Cylinder crosshatch general purpose vs. race

[jed]

I admire the dedication of those producing round, straight bores with the correct cylinder surface finish for their purpose. As machinists that's a challenge we can quantify and determine success by accurate measurements.

However, doing it on a cored cast iron production block and understanding what happens when that relatively thin cast iron cylinder sees operating loads from pressure and piston loads are not at all intuitive. Cast iron has a relatively low Young's modulus, it's not particularly resistant to deformation from applied loads. That cylinder becomes a flexy flyer during high BMEP operational loads, it might be round and straight when you measured it but it is far from it during operation. One of the great things about cast iron most people don't know is that it is not susceptible to fatigue. It's immensely flawed at birth, that saves it from fatigue death.

Rings work in those heavily distorted bores if they can bend enough under pressure loads to conform to the distorted cylinder. Race on guys!

All of the draw backs posted above of "cored cast iron production block" leave me questioning
The real benefit of hot honing and torque plate honing.
Does any one have real back to back testing using a torque plate??

I know first hand of a very reputable sprint car engine builder whose engines have won the
Silver crown at least twice stop using his hot honing machine and his cv10 when he got
His new sv21.
He said sense he started using hid sv21 his engines were sealing up faster and making more power.

[twl]

My take is that it is impossible to replicate all the possible dimensional effects of various loads and rpms and stresses that any/all conceivable engines may encounter.
Therefore, people use whatever they can to try to simulate expected conditions as well as they can, given their particular understanding and experience and equipment.

[createaaron]

Does any one have real back to back testing using a torque plate??.

Many many test have been conducted with a torque plate. Especially in production blocks the bores move around. Aftermarket blocks are a different story i think. The LS blocks are extremely susceptible to bores moving around because of it being a modular design and the long head bolts. Guys have even been bolting both heads on when align honing because it distorts the main bore so much. The same with cylinder honing, they will bolt a dummy head to the opposite side. There are so many factors in torque plate honing... the type of fastener (a big one), the type of lubricant, the head gasket thickness, sometimes the material of the torque plate, the depth of the fastener in the threads of the block etc... I cant say ive personally done this testing but i know theres pros out there that have.

[createaaron]

. Cast iron has a relatively low Young's modulus, it's not particularly resistant to deformation from applied loads. That cylinder becomes a flexy flyer during high BMEP operational loads

I agree. It brings up the discussion when its time to pull the trigger on a aftermarket block.

[machinedave]

1st picture is just a few strokes of the hone. Each picture is an additional .0005" honed.

[digger]

. One of the great things about cast iron most people don't know is that it is not susceptible to fatigue. It's immensely flawed at birth, that saves it from fatigue death.!

This is plain wrong. Grey cast iron is less notch sensitive than steels particular high strength ones but it is still susceptible to fatigue

[createaaron]

1st picture is just a few strokes of the hone. Each picture is an additional .0005" honed.

How do you finish your cylinders on a typical cast block?

[David Redszus]

The type of block material will significantly determine the Ra finish that will be produced for a given grit.
Material.................grit size 150.......400 sc
...............................Ra finish
Hardened steel.............20................5
Cast iron....................30-40.............6
Aluminum...................80...............16

The use of a deck plate when boring and honing a block is indisputable; you need a deck plate. Period.
Even with the use of a deck plate to induce pre-distortion, combustion pressures will deform the cylinder shapes and is simply un-avoidable. The distortion telltale is a local, ring polished surface, produced by cylinder deformation.

Heating of blocks during honing has shown no real benefit. During actual operation, the cylinder surface has different wall temperatures top to bottom, altering its dimensions.

While most steels have very similar E modulus values, cast iron modulus numbers vary considerably depending on the type of cast iron. Blocks typically use grey cast iron which has a fairly low value, while m and n cast irons are similar to many cast steels.

[createaaron]

Just had a thread pop up in a FB group im in.... Its about whether or not people are finishing with brushes fixed to the honing mandrel, or drill mounted brushes or stones/ball hones. We kind of covered this but again its still up for debate. Im wondering how many people will hone with the 120 grit (assume were using stones), then the 220 ish grit, then do a few strokes with a 400 grit stone. Do you still use like a drill mounted brush when you clean? Ive never tried this but am gonna give it a whirl.

[statsystems]

Just had a thread pop up in a FB group im in.... Its about whether or not people are finishing with brushes fixed to the honing mandrel, or drill mounted brushes or stones/ball hones. We kind of covered this but again its still up for debate. Im wondering how many people will hone with the 120 grit (assume were using stones), then the 220 ish grit, then do a few strokes with a 400 grit stone. Do you still use like a drill mounted brush when you clean? Ive never tried this but am gonna give it a whirl.

I used the Peterson machine tool brushes in the hone. 8 strokes at 50-60% load was all it took. Almost fool proof.

Edit. For most street stuff I finished with a 280 grit and a brush. If it was a race deal I'd use 320 and the brush. Aftermarket blocks got a 400 finish and a brush.

[machinedave]

1st picture is just a few strokes of the hone. Each picture is an additional .0005" honed.

How do you finish your cylinders on a typical cast block?

For the most part I use 70 grit stones until I am .003" to final size then I switch to 220 grit stones until .0005 to final size then I switch to 280 grit stones. After reaching final size I check back every few hours and recheck the bore sizes. I like to leave it sit overnight and recheck in the morning. I have experimented with IR thermometers and found some interesting results. You can measure the cylinders of the block with a temperature at 70 degrees hours after you've last honed the block and come back the next day and check the block at the same 70 degrees and have it shrink by .0002"-.0003". After I am satisfied that the block is done shrinking then I install the honing brushes and make just two strokes up and down with light pressure.

[David Redszus]

Just what purpose does the brush serve that a 400 grit stone does not?

Does anyone have some actual surface profilometer data or are we just talking?

[4sfed]

Just what purpose does the brush serve that a 400 grit stone does not?

Does anyone have some actual surface profilometer data or are we just talking?

Brush Research has published some microphotographs of a cylinder surface before and after using their product. The folded-over burrs from using a rigid hone were removed . . . much like the wire edge can be removed from a freshly sharpened knife blade using a strop. The brush hone can be rotated in both directions to accomplish this. I don't think that difference would show up using a profilometer.

[statsystems]

Just what purpose does the brush serve that a 400 grit stone does not?

Does anyone have some actual surface profilometer data or are we just talking?

I used to have a bunch of date on the PMT brush stuff but it stayed with the company when I quit. Then they went tits up and I tried to get the info from the new owner who bought out the old owner and basically told me to eat a poop sandwich. I have no idea why he didn't want to part with it and I have no idea what happened to it.

[modok]

For the most part I use 70 grit stones until I am .003" to final size then I switch to 220 grit stones until .0005 to final size then I switch to 280 grit stones. After reaching final size I check back every few hours and recheck the bore sizes. I like to leave it sit overnight and recheck in the morning. I have experimented with IR thermometers and found some interesting results. You can measure the cylinders of the block with a temperature at 70 degrees hours after you've last honed the block and come back the next day and check the block at the same 70 degrees and have it shrink by .0002"-.0003". After I am satisfied that the block is done shrinking then I install the honing brushes and make just two strokes up and down with light pressure.

That's a good standard.

I have a slightly different take on it. Mostly 220 is my base finish, so I set the size in this step. So I hone basically to indicated size(measured hot, so probably .0005 short), then let it sit, then come back later and hone some more as needed, so I essentially finish the cylinder to the base finish being .0002-.0005 short of my actual target size (depending on what follows).
THEN, when I am satisfied with it, I hone a --limited number of strokes-- of 280 and/or 400 and/or a brush (depending on app) and then it's done. If it ends up a few tenths smaller than I wanted I am NOT going to go back and hone any more, if it's one or two tenths over..... too bad, it's done. Not sure if there is a name for that.