Cylinder crosshatch general purpose vs. race

[jed]

Thank u Modok for that information. Very informative. Just what David needed.
Now David u need to anty up the same information using a ball hone. Please

[jed]

There is a lot talk about cylinder wall deformation. What about piston deformation?.
If the ring lands were to bend or twist .0005 with the ring in it at 7000 what
does that do to ring seal???

[David Redszus]

First, Sunnen is attempting to sell a product that competes with Brush Research without violating patent laws.
When we attempted to obtain surface texture information on their brush hones, their web site was inoperative.
Reading their publication," Cylinder head and engine rebuilding handbook", I find all sorts of errors and obsolete statements.

The CP web site regarding a plateau finish is completely wrong with regard to cross hatch angle and non-specific in other areas.

With regards to surface finishing techniques and measurement, I would refer interested parties to the Mitutoyo Surftest manual, to Mahle technical publications, and to Federal Mogul publications.

For a detailed overview of the plateaued finish process, the best information source is the Brush Research Technical manuals, available on their website.

With regard to piston deformation, the most informed source is Mahle. While piston skirts will expand and collapse, depending on axis and engine stroke, the ring lands are relatively unaffected. However, the rings can and do twist in their grooves, presenting a distorted sealing surface and pressure leakage.

I have white papers on plateau honing procedures and measurement which I can email to those genuinely interested in a complex subject. This includes surface textures produced by Sunnen rigid stones and Brush Research ball hones as well.

[createaaron]

I have white papers on plateau honing procedures and measurement which I can email to those genuinely interested in a complex subject. This includes surface textures produced by Sunnen rigid stones and Brush Research ball hones as well.

I would have great interest in this. I'm always trying to better understand surface finish as i feel its impertive to performance and ring seal.

[createaaron]

Started to hone a SBC today. I originally bored this on the CNC, boring from .040 to .060". It didnt clean up on the bottom 2 inches of the bore on the major thrust side. I assume that this was from the deck not being parallel when it was orginally bored. Anyway, not the point here. I began honing it today and started with what I think is a 100-120 grit stone then went to a 220 or 280 stone. (im unsure as there are no packages for which the stones came in and i didnt install them on the holders, but theyre what we use for every block honed on the Sunnen) I honed with the rough grit and left about .002" to go then finished it out with the 220. Then i finished the bore with a 400 grit with 3 strokes at 40% load. Tested with a profolimeter and the RPK was around 30, and the RK and RVK were in the 80s.. Then i stroked it a few times with a brush and the RPK dropped about 10 numbers and the RK/RVK stayed the same.. Im at my final bore size. .006" piston to wall. Next bore do the same process except when i finished it i used the ball hone ( 5 strokes) then the rigid mounted brushes in the holders for about 3 strokes.. RPK came out about 10 but the RK/RVK were still around 70-80.... Thoughts? Am i taking to much out with the finer grit stone? seems like there is not enough RVK or valleys...

[Eagle1903]

Started to hone a SBC today. I originally bored this on the CNC, boring from .040 to .060". It didnt clean up on the bottom 2 inches of the bore on the major thrust side. I assume that this was from the deck not being parallel when it was orginally bored. Anyway, not the point here. I began honing it today and started with what I think is a 100-120 grit stone then went to a 220 or 280 stone. (im unsure as there are no packages for which the stones came in and i didnt install them on the holders, but theyre what we use for every block honed on the Sunnen) I honed with the rough grit and left about .002" to go then finished it out with the 220. Then i finished the bore with a 400 grit with 3 strokes at 40% load. Tested with a profolimeter and the RPK was around 30, and the RK and RVK were in the 80s.. Then i stroked it a few times with a brush and the RPK dropped about 10 numbers and the RK/RVK stayed the same.. Im at my final bore size. .006" piston to wall. Next bore do the same process except when i finished it i used the ball hone ( 5 strokes) then the rigid mounted brushes in the holders for about 3 strokes.. RPK came out about 10 but the RK/RVK were still around 70-80.... Thoughts? Am i taking to much out with the finer grit stone? seems like there is not enough RVK or valleys...

Hello,
I am real beginner to honing and engine machining but very much committed to learning. I had a recent thread running at the " shop tech " section of ST. It has started with a topic " truing the stones .... ".
Please have a look at that topic as well. Many friends contributed that post and you may also find very valuable information there.
As a matter of fact, I have already tested JED's method. 150-400-Sunnen Brush method. In my test cylinders it really worked but what I have learned so far is; number of strokes, stone pressure, stone hardness, cylinder hardness are all vitally important parameters. Some of my tests produced near perfect results but in some tests the result was totally unacceptable. It is really hard to get it right but I had a big handicap to begin with. I am just trying to learn and improve my local made honing machine and believe me, the machine controls and the stone pressure control ( friction feed in my case ) takes some time to get used to it.
For example, when I have produced an unacceptable result; the main reason was I have applied too much pressure and too many strokes with the 400. It basically erased the crosshatches that I have nicely produced with the 150. I have used the Sunnen plateau brush after 400 and that might even erased further, but I am not sure about it. May be, the brush only cleans but does not erase or create dullness. I am sorry, I am not able to speak with the Ra Rz... numbers as they are not with me at this moment but I have actually measured them.
Then, I wanted to save that cylinder with the Flexhone ( 320 grit ). It actually worked. I had a great finish as far as the required values go. I was surprised. That dull cylinder produced excellent values with 320 Flexhone in my case. I thought of using the Sunnen brush after the Flexhone but I didn't. However, next time I am testing, I will certainly try. For me, there is a long way to go with these tests. But then, as JED says, numbers, values are something to look at but will the rings seal on that surface, this is something else.
I think when it comes to surface finish, there are certainly different ways to reach to the desired values in terms of techniques, one could develop and apply.

[MotionMachine]

The block is too soft to go from 220 to 400. You've made deep valleys with the 220 grit. On hard blocks going from 220 to 400 or even 500 is sometimes required because the 220 won't scratch as deep a valley on the hard surface. Not the case with your block, it needed a 280 or 320 next so as to reduce the valley depth. I would start from where you are with 280, take about 6 strokes, then re-measure. I'll bet it cuts you valley depth and Rk way down. If the peak is a little high now, just hit it a few times with 400. You won't take any appreciable amount out.

[David Redszus]

Using a silicon carbide stone on cast iron will yield the following Ra values.
Grit....Ra
150....30-40
220....20
280....12
400.....6

The larger the Ra value, the more coarse the finish and deeper are the scratches. The Ra value also affects the distance between scratches.

[createaaron]

Hello,
I am real beginner to honing and engine machining but very much committed to learning. I had a recent thread running at the " shop tech " section of ST. It has started with a topic " truing the stones .... ".

Ill check this thread out, thanks.

Then, I wanted to save that cylinder with the Flexhone ( 320 grit ). It actually worked. I had a great finish as far as the required values go. I was surprised. That dull cylinder produced excellent values with 320 Flexhone in my case.

I did try to run a flex hone done it. The problem with our flex hone is that its basically just rounded balls at this point. No grit whatsoever.

[createaaron]

The block is too soft to go from 220 to 400. You've made deep valleys with the 220 grit. On hard blocks going from 220 to 400 or even 500 is sometimes required because the 220 won't scratch as deep a valley on the hard surface. Not the case with your block, it needed a 280 or 320 next so as to reduce the valley depth. I would start from where you are with 280, take about 6 strokes, then re-measure. I'll bet it cuts you valley depth and Rk way down. If the peak is a little high now, just hit it a few times with 400. You won't take any appreciable amount out.

I ended up with about 9 on the RPK but my RK and RVK were wayyyy to high... Im right at my piston to wall Im hesitant to take anymore strokes and make my PtoW to large. Ill see if i can come up with a 280 and school. When i initially hit it with the 400 it didnt seem to change the RK/RVK hardly at all going from 3 strokes then adding 3 more..

[modok]

If they are sunnen stones then they will be marked, probably on the end there will be tiny letters or numbers. I have many of them memorized. If it's not on the list ask. Make a chart, or Download a chart. Teach the instructor what the letters mean
Most common ones are

ehu 412=180 grit, soft, for base finish for some industrial engines.

-Aluminum oxide 220 grit
ehu 525=general purpose 220 grit, for chebby 350 and old soft iron blocks.
ehu 518= softer, for harder iron or steel, which is, these days the majority.
enh 512=soft, longer 3" stones, good for for longer cylinders, or shorten them to suit and even softer than 518


silicon carbide 280 grit
jhu 625= general purpose
Jhu 623=softer, for hard to cut materials or aluminum, I use this one A LOT, but mostly 6-10 strokes at a time.

silicon carbide 400 grit
jhu 820
jhu 818=softer

Your 220/400 finish probably would work ok, for lets say, steel rings.
If they were OE width moly I'd put a 280 step in the middle.
If it's for cheapo cast rings or wide chrome for last step I'd do 7-9 strokes of jhu-623 at light load and nothing finer. That's what I'd do, not saying it's the only way, but it works. I don't gamble. If I gamble it's on by co-workers and family and friends stuff. which is why some of them work fantastic and some burn a little oil

YES you ask ten people you will get ten different answers, but I think the thing do to is remember, and try for yourself, you decide what works for you. If you MIX UP every bodies advice you will get mixed up results. The racer guys always want to go finer. Maybe they are right maybe not.
If finished with too many strokes of fine grit, they can scuff or wear out pre-mature. I see that sometimes, but it wasn't me.

[createaaron]

If they are sunnen stones then they will be marked, probably on the end there will be tiny letters or numbers. I have many of them memorized. If it's not on the list ask. Make a chart, or Download a chart. Teach the instructor what the letters mean
Most common ones are

ehu 412=180 grit, soft, for base finish for some industrial engines.

-Aluminum oxide 220 grit
ehu 525=general purpose 220 grit, for chebby 350 and old soft iron blocks.
ehu 518= softer, for harder iron or steel, which is, these days the majority.
enh 512=soft, longer 3" stones, good for for longer cylinders, or shorten them to suit and even softer than 518


silicon carbide 280 grit
jhu 625= general purpose
Jhu 623=softer, for hard to cut materials or aluminum, I use this one A LOT, but mostly 6-10 strokes at a time.

silicon carbide 400 grit
jhu 820
jhu 818=softer

Your 220/400 finish probably would work ok, for lets say, steel rings.
If they were OE width moly I'd put a 280 step in the middle.
If it's for cheapo cast rings or wide chrome for last step I'd do 7-9 strokes of jhu-623 at light load and nothing finer. That's what I'd do, not saying it's the only way, but it works. I don't gamble. If I gamble it's on by co-workers and family and friends stuff. which is why some of them work fantastic and some burn a little oil

YES you ask ten people you will get ten different answers, but I think the thing do to is remember, and try for yourself, you decide what works for you. If you MIX UP every bodies advice you will get mixed up results. The racer guys always want to go finer. Maybe they are right maybe not.
If finished with too many strokes of fine grit, they can scuff or wear out pre-mature. I see that sometimes, but it wasn't me.

Cool, great info. Never thought to look at the stone itself for a part number. Ill check that out tomorrow to confirm what im working with. Would you have any advice for what i could do next for the previous hone im working on? finished at about 10 RPK and 70-80 RK and RVK. Thinking i didnt go fine enough (280) before i went with the 400. I used the 400 for about 6 strokes the first bore and it turned out how i stated earlier.. little lost. I think i took too much advice in at one time and over thought the process... its a moly ring i think 1/16" mid 500 hp .006" piston to wall right now...

[modok]

It'll work as-is. I'd run it. Probably --could have--- done a few more strokes with 400, but going back the next day....nope. Probably won't hone evenly. Don't do it.

If you want to hone a bit more it now, you need to use a dingleberry hone, and I don't know much about that. Ask David

OR....do both sides different. See which one works best. It's an experiment right?

[David Redszus]

One fact that has amazed me for many years is that many engine builders have discussed and even used plateau honing but do not know what the finished surface actually looks like. Nor can they draw a picture of it.

Also, many machine shops either do not own a profilometer or simply do not use the one they have because they don't know how.

There is a little trick that might be useful to the amateur engine builder to help visualize and inspect the honed surface.

First hone the cylinder using what ever techniques or process you like. Wash the honed surface throughly to remove all oil and loose metal particles from the surface and grooves. Obtain a 2 to 3 in square of acetate film and a small can of acetone from the hardware store. Paint the honed surface with a liberal amount of the acetone and while still wet, apply the acetate film and hold firmly in place against the cylinder wall for about 2 minutes.

The acetone will dissolve the acetate and will form a casting of the honed surface which can be viewed under a microscope using a side light. The shapes of the plateaued islands, the grooves and the micro grooves on top of the islands will be clearly visible. I call it the poor man's (that includes virtually all racers) profilometer and its a great way to visually compare various honed surfaces.

[digger]

With regard to piston deformation, the most informed source is Mahle. While piston skirts will expand and collapse, depending on axis and engine stroke, the ring lands are relatively unaffected. However, the rings can and do twist in their grooves, presenting a distorted sealing surface and pressure leakage.

the lands do not stay flat under load, fortunately the ring is most flexible in the direction of deformation being it is their thinnest diection and thus lowest second moment of area so conformance is good profoivided the piston is designed to not have abrupt changes in stiffness which cant be conformed to