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post #31 of 67 (permalink) Old Sep 26th, 18, 2:11 AM
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Re: Main Bearing clearance too tight?

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Originally Posted by 540Hotrod View Post
I've done it by measuring the crank with the outside Mic. Whatever it reads is what it reads. Certainly you're looking for accuracy....but if you don't have mega $$ tools...it works.

So measure crank with outside Mic and lock it. Then set the inside mic to zero against the outside Mic. Then measure the inside diameter of the torqued assy's and note the difference. Even low $$ ones can easily show an accurate reading of the difference from what you zero'd it against. This eliminates any concerns about the accuracy of the standards.


I've actually tested some really cheap swap meet dial bore Mics against some high $$ stuff and found they weren't so terrible. Like any tool....take care of it and don't let others use them. Much more variable in the operator than the tools.


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Quote:
Originally Posted by jackie schmidt View Post
I have been Machinist my entire Adult life. I also own a successful Machine Shop.

I trust a outside micrometer and a set of inside micrometers standardized together more than anything.

You can usually pick up a set of both at a pawn shop rather cheap.

If you have a set, a set of ball mic's to check bearing shell thickness can come in handy.
Glad to hear from folks who understand how a trained machinist measures and calculates bearing clearances, which is actually quite simple when compared to machining piece-parts with multiple tolerances in tenths throughout a production run.
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post #32 of 67 (permalink) Old Sep 26th, 18, 2:23 AM
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Re: Main Bearing clearance too tight?

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Originally Posted by David Bates View Post
I believe Mike Lewis has several Mitutoyo dial bore gages he apparently trusts. I have a couple also and they are not "consumer quality" by any stretch of the imagination.
Yes, Mitutoyo manufactures quality inspection-grade instruments, as did Starrett and Brown and Sharpe...back in the day. Not certain what they are building these days.
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post #33 of 67 (permalink) Old Sep 26th, 18, 9:29 AM
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Re: Main Bearing clearance too tight?

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Originally Posted by Saltherring View Post
Yes, Mitutoyo manufactures quality inspection-grade instruments, as did Starrett and Brown and Sharpe...back in the day. Not certain what they are building these days.
I should have added that these are Mitutoyo 545-134/5/6 series dial bore gages with 0.0001" minimum scale subdivisions (not to be confused with accuracy) and large radius of curvature carbide contacts. They have been discontinued for many years. What they offer now I do not know.
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post #34 of 67 (permalink) Old Sep 26th, 18, 11:50 AM
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Re: Main Bearing clearance too tight?

ID mic and using a C mic takes a lot of feel. What most guys don't realize that when properly calibrated, a C mic needs to have a certain amount of tension on it. That's what the friction thimble is for. It loads the frame on the mic to a calibrated amount of preload. When you're trying to measure tenths and using your C mic to measure your ID mic or snap gauge, it's really hard to use the friction thimble so you rely on "feel". Some guys are heavy handed on measuring tools, some are light handed. This is also why it's not a good idea to set your dial bore gauge with a C mic. No preload. Dial bore gauges should be set with ring gauges or a setting fixture. Can you get away with other methods and less expensive tools? Obviously...but you're not getting the measurements you think you're getting. I spent a day at my machinist's shop when I first moved here so we could get on the same page as far as measuring things. Fortunately, we were very close to each other as far as feel and method. I know when he says a tenth, it's pretty much the same as my tenth.
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post #35 of 67 (permalink) Old Sep 26th, 18, 12:13 PM
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Re: Main Bearing clearance too tight?

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Originally Posted by steelcomp View Post
ID mic and using a C mic takes a lot of feel. What most guys don't realize that when properly calibrated, a C mic needs to have a certain amount of tension on it. That's what the friction thimble is for. It loads the frame on the mic to a calibrated amount of preload. When you're trying to measure tenths and using your C mic to measure your ID mic or snap gauge, it's really hard to use the friction thimble so you rely on "feel". Some guys are heavy handed on measuring tools, some are light handed. This is also why it's not a good idea to set your dial bore gauge with a C mic. No preload. Dial bore gauges should be set with ring gauges or a setting fixture. Can you get away with other methods and less expensive tools? Obviously...but you're not getting the measurements you think you're getting. I spent a day at my machinist's shop when I first moved here so we could get on the same page as far as measuring things. Fortunately, we were very close to each other as far as feel and method. I know when he says a tenth, it's pretty much the same as my tenth.
Training and working many years in a machine shop that specializes in close tolerance work will help give one 'feel' consistent with the feel of others, and especially the feel of the inspector, who ultimately determines whether parts meet drawing tolerances.
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post #36 of 67 (permalink) Old Sep 26th, 18, 12:35 PM
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Re: Main Bearing clearance too tight?

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Originally Posted by Saltherring View Post
Training and working many years in a machine shop that specializes in close tolerance work will help give one 'feel' consistent with the feel of others, and especially the feel of the inspector, who ultimately determines whether parts meet drawing tolerances.
Most measurement systems are designed to eliminate the need for feel, (like using the friction thimble on a c mic) but I agree...sometimes we work with what we have and do the best we can.

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post #37 of 67 (permalink) Old Sep 26th, 18, 2:38 PM
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Re: Main Bearing clearance too tight?

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Originally Posted by steelcomp View Post
I spent a day at my machinist's shop when I first moved here so we could get on the same page as far as measuring things. Fortunately, we were very close to each other as far as feel and method. I know when he says a tenth, it's pretty much the same as my tenth.

Sounds familiar. I hauled all of my measuring stuff down to the School of Automotive Machinists (SAM) and did the same thing. I worked with the Instructors I knew and made sure I was getting same measurements they were. I don't like to trust anyone on my engines. Like to make sure I agree with what we think the clearances are. There IS a lot of feel in this stuff and I've seen some hacks with some real nice equipment barf up a lot of stuff.



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post #38 of 67 (permalink) Old Sep 26th, 18, 3:04 PM
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Re: Main Bearing clearance too tight?

Quote:
Originally Posted by steelcomp View Post
Most measurement systems are designed to eliminate the need for feel, (like using the friction thimble on a c mic) but I agree...sometimes we work with what we have and do the best we can.
I have never used a micrometer thimble as I consider my trained and laboratory-tested feel to be superior to a thimble. And that was not only me but also the hundreds of machinists, toolmakers, machined parts inspectors and calibration lab technicians who worked at the Naval Undersea Warfare Center.

This is not arrogance, it is simply professional preference relating to how I was trained. And as you stated in your previous post, MY "tenth" needed to agree with the "tenth" others read with the same mic. And yes, we worked daily to drawing tolerances in tenths (.0001)
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post #39 of 67 (permalink) Old Sep 26th, 18, 3:05 PM
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Re: Main Bearing clearance too tight?

Quote:
Originally Posted by 540Hotrod View Post
Sounds familiar. I hauled all of my measuring stuff down to the School of Automotive Machinists (SAM) and did the same thing. I worked with the Instructors I knew and made sure I was getting same measurements they were. I don't like to trust anyone on my engines. Like to make sure I agree with what we think the clearances are. There IS a lot of feel in this stuff and I've seen some hacks with some real nice equipment barf up a lot of stuff.



JIM
when I was in school at NASA we had known spec testing equipment, everything I got was mitoyo from the school. I purchased some known good brands of digital calipers and a small digital mic. both where brands the instructors recommended, we made test bars for the different sizes while in school as a project and I still have them to test my mics and calipers to zero them. Also have precision ground rings to test bore mics even though I do not have any big enough for engine work.
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post #40 of 67 (permalink) Old Sep 26th, 18, 7:18 PM
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Re: Main Bearing clearance too tight?

Quote:
Originally Posted by Saltherring View Post
I have never used a micrometer thimble as I consider my trained and laboratory-tested feel to be superior to a thimble. And that was not only me but also the hundreds of machinists, toolmakers, machined parts inspectors and calibration lab technicians who worked at the Naval Undersea Warfare Center.

This is not arrogance, it is simply professional preference relating to how I was trained. And as you stated in your previous post, MY "tenth" needed to agree with the "tenth" others read with the same mic. And yes, we worked daily to drawing tolerances in tenths (.0001)
I've been a machinist since the late 70' and most of my experience came from building under water sonar equipment, mostly for the government and military. Back then tenths were a brick. I was just sharing information about the tools some of us use that most people don't realize and actually something I've recently learned...as good as my training was. I've developed a good enough feel to not need the friction thimble for most things, but there is a reason it's there. I quit using my C mics for setting my dial bore gauges when I understood the preload requirements for a C mic to read properly. I could never get my dial bore gauge and my ID mic to read the same...and I've got a pretty good feel. I sent the dial bore gauge in for calibration and it was dead nuts over 72 hours...never changed a tenth. Then the gentleman who was doing the calibration explained to me how a C mic works. There is clearance in the threads of the mic. There is actually a torque spec for the barrel and thimble. You need to have enough preload on the mic to take up the clearance in the threads, especially if you're working in tenths. The friction thimble is designed to apply just enough load to the threads as to take up the slack, but not deform the frame. I figured that I was fooling myself thinking I was good enough to have the same repeatability and consistency as that friction thimble and now I use it when I think it's necessary. The ID mic is purely a "feel" thing, especially if you're using a C mic to read it. Same with telescoping gauges or "snap" gauges. Ever since I bought a few XX-class gauge rings to set my dial bore gauges, I've learned a little about how much difference these things can make. And yes, my engine room, which is where I do my precision measuring, stays the same temp year round. I hope I never get too old or too complacent to think I have it all figured out or can't learn something new.
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post #41 of 67 (permalink) Old Sep 26th, 18, 9:04 PM
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Re: Main Bearing clearance too tight?

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Originally Posted by steelcomp View Post
I've been a machinist since the late 70' and most of my experience came from building under water sonar equipment, mostly for the government and military. Back then tenths were a brick. I was just sharing information about the tools some of us use that most people don't realize and actually something I've recently learned...as good as my training was. I've developed a good enough feel to not need the friction thimble for most things, but there is a reason it's there. I quit using my C mics for setting my dial bore gauges when I understood the preload requirements for a C mic to read properly. I could never get my dial bore gauge and my ID mic to read the same...and I've got a pretty good feel. I sent the dial bore gauge in for calibration and it was dead nuts over 72 hours...never changed a tenth. Then the gentleman who was doing the calibration explained to me how a C mic works. There is clearance in the threads of the mic. There is actually a torque spec for the barrel and thimble. You need to have enough preload on the mic to take up the clearance in the threads, especially if you're working in tenths. The friction thimble is designed to apply just enough load to the threads as to take up the slack, but not deform the frame. I figured that I was fooling myself thinking I was good enough to have the same repeatability and consistency as that friction thimble and now I use it when I think it's necessary. The ID mic is purely a "feel" thing, especially if you're using a C mic to read it. Same with telescoping gauges or "snap" gauges. Ever since I bought a few XX-class gauge rings to set my dial bore gauges, I've learned a little about how much difference these things can make. And yes, my engine room, which is where I do my precision measuring, stays the same temp year round. I hope I never get too old or too complacent to think I have it all figured out or can't learn something new.
Yes, Scott, I also began my machinist apprenticeship in the 1970's (1976), graduating in 1980 from what was then considered perhaps the best apprentice school in the nation, at Puget Sound Naval Shipyard. But while the shipyard was engaged in ship repair, we, at the NUWC production machine shop, produced undersea weapons (mostly torpedo) components, which were mostly machined from 6061-T6 aluminum or 302-304 stainless steel.

All that said, I nod approval to all you write, but still read mic's by feel. Take care, my friend and fellow machinist.
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post #42 of 67 (permalink) Old Sep 26th, 18, 9:38 PM
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Re: Main Bearing clearance too tight?

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Originally Posted by Saltherring View Post
And yes, we worked daily to drawing tolerances in tenths (.0001)
So most of my engineering experience is electrical but if I'm not mistaken .0001 is one millionth. Is that machinist talk for a tenth of a thousandth or am I way off base? I've seen other machinists use that term for that figure and it confused me. Just trying to get on the same page, not being argumentative.

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post #43 of 67 (permalink) Old Sep 27th, 18, 1:21 AM
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Re: Main Bearing clearance too tight?

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Originally Posted by Tommy the Cat View Post
So most of my engineering experience is electrical but if I'm not mistaken .0001 is one millionth. Is that machinist talk for a tenth of a thousandth or am I way off base? I've seen other machinists use that term for that figure and it confused me. Just trying to get on the same page, not being argumentative.
.0001 is one ten-thousandth of an inch...or one "tenth" in machinist talk. Half of that amount is .000050, or "fifty millionths". One millionth is .000001. I have seen parts ground to tolerances of +/- 50 millionths in a climate controlled room. I have machined many different parts where numerous lengths and diameters were toleranced in "tenths", such as +/- .0003, or +.0005/-.0000. This is very common in torpedo components where precision bearings are pressed into tightly restricted bores. We usually measured such bores with dial bore gauges that were calibrated daily, or even twice daily, during a production run. Before cutting any metal, these machines were cycled to warm the cutting fluid, although dimensions had to be closely monitored early in the shift, as dimensions "moved" until the machine, cutting tools and coolant were fully warmed.

I did most of this close tolerance production work on Warner & Swasey 0, 1,2 and 4 AB and AC bar and chucker lathes. These were non-numerically controlled, or "conventional" machines, so no computer controls. All tooling was adjusted by hand. The best precision boring bars and turning tools for close tolerance production lathe work were of the DeVlieg micro variety, which were adjusted using a graduated dial and locking screw.
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post #44 of 67 (permalink) Old Sep 27th, 18, 1:25 AM
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Re: Main Bearing clearance too tight?

funny how this turned into a machine tool and trades convention.lol

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post #45 of 67 (permalink) Old Sep 27th, 18, 1:37 AM
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Re: Main Bearing clearance too tight?

Many machinists were (are) car guys, and many car guys are machinists. Although I've never machined engine blocks, heads, crankshafts or connecting rods, it involves the same trade theory/application, while using different machines and sub-skill sets.
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