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Posted on September 12, 2012:
Hello again everyone!! The next task at hand is to machine the timing lever. This part is made from a bronze casting (seen below) and is used on the engine to advance or retard the ignition timing as needed.
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First off I used my belt sander to remove the sprue and molding flash from the lever as usual. You could do this later although I find it easier as there are no finished surfaces to mess up if you should slip with the file ;0)
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I lightly mounted the lever in my three-jaw chuck while using the rear-end of a tool bit to “square” up the part as the lathe was slowly turning. I then tightened the chuck to lock in the alignment.
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The first machining operation was to bore a 9/32” hole in the center of the lever.
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I now followed the drill with a 5/16” chucking reamer...
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I mounted up an indexable carbide tool holder and machined the rear face of the handle in about .010” to square up the “rear” face to the bore.
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Now that I have a flat surface to align to I can reverse the handle and square it up to the chuck using a set of parallels as seen below. Once the chuck is tightened I can remove the parallels and start machining.
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I now faced the front side of the handle to achieve a thickness of about .188” from the back side of the pivot.
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The contact stud boss needs to be trimmed down at this point. I shaved down the boss to .438” from the front face of the handle...
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I moved the handle over to the milling vise and squared it to vertical. I then used the wiggler to locate the machined face of the handle (not shown). The table was then moved over .313” to locate the contact stud hole as seen below.
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Once again I used a #2 center drill to spot the hole. Note: In most cases (whether shown or not) I use a center drill to “spot” important locations as center drills have a larger solid shank compared to a common twist drill. This eliminates deflection of the bit and centers the hole more accurately than a twist drill which can “walk” to one side when drilling. The center drill is only used to make a small divot to center the appropriate drill size later on...
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And now for a 11/64” hole...
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I now followed the drill with a 3/16” chucking reamer. Note: The common speed used to ream with a chucking reamer is about half of what you drilled the hole with. Sometimes I may choose to ream even slower than that depending on the material being reamed. I usually stop the spindle once the reamer has passed through completely and then withdraw the reamer while stationary to prevent “spiral marks” in the bore...
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The last step is to spot face the hole with a 3/8” end mill. The prints call for 1/4” but “show” a 3/8” diameter on the drawing.
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I tossed the finished handle in the tumbler for a “polish” and another small part was finished :0)
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The next part to machine is the timing gear sleeve. This part is made from 3/8” steel rod which is provided in the materials kit
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I started out by boring a 9/32” hole 1” into the end of the rod...
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A 5/16” chucking reamer was now used to chase the hole.
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I now took the opportunity to sand and polish the outside of the sleeve while still connected to the rod...
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A parting tool was now used to cut off the polished sleeve at .710” from the end.
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I chamfered the ends of the sleeve (not shown) and another part is off the list!!!
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The next small part is the timing gear bushing. This is made from a factory made oil-lite bronze bushing which is included in the basic kit.
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The bushing only needs to be trimmed down on the lathe to a length of .700” for completion. Note: I used a 3/8” steel rod under the bushing so that the lathe’s chuck does not crush the fragile part while trimming it (seen below).
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I now tested the sleeve, bushing and handle on the timing gear shaft...
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The next part to machine is the big timing gear. This is a factory made 48 tooth gear that is included in the kit. These factory gears speed up the building process however machining my own gears would be a great learning experience. Maybe on the next machining project I can try my hand at cutting gears ;0)
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The first step is to bore out the hub with a 15/32” drill bit. You will notice that I am using a tool bit to steady the drill as it cuts the hole (seen below). This is done with just enough pressure to eliminate any wobble in the bit’s trajectory. Once the bit is tracking straight I retract the tool bit and continue drilling.
Note: It is important to position the drill so the flutes are horizontal so that the bit does not “climb” the tool bit and ruin the hole being drilled. The tool bit must also be positioned high enough to push on the side of the drill and not on the underside which will also cause the bit to climb. Lastly it is important that you use the back side of the tool bit as to not shatter the carbide side and ruin you tool bit :0P
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A boring bar was now used to finish off the hole at a diameter of .500”.
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I decided to use my “turning arbor” for the next series of operations. This will ensure that the cuts will be concentric with the bore of the gear.
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I started turning down the diameter of the hub for the insulating collar.
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I cut the hub to a diameter of .750” and faced the outer side of the hub flush with the existing side of the gear.
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I carefully mounted the gear in a set of “outside” jaws and trimmed the end of the hub to about .250” from the face of the gear. I was very careful to not damage the teeth of the gear when positioning it in the chuck’s jaws...
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I now moved the gear over to the mill and positioned the spindle over the contact stud hole in the hub of the gear.
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A 9/64” drill was now used to cut the stud’s hole as seen below...
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I followed the drill with a 5/32” chucking reamer to finish the gear.
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Lastly, I wanted to replace the “Parkerized” finish of the gear so I used some gun blueing fluid to blacken the exposed steel. It worked quite nicely :0)
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Another part to check off the list...
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The next part to machine is the insulating collar. This is made from a 1” diameter Delrin plastic rod which is supplied in the materials kit.
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I started this part by boring a 1/2” hole .5” deep into the end of the rod.
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The boring bar was then used to widen the hole to .748” for a snug fit on the gear hub.
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I now parted the collar off at .250” as seen below.
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I drilled a 9/64” hole in center of one side of the collar and then followed it with a 5/32” chucking reamer to finish off the part.
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The collar was now pressed onto the gear as seen below...
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I am now ready to machine the copper contact stud and press it into the gear assembly. Please join me again for the continuation of the Red Wing engine project. Till then, machine safely my friends!!!
Don Giandomenico
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