automotive engine boring on a mill

FWIW, my ISP has been screwing around and I've lost days worth of messages, but Sunnen was my pet subject for a couple of years, and the hones they make today (non-automotive as well as automotive) make their own way in a hole, pretty much, and often are used to make near-perfect cylinders in crappy machined bores, in OEM production. They can straighten a bore that's cockeyed as hell. They're amazing.

I presume this is what Dave said, in which case, 'sorry for being redundant.

Ed Huntress

I'm going to second the motion for this idea. Not something you want in a tiny garage, but if you have the space it's the way to go..cheap, beefy, and suitable to the task. I have seen pictures of V8 diesel engine blocks being machined in a bed-type 50 taper horizontal (it looked like anyway). The setup looked like it was setup for boring-IIRC, the block was mounted vertically on the bell-housing deck, and it was setting on a rotary table. With that setup, you could deck it and do all 8 bores in one set-up. The crank center line would be easy to pick up by mounting the crank bores over a spud. The disadvantage with a purpose built automotive boring machine is just that- you can only do one thing with them, but a mill can earn its keep in other ways. Disclaimer-just my opinion, my expertise is not in automotive machining. Brent.

Dave sez, smugly: "I have to conclude that if you think that honing can't create a perfect bore

So Dave! Whyn't you make up one of your Cockney stories to go with this?

Bob Swinney

I'm not sure who your customers are, but do different customers ask for different tolerances on those parts?

I find it interesting to see the difference between the quality requirements between the various OEMs and Tier 1s.

Regards,

Robin

You are right that's the one to get, also it lines up to the crank center line. Kwick way (Spelling?) makes one kinda like it to.

Buzz. Please don't preface your comments with buzz again. It comes across as horribly pretentious.

I'm not sure why you think you need to measure anything with a machine capable of ten times the resolution of the dimension you are seeking to measure. I don't claim that my Mercer will measure to 0.0001" repeatably but it will measure to 0.0002" or 0.0003" repeatably. It's certainly within the realms where temperature variations make a bigger difference to the bore size than the accuracy of the honing operation. I have to let blocks stand overnight after honing to be absolutely sure of the final dimension.

Every time you use a micrometer calibrated in tenths do you just ignore the tenths and call it to the nearest thou? I'm damn sure no one else does.

Yes there's no such thing as a perfect bore in absolute terms but that's not what I or anyone else mean. Perfect means perfect in terms of the tolerances that empirical testing has found to be insignificant in altering the component's performance. I'm more than happy that what I produce far exceeds the accuracy requirements of OE production and matches the best that any other race engine builder in my line of work produces.

As for OE tolerances, they seem to have gone to hell in a handbasket recently.

30 years ago Ford used to grade their pistons in intervals of a few tenths to match the measured bore size as blocks came off the production line. I measured a couple of brand new 2 litre Zetec engine blocks some time ago and they had about 1 thou difference between the smallest and largest bores on the same block and about the same error on taper and ovality. I'd expect better than that from a lawnmower engine made in India.

However, engines are amazingly tolerant of bore errors. Piston rings, once they have bedded in, cope happily with quite large ovality and taper errors and frankly most of the stuff you read about the importance of blueprinting engines is pure bullshit. It's fine to aim for in theory but makes sod all difference in practice. Even if you work to the finest tolerances the engine does its best to ignore your work when it's running. Bores, cranks, rings vibrate like the bloody clappers when engines are going full tilt at 7k plus rpm and your tenths tolerance on the original machining are swamped by the thous of movement in the components when they are under load.

"Robin S." wrote in news:pM9td.13433$l% snipped-for-privacy@news20.bellglobal.com:

Yes. The tolerances do change from customer to customer. They also change due to the design of the engine and piston. There is a complete book of 'standard' or default tolerances to go along with that. From what I have seen, the Tier 1's are usually held to a considerably tighter quality standard than are in-house products. This is not true of all of the OEM's...

"Robin S." wrote in news:Dc9td.12722$l% snipped-for-privacy@news20.bellglobal.com:

Agreed.

snipped-for-privacy@aol.comNoEmails (Dave Baker) wrote in news: snipped-for-privacy@mb-m28.aol.com:

Because that is precisely what just about any nationally/internationally recognized quality standards require. Your gauge must have an R&R of less than 10% of the tolerance you are measuring, and this must be documented and certified yearly. (Just out of curiosity, when was the last time your gauge was certified?)

I don't claim that my Mercer will measure to 0.0001"

That doesn't even qualify it to guage a 0.001 tolerance.

Agreed on the method of allowing cool time.....but at what temperature? Quality standards specifiy at what temperature, and humidity, the parts should be measured. Do you have a temperature controlled lab you are allowing the block to stabilize in?

In my work, I use certified, tested, and traceable gauging that meets or exceeds the 10% R&R standard.

Want to put a wager on that?

You measured this with a gauge that can only be certified repeatable to

0.002 or 0.003, how much difference was in the gauge itself, and how much of this difference was in your human measuring error? Fact is...at this point, you do not know.

Yes...they can cope...for some amount of time...but how much power are you losing? Blueprinting an engine is not bullshit...it is a demonstrated fact. Proven with test after test. All the thermal expansions you speak of are calculated into the design. As are the thrust forces, vibrations, flexing and the like. Did you know that pistons are not round....nor are they cylindrical in vertical shape. There are reasons for that, a lot of those are thermal, flex and force driven. When you measure a piston for fit, where do you measure it?

Taper, ovality, etc, play an important role in ring sealing. As I said in my other post, 4 to 5 *microns* of difference in the ring groove waviness makes a significant difference in horsepower. This is due to better ring sealing. But all that quality in the piston, means jack when you put it in a bore of poor quality.

I know for a fact Ford bores are held to within microns, the same as our parts that go into that bore. There are many reasons for that, emissions, NVH, etc. But the fact is...they are held that tight. Now, I am not saying that those bores weren't out that much, *but* you do not know that, and neither does anyone else. Your gauging capability doesn't allow you to know with any amount of certianty.

Yes, you're right. But then I seem to remember a history.

Certainly not.

You have a tolerance of +/- .001" The component is actually out by .0009" Is your instrument (which measures to within .001") going to tell you if the part is in spec?

Simple example but so very relavant.

I understand what you're saying however. The real issue is that we come from different worlds.

Well, it WAS a Ford....

While that may be true, I expect my Toyota's engine and transmission to last

300,000km. Small errors tend to come out over milllions or billions of cycles (I'm not going to do the math).

Regards,

Robin

This thread is about the boring and honing of engine blocks for engine reconditioning. I don't know why you and Robin keep trying to drag it into an argument about production line metrology which has nothing to do with the needs of a man trying to bore and hone the one engine he has in front of him at the time so that the bores are X thou bigger than the one set of new pistons he has in front of him at the same time.

I don't really want to debate your topic and you don't seem to have anything to add about engine cylinder bore reconditioning.

Heaven help me for adding fuel to this, but the logic behind gage R&R is really going to confuse some people if it isn't explained. And I'm in no mood to explain it -- nor do I trust my memory enough to do it off the top of my head.

The point of it, though, is in transferring a dimension *forward* from a certified gage, or *backward* to a certified gage. In other words, if you're using a micrometer that's set to your company's QC-lab gage blocks, and they're qualified from the master blocks you keep in the lab safe, and THEY'RE the ones you send out every six months to Gaithersburg or wherever to have certified, you're going to need that 10% tolerance throughout the chain of instruments and standards. You're also going to need it to get any kind of ISO certification that serious manufacturers require.

However, two gages, RELATIVE to each other, don't require it. Depending on the relative accuracy required between, say, an inside and an outside mike, if they're both set to the SAME gage block, for example, the second one only has to be able to resolve less than 50% of the required tolerance.

I wrote this down once, years ago, and I hope I have repeated it correctly above. I certainly don't remember the details. But that was something I worked out on paper with one of Mitutoyo's top engineering guys for an article. He was an expert at it, who had a regular path beaten back and forth to Gaithersburg.

None of this accounts for such things as measuring errors due to an individual's inconsistencies or thermal expansion, etc. But neither does anything else. The gage R&R business must be in close control and perfectly systematic to have any meaning, too.

Ed Huntress

Thanks, Ed! More "voice of reason" from you. I can't understand why anyone would want to argue with the 10:1 convention. It is the instrumentation criterion that is usually quoted in text books and etc. I've heard of it and seen it most all of my life. Anyone choosing to contest such criteria is only revealing his own lack of engineering appreciation and perhaps his training as well.

Bob Swinney

snipped-for-privacy@aol.comNoEmails (Dave Baker) wrote in news: snipped-for-privacy@mb-m07.aol.com:

Huh?

Obviously, you did not even read the remainder of my post. This relates directly to the quality of the bore. But if you can't measure that quality, and from your previous posts, it is obvious you may not even understand what entails a quality bore, what influences other machining operations have on that bore (if you do not understand, or know what is required of a true quality bore in an engine, you certainly cannot understand what effects other machining processes have on that quality), and the reasoning behind those quality requirements, it is a mute point indeed.

snipped-for-privacy@aol.comNoEmails (Dave Baker) wrote in news: snipped-for-privacy@mb-m07.aol.com:

BTW....since you obviously didn't read enough of my post to answer my question, and you brought the subject up again here...Just where (on the piston) are you measuring the diameter of the piston to get the bore size?

"Ed Huntress" wrote in news:1Ywtd.1328$ snipped-for-privacy@fe12.lga:

Actually Ed, there is an R&R Study requirement for hand gauges that includes the human element. The basics...are that you aquire a set number of parts (usually 10), and two or more operators. Each part is numbered. Each operator separately gauges each part, and the measurments are recorded by an independent third party, either another person, or by electronic means. Then the range and averages are calculated with respect to the tolerance of the feature, the gauge precision, and other factors to arrive at the repeatability of the gauge, including the human element. Per the quality standards we have to live by, the R&R you spoke of, in combination with this R&R including the human element, must total less than 10% of the tolerance. It is not an easy target to achieve, by any means.

Yeah, there are several components to the whole R&R idea, and anyone who has to deal with today's QC and dimensional measurement, or who might have to know what a customer is talking about, ought to read about it. There are some experts in the business who have written compact little books and so on that describe all of it.

I think SME has a good one or two on its book list.

Ed Huntress

This is a restatement of my experience that "the new guys always gage parts *small* on the OD, and *large* on the bores.

This is because consider the reading correct when the micrometer or caliper is cranked on/in there really tight. I used to tell them to run the parts tight/loose as the case would be, to get their lot to come in on target. But picking up a job that had been run unsupervised by a "new guy" during the day would invariably start with double-checking any measurement which required any kind of sensitive feel when gaging.

Jim

I really can't see what this has to do with my bore gauge (bore comparator if you will) which compares to 0.0001". That's plenty accurate enough for what I need to do to size a race engine bore to the accuracy I need to size it to and nothing to do with production line tolerancing which isn't something I get involved in.