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Winner Pm Research Engine #7
- Thread starter tomw
- Start date
- Status
- Joined
- Jan 24, 2015
- Messages
- 239
Hi Ken,
The v-blocks are made from aluminum. I squared up a piece of 1/4" aluminum flat stock, then cut it in half. The two bits of aluminum were CA glued together, and both were then milled square. I then mounted my vise on a tilt table, and used a 45° angle gage to set the angle of table. I milled out one side of the blocks, flipped the part, and milled out the other side. In this way, I was pretty sure I had matching vees. They are not ground precision v-blocks, but they seem to work for off-centering small stuff in my 4 jaw chuck.
If that is completely mud as an explanation I can make a crude drawing that might be clarifying. Emphasis on might.
I hope you are enjoying the far more pleasant weather here before you head north.
Cheers,
Tom
The v-blocks are made from aluminum. I squared up a piece of 1/4" aluminum flat stock, then cut it in half. The two bits of aluminum were CA glued together, and both were then milled square. I then mounted my vise on a tilt table, and used a 45° angle gage to set the angle of table. I milled out one side of the blocks, flipped the part, and milled out the other side. In this way, I was pretty sure I had matching vees. They are not ground precision v-blocks, but they seem to work for off-centering small stuff in my 4 jaw chuck.
If that is completely mud as an explanation I can make a crude drawing that might be clarifying. Emphasis on might.
I hope you are enjoying the far more pleasant weather here before you head north.
Cheers,
Tom
- Joined
- Jan 24, 2015
- Messages
- 239
Ken,
I forgot to add: but this would be morally suspect and could lead to leprosy. The safe thing to do is get a tilt table.
- Joined
- Jan 24, 2015
- Messages
- 239
The next step was the crossheads and associated pieces.
The raw stock for the crossheads themselves was a small piece of brass flat stock. For the first step I put the stock flat in my vise and squared up the ends by side cutting with a1/2” end mill. The next step was to drill the hole for the gudgeon pin (wrist pin). The piece was repositioned in the vise, and the end and center found. I then center drilled and drilled the hole in the hopefully correct location. This is a small drill bit, and it needed to go a relatively long distance through the material. I therefore did peck drilling, being sure not to put too much pressure on the bit. In my limited experience, if I use too much force, small bits really want to wander off, take their own path, or just come to a fork and take it.
Center drilling to locate the hole for the gudgeon pin.
The next step was to mill the slot for the small end of the connecting rod. I positioned the piece vertically in my vise, and used the usual methods to find the center. The slot is a tad over 1/8”, so I used a 3/32” end mill. I plunge cut the center of the slot, and then used conventional milling to widen it to .135. The outer profile was then milled, also by plunge cutting and then conventional milling to final size.
Milling the connecting rod slot to final size with a 3/32 end mill.
Milling the outer relief on the crosshead using a tiny end mill.
The piston rod screws directly into the crosshead. As this is a through-hole, I drilled it next. Again, a skinny drill bit, so lots of pecking at the maximum spindle speed (2800 rpm). As the piece has not been cut-off from the stock, I only drilled down far enough to make sure it would clear the full height of the piece.
Drilling the hole that the piston rod will screw into. Or, into which the piston rod will be screwed.
Next the step was cutting the crosshead from the stock. I used a .062 kerf-width slitting saw. I took multiple passes with the saw, each .050 deeper, until the piece separated from the stock. I used lots of lube as well. Because the brass was kinda gummy, the blade would grab if I tried a deeper cut. I then 5-40 tapped the through-hole for the piston rod. All edges were then deburred and given a little smoothing with some 400 grit aOx (aluminum oxide) paper.
Cutting off the crosshead using a slitting saw.
Are these posts too detailed and thus a bit boring?
The crossheads.
The next pieces that I did were the crosshead caps. These come as bronze castings.
Crosshead cap castings as received.
The first step was to remove the sprue and flashing from each piece. I did this with a combination of my belt sander and files. Then I sanded the bottoms of the caps using 320 grit aOx paper. As with the base, I did this gently, using a figure eight pattern for the motion of the part over the paper. I sanded until I guesstimated the contact area was around 80-90%. I could have kept going, but I was really bored, and that seemed sufficient in my mind. Please tell me if I am wrong.
Sanding the bottom of the crosshead caps to make a smooth and flat surface.
These were sanded until between 80-90% of the piece came into contact with the sandpaper.
The castings were then mounted on parellels in my mill vise (which was set square to the table).
Casting mounted in my vise.
There are three holes that needed to be drilled in the castings. On each end are the clearance holes for the 5-40 machine screws that mount the casting to the base. In the center there is a small oil port where I will mount an oil cup. The critical distance is between the two holes used for mounting them to the base. I used my eyes and a center drill to find the middle of the middle, or the center of the center. I then checked that the center of the center drill followed the rib down the center of the piece along the X axis. Because this is central and needs to be centered. Once I was certain the center was centered, I set my DRO to 0,0 and drilled the central hole for the oiler using a center drill followed by the correct sized twist drill.
Imagine, if you will, a photo here of me drilling a centrally located central hole, and that this is the caption for the photo.
I then used some centering math and the DRO to find the central location for the mounting screw clearance holes. I center drilled at these points and then used a 9/64 twist drill to finish them off. And here is where I ran into trouble.
She was a sexy red head with a whiskey voice, the kind girl you would apologize to when she rams your car. And here I was, fresh out PI school, wet behind the ears, and hungry for action. Oh, I should have known better than to take her case….Oops, back to the narrative.
My 9/64 bit really wanted to dive into the casting and rip it from the vise. In deedly-do, it did that on the first piece. For all subsequent holes, I first drilled a 5/64 pilot hole, followed by the 9/64 bit. This approach worked for me. A better approach, so I hear, it to modify your bit so it is not so grabby. Of course, then the bit is only good for grabby metals.
After the hole was started with a center drill, a 5/64 twist drill was used to make a through-hole.
This was then followed by a 9/64 drill.
The crosshead caps finished. Note that I left the top of bosses for the mounting screws un-machined.
Spacers. They occupy that region between Mars and Jupiter, mining vital minerals for the expansion of our industrial efforts. Oh, wait.
The last bit for this post is making the crosshead cap spacers. These little hollow tubes, of a specific length, set the distance between the crosshead rails and the crosshead caps. I started with some 3/16” model pipe (as recommend by Dean). Using the lathe I drilled out the pipe to 1/8” diameter and then parted off appropriately long bits. These bits were then de-burred by putting them back in the chuck and using my 45° countersink deburring tool. Easy.
Drilling out 3/16" model pipe to 1/8" I.D.
Parting off the crosshead spacers.
A passel of crosshead spacers, waiting to be de-burred.
Next time there should be a picture of the engine assembly as it stands.
Your humble correspondent,
Tom
The raw stock for the crossheads themselves was a small piece of brass flat stock. For the first step I put the stock flat in my vise and squared up the ends by side cutting with a1/2” end mill. The next step was to drill the hole for the gudgeon pin (wrist pin). The piece was repositioned in the vise, and the end and center found. I then center drilled and drilled the hole in the hopefully correct location. This is a small drill bit, and it needed to go a relatively long distance through the material. I therefore did peck drilling, being sure not to put too much pressure on the bit. In my limited experience, if I use too much force, small bits really want to wander off, take their own path, or just come to a fork and take it.
Center drilling to locate the hole for the gudgeon pin.
The next step was to mill the slot for the small end of the connecting rod. I positioned the piece vertically in my vise, and used the usual methods to find the center. The slot is a tad over 1/8”, so I used a 3/32” end mill. I plunge cut the center of the slot, and then used conventional milling to widen it to .135. The outer profile was then milled, also by plunge cutting and then conventional milling to final size.
Milling the connecting rod slot to final size with a 3/32 end mill.
Milling the outer relief on the crosshead using a tiny end mill.
The piston rod screws directly into the crosshead. As this is a through-hole, I drilled it next. Again, a skinny drill bit, so lots of pecking at the maximum spindle speed (2800 rpm). As the piece has not been cut-off from the stock, I only drilled down far enough to make sure it would clear the full height of the piece.
Drilling the hole that the piston rod will screw into. Or, into which the piston rod will be screwed.
Next the step was cutting the crosshead from the stock. I used a .062 kerf-width slitting saw. I took multiple passes with the saw, each .050 deeper, until the piece separated from the stock. I used lots of lube as well. Because the brass was kinda gummy, the blade would grab if I tried a deeper cut. I then 5-40 tapped the through-hole for the piston rod. All edges were then deburred and given a little smoothing with some 400 grit aOx (aluminum oxide) paper.
Cutting off the crosshead using a slitting saw.
Are these posts too detailed and thus a bit boring?
The crossheads.
The next pieces that I did were the crosshead caps. These come as bronze castings.
Crosshead cap castings as received.
The first step was to remove the sprue and flashing from each piece. I did this with a combination of my belt sander and files. Then I sanded the bottoms of the caps using 320 grit aOx paper. As with the base, I did this gently, using a figure eight pattern for the motion of the part over the paper. I sanded until I guesstimated the contact area was around 80-90%. I could have kept going, but I was really bored, and that seemed sufficient in my mind. Please tell me if I am wrong.
Sanding the bottom of the crosshead caps to make a smooth and flat surface.
These were sanded until between 80-90% of the piece came into contact with the sandpaper.
The castings were then mounted on parellels in my mill vise (which was set square to the table).
Casting mounted in my vise.
There are three holes that needed to be drilled in the castings. On each end are the clearance holes for the 5-40 machine screws that mount the casting to the base. In the center there is a small oil port where I will mount an oil cup. The critical distance is between the two holes used for mounting them to the base. I used my eyes and a center drill to find the middle of the middle, or the center of the center. I then checked that the center of the center drill followed the rib down the center of the piece along the X axis. Because this is central and needs to be centered. Once I was certain the center was centered, I set my DRO to 0,0 and drilled the central hole for the oiler using a center drill followed by the correct sized twist drill.
Imagine, if you will, a photo here of me drilling a centrally located central hole, and that this is the caption for the photo.
I then used some centering math and the DRO to find the central location for the mounting screw clearance holes. I center drilled at these points and then used a 9/64 twist drill to finish them off. And here is where I ran into trouble.
She was a sexy red head with a whiskey voice, the kind girl you would apologize to when she rams your car. And here I was, fresh out PI school, wet behind the ears, and hungry for action. Oh, I should have known better than to take her case….Oops, back to the narrative.
My 9/64 bit really wanted to dive into the casting and rip it from the vise. In deedly-do, it did that on the first piece. For all subsequent holes, I first drilled a 5/64 pilot hole, followed by the 9/64 bit. This approach worked for me. A better approach, so I hear, it to modify your bit so it is not so grabby. Of course, then the bit is only good for grabby metals.
After the hole was started with a center drill, a 5/64 twist drill was used to make a through-hole.
This was then followed by a 9/64 drill.
The crosshead caps finished. Note that I left the top of bosses for the mounting screws un-machined.
Spacers. They occupy that region between Mars and Jupiter, mining vital minerals for the expansion of our industrial efforts. Oh, wait.
The last bit for this post is making the crosshead cap spacers. These little hollow tubes, of a specific length, set the distance between the crosshead rails and the crosshead caps. I started with some 3/16” model pipe (as recommend by Dean). Using the lathe I drilled out the pipe to 1/8” diameter and then parted off appropriately long bits. These bits were then de-burred by putting them back in the chuck and using my 45° countersink deburring tool. Easy.
Drilling out 3/16" model pipe to 1/8" I.D.
Parting off the crosshead spacers.
A passel of crosshead spacers, waiting to be de-burred.
Next time there should be a picture of the engine assembly as it stands.
Your humble correspondent,
Tom
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