General steam port drilling question

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smittman

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Hi, being new to building steam engines my wife and I pretty well have a basic understanding of the concept and machining except for the steam ports. Luckily she is as excited about out first build as i am.
We`re about to begin our first build and i`m not sure of how to best make to steam ports.
I notice most plans show them being located close to the center with them being drilled to the top and bottom edge of the inside of the cylinder at a angle. It looks like they mill a small area in the end of the cylinder to drill from and let the steam in after the cap it on.
Ive searched but have only found a couple bits on the approach of how to do it.
In a old machinist guide amateur mechanics July 1883 article it said to drill the ports then use a drill rod that was ground and hardened to act as a chisel to open the area between to 2 or 3, 1/16" drilled passages between the center and the end. OK maybe in wood but in brass?. Is this still the way in 2017. I don't know if i can try to mill the opening from the end towards the center after the holes are drilled. Maybe i`m overthinking this (something my wife tells me i do frequently lol).
Any help or guidance would be appreciated. Also anyone in Ft Myers Punta Gorda Fl area into the hobby that would like to chat let me know. I really enjoy the articles and how you all try to help each other. Thanks Dave and Tammy

In the pic below it shows the ports towards the end of the cylinder unlike most of the plans i have found online where the ports are closer to the center.

question.JPG
 

Jasonb

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Back in the day most modelers did not own milling machines and a chisel was one of the ways to make grooves and yes it will work fine in brass.

Today with cheap imported mills you will be best off milling and yes drill the ends first before milling out the rest as it will make it easier. But unless you are going to need the engine to do actual work just 3 drilled holes will do the job without any milling and a single hole across from the port face to the exhaust hole comming up from below at the same dia.
 

kwoodhands

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I bore the angled hole only. First I cut a wood block slightly narrower than the cylinder and at the angled needed.
I'll use an example of some of Elmer Verduz 's engines which use a 16-1/2° angle. If the cylinder is 1" wide the wood angle block is cut to 15/16" or so thick. I cut the block on a miter saw for accuracy. Place the block with the cylinder on it in the vice. Temporarily install the drill bit. Center the drill bit on the cylinder face . The bit should be just inside of the face. The holes should clear the heads when installed. Often the heads have a slight raised portion inside to assist in centering the head. Often only 1/32" but possibly enough to block the port holes. Remove the bit and install a 1/8" end mill. Mill a flat spot about .0100 deep. Enough to be able to start the drill bit on a flat surface.
Use a center drill to start the hole. I often do not use a center drill but use a 1/4 " drill bit instead. I turn the chuck by hand, slight down pressure on the quill. Only takes a few turns to spot drill a point. Then slowly bore with the correct bit til the bit comes thru the cylinder valve face. Repeat for the other side, The exhaust port is done similar but with a different angle.
Make sure the angle of the bore will come thru the block to the valve face. Use a sharp drill and go slow.
I used to practice on a wood block to make sure the bit would come thru where I wanted it to. I would try that if I were you since this is your first go at drilling a cylinder. Better to practice on wood than expensive piece of brass.
mike
 

smittman

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Thanks for the great advice. This is the only thing that had me scratching my head. I really like the block method and will definitely try it on a wood cylinder first.
Thanks Dave and Tammy
 

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