-
Welcome back Guest! Did you know you can mentor other members here at H-M? If not, please check out our Relaunch of Hobby Machinist Mentoring Program!
Mike's P.M. Research No. 6 Steam Engine
- Thread starter macardoso
- Start date
- Joined
- Mar 26, 2018
- Messages
- 2,719
I purchased a 3' bar of precision ground 12L14 steel in 5/8" diameter. This stock is straight and round, but soft and easy to machine. I parted off 2 bars which will become part of the crankshaft. They will require later processing to add keyways.
Next I made the valve rod packing nut
The OD was turned from 1/2" hex barstock. The part was drilled, tapped, and reamed thru to 3/16"
I used an internal LH threading bar to chamfer the hex.
I packed the parts inside expanding plastic mesh to protect them.
Next I made the valve rod packing nut
The OD was turned from 1/2" hex barstock. The part was drilled, tapped, and reamed thru to 3/16"
I used an internal LH threading bar to chamfer the hex.
I packed the parts inside expanding plastic mesh to protect them.
- Joined
- Mar 26, 2018
- Messages
- 2,719
Next I started on one of the more complicated pieces, the Frame.
I began with some bench work to remove the flash and seam lines with a file.
The part was then clamped on the milling machine and the feet were cut flat. Care was taken to make sure the bore was parallel to the table and the feet were level.
I left some meat on the casting to allow me to come back and finish them to size after cutting the bore.
I spent about an hour and a half aligning the part on the lathe such that the feet and bore were parallel to the bedways, and the bore was centered. PM Research doesn't give you a ton of extra meat on the castings, so you need to be fairly accurate in the alignment.
I used a 3/4" boring bar with a few different CCMT inserts to finish the bore to 1.5003-1.5006" which was exactly what I was shooting for. I had about .0002" of taper across the 5" part with about .0002" of bow in the center of the unsupported section of the bore. Not much I can do about that without grinding.
The finish on the bore is very smooth with no chatter. The grainy look is due to the normal tear out of graphite from grey cast iron. Those rough edges were hand filed smooth later on.
The part was placed back on the mill and I used a DTI to carefully shim the part such that the bore was parallel to the bed of the machine.
Checking the machined height on the machine.
Made a big oops by hitting the "Page Down" key while facing the part by hand. This jogged the Z axis into the part. I carefully removed a thin web of material from the middle to create "feet" for this Frame. It was a mistake but I made it look OK.
Finally the feet were drilled. The holes are perfectly placed, however the casting itself is crooked hence why the holes aren't centered on all the feet.
All that is left is drilling the bolt hole pattern for mounting it to the cylinder head and tapping a hole in the top for a drip oiler.
I began with some bench work to remove the flash and seam lines with a file.
The part was then clamped on the milling machine and the feet were cut flat. Care was taken to make sure the bore was parallel to the table and the feet were level.
I left some meat on the casting to allow me to come back and finish them to size after cutting the bore.
I spent about an hour and a half aligning the part on the lathe such that the feet and bore were parallel to the bedways, and the bore was centered. PM Research doesn't give you a ton of extra meat on the castings, so you need to be fairly accurate in the alignment.
I used a 3/4" boring bar with a few different CCMT inserts to finish the bore to 1.5003-1.5006" which was exactly what I was shooting for. I had about .0002" of taper across the 5" part with about .0002" of bow in the center of the unsupported section of the bore. Not much I can do about that without grinding.
The finish on the bore is very smooth with no chatter. The grainy look is due to the normal tear out of graphite from grey cast iron. Those rough edges were hand filed smooth later on.
The part was placed back on the mill and I used a DTI to carefully shim the part such that the bore was parallel to the bed of the machine.
Checking the machined height on the machine.
Made a big oops by hitting the "Page Down" key while facing the part by hand. This jogged the Z axis into the part. I carefully removed a thin web of material from the middle to create "feet" for this Frame. It was a mistake but I made it look OK.
Finally the feet were drilled. The holes are perfectly placed, however the casting itself is crooked hence why the holes aren't centered on all the feet.
All that is left is drilling the bolt hole pattern for mounting it to the cylinder head and tapping a hole in the top for a drip oiler.
- Joined
- Mar 26, 2018
- Messages
- 2,719
The next part I tackled was the Base. It is a fairly large casting and requires facing the top, bottom, and drilling/tapping 16 holes.
I first clamped the part upside down. I used a 1/2" HSS roughing endmill to face the bottom of the part, moving whichever clamp was in my way. The change in clamping pressure around the perimeter created a few steps in the face but they won't be visible when this is assembled. Not sure how to do it better. After about 1/3 of the way around the part, my spindle load meter started to climb, the finish got worse, and the cut got louder. I stopped to find my endmill was worn to a smooth corner. It must really not like the scale right at the surface of the casting. I switched to a carbide roughing endmill from Hanita and has no further issues.
I then flipped the part and skimmed the top faces for full cleanup. This actually took the part underside on the height, but was the preference of my friend who owns the kit.
Right before I started on this side, my CNC computer had a glitch and wouldn't respond to the mouse or keyboard (touchscreen was fine). I had to fully reimage the PC including setting up Mach 4 again. That sucked and chewed up 2 weeks of shop time. But everything is running fine again.
After taking 2 weeks off from working on this, I wasn't in my flow, wasn't paying attention to the print, and made a big oops. The mounting pads shown below were for 10-24 screws, but I pre-drilled them #7. With permission from my buddy I will have to modify the plans to use 1/4-20 bolts here for the pillow blocks instead.
The process of indicating this part to be straight on the table without any precision surface to reference, and to center the holes on the various bosses took many hours of fiddling with the indicator. I probably spend twice the time on setup as I do actually cutting.
Here is the mating part with the intended screw (left) and the 1/4-20 screw (right). It will look and function fine, but I'm mad at myself for not paying attention.
Here are the pads completed. I also drilled the 4 mounting ears at the bottom.
Kate needed to do a final QC.
There was also several hours of bench work to remove the flash from the edges of the casting.
-Mike
I first clamped the part upside down. I used a 1/2" HSS roughing endmill to face the bottom of the part, moving whichever clamp was in my way. The change in clamping pressure around the perimeter created a few steps in the face but they won't be visible when this is assembled. Not sure how to do it better. After about 1/3 of the way around the part, my spindle load meter started to climb, the finish got worse, and the cut got louder. I stopped to find my endmill was worn to a smooth corner. It must really not like the scale right at the surface of the casting. I switched to a carbide roughing endmill from Hanita and has no further issues.
I then flipped the part and skimmed the top faces for full cleanup. This actually took the part underside on the height, but was the preference of my friend who owns the kit.
Right before I started on this side, my CNC computer had a glitch and wouldn't respond to the mouse or keyboard (touchscreen was fine). I had to fully reimage the PC including setting up Mach 4 again. That sucked and chewed up 2 weeks of shop time. But everything is running fine again.
After taking 2 weeks off from working on this, I wasn't in my flow, wasn't paying attention to the print, and made a big oops. The mounting pads shown below were for 10-24 screws, but I pre-drilled them #7. With permission from my buddy I will have to modify the plans to use 1/4-20 bolts here for the pillow blocks instead.
The process of indicating this part to be straight on the table without any precision surface to reference, and to center the holes on the various bosses took many hours of fiddling with the indicator. I probably spend twice the time on setup as I do actually cutting.
Here is the mating part with the intended screw (left) and the 1/4-20 screw (right). It will look and function fine, but I'm mad at myself for not paying attention.
Here are the pads completed. I also drilled the 4 mounting ears at the bottom.
Kate needed to do a final QC.
There was also several hours of bench work to remove the flash from the edges of the casting.
-Mike
- Joined
- Mar 26, 2018
- Messages
- 2,719
Next I worked on the valve head (outboard exhaust) using the included piece of 1018 CRS.
OP1 was to finish the 0.62" diameter and the predrill, then part off to length
Then the part was filpped in a 4 jaw chuck, indicated within .0002" of runout, and the precision diameter was turned and the part made to length.
I didn't own the 1/8" NPT tap when I started this part so I tried to tap it later. Held in in a chuck while tapping but it slipped and really mucked up the precision diameter. I could probably salvage it, but it was easy enough to make that I'll just make another and tap it before parting off. Kinda bummed about that.
I'm really enjoying working on the lathe, so I'm saving a lot of the drilling of the bolt holes for later.
OP1 was to finish the 0.62" diameter and the predrill, then part off to length
Then the part was filpped in a 4 jaw chuck, indicated within .0002" of runout, and the precision diameter was turned and the part made to length.
I didn't own the 1/8" NPT tap when I started this part so I tried to tap it later. Held in in a chuck while tapping but it slipped and really mucked up the precision diameter. I could probably salvage it, but it was easy enough to make that I'll just make another and tap it before parting off. Kinda bummed about that.
I'm really enjoying working on the lathe, so I'm saving a lot of the drilling of the bolt holes for later.
- Joined
- Mar 26, 2018
- Messages
- 2,719
Next I did the Inboard Valve Head. I don't have a picture of the print for this one, but it was very similar to the other valve head except it has a 3/8-24 thread on one end with a 3/16" reamed hole through, instead of the 0.62" diameter with a 1/8" NPT through.
I turned the thread diameter and single point threaded away from the chuck. I feel I'm getting better at this and can get within a 2A tolerance very comfortably now, usually within a half thou of nominal.
I checked the thread over wires and also against the packing nut that it mates with. The fit is excellent but it cannot bottom out due to the tap runout inside the packing nut. I may retap it deeper or relieve the threads inside.
I parted off the chunk I needed and saved the off-cut to use as a fixture for OP2. I tapped it 3/8-24 then faced it to clean it up.
Here was my single point threaded first operation.
The part was then threaded onto the fixture nub and indicated true to the OD and the machined face.
This allowed me to easily access all of the features for OP2.
And the part is finished except for the bolt holes. To be done at a later date.
I turned the thread diameter and single point threaded away from the chuck. I feel I'm getting better at this and can get within a 2A tolerance very comfortably now, usually within a half thou of nominal.
I checked the thread over wires and also against the packing nut that it mates with. The fit is excellent but it cannot bottom out due to the tap runout inside the packing nut. I may retap it deeper or relieve the threads inside.
I parted off the chunk I needed and saved the off-cut to use as a fixture for OP2. I tapped it 3/8-24 then faced it to clean it up.
Here was my single point threaded first operation.
The part was then threaded onto the fixture nub and indicated true to the OD and the machined face.
This allowed me to easily access all of the features for OP2.
And the part is finished except for the bolt holes. To be done at a later date.
- Joined
- Mar 26, 2018
- Messages
- 2,719
Next I started on the valve. The critical diameters are .623-.624 and they are used to seal the steam in the valve cylinder. The stock is only .6245 to begin with, so I needed to be very accurate in centering the part in the 4 jaw. Unfortunately I couldn't get both diameters within .0005" TIR for whatever reason (cheap 4 jaw?) so I dialed in the runout near the end of the valve and cut that diameter as well as the middle of the dogbone. I used some new tools including a RH and LH VCMT tool which made grooving the dogbone very easy. The center is drilled and reamed to partial depth as .5010" and drilled and reamed through .1875". The sealing diameters were cut to .6238"
I re-indicated closer to the chuck to finish the second diameter, adjusting it by only a few tenths.
The part was cut off and flipped to finish the second side. I held the valve in an aluminum split ring fixture to prevent scarring on the part from the jaws.
Here is the nearly finished valve. There are two cross holes that need to be done on the mill which I haven't done yet.
I re-indicated closer to the chuck to finish the second diameter, adjusting it by only a few tenths.
The part was cut off and flipped to finish the second side. I held the valve in an aluminum split ring fixture to prevent scarring on the part from the jaws.
Here is the nearly finished valve. There are two cross holes that need to be done on the mill which I haven't done yet.
- Joined
- Mar 26, 2018
- Messages
- 2,719
Next I worked on the Inboard Cylinder Head. It is a casting that is cleaned up on all sides.
I held onto the little nub of material to finish all the cylinder side features in one setup. A CCMT insert with a large corner radius was used to rough in the casting and one with a small radius was used to finish it.
There was not enough material on the casting to finish this diameter to spec, however it is non-functional, so my buddy and I decided to reduce it to full cleanup.
After this picture I drilled and tapped the 1/2-20 hole for the packing nut.
Here is that part fit to the Frame. There is no play between the bore and the pilot diameter
Shown with the packing nut installed in the frame. This seals the piston rod for the return stroke.
I held onto the little nub of material to finish all the cylinder side features in one setup. A CCMT insert with a large corner radius was used to rough in the casting and one with a small radius was used to finish it.
There was not enough material on the casting to finish this diameter to spec, however it is non-functional, so my buddy and I decided to reduce it to full cleanup.
After this picture I drilled and tapped the 1/2-20 hole for the packing nut.
Here is that part fit to the Frame. There is no play between the bore and the pilot diameter
Shown with the packing nut installed in the frame. This seals the piston rod for the return stroke.
Similar threads
