Screw threads: British vs. American

This will likely be of interest to owners of British-built Vandercooks: Chip Coakley (the Jericho Press) emailed me with the serial number on his No. 4 made by Pre-Press Ltd. and to let me know that its original brass bearing blocks had British Standard Whitworth interior threads. When he bought replacement blocks from NA Graphics, he found that he had to make a supplementary order for the bolts and screws. Does this means that BSW screws were used on the other Vandercooks built under license: Pre-Press Ltd. (formerly Western Mfg.), Hunter-Penrose Ltd. and FAG Equipment Ltd?

BSW screws, used for British machinery from the 1850s into the 1970s¹, have a thread form with a 55° angle and a rounded crest. Chicago-built Vandercooks used the American Standard² thread with a 60° angle and a flattened crest. Even though the pitch (threads per inch) may be the same, if the the angle between interior threads on a block and exterior ones on a screw don’t align then either the screw wont advance or becomes stripped if forced.

I have yet to see a British-built Vandercook or an operator’s manual, so here are my questions:

  • Do these presses use BSW screws on some assemblies and American screws on others?
  • Since FAG Ltd., was a subsidiary of the Swiss firm, did their Vandercooks have metric screws?
  • Is it difficult to find common American screws in the UK, continental Europe, or Down Under?

 

¹ During WWII the British embraced the American Standard thread, but the transition took many years, and before industry could comply, the European Common Market adopted the metric system. Parliament urged metrication in the mid 1960s, prior to joining the EU in 1973.

² American Standard threads, now regulated under the Unified Thread Standard (UTS), are divided into two main categories National Coarse (NC) and National Fine (NF), which refers to the size of the threads relative to the screw diameter, not threads per inch. A screw or bolt is specified by diameter, pitch and length. For example, the set screw on the Vandercook hand crank is ½-13 NC x ½ and the lock screw on an SP15 form roller bearing block is 8-32 NF x ¾. Often the category is omitted in the spec.

 

 

Screw threads: British vs. American

10 thoughts on “Screw threads: British vs. American

  • May 11, 2011 at 2:27 am
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    Eric- I’m not sure as I was in a rush to get the press disassembled and reassembled before i had to catch a train home. But I will look closer next time and take some photos. There were some other difference too (roller frame width) that I need to pay attention to in order to figure out whats going on.

    Paul – I didn’t get the serial numbers this trip, but next time i will. I also have a number four in ireland, a fag, seroglia, and western in italy, and a few more vandercooks in the UK, including a HUGE 232P. I’ll get the numbers together when I get a moment to breathe.

  • May 9, 2011 at 2:53 pm
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    Alex, you can tell which type of thread by shape; US National Standard threads are flat at the crest, and Whitworth threads are rounded at the crest and root. My reference mentions that because of that shape, a different tool is needed to cut each pitch, where a single tool can turn multiple NS threads on a lathe.

  • May 8, 2011 at 9:57 pm
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    Thanks Alex. Did you happen to write down the serial numbers? These presses are not in the census.

  • May 8, 2011 at 2:40 pm
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    I looked at two inking assemblies from #4’s at St.Bride this weekend. One was from an american made Vandercook #4 and one was from an English made Western #4. The main roller adjustment screws were interchangeable by hand, so I assume they are threaded the same. The retaining pin from the clutch mechanism (the pin that attaches the clutch disc to the clutch piston pin) was threaded differently – both had the same thread count and diameter, but were not interchangeable and the threads were visibly different.

    Not conclusive, but I hope that helps. I’ll keep paying attention as I see more.
    -Alex

  • May 7, 2011 at 2:44 am
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    I had a long search for 1/2 12 bolts for guillotine blades – the blades are quite expensive and the bolts are hard to find. I finally found some in a scrapped linotype.

    I’m going to St. Bride to look at one of their vandercooks. I don’t have a thread gauge, but I’ll see if there’s anything I can see.

    Happy derby day everyone – drink a mint julep! remember, the key is to muddlie the mint and sugar BEFORE you pour the bourbon in!

    -alex

  • May 6, 2011 at 11:51 am
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    Gerald is correct that many Vandercook screws are NF, but some are NC, such as gripper bar screws (NR-221) which are 5/16 -18 NC. (It’s the long fillister head and steel grade that makes them a specialty screw.)

    Steel, which has high tensile strength, can bear the shallow profile and greater threads per inch on NF screws to provide a very strong hold. Conversely, for cast iron, a weaker material, shallow interior threads can crumble, while the deep profile and fewer threads per inch on NC screws provide a wider bite into the body of the part for a better hold (just as coarse wood screws sink into wood).

    So, a rule of thumb is that NF are used to fasten steel parts and NC on cast parts.

  • May 4, 2011 at 11:33 pm
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    I have only encountered NF threads on Vandercooks. Whenever I have a problem with bolt or screw or nut I just convert NC or whatever threads to NF with tap or die and all is fine. Am I missing something here? First thing I recommend to anyone buying a Vandercook, after you buy the micrometer, get yourself a NF tap and die set. Or kill it with neglect and Crisco, etc. Whatever.

    Gerald
    http://BielerPress.blogspot.com

  • April 28, 2011 at 12:01 am
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    Actually, I’m non-standard. My info came from two important machinist’s sources, the “Audel’s” and “Machinery’s” handbooks.
    I never gave this any thought until I had to replace a 1/4-24 machine screw on a Linotype, and oddly enough, I had inherited a tap that NS size, and later found a matching die at McMaster-Carr. Then other seemingly odd Linotype threads sort of clicked into place, some of which, I think, fit the C&P.
    These old machines were designed before the S.A.E. standards introduced by the automotive industry, so we printers have to keep looking backward to stay ahead.

  • April 27, 2011 at 3:32 pm
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    There’s more to threads in US printing than NC and NF. There’s also NS (Special), and also some obsolete standards like 8, 12- and 16-pitch standards. Much letterpress equipment is 50, even over 100 years old, so on a C&P or a Linotype you may find such things as (12-pitch) 1/2-12 (rather than the NC 1/2-13 thread). For what it’s worth, 1/2-12 is also a Whitworth standard thread, the only one that doesn’t correspond to US standard threads.
    You may find some NS threads at the hardware store, but for others you’ll need to go to a supplier like MSC or McMaster-Carr.

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