Machining Cylinders - How to Do?

[dampfmann]

Hello,

I purchased a set of cylinders for my 3/4" scale A3 0-4-0 from John at Friends Models Yankee Workshop. This is my first time machining locomotive cylinders and I would like to complete the process without having to purchase another cylinder. (Sorry, John.)

I searched YouTube and this forum, but didn't find much depicting how to machine cylinders with slide valves and this scale. The information I found dealt with larger cylinders with piston valves.

I am wondering where to begin? Should I start with facing the cylinder and drilling and boring or should I mill the valve and frame-side faces?

Thanks for your input and suggestions.

Marty

(I inserted the picture both up-side-right and up-side-down and got the same up-side-down results. Sorry about that.)

[gwrdriver]

Marty,
How you do it kind of depends upon what machine capacity you have, but in general I would begin by facing the mounting (to the frame) surface, followed by the valve face, and then locate the bore relative to those surfaces. I would finish the cylinder end faces by mounting the casting on a chucked mandrel turned to fit the bore. YMMV

[RickBarb]

Marty, I just finished two cylinder castings for a Stuart Double 10. Their instructions were to center the exterior of the casting to run as true as possible and not to worry about the cast in bore as there should be enough "meat" on the casting to allow for the cast bore to be a bit off center. Then bore the casting. After the casting his bored, turn a mandrel to fit the bore and face each end. This will insure the faces and the bore are perpendicular to each other. What I do for the mandrel is to turn a piece of steel to just slide in to the bore. Mill a flat on the mandrel that is 10% of the diameter. Slide the casting on to the mandrel. To lock the casting on to the mandrel just take a piece or rod/wire that is a bit smaller than the 10% milled off the and slip it into the gap, give it a twist and the casting will be locked on to the mandrel. To remove it, just give it a reverse twist and "Bob's your Uncle"! It sure beats trying to turn a mandrel with a taper to lock the cylinder. Hope this helps. Rick

[Mike Walsh]

Marty, I just finished two cylinder castings for a Stuart Double 10. Their instructions were to center the exterior of the casting to run as true as possible and not to worry about the cast in bore as there should be enough "meat" on the casting to allow for the cast bore to be a bit off center. Then bore the casting. After the casting his bored, turn a mandrel to fit the bore and face each end. This will insure the faces and the bore are perpendicular to each other. What I do for the mandrel is to turn a piece of steel to just slide in to the bore. Mill a flat on the mandrel that is 10% of the diameter. Slide the casting on to the mandrel. To lock the casting on to the mandrel just take a piece or rod/wire that is a bit smaller than the 10% milled off the and slip it into the gap, give it a twist and the casting will be locked on to the mandrel. To remove it, just give it a reverse twist and "Bob's your Uncle"! It sure beats trying to turn a mandrel with a taper to lock the cylinder. Hope this helps. Rick

I used an expanding mandrel on a tapered shaft... They can be had online. I managed to snag a full set, allowing me to go down to 1/2" dia, up to 2" dia. bores I'll post photos later if I remember.

[Glenn Brooks]

Good info on the setup. Often overlooked are boring the ID to a smooth finish so the piston rings seal properly. Any thing special about grinding HSS tooling, geometry or feeds and speeds for the boring bar? Photo closeups would be interesting and useful.

[RickBarb]

I lap the cylinders with a DIY lap using "Timesaver" lapping compound. Cast Iron is usually pretty easy to bore. A sharp and rigid boring bar will give good results and require a minimum of lapping to get a good surface. I use O-rings in lieu of packing or rings. Ignore the manufacturers recommendation for compression. I usually shoot for around .005" compression. Anything more will greatly increase the friction between the ring and the cylinder wall. Rick

[Builder01]

I used an expanding mandrel on a tapered shaft to finish machining my cylinders to length. I did the ports first with the cylinder slightly long, then machined the ends so they are exactly the correct distance from the ports. For me, this was easier than positioning the ports an exact distance with the finished end as reference. Does not really matter as long as you end with the correct result. Attached are a few random photos of my cylinders as I machined them.

David

[VO4454]

Marty,
I know you are asking about slide valve cylinder blocks. Below is a link to Jack Bodenmann's 3/4 inch 0-6-0 project. Although the cylinders are piston valve, there is a wealth of machining information and fixturing pictures. Definitely worth the read.

Vic

viewtopic.php?f=8&t=83490

[Dick_Morris]

You can also mill the flat surfaces and then clamp the cylinder block to an angle plate bolted to the lathe face plate to bore and face the crosshead end in one setting.

[FKreider]

They can also be done completely on the mill with a boring head.

[hoppercar]

I.guess it all comes down to, what type of machinery you have at your disposal, and if your comfortable doing it?..there are plenty of guys in the live steam world, who could lend a hand with them...theres about as many ways to set them up and machine them as there are guys to think.it up. Dont be afraid to use the people at your club if help is needed, there a great resource...thats what are hobby is all about....helping out !!!

[FKreider]

Here is a neat video I just came across yesterday showing the restoration (re-boring and machining mating faces) of a stoker engine from the Nashville, Chattanooga & St. Louis Railway No. 576 steam locomotive that is currently being restored.

The boring and machining shown in this video is done on a very large Giddings and Lewis Boring Mill however the operations are the same for small hobby steam engine cylinders when done on a Bridgeport style knee mill, just in the vertical orientation.

https://www.youtube.com/watch?v=pLzZ3JYPXOg

Brian Block does some cool work with large machines, check out some of his other videos if you have not seen them, the work he did to the old barn that his shop is in is also incredible, you have to go back to his older videos from several years back to see how much work he did to that building, basically by himself!