Red Wing Engine Project 9/27/12






	Posted on September 27, 2012: Hello again everyone :0) I am continuing work on the fuel mixer assembly and the next part to tackle is the fuel orifice cap. This part is made from a piece of 11/16” brass hex stock that is included in the materials kit.



	I started out by boring a 11/32” hole into one end of the hex to a depth of .750”. Note: The prints call for an “R” sized drill although the 11/32” will work as well...



	The next step is to lay out two cut lines at .250” and .375” from the end of the rod (not shown). This was done by turning the lathe slowly and drawing a caliper across the hex at the desired measurements as seen here. I then turned down the hex to a .495” diameter up to the first cut line as seen below.



	I now turned down the diameter of the hex to .688” to the next cut line (not shown). This leaves the cap with a two-stair step profile with the taller one being about an 1/8” wide. To finish off the top step I needed to cut a rounded groove just under the .375” line (seen below). I used an .058” wide HSS parting tool that was ground to a round point to cut this groove and finish the step. Note: The rounded groove is purely aesthetic. I also cut a thread relief just under the taller step with the square end of the .058” parting tool to a depth of .028” (shown in a later photo).



	I now needed to thread the cap with a 1/2-20 thread so I decided to custom grind my HSS parting tool to cut 60° threads. I used a threading gauge to set the angle of the ground tool bit as seen below.



	I changed the gears on the lathe for cutting 20 TPI threads and went to work.



	A quick fit check revealed a proper fit :0)



	I now used the parting tool to remove the cap at a 1/2” from the other end of the fitting.



	I now used a 1/2-20 barrel nut in the lathe’s chuck to support the orifice cap as seen below. I then faced off the cap and cut chamfers on both sides of the exposed hex for a finished look...



	The next step is to tap the fitting with a 1/8-27 NPT tap. This was an effortless operation using the VFD drive on the lathe.



	I could now check another part off the list :0)



	The next part to work on is the mixer valve. This part is made from more of the 1/2” brass rod used to make the filler cap.



	I started by laying out a cut line at 1.094”. I then turned down the stem to .122” up to this cut line. Note: You may choose to use a live center to support the tail end of the stem for this process. I chose to forego the support and make light cuts as to not warp the stem with excessive tool bit pressure...







	I decided at this point to trim down the margin (top OD) of the valve to it’s proper size of .430”...



	I now moved the compound rest to a 45° angle so that the face of the valve could be machined. Note: Whenever I do an operation that requires the carriage to be stationary I usually disengage the lead screw drive and then engage the half-nuts on the lead screw so that the carriage does not move. This could also be done by disengaging the carriage from the lead screw and then tightening down the carriage lock screw. The latter option may be necessary if your lathe does not have a tumbler reverse feature...



	I turned the face of the valve by drawing the tool bit across the valve as seen below.



	I finished the cut when the valve’s face almost reached the stem...



	I now removed the valve head from the rod with my band saw and then remounted the valve in the chuck to trim down the head. I stopped cutting when the valve’s margin was at .030” tall...





	Before moving onto the cotter pin hole in the stem I decided to lap the valve into the seat of the mixer.



	I applied some of the Permatex valve grinding compound (used earlier on the head valves) to the mixer valve and carefully placed it into the body.



	To turn the valve I used my “tap handle” 3/8” chuck to grip the stem as seen below. I gently spun the valve in a back-and-fourth manner for a couple of minutes to lap the valve. Note: This method could be used to lap the valves in the cylinder head in lieu of the method I used earlier. In fact I will probably use this method from now on ;0)



	A quick inspection revealed a beautifully lapped valve :0)



	The last step to perform on the valve is to drill the 1/16” cotter pin hole at the end of the valve. I laid out the hole at .060” from the end of the stem...



	I used a #1 center drill to spot the hole as the drill bit will surely “walk” right off the stem if not spotted.



	And now for the 1/16” drill...



	The finished valve...



	The next part to machine is the spring retainer washer which is made from a piece of 1/4” brass rod that is included in the materials kit.



	First I faced the end of the rod to square it up.



	I then bored an 1/8” hole to a depth of .250”.



	Lastly I parted the washer off at .047” wide to finish the washer.



	I now gathered up the valve parts including the valve spring that is supplied with the basic kit for a fit check.



	I installed the parts and then tested the seal of the needle valve port with low air pressure (not shown). This was done to ensure that the valve was seated correctly and that fuel would not leak out of the mixer later on. Luckily the seal was perfect so I could move on to the next part :0)





	The next part to machine is the needle valve fitting which is made from a piece of 3/8” brass hex stock that is included in the materials kit.



	The first task on this part is to drill a #29 hole to a depth of .375” in one end of the rod.



	The next step is to continue drilling a #33 hole past the first one to a depth of .625” (1” total depth).



	I now applied some layout fluid to the hex and scribed two cut lines at .280” and .410” from the end of the rod...



	I then set up my carbide parting tool in the tool rest and turned down the diameter of the end of the rod to .312” right up to the 1st scribed line.



	I now moved over to the other side and cut a .400” wide neck at the same diameter (.312”) to the left of the 2nd cut line.



	Next I cut two thread reliefs on either side of the hex portion with my HSS .058” wide parting tool to a depth of .026” (.260” diameter).



	I now needed to thread both sides of the fitting with a 5/16-24 thread so I used my custom ground parting tool to scratch them out.



	The next step is to cut a chamfer on either side of the hex as seen below.



	Now back to the parting tool to cut the fitting off at a length of .690”...



	I installed a 5/16-24 steel nut on the fitting and then back into the chuck so the 6-40 needle valve threads could be tapped out in the side with the smaller hole (#33). Note: you could omit using the “fixture” nut and just clamp onto the fitting directly if you like...



	Lastly I cleaned up the ends of the fitting so there were no sharp edges. I paid close attention to the “non-threaded hole” side of the fitting as it will be seated against the needle valve O-ring.



	The mixer is coming along quite nicely and I can’t wait to make the needle valve and compression nut to finish the mixer. Please join me again for the continuation of the Red Wing project very soon!!! Till then my friends... Don R. Giandomenico