Bikes & Tools  

 REAMERS AND THREAD CUTTERS FOR STEEL FRAMES

  The international standardization organization ISO is charged with coordination of agreements about industrial standards; one being the threads used in bicycle frames. The European norm for racing bikes is EN 14781. In the ISO standard for the bicycle industry, the British Standard Cycle thread (BSC) is still leading. In Germany this thread is called Fahrrad Gewinde (FG) and  in the Netherlands NEN ; it is all identical to the English standard BSC. The French have stuck to their own metric system of measurement for years. We sometimes come across them in old Spanish, Swiss and Walloon bicycles. The bicycle manufacturers in China work for the global market; even in France we only see English sizes for new bicycles. So now we still work with measurements and measurements in inches (1inch = 25.4mm). The parts that we use to turn a frame into a bicycle also have these threads.

    The most important data of a screw thread are: the diameter of the external thread D and the pitch P; further the diameter of the inner thread d, and the apex angle ɑ; this last value is usually 60°, but in the old English Whitworth (WW) standard and in the Italian bicycle threads (F) 55°. The pitch P in the metric screw thread is the number of mm's that the nut or bolt moves per revolution. In an English standard thread size, this is indicated in TPI (turns pro inch). The number of revolutions it takes to travel one inch. So the size 24 TPI is similar to our 1mm pitch, but actually 1,058mm.

     Another strange phenomenon of English sizes can be seen when displaying spoke thickness. That is done in Standard Wire Gauge (SWG): no.12 is 2.64mm and no.13 = 2.34mm, no.14= 2.03mm and no.15=1.83mm. The thinner the spoke, the higher the number. The steps between the numbers are not linear, but more or less exponential and are increased incrementally in groups; you cannot calculate them. The thread is very shallow + or - 0.25mm. The top angle in the thread is 60° and the thread always has 56 TPI from no. 12 to 15. This is a pitch of about 0.45mm; so every time the nipple tensioner goes around, the nipple moves 0.45mm. When there is tension on the spoke, this is no longer the case: the hub flange deforms, the spoke stretches, and the nipple and rim also deform; only the last piece moves 0.45mm.

   In the dimensions of Italian standard thread F we often see strange mixes of metric and English sizes, such as 36x24F (=36mm x24TPI). The outer and inner dimensions are indicated in mm and the pitch in TPI; the apex angle is 55°. Mounting a headset with Italian thread on a Reynolds front fork can therefore cause minor damage due to the poor fit; usually no problem arises. Only the aluminum thread on an old rear hub can cause damage due to frequent changing of gear blocks with Italian and English threads. Officially, the English size is 1,370"x 24TPI and the Italian size is M35x 24TPI. Of course, the French have their own thread: M34.7x 1. You can screw a non-French freewheel onto it, but you are guaranteed to ruin the thread!

   We often see numbers in inch fractions in the sizes of English bolts and nuts, an example: 9/16"x20 BSC; in Germany they talk about FG 14.3; the outer diameter of this thread is 14.288mm (the pitch is 1.270 mm). We find this thread on pedals. Metric threads are represented by: an M, a millimeter measurement for the outer diameter, and the pitch in mm 's. M14x 1.25 is a French thread for pedals. For the French crank, the hole is slightly smaller, so it can be tapped with an English thread. Do not mount pedals with a French thread in 9/16" BSC; this leads to loosening of the pedals and destruction of the threads.

   The thread of pedals is the same as the direction of rotation of the balls in the bearing; therefore the left is a left thread and the right is a right thread; this prevents the pedals from loosening. From England the meaning of the R and L on the pedal will be clear. In France D is right and G is left, in Italy D is right and S is left, and in Spain D is right and I is left (just in case you come across Zeus pedals). Just paying close attention is also sufficient. In children's bicycles and in Fauber (one-piece) cranksets, there is usually 1/2" x 20TPI thread.

    Many BSC threads are made in 24 or 26 TPI, even in large sizes. This is because, in addition to mounting, the bearings of axles, headsets and bottom brackets are also adjusted via the thread. The size 1 1/8"x26 BSC, for example, is a thread for the headset of tandems and oversize mountain bikes. Usually the headset is 1"x24 BSC, but in old English bicycles 1"x26 BSC is also found; in children's bicycles sometimes 7/2" 8" x 24TPI. French headsets are made in M25x1, sometimes M28x1 for tandems; M23x1 is found in children's bicycles.

    The thread in the derailleur hanger is usually M10 x 1; Simplex had a derailleur hanger with a 9mm hole but without any thread (this is easy to tap with M10 x 1); the thread of the adjusting screw of the rear drop-out is M3 x 0.5; except for Huret, who had M3 x 0.6. The bottle holder cage thread is M5 x 0.8; mudguard fender mountings usually are M5 x 0.8 too, but sometimes M6 x 1. The thread used for a traditional Campagnolo down-tube gear lever mounting is M5 x 0.8.

   The standard for bottom brackets is 1,370" x 24 BSC; in old bicycles we sometimes have a 1 3/8" x 24TPI (almost identical), but in old Raleighs or old Humbers 1 3/8" x 26TPI can also occur, with Raleigh sometimes even until the early 1970s. Older bicycles with parts from BSA, Chater Lea, Haden, etc., also use these English sizes.

    The threads of bottom bracket bearing cups are provided with left-handed and right-handed threads in English cups. The French and Italian bottom brackets only have right-handed threads, and must be mounted very tightly on the drive side, to prevent unwanted accidental loosening. In French frames the thread is M35 x 1; if the drive side is equipped with a left-handed thread of M35 x 1, we are talking about a "Swiss" standard thread. In the absence of right parts, these threads are often re-tapped in the English size (a useful remedy). The Italian size designation is 36 x 24F (= 36mm x 24TPI), with right-handed thread only. If an English or French thread is damaged too far, it can be removed with a reamer and cut again with an Italian tap.

Cyclus  and Parktool supply dozens of wrenches with modern sizes for modern frames, which are unfortunately necessary for today's variations in dimensions for the bottom brackets and headsets; for Cyclus see FIG.3 and 4 .

Parktool for headsets : https://www.parktool.com/blog/repair-help/standardized-headset-identification-system 

Parktool for brackets: https://www.parktool.com/blog/repair-help/bottom-bracket-identification    More about brackets:  https://wheelsmfg.com/bb-standards  

FIG. 3 Cyclus fitting tools for brackets.                                                                                           FIG.4 Cyclus reamers and cutters, for modern head sets. 

BALL BEARINGS

      The purpose of bearings is to support rotating shafts. These bearing axes can be used either "axial" (in the longitudinal direction of the axis) or "radial" (perpendicular to the axis). There are 2 groups of bearings: plain bearings and rolling bearings; In bicycles we mostly work with rolling bearings. We often encounter variants of the ball bearing in headsets; sometimes there are needles or rollers instead of balls. The old-fashioned adjustable "cup and cone" construction of bicycle bearings (actually a single-row angular contact bearing) has largely been replaced by the use of groove ball bearings, mounted inside a sealed unit. These are not adjustable and that means that they must be replaced when worn (usually as an entire unit). For the cartridge bearing unit, the installation time in the factories is shorter, and easy to automate (the most important advantages, at least economically).

     See the NSK guide to the common types of bearing that are available -- but be aware that bicycles sometimes use unique non-standard bearings, that are not generally available.

      In FIG.5 we see that the groove ball bearing can take forces from all directions; which is not the case with the other two.

The choice for groove ball bearings is cost savings; installation and replacement is easier and takes less time, but it requires a slightly different way of working and different tools. In general, we use a slight interference fit to secure each bearing unit in position, installation is done by applying pressure to the inner and/or outer ring of the bearing via an auxiliary bushing. Applying that pressure can be done via a press (FIG.7) or a hammer, for example from the SKF hammer tool-set (FIG.6); This hollow plastic hammer contains loose grains. This gives a pleasant, recoil-free, and controllable tap. 

     The pressure-plates shown in FIG.8 and FIG.9, show that the force applied to a bearing must be on the ring which is subjected to friction during pressing. The pressure should not be exerted to the other ring, to prevent the pressure being transmitted via the balls, which might cause damage to the bearing unit. Unfortunately, the designers of hubs, for example, are not always concerned with maintenance problems. In any case, when disassembling (tapping out), the bearings must be properly checked and replaced if necessary (noting the cause of any damage to the bearing -- such as a damaged seal-disc).

    The fit of the bearing to the axle (on the inside), and into the housing (on the outside), must be a slight interference fit. Depending on the diameter, of the order of thousandths or hundredths of a millimetre.  If a bearing does not fit properly, particularly if it is loose, it can cause damage, or be dangerous, an example of this is if a headset bearing is loose, the steering may be unpredictable and dangerous, which is another reason to check that the correct bearings have been fitted in the correct way (including in the correct orientation).

     In industrial applications, interference fits can be graded and classified, but this is not the case in the bicycle industry, where standards are much more casual and random.

For ISO industrial standards see the NTN guide (2203E) to the fitting tolerances of bearings (Limits and Fits tables).

    The most important dimensions of the bearing are outer ring size, inner ring size, and bearing width. The quality of the materials used, and therefore life expectancy, cannot always be properly estimated. Big names (such as SKF) provide more certainty, but there are different quality classes; Unfortunately, the prices of the better classes of bearings are significantly higher. The highest class available is something for space technology, (where sending a mechanic is not an option); the price is often corresponding.

Some more detailed information from one of the major bearing suppliers (particularly for cars)  https://medias.schaeffler.co.uk/en/bearing-data

 A good way to check the dimensions of a bearing, is to use a digital vernier caliper measuring instrument, from a reputable manufacturer.

THE TORQUE WRENCH

     Until 1990, most bicycles were made of steel. The mechanic simply secured all the bolts and bolts sufficiently. This practice is outdated with modern carbon and aluminum frames. To mount parts safely and damage-free, you must work with a torque wrench.

    The moment we use to secure a bolt depends on the length of the lever and the force we exert. Moment is: force x arm. So if we have a longer key, we need to apply less force for the same moment. If you don't have a torque wrench, but you do have a handheld weighing scale to determine the weight of the suitcase at the airport, you can actually also measure the torque. Suppose you have to tighten a bolt with 10 Nm; you have a ring wrench of 20 cm. Then you have to put on your handheld weighing scale up to 50N (= 5kg) to get 50N x 0.2m = 10Nm.

     There are several types of torque wrenches. The lever type (torsion arm, see FIG.1a) is the simplest. In fact, the arm bends over the entire length when a force is applied. Unfortunately, these types of torque wrenches can be difficult to read, and require a lot of space when used; which is often just not there. During normal use, this sort of meter remains accurate, and we can use it to calibrate other torque wrenches. The one shown here is suitable for up to 300Nm; We don't encounter that high a torque level in bicycles. With modern carbon and aluminum bicycles, the torques used for small bolts are between 4-10Nm. Cranksets may sometimes have 50-70Nm. Please note whether the parts manufacturer recommends using grease or a retaining liquid. Prescribed torques are often given as "dry". If you use grease or a locking fluid, tightening is easier, and there is too high a tension on the bolt.

FIG.2  The "click" torque wrench. By tightening the spring in the handle, we set a value that produces a "click" sound when it reaches the preset value.

     Most “click type” torque wrenches, as we can see in FIG.2. Over time, these keys may differ slightly from the set value to be read. The cause of that decline lies in the construction of the torque wrench. The tool works with a spring that is tensioned, via the screw handle with vernier. That spring presses on a ball, that fits into a hole, in the movable head of the key. In the photo we see the rotating shaft with retaining ring under the head. When the ball shoots out of the hole, you hear a "click". We then have to stop energizing immediately, because the connection is not broken, so we could just tighten the bolt further. The small torque wrench has a 1/4" head, and can be set up to a maximum of 25 Nm. The large torque wrench has a 1/2" head, and can be set up to a maximum of 200 Nm. Using an adaptor, we can also provide both heads with a 3/8" head, depending on the socket set used. Obviously a 1/4" head is weaker than a 1/2" head, and can only withstand smaller torque levels. While a small tool may be useful to fit into a small space, for safe operation it is better not to overload a tool, especially a calibrated torque wrench.

     The spring in the handle is intended to keep a little pressure. If the pressure disappears, parts of the mechanism can become loose or defective. So it is better not to turn the spring all the way back to zero, but keep the tool with, for example, 10% of the maximum torque value as a setting. When first put into use, it is recommended to extend to the maximum torque setting a number of times (>5), to push away any burrs or dirt inside the tool. Then the tool is worn-in.

     If the torque wrench tools are frequently used, it is recommended to check their accuracy every month, by comparing them with a torsion arm torque wrench, or electronic torque wrench. This way you can prevent the tightening torques from slowly becoming lower and lower, and being inaccurate.

The designer prescribes a certain tightening torque. This depends on the construction, and the materials used; it is always lower than the maximum possible torque for that bolt, there must be a safety margin, such as to take account for possible corrosion.

The head of a bolt sometimes indicates the steel quality used with an ISO code, for example "8.8" or "12.9". The number ahead of the decimal point is 1% of the tensile strength, in N/mm². The number behind the decimal point is ten times the yield stress/tensile strength. It is recommended to use the manufacturer's supplied bolt; if you replace a bolt, it must have at least the same quality class as the original part. Once a bolt is rotated over the yield stress limit, turning becomes easier and easier, until complete fracture occurs.

Because the failure of a bolt could result in a crash, it is vital that bolts are not over-tightened and damaged, if there is any doubt -- inspect the parts, if you are not sure about the safety of a part, then it is wiser to replace it if possible. Remember that professional riders have their bicycles inspected, checked and serviced after any crash, modern racing bicycles are often made with lightweight parts, which frequently only have a limited service life, there is always a trade-off between lightweight and reliability, fragile components must be treated with respect, they are not designed to last forever.

Clamping carbon seat posts and steering parts is difficult, because the part will sometimes still move after the maximum tightening torque has already been reached. It is recommended that the item be removed, and that a carbon mounting paste be used between the parts, to increase the friction between them -- the opposite effect to a lubricant. This type of friction-paste contains a fine abrasive that improves grip, without damaging the parts. For example: https://tacx.com/nl/product/carbon-montagepasta/ 

TOOLS FOR BICYCLE WHEELS

       The wheel truing jig, the nipple tensioner key, and the wheel hub aligner dishing stick, form the tools for the wheel builder. The nipple tensioner is the cheapest part, but don't try to save money on it. If the steel of the tool is not hard enough, the nipples can be damaged and deformed -- which can make truing a wheel very difficult. The 'Spokey' model of nipple key is cheap, and usable for up to No.14 size nipples. The hub aligner dishing stick is the least critical tool; I am very satisfied with my low price Minoura tool.

      I used cheap wheel truing jigs for many years (see FIG.1). I then treated myself to a second-hand VAR 'Preciray' (see FIG.2 and https://www.youtube.com/watch?v=H7b2ZXAZwVw&t=102s ; perhaps I should have used such a tool earlier. Nowadays there are even nicer ones, for example 'P&K Lie'; beautiful but very pricey: https://www.wheelfanatyk.com/blog/category/pk-lie-truing-stand/   (see FIG.3b)

      Via Wheels2build you can also order tools, including a Chinese model, (inspired by the P&K Lie wheel truing jig), for more than 200 Euros (FIG.3a), also found at AliExpress.

      For wheel building nowadays you also need a spoke tension meter. An affordable and widely used one is the Park-Tool 'TM-1'. The operation of this gauge (FIG.4) is as follows: The device contains a spring with a certain bias tension. You keep the spoke located in two places (at the bottom of the dotted line) and release the spring. The spring presses the third contact point in the middle -- between the two pegs, (FIG.6) outward over the height h max. 5mm -- usually the effective measuring area, (spoke tensions between 500N and 1500N, are limited to approximately 2mm). The meter will move over part of the scale at the top of the tool (the scale is divided into 50 tenths of a mm).  The designated number reading from the scale is then compared with a table (FIG.5), in which the spoke thickness and shape are incorporated.

In fact, the accuracy of this type of meter is very limited. To improve this slightly, I read the measured values at 0.5 (estimate). I then average the numbers on the conversion table of (FIG.5).

The resistance of the spring should not be too great (e.g. 10-20N), so as not to affect the result of the measurement too much.

       There are manufacturers that offer much more accurate spoke tension meters, like DT-Swiss; in FIG.8 and FIG.9 we see two models, an analog FIG.8 (approximately €500) and a digital meter FIG.9 (approximately €1000). At these prices these tools are something for top racing mechanics, professional wheel builders, and wheel manufacturers. The measured values of the digital DT device can be processed directly into the computer (via a USB cable). Hozan FIG.10 (about €480) also provides such meters. AliExpress and Ebay also have many copies of these meters for sale, for a fraction of this money. My DT copy (FIG.9a) was beautifully finished, with a digital dial indicator, and was delivered to my home for only €50 (1/20 of the cost of a DT digital meter). But the supplied measured value table is a joke!

     Fatal mistake! Such a Chinese copy is not a bargain! You don't just buy a thing, but a whole measuring system.  Quality has a price, see the tables from DT:  http://www.dtswiss.com/Products/Proline.aspx 

       This picture  (FIG.10b) is a home constructed spoke tension meter, with Bluetooth connection. When you use an associated Excel file on the computer (see FIG.10c), the light orange fields can be filled in by the user; you register the spoke tension meter as a Bluetooth keyboard. At the touch of a button (at the top right of the meter's display), the measured value (mm) is entered into the Excel file, and is automatically converted into Newtons. The data from the spoke tension meter appears in a table, (where you enter separately, first side A, and then side B). These values are also shown in a radar graph.

       I had already written an Excel file for the Parktool 'TM-1' spoke tension meter as an exercise. You can see what that looks like in the picture below. This is not a real wheel, but an example of how a 28 spoke wheel, with No.13 spoke is displayed on the computer. A printout can be included as a quality inspection with a new spoked wheel. A new wheel, with good quality parts, must be able to be made within limits of + or - 10% of the average spoke tension (minimum 90% tension, and maximum 110% tension).

      Making those Excel files for different spoke thicknesses, butted spokes, and various numbers of spokes per wheel, is a lot of work; and it is especially boring! If a dozen ascending values for a type of spoke are known, I determine a calculation formula in Excel with curve fitting, to translate the measured mms into Newtons (or, if necessary, old-fashioned kilogram force).

      If you work with the Parktool 'TM-1' spoke tension meter, it is better to use the online WTA app; it has some extra options.

        The stocks of spokes available have continued to decline; everything has a long delivery time, and is only available in larger order numbers. It is becoming increasingly difficult to get a different spoke size. Professional spoke thread rolling machines, such as Cyclus, cost approximately 3000-4000 Euros. Morizumi is a Japanese variant, and certainly just as expensive; the American manufacturer Phil Wood makes one, which is even more expensive. The cutting plates of Phil Wood, Morizumi, and Cyclus, probably last 50,000 to 100,000 spokes; replacement cutting plates for the Morizumi machine cost around €250, Phil Wood's around €500, and Cyclus €1200. These expensive machines do provide a nice constant thread length and constant thread depth, unlike my cheap Hozan machine (FIG.11), which does not produce consistently good results, unfortunately.

       Hozan now has an electric machine in production, see FIG.13 (approximately €900) with an improved head (type 'C-706'; €70 via Ebay); it also fits the roller 'C-700' of FIG.11. Anyway, the quality of the thread is determined by the roller head, which is only mediocre. The roller of FIG.11 has a really lousy bearing, and the spoke clamp is bizarrely annoying. It has now been replaced by a home-built one, with a suspension clamp that is "open" as standard, but still with the 'C-706' roller head. Also Hozan has a new roller with an improved clamp 'C-702' (€170 via E-bay).  I am making a roller based on the Morizumi cutting plates; unfortunately it is difficult to achieve the fine tolerances needed to get a nice even rolled thread.

       The pliers (at the bottom right of the picture) make a "Z" bend in the end of the spoke, in place of the enlarged head on a J-bend spoke. Using this tool we can create a spoke to length, by first cutting off the head, and using the "Z" bend of the bayonet as a new end of the spoke. An advantage is that this type of spoke can be mounted without removing the gear cassette. We can even leave the wheel in the frame; usually these are emergency solutions for a spoke breakage on the road. It is also a cheap and fast way to make old bicycles usable again. But one should not expect this to be a good quality solution for shortening spokes, where rolling a new thread is a far better thing to do (with the right equipment).

        When building wheels, it is recommended to lubricate the nipples with a drop of linseed oil. There are also special products available (such as 'SpokePrep' or 'SpokeFreeze'). Use of these products is necessary to prevent the nipples from loosening, especially at spoke tensions above 1000N. Factory wheels often contain nipples with a hexagon on top, to reduce that vulnerability. Usually such nipples are used on wheels made using robot machines. There are also nipples that are pre-processed with internal micro capsules of glue, to fix the spoke in place and stop it from moving. There are several different methods of locking a nipple in place, volume wheel makers seek out cheap solutions, that can be used easily on a fast production line, with robots.

A section about wheel making robots can be found at the end of page 17: Wheels & spokes.