Pottyengineering Horizontal Mill Engine - Imperial - Mike's 3rd Engine

[b.lindsey]

From your description Mike, it sound like you nailed the size. Nice updates!!

Bill

[mikehinz]

Another post showing the remaining parts that I've done so far.

First is the piston valve.  I turned the piston valve from .25" drill rod.  I used a 2mm carbide turn/grooving tool for the entire part.  This sort of insert is nice for this type of op as you can cut to the side rather than just plunging straight in, although admittedly the inserts cuts more easily when being plunged straight in.  What I find is the best way to use this sort of insert is to plunge in at multiple points until you're close to the final OD and move sideways across the part bring it to the required OD. 


Reaming a very shallow 1/8" counterbore in the end of the valve.


Tapping 2-56 for the valve rod.  I had to use a bottoming tap as there is very little length available for the threads.


Finishing piston valve on print.


Turned the valve body end closure from a piece of brass stock.  Very straightforward so I didn't show the op.  This is the finished part on the print.


Shown assembled on the valve body.  The fit is pretty tight but I'll go ahead and put just a bit of Loctite on it whenever i do the final assembly.


Shown is the valve guide stuffing box.  I didn't show the ops.  Here's the finished part assembled in the valve body.


And the final parts so far, the thrust washers for the cross slide assembly.  Again, no ops shown, just the finished parts on the print.


Hopefully I'll have a good amount of time in the shop tomorrow.  I'd like to get this engine finished in the next few days and see if I can get it running!

All for now.

Enjoy!

Mike

[mikehinz]

I had  a fair bit of time in the shop today so I decided to get started on the air inlet connection and the valve rod guide.  Both are brass so some easy turning!

First was the valve rod guide.  I had a piece of 3/4" brass rod and this pix shows it being turned down to 5/8" and then a small spigot turned down to .25".  Nothing fancy here.  I used the AL specific CCGT insert for this and it cuts brass like cutter.  I didn't push the speed up too high, I think I ran all ops at 460 rpm. 


Spot drilled and drilled thru for the valve rod.


Parted off using a 2mm wide carbide insert tool.


On to the air intake connection.  This is a 1" OD piece of brass I had and the largest dimension needs to be 1" for this part.  I'd turned down the top spigot and am threading it 10-32 to take either a barb fitting or maybe a push to connect air tubing fitting.  I just held the tap in the tailstock chuck, kicked the lathe out of gear and rotated the collet by hand.


I did follow up with a 10-32 bottoming tap, just turning it by hand with a tap wrench, to make sure I had full depth threads for whatever will provide the air connection.  Brass sure taps easy!


Here I've turned the part around and am holding it with a 5C collet on the previously turned spigot.  I needed to create a spigot on this end that was only .156" OD and 1/8" long.  It's perhaps not clear, but I simply plunged from the OD to the required dimension on the spigot with the CCGT tool.  This worked fine and I took about .062" depth of cut so this was done in 2 passes plus a very light clean up pass on the spigot and on the face of the air connection.


The 2 parts are shown where they are to be installed.  There are obviously more ops to come but at least the spigots fit properly!


I started making the necessary filing buttons since I had the 5C collet setup installed.  This pix shows the general arrangement for one of the parts and the filing buttons.


This pix shows both parts along with all the filing buttons needed to finish the parts. 


I made each filing button at least .20" thick or a bit more as needed to cover the spigots on the parts.  Is that usually about how wide these filing buttons need to be or should they be wider yet?  I don't plan to harden these, although I could as they are made from either W1 or O1 drill rod, depending on the size.  I figure with brass, since it files so easily, I won't tend to chew up the buttons if I'm a bit careful.  Is that ok, or should I go ahead and harden 'em? 

That seemed to take a long time!  I didn't really attempt to figure out a way to make those buttons faster so I took much longer at that task than I should have.

All for today.

Enjoy!

Mike.

[gary.a.ayres]

Great thread, with a good-looking engine nearing completion.

I have started my trajectory with a boiler, and haven't yet built an engine. The Potty Mill (metric, possibly to x1.5 scale) is on my list for when I do (after cutting my teeth on an oscillator or two). Your thread here will be an excellent resource for me when I get to that point.

Looking forward to your next steps and the finished engine!

 

[mikehinz]

Gary, thanks for the kind words!  I'm making slow but steady progress on the last few parts.  I'd really like to get this engine done in the next few days unless something really gets in the way.  I will continue to document the build as best I can but I'm pretty much a beginner to model engineering.  There are many on this forum that have loads more experience than I do and do some fantastic work! 

Mike.

[b.lindsey]

Mike, this is all looking pretty fantastic to me. You are doing a wonderful job on this!!

Bill

[mikehinz]

I ended up spending almost 2 full days working on these 2 small brass parts, the valve rod guide and the air inlet.  I'll describe my problems in this thread as it was certainly a learning experience!

Two days back I had turned the 2 parts from brass round stock and get the overall dimensions done.  To drill the clearances holes for the 2-56 bolts that secure both parts onto the valve body, I held each one in a collet block and then put it in the mill vise.  First pix shows making sure that the block is square with the table and vise in the X axis. 


Then used a DTI to center the part under the spindle.  I did this for each part but I'm only showing on pix of each as the op is exactly the same in each case.


Then spotted and drilled thru each part with a #43 for the clearance holes for the 2-56 bolts.


Then, since the part was already in the mill and centered I took a few passes with an end mill just to bring the width to the required size.  That's a 4 flute HSS end mill running at about 1500 rpm.  The brass cuts like butter.


Now the trouble started.  The following pix shows the first attempt at assembling the filing buttons on one of the parts.  The first problem I had was that due to the small size of the parts and the relatively large radius(s) required, the buttons interfered with each other.  So the first thing I did was to grind off the side of each of the smaller buttons until everything could be bolted up.  This pix shows the buttons all actually fitting on the one of the parts.  But to get to this point took quite some time.


The smaller part was really a pain!  Since it's so small,  the head of the 2-56 bolt and nut were too large to clear the filing button in the center.  After some thought, I decided to try to do only one side at a time and stacked 2 of the filing buttons on each side to get the head of the bolt and the nut into free space.  That setup worked, kind of sort of..............and soon another problem was revealed!


I started trying to file the brass.  That turned into a miserable experience for a couple of reasons.  First I could not hold the parts successfully no matter what i did.  I have some AL soft jaws in the bench vise but they're only held onto the steel jaws with magnets so if the part to be held is near the top, they fold in as soon as you try to tighten the vise.  So a near future project will be to make some replaceable vise jaws out of AL.  Second, I suck at filing.  For whatever reason, I just couldn't get the appearance right and started making a mess of the parts.  So, late yesterday I stopped working on them and had a think about what to do next. 

Today, I started working on the parts again but this time, rather than filing, I used my belt sander with a fine 150 grit belt installed on it and gently applied the each part to the sander until I just got to the filing buttons.  I felt pretty good at this point, but when looking at the parts it was obviously that i had used a bit too large buttons for the small end of each part.  I followed my print but it looks like you have to make the buttons just a bit smaller in radius than the radius that I designed in CAD.  Soooo, off to remake some more buttons!  After doing that for both parts and touching them up on the belt sander again, I ended up pretty happy with the results.

Here are both parts laid on top of the drawing.


The finished air inlet in position on the valve body (without the fasteners).


And the valve rod guide in position on the valve body, again without fasteners.


I was happy with the end results, but man that was some tough work for two very small parts!  Any hints and tips on properly using filing buttons would be greatly appreciated!  I clearly need to study more and need a LOT more experience on using those devilish little things!

Since I got those parts out of the way, I made a start on the crosshead.  I had some 3/8" x 1/2" stock and cut a chunk of it off and brought it to dimension and left it about 2.5" long, just so it could be gripped easier for the initial ops.  First pix shows the rectangular bar being held in the 4 jaw and the end being turned down to .25" OD.   Since this was an interrupted cut I fed in only about .010 or .015 per pass and turned the lathe pretty slow at about 230 rpm until I got to a circular section.  The insert is a CCMT and worked very well.  No issue with the interrupted cut.


Then I put a radius on the rectangular section just to blend it a bit to the circular section.  I used a HSS form tool that I had previously ground to 3/16" radius.  I left the lathe turning slowly and slowly hand fed in on X and Z until it looked more or less OK to me.


Then I parted off the round section to .040" from the body and drilled and tapped for 8-32.  Shown is the spring follower and a small tap wrench that I often use.  I used a plug tap and it went pretty well as I'd drilled to give 50% threads.  For drill sizes for tapping, I have a copy of the LMS tapping guide pinned to the wall in my shop.  It's one page for metric and one page for imperial and is quick and handy to use. 


Then I took the part out of the lathe and put it in the mill vise.  Quickly did the edge finding and located the hole use the DRO and drilled 15/64" for the pin.


I didn't show the op, but I reamed the hole to .001" over 1/4" so .251".  The last pix for today shows the crosshead pin installed in the half finished crosshead.  The fit seems good.


All for today.  I think I'll be able to spend a fair bit of time in the shop over the next few days but given my slow progress on these small parts, it may take me awhile to get to the finish line!

Enjoy!

Mike

[gary.a.ayres]

I was happy with the end results, but man that was some tough work for two very small parts!

It is often the way, isn't it? Plain sailing through the bits that you think will be difficult, then the unexpected brick wall!

You got there, though 

When I first started using my belt sander (in fact a belt sanding attachment on my multi-function wood lathe) it was a revelation to me. Immediately wondered how I ever managed without it!

[b.lindsey]

Despite the tedious nature of the work, the parts turned out great Mike. Nicely done.

Bill

[mikehinz]

I'd left off the other day with the crosshead not quite completed.  So the first order of the day was to finish up the crosshead.

I put the part back in the mill vise, did the normal edge finding and using a 1/4" 4 flute carbide end mill, cut the slot.  I had to step over a bit to get to the .275" slot with called for but that gave me a nice finish in the slot.   As can be seen, I left a solid end on the part as I've had bad experience trying to mill an open slot.  The vibration in that situation can be terrible.  So in this case I just went to the required dimension on the piston rod end and went a bit further on the opposite end.


Then I removed the part from the vise, cut if off in my bandsaw and then brought the part to length using the same 1/4" end mill.  Notice I held the part in such a way to try to avoid vibration and chatter when making the cuts to length.


Then to make the corner radii on the part, rather than using filing buttons, i put some Dykem on the part and used a 1/4" radius gage to scribe the radii on each corner that called for one.


I used my belt sander to made the radii.  I just held the part firmly on the cable and slowly worked the part until the scribed lines just disappeared.  Then a bit of deburring and I called the part good.  I do need to do a bit more polishing but it actually looks better in person vs the photo.


And the last pix of this part, shown assembled on the piston rod with the crosshead pin also installed.  It all fit!


Since I had the 4 jaw installed on the lathe, I decided to work on the eccentric assembly. 

First was the eccentric strap.  I had a piece of 1 1/4" brass and shown is just centering up the work and getting ready to turn down the OD to 1.20" as per the print.  That's my home made dual indicator holder.  I use it a lot as it makes setting up work in the 4 jaw very easy, at least after a bit of practice!


Then there's to be a fairly precise .80" hole thru the center.  Shown is drilling a hole to start.  That's a 3/4" drill that will get close to the required ID.


Then boring the ID to .800"  I went just a bit over as there needs to be a bit of clearance so I brought it to .802.  For boring in these blind holes, I usually run the bar in to whatever depth I need and set the Z zero on the DRO at that point.  Then when boring I find it much easier to not confused as to where to stop! 


Measuring the ID with a telescoping gage.


Parting off the ring to .25" width.  2mm carbide insert parting tool with the lathe running at 430 rpm.  Parting brass is a dream.


Finished eccentric strap on the print.  To be fair I do have to drill/tap a 5-40 hole in it but I'll do that later on the mill.


Then I got started on the eccentric outer.  I had a bit of 1 3/8" 'Mystery" steel and used it for the part.  I turned the OD to 1.20" and then turned a section .255" long to .80" OD.  I didn't show those ops but I needed a 5/8" hole thru the part with the hole needing to be on size.  I first drilled thru with a 9/16" bit shown here. But I didn't show boring the hole to size, but it's just the same as the previous op. 


Checked the fit of the eccentric strap on the eccentric outer.  Fit was good.


I didn't show parting off but that op worked fine with the same 2mm carbide insert tool.  I did reduce the rpm to about 260 since the OD was larger and I was parting off steel.  Shown is the finished part on the print.


And a pix of 2 of the eccentric parts that I've finished so far.


And last pix is the 2 parts assembled to check fit again.


That's it for today.  I think I'll have a fair bit of time to spend in the shop this week and the weather is supposed to fairly good so I'll be able to get out there a bit earlier in the day since the temp won't be so bad. 

Enjoy!

Mike

[gary.a.ayres]

Looking great!

 

[Mike OConnor]

Hi Mike,

Following along. Great job on the parts and documenting your build!

I understand that the slot you were machining with the 1/4” 4-flute end mill was to finish at 0.275”, so in this case didn’t matter, but if you need an on-size slot use a 2-flute end mill. The 4-flute end mill will tend to deflect and cut oversize.

Nice job planning and executing that open slot. Those parts came out great.

When you have a small part like that link on one side of a large Kurt vise, the moving jaw won’t have the best grip on it. If you place a similar part or a same width piece of stock at the other side of the vise, the moving jaw will clamp the parts more securely. The Kurt vise screw/nut applies the force to the moving jaw with a spherical pivot in the center. For a 6” length jaw, if I have a part that is 1” in length or less that I want to clamp on one side of the vise, I will put an identical width and clamp a similar length on the opposite side of the vise to balance the clamping.

Your build log is awesome! Looking forward to seeing your next parts.

Kind regards, Mike

[b.lindsey]

More nice progress Mike and nice looking parts too!!

Bill

[mikehinz]

So far this week, I've not had as much time in  shop as I'd hoped.  Between my very elderly mother-in-law visits and trips to the doctor for her, I'm in the midst of a bit of a medical procedure, scheduled for tomorrow that for today, kept me very near the bathroom.  Not fun, but I did manage to get one more part done and I have a bit of time to post about it here, the part being the eccentric inner.

I previously turned a bit of stock to 1.20" OD with enough length to be able to make the inner (at least 1/2 of it) without rechucking the stock.  Shown in the pix is reducing a portion of the OD down to 5/8" so the inner and out pieces slip together.


Checking the fit of the outer and inner parts.  Nice fit, slightly tighter than a 'slip' fit.  These parts will be Loctited together when finished.


Making sure that the eccentric sheath rotates freely when both parts are together.  Fit seems to be nice and free.


Then I parted off the 1/2 finished piece for the next operation, turning the offset eccentric.  RPM was 260 using a 2mm width carbide insert parting tool


Then I cheated to mark out the eccentric center.  I put the part in the mill vise, centered it under the spindle using a DTI.  That op is shown here.


Then i drilled a shallow center hole after offsetting the part .138" from the center.  I also put a very small mark on center just to check that everything was correct.


I still haven't made a 'pump center' for centering up on offset turning, so I used a mill wiggler with a sharp point and very, very gently made sure the point of the point is in the middle of the drilled center hole.  This was all a bit slow and certainly I'll make something better for this job, probably right after I finish up this engine.


Commencing turning the offset part.  I slowed the lathe down to 260 rpm since this was an interrupted cut, but it went fine.  This pix was take just as I got the spigot to round.


Then I deepened the spot drill and drilled thru 1/64" under 5/16"


Then reamed to 5/16".  RPM was 260 and I liberally coated the reaming with oil prior to the op. 


Checked the fit of the part on the crankshaft.  Very good fit.  It slipped on but with no discernable play.


The 3 almost completed parts on the print.


Another view of the 3 parts assembled.


A view of the other side of the assembled parts.  I'll clean this side up a bit more later.  It's not as rough as the photo makes it look like.


A quick mock-up assembly just to make sure that everything looks ok at this point.


Then back to the mill.  After edge finding, I drilled and tapped 5-40 for the eccentric rod.  I kicked the mill out of gear and rotated the tap into the work by hand. 


I did basically the same thing for the grub screw location.  Did the edge finding, center drilled, thru drilled and then rotated the tap into the work by hand with the mill out of gear. 


And the last pix of the day.  I used some Loctite 603 to hold the inner and outer pieces together and just lightly squeezed the parts together in the bench vise to make sure they were seated together completely.  I also verified that the eccentric shealth still freely rotates. 


That's it so far.  I'm not sure exactly when I'll feel like getting back in the shop, hopefully maybe on Saturday. 

Enjoy!

Mike

[crueby]

Beautiful parts!