beth Posted February 16, 2012 Share Posted February 16, 2012 my friend wants me to straighten these bike pedals , they are cast, and i really cant understand how they could have been bent like they apparently have, he assures me they should and would have been straight, and i just wondered if it was ok to heat and try to persuade them back to straight - im happy to try but worried that the casting with crack? Quote Link to comment Share on other sites More sharing options...
MattBower Posted February 16, 2012 Share Posted February 16, 2012 Are you certain they're cast steel, not cast iron? Quote Link to comment Share on other sites More sharing options...
beth Posted February 16, 2012 Author Share Posted February 16, 2012 no matt, but they are quite pale colored although maybe they are coated... i will check with my friend... Quote Link to comment Share on other sites More sharing options...
Dodge Posted February 16, 2012 Share Posted February 16, 2012 If they are for a motorcycle, I'm betting they are cast steel. I used to heat bend, weld, torch cut, etc gear shift levers and such all the time on old Hondas Quote Link to comment Share on other sites More sharing options...
beth Posted February 16, 2012 Author Share Posted February 16, 2012 yeah its for a 50's BSA dodge - i think its steel but i was just presuming, i dont know that... i always thought cast metal of any type was not so malleable but am i just making that up? thanks dodge i will bend away at em then with your blessing :) Quote Link to comment Share on other sites More sharing options...
pkrankow Posted February 16, 2012 Share Posted February 16, 2012 Those look like drop forgings, which means they will be good steel to work with. I say this because of the wide parting line, and the application. Phil Quote Link to comment Share on other sites More sharing options...
beth Posted February 16, 2012 Author Share Posted February 16, 2012 which explains how someone bent them originally then. ? what is drop forging - im not sure i understand what that is.. thanks phil.. Quote Link to comment Share on other sites More sharing options...
bigfootnampa Posted February 16, 2012 Share Posted February 16, 2012 If they can be cold bent without breaking then hot bending back ought to be a cinch, though heat treat might be a concern. I'd try to keep the heat localized and avoid heating the machined area. Drop forging is done with a giant hammer (weight) that drops onto the hot metal and forces it into dies that are more like molds (similar to using top and bottom tools when hand forging). Sometimes the parts are completely formed with a single strike but larger and more complex parts might take more hits and sometimes also require multiple stage dies. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 16, 2012 Share Posted February 16, 2012 I'd bet on drop forging too, which means there were hot forged to shape to start with and so should be able to be hot forged back into shape. Quote Link to comment Share on other sites More sharing options...
beth Posted February 16, 2012 Author Share Posted February 16, 2012 great. :0 so how can you tell - phil said the wide parting line, i have seen this before on things, is this always the case? thanks for the information, i might as well know while im here :) Quote Link to comment Share on other sites More sharing options...
MattBower Posted February 16, 2012 Share Posted February 16, 2012 I would have guessed from the texture that they were sand castings, but I defer to you guys on this. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted February 16, 2012 Share Posted February 16, 2012 great. :0 so how can you tell - phil said the wide parting line, i have seen this before on things, is this always the case? thanks for the information, i might as well know while im here The wide parting line is a clue, it typically means that a portion of excess material was cut away, this material is called "flash" and is excess material that gets squeezed out of the die cavity. This is usually hot-sheared off in the next operation using a punch press. Drop forgings have favorable material properties for high stress applications. The forces of forging will prevent some types of defects, and the material that is used to start with will be defect free piece of bar stock. Castings often have a thin parting line meeting at a point or edge. Casting does not normally produce much flash, and thick flash is an indication that something may have gone wrong in the process causing the top of the mold (cope) to float on the bottom (drag). Castings will also have small areas that are machined (or broken) for the sprue (where the metal was poured in) and risers (where extra metal was collected to feed the part as it shrinks in cooling) instead of a rim that goes much of the way around the part. Castings are subject to material defects such as porosity and inclusions from mold material that may break away (typical with sand casting) This makes casting less suitable for thin highly stressed parts. Phil Quote Link to comment Share on other sites More sharing options...
dan_m Posted February 16, 2012 Share Posted February 16, 2012 I would have guessed from the texture that they were sand castings, but I defer to you guys on this. I thought they looked sand cast as well...and there is definitely some pitting on the top one. From the way you look at it in the picture, it's just to the left of the splined section, along the bottom of the bar. My guess would have been that it was porosity from the casting, but if they got rusty at one point it could have been from that too. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted February 16, 2012 Share Posted February 16, 2012 I would have guessed from the texture that they were sand castings, but I defer to you guys on this. I thought they looked sand cast as well...and there is definitely some pitting on the top one. From the way you look at it in the picture, it's just to the left of the splined section, along the bottom of the bar. My guess would have been that it was porosity from the casting, but if they got rusty at one point it could have been from that too. That fine texture is from scale that formed after the forging process while the part was still very hot. The part was probably pickled after it was cool, and was likely allowed to cool in an open air bin. You will also notice that the texture is in the sheared area of the parting line as well as on the surface of the part. Phil Quote Link to comment Share on other sites More sharing options...
beth Posted February 16, 2012 Author Share Posted February 16, 2012 thankyou phil i have made cast things before, and i mistook that line as badly finished casting. it does look rather pourous, but that wide parting line is very noticeable, so i guess its what you say, drop forged. Quote Link to comment Share on other sites More sharing options...
dan_m Posted February 16, 2012 Share Posted February 16, 2012 Thanks Phil, I didn't notice the texture was continuous across the parting line. Quote Link to comment Share on other sites More sharing options...
SmoothBore Posted February 16, 2012 Share Posted February 16, 2012 There are a variety of Iron based materials that can be cast, ( Cast Iron, Ductile Iron and Maleable Iron, to name a few ) that have very different properties. The parts pictured are NOT Cast Iron, ... and are most likely Forged Steel. The above explaination about the wide "parting line" is completely correct. In a Sand Casting the parting line will be very narrow, because the surplus metal flows into a "riser" or into "overflow vents" in the mold.( Vents are necessary, to let the air OUT of a mold, as it is being poured, ... and the "riser" acts a a resevoir of molten metal, that is sucked back into the part as it cools, and shrinks. This helps prevent "pourosity" in the casting. ) While on a part that's "Drop Forged" the air, and surplus metal flows out through the wider parting line,( The "slug" that is used to make the Drop Forged part, is intentionally oversized, to insure enough material to completely fill the die. ) The wide parting line in the "Die" is located in such a way, that the "Flash" that flows out that gap, insures that the extremities of the Die are filled. But getting back to the pictured parts ..... The female splines inside the bore, where the Pedals mount, would quickly wear out, and fail, in a Cast Iron part. In the 1950's a Steel Forging would have been the most practicle and durable means of making those parts.Today, I suspect a "Powdered Metal" process would be employed. . Quote Link to comment Share on other sites More sharing options...
MLMartin Posted February 16, 2012 Share Posted February 16, 2012 Its nice to read good comments from smart folks. I have known about drop forging and casting, but good explanations on how to know one from the other at a glance are well worth hearing about. Thanks Quote Link to comment Share on other sites More sharing options...
forger Posted February 16, 2012 Share Posted February 16, 2012 Hi, Here are a couple of photos of a drop forged brick hammer from before it was sheared out of the forging. It helps by showing the flashing. I just use this for a wall hanging. Mike Quote Link to comment Share on other sites More sharing options...
Rich Hale Posted February 16, 2012 Share Posted February 16, 2012 I have an entirely differnt view than most of the world.....I see these as one of two things,,useable or not. If they are not then there is nothing you can do to them that will change that in a bad way. If they are usable and the owner wants them to look new, I would try and bend. I have bent pedals on dirt bikes cold and hot, they all worked fine. I would expectg these to do the same..just so the owner knows that something couild go wrong in the process. My guess is that there is not a ready supply of replacements for these. Quote Link to comment Share on other sites More sharing options...
ptree Posted February 18, 2012 Share Posted February 18, 2012 Having worked in the drop forged industry for 21 years, I would say drop forged. As Phil notes the wide trim line is a strong indication these are forged. The texture is probably from shot blasted after cooling. This shot blasting uses steel balls to remove the scale and if done correctly also shot peens the surface, reducing surface stress that can lead to cracks later. Beth, in England drop forging is usally called die stamping I believe. As phil notes the drop forge process is used for highly stressed parts that need minimum part size. All steel starts as a casting in the beginning. It will have all the defects that casting typically have. This huge casting usually has the end cropped off to remove the worst of the defects and is then hot rolled, at full forge(Weld) temp, and the more reductions under the rolls the sounder the steel. The hot drop forging process is the last chance to close up and weld solid any internal defects. Rolled steel also has a grain structure that is somewhat like wood fiber. It runs the lenght of the bar, unlike cast which has totally random grain, much like packed sand. Thus in drop forging you can plan the grain flow to get the grain to flow around corners making the part stronger than the same size/alloy cast part. Now a relatively new process is continous cast bar. This is a casting that is made to near finished bar, and is usually "Rotary forged" to remove the "Pipe" shrinkage down the center of the bar. I have seen continous cast stainless bar that was machined into a valve stem that would leak steeam right up the center of the stem (We had to scrap 100,000# of steel as un-usable. The rotary forging process has hammers in a ring around the slowely moving hot bar as it comes from the continous caster. We had to specify no continous cast for our machine only stock. The state of the art may now be better. For those not used to drop forges, you always put more steel in the billet than can fit in the impressions in the dies. This ensure a complete fill out of the forging. This excess is extruded out over the "Gutters" which make a controlled this section at the trim line and also help control how close the dies come together as the steel cools at the gutters more quickly and slows down the dies. From the forge the forging is placed into a trim die and pushed thru by a press, somewhat like a punch press, but usually with more stroke. Some trim die will have several openings, the first to trim out an internal hole then pushed thru the outside trim to clear that flash. The giveaway between a casting mold line and a forge trim line is the direction of the marks. A casting will have been ground with a big snag grinder and the grind marks will not all be in the same direction. Forge trim lines will run perpendicular to the raised trim band. I would also guess that straightening these should be a hot process, and should be fine. Quote Link to comment Share on other sites More sharing options...
beth Posted February 18, 2012 Author Share Posted February 18, 2012 thanks ptree - thats very interesting, and now you come to mention i did have some conception of die stamping, i may have heard that term used. its useful to know extra indicators like directions of marks at the line, you are clearly a man to ask about this subject !!! thanks for the detailed explanation :-) forger i LOVE the hammer wall decoration - that looks wicked! would love to have one of those :) Quote Link to comment Share on other sites More sharing options...
John B Posted February 18, 2012 Share Posted February 18, 2012 Hi Beth, You have had the answers ref how they were made, A couple of other questions. Now, is the pedal part bent, or is the arm twisted? They should go back cold, heating them could make them more susceptible to the same thing happening again What type of bike are they off? They look more like kick start forgings (or gear change levers)than bicycle type pedals, Most bike pedals had cone bearings on the pedal axle and either screwed into the arm, or were machined to fit bearings/pedal assembly. The splines also indicate positioning at different settings, and again bike pedals normally were attached through the frame to a plain diameter axle with flats on at opposing sides and they were held in place using tapered a cotter pin, washer and nut to secure each arm to the shaft. Anyway, with or without heat, have fun. Quote Link to comment Share on other sites More sharing options...
beth Posted February 19, 2012 Author Share Posted February 19, 2012 sorry john that took me ages - couldnt find them! yes looks like they are twisted to me, both have splines till half way through inside them, no flats, although its peculier cos i cant work out how they go on, or why they would have been twisted, youd have thought because someone wanted to raise the end so that they did not hit the ground when cornering? but they are worn in different places when held at the same angle...?? anyway i will def try to heat them now i know they are almost certainly drop forged. hey how did the course go? am frustrated to miss it! .... Quote Link to comment Share on other sites More sharing options...
John B Posted February 19, 2012 Share Posted February 19, 2012 Hi Beth, Course went well, we were stuck at it until turned 7 tonight, 3 out of the 5 completed a hanging basket bracket, plus a hole punch for the fixing holes and rivets, and a square punch for the tenon. They were probably damaged by decking the whatever they came from, which would twist them As to location I would guess they were lined up and the ends of the shafts they were on had a large washer and retaining mechanism of some sort. to stop them sliding off. Quote Link to comment Share on other sites More sharing options...
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