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Excellent!
It sounded pretty good, except the soft swishing cut I am used to is verging on a squeal with your boring tool. Of course, the sales are good for people who make these adjustable boring tool holders, but I rarely use mine. The tool is 10mm diameter on mine. Compared to the stiffness of my "proper boring bar" - a piece of 3/4inch ground steel round with holes for a tool insert and locking screw - held in a collet into the quill of the milling machine. Need a micrometer and calculation to adjust each cut. But doesn't make the "squeal" you have. Because you are at your lowest speed, and using that type of tool - you suggested it is ground for cutting Aluminium? - you have done the job "successfully" - but not the same as I would have done it. Boring in the vertical machine, or lathe, where the tool rotates and translates through the bore is the best way to ensure a round and parallel bore. I hope you agree it was the best set-up? Holding the workpiece in the lathe chuck and approaching a rotating part (of unknown alignment) past a fixed tool is not good enough for cylinders, IMHO. (I have made cylinders that way and they felt tapered when I inserted the piston! Ok at one end but tight at the other.). So I always keep the work stationary and rotate the tool.
I was taught (in the 1960s - Memory still good!) to listen to the work being cut. I.E. Cast materials at the correct speed make a lovely smooth "Swish" noise. - No squeal. and because of sound reflections the "whow-whow-whow" sound is a result of the cut being from the far side (so you hear sound waves directly, with some echoes from the bore, then near-side, where you hear sound waves that have to come up the bore and reflect before they come to the ear. Those slight variations of sound line from cutting point to ear give the "whow-whow-whow" effect. Compare that to when you are on the lathe, the workpiece is rotating, and the tool passing along a length of cut, so the passage of sound from point of cut to ear does not change as the part rotates. The rate of "whow-whow-whow" relates to the rotational speed, and not an indication of an uneven cut. But the "Squeal " relates to a vibrating point of contact - like a violin bow stops and starts as it is dragged across the string to excite the string note, or not. So any squeal and you should slow the cutting speed - if you can - or stiffen the tool/mounting/whatever - if you can. But the best cuts need the correct cutting angle and relief at the tool, so only the leading edge of the actual cutting point contacts metal, without any flat behind dragging over the surface. Then you get just the "Swish" noise. So as you cannot improve speed, mounting etc, next time do not use a tool ground for aluminium, but a sharp tool ground for cast iron, with relief to clear the bore internal radius. I suspect that if you examine your tool, you will see some polishing below the sharp cutting point, where the cast iron had ground/polished the surface of the tool at the cutting point so the relief is rubbing on the bore as the cut progresses. An indication of rubbing, not cutting, as the speed is too fast and the tool is being ground by the cast iron, not being cut properly.
Use a strong light and magnifying glass to examine the tool.
Enjoy! You are obviously newly experiencing this and learning a lot. - Good presentation too.
I look forward to you linishing of the bore. Make particular attention to the linishing bar/tool to make sure it only erodes the peaks of the cut lines, and not increases the diameter more than 0.001" !! (or the depth of machined lines). You Must also ensure you do not make bell ends, where the ends open wider than the main bore, and aim for a 30 degree criss-cross on lines from the linishing. You should stop linishing when the machining grooves are still JUST visible, so you don't go too far. I linish at a slow speed - like your speed for boring. - lubricate with light oil - or paraffin is better (I use paraffin with a drop of lube oil), to keep washing the junk out while linishing. Although using proprietary Hones on cast iron bores of engine blocks we did not use anything, when I was a lad. Like this:
1721892865324.png

I.E. Open so the dirt can fall out easily through the open array of stones, and to the floor. The exhaust blow from the driving motor also blew a good draught through the bore.
But for con-rod ends to fit gudgeon pins on a Delapina honing machine we always used paraffin with a drop of oil, for the finest finish, as the bar filled the hole and needed something to wash the residue out from the stones. (a paint brush a jar of paraffin!). Like this:
1721892943150.png
This is like my honing of small model cylinders, on a bar on the lathe. The long square stone is set into a groove, with 2 small springs beneath. - on mine.. On a Delapina machine and bar the stones sit on a slightly tapered bar, that is drawn through the middle of the honing bar to get incremental advance of the stone in tenths of a thou.
Hope this is of some use?
K2
 
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I also use the "aluminium" inserts on all materials these days, they are ideal for the lighter hobby machines be that mill or lathe due to having a much "sharper" edge they put less strain on the machines be that turning load on the motor or making the machine flex and pushing the cutter off the work.

Thay don't have much of a problem on the skin of a casting or even hard chilled areas being able to cut straight through where as a chilled spot will take the edge straight off of HSS. The carbide also allows the machine sto be run a lot faster so you get the motor of the variable machines running where it is developing more of it's power. So the order of the day is fast light cuts with a fine feed.

I have A warco 280 which would be similar to a Chester DB11 with variable speed DC motor. If I were to use the old school approach on say a 9" cast iron flywheel that would be 50rpm and a deepish cut to get under any skin it will stall. My method is to use carbide and run around the 300rpm mark that is 6 times faster Take a 10 to 15 though deep cut and the machine will be happy and the work will have a good chatter free finish.

Likewise with boring, K" mentions 180rpm for boring a 1" hole that comes out at 14m/min or 45ft/min cutting speed. I would be around starting around the 5-600rpm mark which is still well within what the carbide can handle at 50m/min. More if I were turning or had the work in a chuck and using a boring bar.

I use my boring head quite often both in the lathe and also in the mill as the power feed the carriage gives usually results in a better cut than hand feeding the quill. I do have several bars for that which are made to take inserts so again run as fast as practical but the out of balance nature of a boring head is what usually limits the speed.

Never heard of linishing a bore, usually honing or lapping, does not need fancy hones the brake cylinder ones are cheap and work and even abrasive round a stick or tube can be very effective and give cylinder bores for IC engines that don't even need their rings fitting to run.

Couple of video of 9-10" flywheels First 10.25" dia and a rigid tool setup so I could run at 300rpm that is 235m/min or 760ft/min that is towards the low end of the speed range given for that insert on grey iron. You can see I am still taking off some of the outer surface



More tool overhang here so dropped it down to 150rpm, 120m/min or 390ft/min cuts with a nice steady sound and no chatter



200rpm 157m/min on this one again getting through the skin and a bit less stick out so speed could be upped



Steam engine cylinder lapped with abrasive wrapped round a tube. Just held onto a flat surface, no oil added to improve seal. Drops straight down until I put my finger over the steam port. That was turned in the chuck using an insert boring bar and CCGT 060202 insert. 24mm bore.


 
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Thankyou both for very long detailed and interesting replies. I am not overly concerned with my surface finish at this stage as I was always intending to build an expanding lap. The construction of this is progressing nicely and will feature in the next update. The design is similar to the one I made in the previous build for the Bolton Mill engine which is also fully documented here.

I must say with regard to inserts that I have recently tried CBN inserts and the results on 4140 steel were amazing. Too late for my cylinder unfortunately.
 
Thanks Jason. Post #42 The best lesson in this I have had in 50 years, since I used industrial machines. I must also check dictionary definitions of linishing etc. as I may have used the wrong terms on wrong places...
K2
 

Part 7 - Cylinder Lapping​

My next task was to build a tool to lap the cylinder bore to make sure it was smooth and straight.
I have built tapered laps before and learned that a good design will include the following features:
  • Threads at both ends so the expanding part can be pushed in either direction and it's location controlled easily.
  • A fairly fine thread pitch to allow fine control of the lap size.
  • Plenty of space either end.
  • Some non threaded parts at either end to allow it to be gripped in the vise when you need to tighten or loosen things.
  • Not too steep a taper so as to allow the thin end to be wide enough to get a boring bar inside.
  • Regular grooves to hold the abrasive and to give some idea of how much lap has been used.
This is what I ended up building:
IMG_9095.jpeg


The all threads were machined on the lathe to 20 tpi.
I machined the taper using a taper turning attachment which I built a few years ago from a Hemingway kit.
mandrel1.jpg


The aluminium lap was machined with a recess at either end and some corresponding disks were made to fit these. Once the lap was slit on the milling machine using a slitting saw I was able to use these disks to support the lap while machining the internal taper. I used a hose clamp on the free end to keep everything nice and tight.
mandrel4.jpg


Once the lap was made I deburred everything and assembled before giving the lap a final trim to ensure it was the right size and perfectly round etc. Then I could cover it with some diamond paste and begin lapping my cylinder at long last!

mandrel2.jpg


It did not take long to sort out any tooling marks and I was left with a very nice finish. I could not measure any differences but I am now about .003" over size. I guess that probably will not be the end of the world.

Last job was to skim the mandrel again to make sure it was in spec and use it as a mandrel so that I could bring the ends of the cylinder into spec. By thhis time the small end was at the limit of its travel so I used the nut from the big end as a spacer.
mandrel3.jpg



Here is the final result which I think will do very nicely.
IMG_9094.jpeg


Next job is to build the cylinder caps. These have some elliptical shapes which is further proof that this engine was designed by someone who deeply hated machinists!
 
Splendid! Next time try to get more like a 30degree inclination on the cross-hatch from lapping. - That is the usual "standard". for oil retention "In" the surface.
(Don't try to change the existing surface, I am sure it will be quite OK). What grit size/particle size did you use? (My Wife won't let me use her diamonds - to make my own grit - and I couldn't grade it anyway). Hydraulic cylinders often have a polished chrome bore, but cast iron for steam engines or infernal combustion have a 600 grit as the finest, in my experience. "Contacting" metal parts then run on the oil film retained by the grooves in the finish. Others (Tribologists?) may have better advice? - My knowledge is from 1960s....
K2
 

Next job is to build the cylinder caps. These have some elliptical shapes which is further proof that this engine was designed by someone who deeply hated machinists!​



But I thought every good apprentice machinist spent their first 6 months learning how to file ;)

Just like full size there parts are typically left cast, you can tidy them up a bit with a file or dremel if needed. I tend to just turn the surface for the nuts to bear on and then paint the oval boss. If you use some filing buttons and mount the gland then both can be shaped to a final matching profile.

There are ways to machine a pleasing shape, boring head set to cut externally will give the two curved flanks and the rotary table can do the ends. Or you can go with a slightly more angular look with 4 tangental edges to a larger radius in the middle and smaller at the ends. These days I will use the CNC.

Boring head
PICT0337.JPG


Tangental

Tid78.JPG
 
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Splendid! Next time try to get more like a 30degree inclination on the cross-hatch from lapping. - That is the usual "standard". for oil retention "In" the surface.
(Don't try to change the existing surface, I am sure it will be quite OK). What grit size/particle size did you use? (My Wife won't let me use her diamonds - to make my own grit - and I couldn't grade it anyway). Hydraulic cylinders often have a polished chrome bore, but cast iron for steam engines or infernal combustion have a 600 grit as the finest, in my experience. "Contacting" metal parts then run on the oil film retained by the grooves in the finish. Others (Tribologists?) may have better advice? - My knowledge is from 1960s....
K2
It would be very difficult to cut a 30 degree spiral for the lapping grooves. I would be very surprised if it made enough difference to warrant the effort.

The diamond paste I used is marked as 40 micron.
 
But I thought every good apprentice machinist spent their first 6 months learning how to file ;)

Just like full size there parts are typically left cast, you can tidy them up a bit with a file or dremel if needed. I tend to just turn the surface for the nuts to bear on and then paint the oval boss. If you use some filing buttons and mount the gland then both can be shaped to a final matching profile.

There are ways to machine a pleasing shape, boring head set to cut externally will give the two curved flanks and the rotary table can do the ends. Or you can go with a slightly more angular look with 4 tangental edges to a larger radius in the middle and smaller at the ends. These days I will use the CNC.

Boring head
View attachment 158735

Tangental

View attachment 158736

I was leaning towards the tangential shape but your examples are pure perfection. Now I will have to revisit the idea of using the boring head. There is no option of leaving the boss as cast because it does not fit within the mating part. In the Tubal Cain book on the engine, he simply states "I'm sorry but I must again confess that I know no simple way of making the oval - not one at a time, anyway!.

See I told you this thing was designed by a sadist!
 
The 30deg is the result of how fast you move the cylinder along the hone/lap. I would say it is more of a honing thing than lapping which tends to just leave an even fine surface. Also depends on what rings you are using, don't want a hatch chewing up an O ring.

Treat "as cast" as not a surface that is leaft bare and machined. As long as it looks nice any slight irregularity from hand work is not critical.

It is also possible to do the longer edges with a simple jig in the lathe, drew this for someone a while back. Also photo of one side one with the boring head
 

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Part 7 - Cylinder Lapping​

My next task was to build a tool to lap the cylinder bore to make sure it was smooth and straight.
I have built tapered laps before and learned that a good design will include the following features:

I absolutely admire your lapping tool and all that went into designing and making it :) !!!

(personally I only use corundum, never diamond, don't want truly indestructible abrasives in my shop)
 
The 30deg is the result of how fast you move the cylinder along the hone/lap. I would say it is more of a honing thing than lapping which tends to just leave an even fine surface. Also depends on what rings you are using, don't want a hatch chewing up an O ring.
Oh I see. I completely misunderstood that comment.
There surface of the bore is very smooth. I think the piston rings will make it even smoother once the engine is completed. It came with some very lovely piston rings and I think it would be a shame not to use them.
 
(personally I only use corundum, never diamond, don't want truly indestructible abrasives in my shop)

It seems to break down very quickly but I am very careful to put down some paper towels to protect my ways.
It's quite similar to corundum.
I also always have a piece of leather on the front of my carriage to protect the ways from swarf.
 
  • ALL abrasives must be washed away from machine ways, and other working surfaces, with paraffin, or other spirit cleaner, then air dried and polished with a clean dry cloth or paper towel. Otherwise you cannot ensure the abrasive will not be trapped in the contact surfaces and cause damage (rapid wear) of your expensive, finely made and precise machine surfaces. Always lubricate with clean oil (preferably one with a corrosion inhibitor) after cleaning.
  • Swarf is much less damaging than abrasive material. If you dry machine, then it is easily removed by brushing (fine paint brushes or similar do this well). Wear tough rubber gloves if handling swarf! (Razor sharp edges, and very fine splinters that can penetrate deep into flesh). If you use liquid coolant or cutting fluid, then it is not too difficult to wash down with more fluid after finishing machining, and drying and oiling after use of the machine. If dry machining, a "Low pressure jet" of air can help cool parts and cutters while machining. NEVER a high pressure blast! - that simply blows swarf EVERYWHERE! (Into eyes especially, causing pain and possibly permanent damage! - I have a friend who had swarf in an eye - surgically removed while he was conscious... You do not want that!).
  • I found this table:
Micron vs Grit
ProductGritMicron
100 Grit Diamond Stone100150
200 Grit Diamond Stone200125
400 Grit Diamond Stone40075
600 Grit Diamond Stone60040

  • Hand-filed ellipses are good, as are cast surfaces, where not required to be machined. Just look at real machines. Cast surfaces everywhere. But you decide if you want the effect of Jewellery, or "real" machinery? Both can be acceptable (Beautiful?) to various beholders. WIll the surfaces be painted (for weather protection as well as cosmetic appearance)?
Enjoy! I am impressed by much of what you do, so keep up the good work.
K2
 

Part 8 - Cylinder End Caps​

Next I decided to tackle the cylinder end caps. The Tubal Caine book rates this as such a simple job that it doesn't bother to provide any guidance. Personally I found it to be quite an interesting challenge. My main concerns were to ensure that the end caps were very concentric and very parallel.

The end cap castings come complete with a very thin boss which I could have held in the 3 jaw chuck, but instead I decided to make use of my recently purchased "Flexi Chuck". This is similar to a set of soft jaws or a pot chuck where you machine a mortice to hold the part. The flexi chuck allows you to do this while the jaws are slightly expanded or flexed, so that once the part is fitted they can be relaxed and will firmly grip the part. The advantage is perfect concentricity, no marking and very good grip.

So I machined a tenon to fit the boss
flexi-2.jpg

Then I fitted each end cap and cleaned up the outer diameter.
flexi-3.jpg
I used this outer diameter to clean up the front faces in a similar way.
flexi-4.jpg
On the lower cap there is a large eliptical gland stuffing box which was an interesting challenge. To fixture this side I first machined some aluminium to fit over the box. I fixed this with some cyanoacrylate glue and then turned it down to ensure it was perfectly concentric with its matching face. I could then flip the part and hold it once again in the flexi chuck.

flexi-5.jpg

Once all faces were machined to size I mounted my cylinder in the milling machine and carefully centered on the bore. I could then use the pitch circle function to drill and tap the various holes for the caps. Having done all of that I was finally able to bolt my cylinder to the bedplate and my engine is starting to look like something and I am very pleased with the progress so far.

IMG_9111.jpeg IMG_9106.jpegIMG_9113.jpeg

I'm not sure what I will tackle next. Perhaps the piston and the crosshead guide.
 
JC. Please check all this with a micrometer level of measuring - A dial test Gauge or something, - whatever you have that will work:
Use your surface plate (or the flat of the lathe bed, or milling table, whatever ground, flat surface you use) and height gauge with DTI to set the surface of the cross-head guide truly flat, then check the piston rod is equally true when extended.
You want the piston rod to be "Exactly" parallel to the cross-head guide. BUT need the piston in the bore, on the end of the piston rod, to check it. So make the piston next, then check the piston rod to the flat surface of the cross-head guide, to be sure it is "true".
Cheers.
K2
 
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JC. Please check all this with a micrometer level of measuring - A dial test Gauge or something, - whatever you have that will work:
Use your surface plate (or the flat of the lathe bed, or milling table, whatever ground, flat surface you use) and height gauge with DTI to set the surface of the cross-head guide truly flat, then check the piston rod is equally true when extended.
You want the piston rod to be "Exactly" parallel to the cross-head guide. BUT need the piston in the bore, on the end of the piston rod, to check it. So make the piston next, then check the piston rod to the flat surface of the cross-head guide, to be sure it is "true".
Cheers.
K2

It's as parallel as I can measure, and it's bang on 0.5"

IMG_9141.jpeg
 
its the parallelism that matters and it looks like you've achieved that, well done !!!, the actual height can be anything with the cross head machined to match it, but I'm guessing you already know that !!!

(as I've said before) the #9 is my favorite Stuart, and if you'd like to see plans for a matching Edison Bipolar Dynamo let me know.
 
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