Are European metric screws a different dimension?????

Laverda · May 16, 2020

This is a problem I have not seen before. I am working on a air compressor made in Germany. I need to replace some 5 mm x .8 pitch screws. I have a number of USA made 5 mm screws and they won't go in the hole. Measuring them, the German screws are 4.70mm on the major diameter and 4.37 mm on the minor diameter. The USA and even asian made ones are`4.83 mm major and 4.46 mm minor. So either I have to re-tap all the holes which are in cast iron or find some smaller screws. My 5 mm tap measures 4.99 mm and it won't go in the holes without starting to cut some metal.

And yes the screw pitch is .8 not .5 pitch.

What is the correct dimension for a 5 mm screw?

Rob F. · May 16, 2020

Are you sure it is not 10-32? 10-32 is SLIGHTLY smaller (.008") than 5mm x .8 and will thread into a 5mm hole, 5mm wont go into 10-32, just as you are describing.

Laverda · May 16, 2020

Thank you, Rob!

The screws are indeed 10-32. Now why everything else on the compressor is metric except these particular screws makes no sense?

You saved me a couple of hours of re-tapping the holes. Compressor is back up and running!

Rob F. · May 16, 2020

That was a common thing years ago building bicycles, always mixing up the 10-32 and 5mm screws. Probably all metric by now.

dian · May 17, 2020

in that case that compressor is not made in germany for sure.

AndySomogyi · May 17, 2020

On VW / Porsche, at least the older ones, the transmission input shaft splines were either 7/8 or 13/16. And caliper bolts spacing was also inch, 3.0 and 3.5 to be exact.

No idea why

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Limy Sami · May 17, 2020

AndySomogyi said:
On VW / Porsche, at least the older ones, the transmission input shaft splines were either 7/8 or 13/16. And caliper bolts spacing was also inch, 3.0 and 3.5 to be exact.

No idea why

Sent from my iPhone using Tapatalk Pro

And IIRC 60's & 70's Volvos were mostly Unified threads and hexs.

MattiJ · May 17, 2020

AndySomogyi said:
On VW / Porsche, at least the older ones, the transmission input shaft splines were either 7/8 or 13/16. And caliper bolts spacing was also inch, 3.0 and 3.5 to be exact.

No idea why

Sent from my iPhone using Tapatalk Pro

And there is some other weirdos also in cars. Like seatbelt mounting bolts that are inch sized even in all the German cars. (Bolt size actually matches some weird metric size too..)

projectnut · May 17, 2020

The 1980's were a nightmare as far as a mix of metric and SAE fasteners were concerned. As far as I know all-American brands also had what seemed like a random mix. As the US was going "Global" they slowly switched over to metric fasteners. The first to change were the non mechanical components like body and interior fasteners. Things like engines, transmissions, and drive train parts remained SAE.

Between 1980 and 1990 more and more fasteners switched to metric. The same model would change slightly from year to year. A fastener that was SAE in 1985 would be metric in 1986. It was frustrating especially if a fastener was stripped or broken. In many cases you had to remove another from the same component to determine which measuring system was being used. The last thing you wanted to do was chase a set of threads, or retap a hole with the wrong size fastener. Can you imagine the nightmare if you had 5 metric and 1 SAE fastener holding a component in place. If that happened it would be almost a given that the fasteners would get mixed up and there would be real problems on reassembly.

gustafson · May 17, 2020

5mm is pretty small, wonder if it is related to something that was changed for the US market. Like the control box.

I avoided most of the changeeover cars, fromt he perspective if actually having to work on them.

Now I have a full metric and full imperial car, and tools at the shop and at home and I am constantly having the wrong tools in hand

L Vanice · May 17, 2020

Limy Sami said:
And IIRC 60's & 70's Volvos were mostly Unified threads and hexs.

My 1969 Volvo 164 had an American Dana rear axle and Warner Gear auto transmission. Most bolts and nuts were standard USA inch sizes. The exceptions were the German ZF brake and steering components, which were metric. I did not mind having an excuse to buy more tools to add metric stuff to my shop.

Larry

Screwmachine · May 17, 2020

I don't know the story with Sweden and inch fasteners but as a Volvo mechanic in the 90s I can confirm they were almost entirely inch up to '75 when they went with a pretty ground-up redesign (ok they used the old B20 motor with inch fasteners for the 4cyl model that year). Was always fun digging through spare nuts and bolts and differentiating between 5/16 and m8.

I thought it was an oddity they had in sort of a vacuum but the Arboga milling machine I used later that decade (and at least 25 years old then) had inch fasteners on much of it too.

Half a century ago the Swiss weren't above using oddball metric on their machines. I recall needing to single point some replacement screws for Hauser stuff and old Agathon had 7mm screws here and there.

AndySomogyi · May 19, 2020

Even my 1960 Clausing lathe is almost all imperial, but the taper attachment is all metric. Weird.

And the bearings, a lot of them were metric also.

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AD Design · May 19, 2020

Limy Sami said:
And IIRC 60's & 70's Volvos were mostly Unified threads and hexs.

I had several Volvo 122's and P1800's from the 60's and they used brake system components and some of the chassis running gear that was also used by Studebaker. Most of the fasteners throughout the vehicles were Unified threads and hex sizes.

Yan Wo · May 19, 2020

projectnut said:
[interesting comments deleted] Can you imagine the nightmare if you had 5 metric and 1 SAE fastener holding a component in place. If that happened it would be almost a given that the fasteners would get mixed up and there would be real problems on reassembly.

It happened! During that era, my neighbor complained that when he replaced his car's water pump it had a mixture of SAE and metric fasteners.

Brett W · May 19, 2020

MattiJ said:
And there is some other weirdos also in cars. Like seatbelt mounting bolts that are inch sized even in all the German cars. (Bolt size actually matches some weird metric size too..)

This is because DOT/NHTSA, etc mandated all vehicles sold in the US have the seat belts secured with 7/16-20 bolts. So any car legally sold in Amurica, had standard fasteners in the body. I have installed harnesses in many cars and everyone of them has had a 7/16-20 thread pitch in the body insert and the seat belt hardware. Even if it has metric heads its a standard thread pitch. Stupid bureaucrats.

gustafson · May 19, 2020

Brett W said:
This is because DOT/NHTSA, etc mandated all vehicles sold in the US have the seat belts secured with 7/16-20 bolts. So any car legally sold in Amurica, had standard fasteners in the body. I have installed harnesses in many cars and everyone of them has had a 7/16-20 thread pitch in the body insert and the seat belt hardware. Even if it has metric heads its a standard thread pitch. Stupid bureaucrats.

If there were a problem with that size bolt WRT seatbelts, I would agree, stupid bureaucrats, but there does not appear to be a problem.

I mean, stupid bureaucrats dealing with every pissant ferrin company wanting a different size bolt for their seatbelts?

Stupid bureaucrats allowing Yugos to have 6mm bolts for seatbelts?

There is a whole bunch of ways to be stupid, and this is one of the least offensive ones

At least in 1972

I don't know if they still require it, and if so, doesn't seem to hurt the imports much.........

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Are European metric screws a different dimension?????

Laverda

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Rob F.

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Laverda

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Rob F.

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dian

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AndySomogyi

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Limy Sami

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MattiJ

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projectnut

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gustafson

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L Vanice

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Screwmachine

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AndySomogyi

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AD Design

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Yan Wo

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Brett W

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gustafson

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