honing cylinders and measuring cylinder diameter

[scott12180]

I'm getting a little frustrated so I thought I'd throw this out.

I've been measuring the bores of my Franklin cylinders with a telescoping bore gauge and a micrometer. I hate the thing.

I get a different number every time and the only way I get an idea of the true diameter is to take LOTS of measurements and use statistics to throw away bad data and take an average of the rest.

Other than the several hundred dollar bore gauges, is there any other way to measure cylinder bores?

Second, I've been advised to hone the cylinders out anywhere from 0.001 to 0.002" for a better clearance. HOW LONG DOES IT TAKE TO REMOVE 0.001" ???? *sheesh* ! I've honed and honed and honed and I keep getting the same numbers for the diameter. I'm afraid to go any further because I don't trust the telescoping gauge readings.

. . . .unless you need to hone with a medium stone for about 20 minutes straight to remove 0.001". I don't have a feel for it, but don't want to ruin my cylinders.

Any help appreciated. This isn't going as well as I thought it would.

--Scott

[jbbuick22]

Scott,

A dial bore gauge is the best way to measure the cyl. I bought one on Ebay for about $50. Snap gauges are a pain.

The hone you are using is for deglazing the bore. A machine shop can hone to the correct size, and keep the bore

round and not bell shaped.

JB

[scott12180]

I should add that I am using a three-armed spring-loaded hone/glaze breaker. Yeah, it's the cheap one at under $30.

So my question is, can a glaze breaker like this remove 0.001 to 0.002" of metal in a cylinder, or is it not designed to do that?

Continued poking around on the net tells me that a hone and a glaze breaker are two different things. True?

--Scott

[Bhigdog]

You have a tool meant to break a glaze and/or put a cross hatch pattern on the walls to aid break in. It's not a "hone". If you do use it to remove metal it will follow any faults in the bore such as taper or out of round and will most likely add a few of it's own..................Bob

[Rusty_OToole]

I'm getting a little frustrated so I thought I'd throw this out.

I've been measuring the bores of my Franklin cylinders with a telescoping bore gauge and a micrometer. I hate the thing.

I get a different number every time and the only way I get an idea of the true diameter is to take LOTS of measurements and use statistics to throw away bad data and take an average of the rest.

Other than the several hundred dollar bore gauges, is there any other way to measure cylinder bores?

Second, I've been advised to hone the cylinders out anywhere from 0.001 to 0.002" for a better clearance. HOW LONG DOES IT TAKE TO REMOVE 0.001" ???? *sheesh* ! I've honed and honed and honed and I keep getting the same numbers for the diameter. I'm afraid to go any further because I don't trust the telescoping gauge readings.

. . . .unless you need to hone with a medium stone for about 20 minutes straight to remove 0.001". I don't have a feel for it, but don't want to ruin my cylinders.

Any help appreciated. This isn't going as well as I thought it would.

--Scott

Your hone will not do what you want to do. It is only meant for cleaning up a cylinder and breaking the glaze.

Take the cylinders to a good auto machine shop and have them do the honing on their Sunnen hone. Find one that does Harley Davidson cylinders. Bring your pistons along so they can fit them to the cylinders.

They will cut the cylinders perfectly true and fit the pistons to whatever clearance you want. There is really no other way to do this without the proper equipment.

[scott12180]

Thanks for your advice, guys.

Yeah, this is the way we learn. Screw up, then figure out what we did wrong.

So now I know the difference between honing and glaze breaking, and the proper tools for each.

And then when we've finally got it all figure out, we die. :-)

But this is fun stuff. Thanks again.

--Scott

[Coley]

What is the reason for the .001-2 increase in bore?

Are you using new pistons, or reusing the originals?

If using the originals, just break the glaze and use them.

Moly filled rings will give you an easy break in, if they are available.

Chrome is probably the hardest to break in.

Just my .02 cents

[scott12180]

What is the reason for the .001-2 increase in bore?

Are you using new pistons, or reusing the originals?

If using the originals, just break the glaze and use them.

Moly filled rings will give you an easy break in, if they are available.

Chrome is probably the hardest to break in.

Just my .02 cents

Not exactly original pistons, but replacement pistons which were not fitted properly. The previous guy who did the engine work wasn't too knowledgeable on 1920's engines, let alone Franklin air cooled.

I had new bearings made for the mains and rods, and in looking over the cylinders discovered that the clearances were set up too tight for my comfort. While it's apart, if I could find someone to hone them in to the correct clearance, it makes sense to get it done right.

[Coley]

Are they cast or forged pistons?

What is the clearance they are set at now?

What are the specs for your air cooled engine?

[NTX5467]

With all due respect, it sounds to me like this whole operation should have been at a machine shop to start with. Especially one that is "Harley-capable", if necessary.

Admittedly, it's somewhat difficult to do the dial bore and micrometer activity if you aren't comfortable using that. In an old MOTOR manual, or similar, it mentions using shims inserted between the piston and the cylinder wall to check clearances, kind of like using a feeler gauge to set valve clearance.

With a dial bore gauge with a roller, the main thing is that you have to have it centered in the bore, laterally. It can also indicate "wavy" walls, too.

In reality, I don't see where the small clearance increase you wanted is worth the effort. Regarding the "how much time per amount of metal removed" question, this is variable with the grit of the stones and pressure of the stones against the cylinder wall surface. Honing is the final touch for clearance in the machining process, BUT can also be the most critical to perform. UNLESS the hone's "stroke speed" is not maintained (where the 60 degree cross-hatch pattern is produced), then it's very easy to start with a straight-cut surface from the cutting tool to a bell-shaped or wavy cylinder wall due to how the hone stroked during that procedure.

On the Sunnen CK-10 (or later designs or from other companies), the "Load Meter" on the hone's motor is a key indicator of if there might be some areas of the cylinder wall which have more clearance than others. It also takes an operator who knows how to interpret that gauge reading, too! AND, of course, the honing operation puts heat into the metal being honed, so there must be "cooling breaks" to ensure the desired end result happens as it should.

For these reasons, plus the fact you have a somewhat irreplaceable item you're desiring to remove metal from, it might be better to get some red scotchbrite pads and work on the piston skirts, using a larger micrometer to measure the progress on a work bench, while not removing any desired oil-retention patterns from the piston's skirt area OR changing it's overall coutours. A different method of achieving the same results . . . I'd certainly hope it's easier to find Franklin pistons than cylinders.

Respectfully,

NTX5467