (Just remember if using a soapy water solution, to COMPLETELY dry the block before leaving it sit.)


The Rigid/Flex Hone:

I'm not going to lie, there are many different names that I have heard this hone called, but today I'm calling it the rigid/flex hone. When most of you think of a hone, this is probably what comes to your mind. It's the one that dad had hanging out in the shop with all the dust on it. May even have had pieces missing out of the stones down at the bottom from going too deep into a bore and hitting the webbing of the block. (I've never done that. )

Flexible rigid hone.jpg


While this is the hone that many do-it-yourselfers use, you need to understand that it has some pretty major handicaps, and some good points about it too.
Lets talk about the good stuff first.
For the most part, most all auto parts stores carry these hones. They are relatively inexpensive coming in at about $40 to $60. The stones (on the better ones) can be replaced and those are usually an in-stock item also. If not, they are usually readily available and come in different grits just like with the rigid hone from above. So, you can choose a grit that works best for the job at hand, and the type of finish you want. This hone works for putting the crosshatch pattern back on the cylinder walls, but still isn't the "perfect" tool for that job either. These hones also work best when lubricated/cooled. They are the most used hone for the home handyman, but not by the engine specialists.

Drawbacks:
The rigid/flex hone is spring loaded, and forms to the shape of whatever you put it into. In other words, if you are using this style of hone before putting new rings in a motor, and the bore is slightly "egg" shaped, or maybe has a high spot in it because of a scored piston, it just forms to that shape leaving you with a smooth version of the cylinder you had before. Not good for a brand new set of perfectly round rings. A non-true/straight bore will cause your new rings to "flex" as they pass over the imperfections in the cylinder wall, causing them to lose their "spring" tension on the cylinder wall. Thus causing high oil consumption and hot spots on the cylinder wall itself as there is more friction in the tighter spots. These hones have a place in my shop, but it isn't inside of an engine. They work well for something that isn't as critical, or something that we know is already round/true such as hydraulic cylinders, or brake cylinders.


The Ball/Rake Hone:

This hone is for finish work only. It is used to put the crosshatch back into a cylinder or for de-glazing. You tractor pullers that bore engines but have problems getting a set of rings to seal, will find this hone very handy as you don't want to take out any material but just need a crosshatch to seal your rings.

Ball hone.jpg


These hones are kind of in the middle of the price range. I've paid anywhere from $30 to $100 for these depending on the size/grit of them. They are available in many different sizes, lengths, and grits. They are great for cleaning up lifter bores, and rusty cylinders prior to boring, and for putting that crosshatch pattern back into a cylinder. You don't have to use them but only for a few passes as they can and will remove metal, and can scratch too deep. They also work better dry than with cutting/honing fluids.


What's "Crosshatch" Anyway?

While we are on the subject, I also want to touch on the crosshatch pattern I keep mentioning. For those of you who don't know what this is, it is the scuffing of the cylinder walls for the purpose of leaving a very slight rough surface. The purpose of this is to actually "wear" the piston rings just slightly so that they conform to the shape of the cylinder wall and "square" themselves into the bore. This fine wearing in of the rings causes them to have the best seal, and increased life inside the engine. Putting the crosshatch in is critical to engine longevity, but is kind of difficult as it is not a cut that can be measured, so knowing if you did a good job comes form experience and practice. You can go too deep, and you can not go deep enough. Not a deep enough crosshatch will wear off before the rings can seat, and too deep can cause them (the rings) to "wear" too long, and can even cause oil consumption if too deep. My advise is, if in doubt, a shallow cut is better than too deep. Too deep and a re-bore may be necessary to correct the condition. I have never cut too deep, and not heard of it happening but only on rare occasion, so don't worry.

Here is an example of what you want this pattern to look like:
Hone_cyl_crosshatch.jpg

You want about a 45° angle of the crosshatch. Too steep, and the engine may burn oil. Too shallow of an angle and the rings won't seat properly.
Crosshatch1.gif


Tips:

When using a hone of any kind, you will find it easy to go too deep into the bore and tear up your hone. To avoid this (sometimes costly) mistake, I put the hone into the bore and find the safe depth (hone just coming out of the bottom of the bore) and then put a piece of tape on the hone's shaft so I know when I need to stop going in, and start coming back out.
You want to move the hone in and out at a steady, but not necessarily fast rate so as to get a uniform cut. Too long in one spot, and you will end up with an irregular bore. Keep in mind, that because you will stop and reverse direction at the ends, that the center is where the hone spends less time. Sometimes if I have to hone a cylinder a lot, I work it in just the center every few passes so as to account for this condition.


I hope you enjoyed or learned something with this edition of "Technical Tuesday". If you have something that you would like explained, or a topic you'd like considered for discussion, e-mail Jonathan at jdbrepair@gmail.com. Please keep all topics within the confines of "cub" related restoration/repairs, tools and equipment, or similar. (No, how does a radio work or something like that.) If I don't know the answer I will research it, and do my best. Otherwise, like with this article, it will be based off experience and knowledge at hand.

[cubs-n-bxrs]

Jon out of curiosity what grit ball hone do you use to put crosshatch back in the cylinder bore? I just got done boring an engine with a sunnen rigid hone and am ready for the cross hatch.

[J-Mech]

Thanks guys!

Kelly, I finish up and put the crosshatch in with a 320 grit.

[Alvy]

I've always been a fan of "taco Tuesday" but I like technical Tuesday. Nice write up with pics, I'm beginning to think you're nocturnal though seeing you on really late all the time. Question, my machinist guy that I'm using now says that he can do my cylinders with his rigid hone instead of boring. It's a real big machine with a catch basin and everything in it, should I tell him to not do it if it needs to go over .010"? I like that he recommended it to me because the price to do it vs boring is less but can a hone machine like that take it further like .020" over?

[J-Mech]

Originally Posted by Alvy

I've always been a fan of "taco Tuesday" but I like technical Tuesday. Nice write up with pics, I'm beginning to think you're nocturnal though seeing you on really late all the time. Question, my machinist guy that I'm using now says that he can do my cylinders with his rigid hone instead of boring. It's a real big machine with a catch basin and everything in it, should I tell him to not do it if it needs to go over .010"? I like that he recommended it to me because the price to do it vs boring is less but can a hone machine like that take it further like .020" over?

Thanks Mike, and yeah, I'm a hoot owl.

He has a honing machine and a cabinet. He probably also has a lot of different stones. I'm not sure why he would use it over a boring bar if going more than .010". Maybe because he can set it to run and leave it? But, he can do that with a boring bar too.... It is just as good as boring, so there's nothing wrong with it. If I had a cabinet like that, I'd probably do it that way too if I wasn't going over .010".


Everyone else, THANKS!