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PeteJ

I know this is the "plastic" modelers society but I couldn't help myself!

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I have been using a Sherline lathe for years now but really wanted to take my builds to the next level. Last week in a weak moment I went over to Sherline(about 5 miles from my house) and dropped a wad of cash on the desk and walked out with a mill and a bunch of accessories. Finally got it set up today and these are the first pieces off the mill. I am taking an old Red Baron kit and planning making everything from metal except the tub and the helmet. Here are my first bits.

 

This is the pattern that I scribed on two pieces of .030" brass strip.

 

DSC00877_zpse0eca6aa.jpg

 

Here are the parts and the original piece. I need to clean them up a bit more and then I can make cross members and suspension parts.

 

DSC00878_zps11f2496e.jpg

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Looks great, but doesn't look thick enough for a frame rail. Remember 1mm = 1 scale inch. So a frame rail would be 2.5mm minimum right?

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Looks great, but doesn't look thick enough for a frame rail. Remember 1mm = 1 scale inch. So a frame rail would be 2.5mm minimum right?

It is .030" as is sits so that scales out to 3/4" I plan on soldering brass strip top and bottom to get an I-beam effect so it will look thinker when done. This is actually a hotrod not a dragster.

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I believe that you guys in the States still work in Feet and Inches.

The UK went metric back in the Seventies.

When I was an apprentice in the early sixties I was brought up on feet and inches.

We used all sorts of imperial threads like Whitworth and British Standard Fine and coarse,

as well as UNC and UNF that I believe were originally American threads.

Since Metric standardisation things are a bit easier with everything divisible by ten and it is a lot easier to work with.

Mind you I can still even now visualise 10 feet in my mind easier than 3 metres!

 

Hope that this little snippet is helpful......Inch to Metric Conversion is as follows......One inch equals 25.4 millimetres.

 

Any full size conversion and subsequent scaling can be worked out from this.basic formula.

Edited by noelsmith

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Noel -

We missed that boat back in the 70's. For a brief period road signs showed both miles and Klics. There is still a residual of that on or speedometers. Good old gov't couldn't pull that trigger. Life would have been much easier in the world if they had. Nice part about the Sherline equipment is that it is calibrated in decimals. As long as my measuring equipment is the same I'm good. Scale conversion works better if I build 1:20 scale, but that is an F1 thing only. 1:24 works much better that 1:25th when I am thinking in inches. Inch =2 feet and I can play with fractions in my head from there. Here the threading I grew up with was Standard and SAE(Society of Automotive Engineers). SAE was a much finer thread.

 

My friend the rocket scientist( really is- he retired from JPL) likes to say, "Standards are great! Everyone has one."

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Hi Pete,

Funny thing that you mentioned roadsigns......Everything else went Metric here in the UK except for the road signage. It is all still in miles and does not look like ever being changed either! Probably the cost would be too much I expect. All the other stuff such as weights, volumes and measures were changed to metric, so all the government had to do was set up a standards board and and sit back as it was left to industry and commerce to make the changes. We had a bit of a laughable situation for a while where Inch drawings were being converted to metric by many companies. it would have been better just to carry on with the old drawings until new designs were required and done in metric at the outset.

Is the 'standard' thread you refer to the the American National Fine and Coarse thread pattern?

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Hi Pete,

Funny thing that you mentioned roadsigns......Everything else went Metric here in the UK except for the road signage. It is all still in miles and does not look like ever being changed either! Probably the cost would be too much I expect. All the other stuff such as weights, volumes and measures were changed to metric, so all the government had to do was set up a standards board and and sit back as it was left to industry and commerce to make the changes. We had a bit of a laughable situation for a while where Inch drawings were being converted to metric by many companies. it would have been better just to carry on with the old drawings until new designs were required and done in metric at the outset.

Is the 'standard' thread you refer to the the American National Fine and Coarse thread pattern?

I love these discussions because I had to go and do some research. Back in my day(I'm 63) there were just the two standards and you could tell them apart easily just by looking at them. Apparently as some point they discontinued the name "standard" and "SAE" which had been around since the early 1900's. It appears that the only thing that they really changed was the name and they are now known as UNC(Unified National Course) and UNF(Unified National Fine). I suppose that makes more sense but it is hard to get use to something new when you have used it 50 years.

 

It appears that the "American National Standard" was also the United States Standard Thread, Sellers Standard Thread and the Franklin institute Thread at one time or the other. Thus, my comment about, standards being great-everyone has one. Then the government gets involved and selects their own standard and really messes things up. Kind of like AN pipe fittings. Good intent, poor execution.

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Fresh out of school I had a job as a machine designer for a university lab where the only person with any real experience was a visiting Israeli aircraft engineer who taught me the ropes. When it became clear our machine shop couldn't handle metric dimensions (most of their equipment was WWII vintage) we settled on dimensioning drawings in both 2-decimal-place millimeters and 3-decimal-place decimal inches, but tolerances were inch-only. Our drawing machines had scales (rulers) with both mm and decimal inches (with 0.02 inch tick-marks), and it got so I could multiply or divide by 25.4 in my head.

 

The Israeli engineer was perfectly happy with UNC fasteners; he said they used them all the time in Israel because they were readily available and were more of a true standard than metric fasteners (any 4-40 UNC screw will fit any 4-40 tapped hole, but order a generic "3mm machine screw" and the pitch and thread-profile is a bit of a crap shoot depending on the country and manufacturer they came from).

 

BTW, either decimal-inch or mm rulers are great for 1:25 scale work; a 1mm tick mark is essentially 1 scale inch, and the 0.02 inch tick marks are half a scale inch (or at least close enough for most modeling work).

 

Don

Edited by Schmitz

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I mentioned the "Standard/SAE" from back in the day. I grew up working of farm machinery in western Nebraska and soon got a lot of experience working with the two different threads. Then in 1966 I got a Yamaha twinjet 100 and the stuff really hit the fan. Nothing I wanted to do with that bike made any sense. The bike came with a cheap and I do mean cheap set of double ended wrenches. Over time I bought a good set of Craftsman metric wrenches and 3/8" drive sockets and Allen wrenches. I think that was the start of my obsessive compulsion to purchase good quality tools. I still have that set of wrenches and sockets and still use them though I have expended my collection considerably since then.

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Fresh out of school I had a job as a machine designer for a university lab where the only person with any real experience was a visiting Israeli aircraft engineer who taught me the ropes. When it became clear our machine shop couldn't handle metric dimensions (most of their equipment was WWII vintage) we settled on dimensioning drawings in both 2-decimal-place millimeters and 3-decimal-place decimal inches, but tolerances were inch-only. Our drawing machines had scales (rulers) with both mm and decimal inches (with 0.02 inch tick-marks), and it got so I could multiply or divide by 25.4 in my head.

 

The Israeli engineer was perfectly happy with UNC fasteners; he said they used them all the time in Israel because they were readily available and were more of a true standard than metric fasteners (any 4-40 UNC screw will fit any 4-40 tapped hole, but order a generic "3mm machine screw" and the pitch and thread-profile is a bit of a crap shoot depending on the country and manufacturer they came from).

 

BTW, either decimal-inch or mm rulers are great for 1:25 scale work; a 1mm tick mark is essentially 1 scale inch, and the 0.02 inch tick marks are half a scale inch (or at least close enough for most modeling work).

 

Don

Don, thanks for the tip. I suppose in the back of my mind I knew .040 was an inch but now it will stick and that is definitely a usable number.

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Don, your comment about Metric Threads being a crap shoot depending on the country of manufacture surprised me a bit, as the Metric system threads should all be made in accordance with I.S.O. (International Standards Organisation) specifications. Possibly this happens with items that are not of European origin and from countries where quality standards are questionable.

Also your mention about machines dating back to the war. When I started my engineering apprenticeship back in 1960, many of the machines were wartime issue, and some were of American origin. I can remember working on Le Blond and South Bend Lathes and Cincinnatti Milling Machine back then. That was before Metrication took place in the UK in the 70's.

Although I was brought up on Feet and Inches from early school days through to the 70's, I did find the Metric system far easier to use once used to it. Also, engineers working in metric just use Millimeters on the drawings for most things.

Pete, you mentioned a passion for buying quality tools. I second that! I still have many of the tools that I bought whilst I was an apprentice way back in the early 60's.

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Noel, I am sure that you have experience the curse of poor quality tools. Cheap tools cost far more than top drawer tools. They either frustrate you and you wind up paying someone to do something you could easily do yourself with the right tools, or they break and have to be replaced or break what you are working on. The real down side to having good tools is I have to say no to friends who would borrow the tools. I really don't want to go into how often I have loaned a tool out and it came back in such poor condition that I just had to throw it in the trashbin. I would have been better off buying a cheap tool for that person.

 

When I was first married, my wife questioned my purchasing tools as I needed them and wondered why I needed so many. My response was, " I could build a house with a Swiss Army knife, but why would I want too?" Never heard another word about it.

Edited by PeteJ

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Don, your comment about Metric Threads being a crap shoot depending on the country of manufacture surprised me a bit, as the Metric system threads should all be made in accordance with I.S.O. (International Standards Organisation) specifications. Possibly this happens with items that are not of European origin and from countries where quality standards are questionable.

 

Noel,

 

I've never worked on a project with metric fasteners; after my first stint as a machine designer I ended up in the software business (that was mid 1980s, much of the manufacturing and design work was leaving the US then and jobs were hard to find). The "crapshoot" opinion came from an Israeli engineer and was probably biased by his experience working on US aircraft in a place where it was hard to buy industrial components. It may have been that the suppliers they had just weren't very careful about specifying what they were selling when it came to metric fasteners; my understanding of the ISO spec is that the thread-pitch is usually implied so suppliers may not have been careful about specifying pitch.

 

Something like this shows up in US fasteners: a #6 machine screw is nominally 32-thread-per-inch, but 6-40 (fine thread) screws are somewhat common in electronics equipment, leading to ruined parts with cross-threaded holes... My Israeli friend simply avoided using #6 screws completely; if a 4-40 wasn't big enough we would jump straight to 8-32. We also used helicoil inserts in all the aluminum parts as standard procedure to prevent stripping - which proved handy as we took stuff apart and put it back together a lot more often than I had suspected.

 

Don

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another hint/tip in metric/inch conversion is 1mm is almost exactly .040 inch.

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Don,

It's ages since I was on this.. Can I put things right about metric thread pitches.

They are not implied, they are actually specified just like any other thread.

 

An Old Engineering joke;

The scientist said 'Let me look and I will have to experiment to arrive at the answer.'

The mathematician said 'Let me look at this and I will have to calculate the answer for you.'

The engineer just looked up the answer on a chart.

 

Another Engineering joke,

The optimist said ' My beer glass is half full!'

The pessimist said 'My beer glass is half empty!'

The engineer said ' The beer glass only needs to be half the size it is now!

Edited by noelsmith

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