Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines
Builds, Repairs, Show Your Machines! => Technical Tips, Builds, and Help => Topic started by: Nu2modlin on September 01, 2020, 06:00:31 pm
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I had to make up my own machining sequences/postions for the engine I built.
Machining castings can be a bit of a trick, but I do prefer castings.
Sometimes the biggest challenge is figuring out where to grip the part.
Looks like a nice build you have going here.
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I believe his name is Tinker John on You tube. He is pretty good with these models.
My next step is to start on the connecting rod castings, the heads and the crank casting.
These are small parts. This will be new to me.
Watching different builders on You tube, learning Turning, Keith Appleton of course and compare their approach to Joe Piezinski of Austin TX.
Joe uses trigonometry, special made one time holding devices and his digital read outs. The fixturing and holding art to this is all new to me.
No super glue.
They all get there in the end.
I hope to be back on the PM #7 in the next few weeks.
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Well i have had a read and it appears you know what you are doing and making great progress.
If i keep up i may learn something .
Cheers
Dennis
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A wonderful build thread you have here.
Looking forward to following your progress.
Charlie
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Looks like you are doing a wonderful job, and more importantly carrying the correct attitude to the work. The reason you are undertaking this project is for the enjoyment of the process, and the successful accomplishment of the goal you've set yourself. Neither can be achieved well by rushing. Doing things slowly, carefully and methodically usually proves to be faster by far, in the end!
Well said!
👏👏👏👏👏
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Stoker, I took the liberty of buying quality spiral flute taps. They seem to require less effort and the chips clear.
Done for today. I need a 3/16-40 model tap and die per the instructions.
I had not seen that in my many overviews of the plans.
I am very happy with today’s results.
9-26-20
I drilled and counter bored the 3/32 holes at 20 degrees as directed. Once again the casting is a bit tricky to set up for machining.
I don’t know what you guys use but I used an 1/8” end mill to cut a flat then used a center drill to guide the drill bit.
It is very satisfying to have good results, as a mistake at this point would be very frustrating.
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Not wishing to assume what you may or may not already know, but just a friendly comment.
With small taps like 4-40, they are rather weak and very brittle, so easily prone to breakage, and there is no need to ask how I know this. Once you start feeling any real resistance to turning forward, go backwards at least 1/4 turn or until you feel the "chip" break away, before going forward again. The smaller the tap, the more gently I progress, but typically find that a 1/2 turn, or a little more forward, and a 1/4 turn back gets me there without the grief of a broken off tap.
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Thank you,
Looking through the instructions, both cylinders need to be faced at the inlet ports, drilled at 90 degrees and tapped, then a 20 degree set up so the steam/air can be delivered to the cylinders to drive the piston.
This will be a careful set up.
I don’t think I have ever tapped 4-40 or drilled down to a set point.
Looking forward to it.
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A most excellent result .... well done!
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Made some progress.
I ordered and received a new cylinder to replace the one I screwed up.
The new method of centering the cylinder body in the four jaw worked beautifully.
I have two identical cylinders within .002”.
They are concentric and true to the bore.
Working with brass is a real pleasure.
Before I go further I need to clean up the castings to get ready for the drilling and tapping operations.
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I received my new cylinder today from PM Research.
Wow, that is good customer service.
I've ordered various things from them over quite a number of years, and they have always been truly excellent for me!
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I received my new cylinder today from PM Research.
Wow, that is good customer service.
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Stoker,
I have been reading your method, it seems like a viable way to go.
The mandrel idea was my first choice but now that I think it through, I really need to measure off the outer rim of the cylinder. Your method of indicating the three jaws is reading off the three point cylinder circumference.
I like it.
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I ordered the cylinder today. The total including shipping was less than $20.
I would say that's well worth it for my piece of mind. The next time I machine a cylinder it will come out much better.
I hope ;)
Not worth messing about at that price. ;)
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I ordered the cylinder today. The total including shipping was less than $20.
I would say that's well worth it for my piece of mind. The next time I machine a cylinder it will come out much better.
I hope ;)
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One way to go is to either use a mandrel, like a gauge pin or just some round stock, that has the same diameter as the cylinder and indicate off of that, with your fourth jaw out of the way. If you don't have such a properly dimensioned piece of bar stock laying around you could just index off the inner or outer jaw faces themselves.
Clamp the cylinder in three jaws of your four jaw chuck, centered by eye to the best of your ability, with the cylinder set deep in the jaws so you can get the tip of an indicator onto the lip of the jaws. Move the jaws as needed to bring all indicated readings to the same number. Back one of the opposing jaws off the very least that you can and still move the cylinder, then bring the cylinder back up to the front of the chuck jaws where you want to work on it, then screw that slightly loosened jaw back in just the amount needed to clamp back up and then bring the fourth jaw in to clamp onto the steam chest bulge. You should be good to go at that point.
Hope that helps settle the mud out a little bit.
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Question for you guys,
How do I center the cylinder in the chuck?
If it wasn't bored it would be easier.
I've been thinking about this. What I have come up with so far is, I place it like before using the mandrel. I then remove the mandrel so it's just outside the rough bore. I measure the three sides of the cylinder to the outside of the mandrel to even out the distance.
Is that clear as mud?
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I really don’t have a choice.
I sent an email to pm research.
I won’t be happy with anything else.
Every time I looked at this model I would say, you should have replaced it and done it right.
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That's a buggar.
A new blank casting is probably best.
It can be tough on morale but learning something means the day has not been a total waste.
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Stoker,
The bore is consistent from end to end. I measure .238" and .239" on the narrow side of my mistake.
I've had the wind cut out of my sail. I need to walk away for today.
Meanwhile, I replaced the bearings in an electric motor I'm overhauling for my son's table saw.
You do have another option to consider here Jeff, and it is the one I'd likely give the most consideration too, were it me.
PM Research does sell individual parts for their kits, so there is that option for you to think on.
Meanwhile .... walking away can be a very good thing sometimes ...... but you'll be back, I've no doubt what-so-ever!!!
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Stoker,
The bore is consistent from end to end. I measure .238" and .239" on the narrow side of my mistake.
I've had the wind cut out of my sail. I need to walk away for today.
Meanwhile, I replaced the bearings in an electric motor I'm overhauling for my son's table saw.
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Very nice progress so far :)
That cylinderbore offers a good reason to upgrade to a slightly bigger bore/piston (if there´s room ofc)...
Learned something and more power to the engine when finished...win-win ;)
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How's the runout on the other end? If I recall correctly, these cylinder castings are symmetrical, and so can be swapped end for end. I would align the best end of the cylinder on the frame and cap the most off center end on the dead end. You may also have enough room to go to a slightly bigger piston and cylinder bore, to bring it back to concentric alignment.
Four jaws are wonderful tools, but can easily get you in trouble. I usually try to just spot face first to provide a check for centering, and do a small bore through to check co-axial alignment, before approaching final dimensions.
Hindsight is wonderful, isn't it ...... but yes I do believe this sort of thing has been done before, a time or three!
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I don’t imagine I’m the first guy to bore off center on these irregular castings.
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Learned something today. In hind sight it was a stupid mistake.
I’ve seen this method of aligning the cylinder to the four jaw but you have to have a perfect casting. I don’t.
I’m not sure what I’m going to do. It is a learning experience but it’s off center .040”. The unfinished bore is off .025”.
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Excellent progress and +1 for taking it steadily. I sometimes have to stop myself from accelerating towards the finish and give myself time to ponder the project.
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Looks like you are doing a wonderful job, and more importantly carrying the correct attitude to the work. The reason you are undertaking this project is for the enjoyment of the process, and the successful accomplishment of the goal you've set yourself. Neither can be achieved well by rushing. Doing things slowly, carefully and methodically usually proves to be faster by far, in the end!
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It was a productive morning.
The grandkids are coming over to swim. That’s always a hoot.
Just a few more things to do on the base. I’m happy with my patience and accuracy.
When I feel like I’m beginning to rush, it’s time to step away.
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Coming along nicely now.
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Cross Head Guides.
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I was able to mill the cylinder mounting faces with this measuring method.
Now I can mark, center punch and drill for the cross head guides.
Once I drill and tap the eight holes, that completes the base.
On to the brass.
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Yep, last I knew he was still with us ... but he had left us behind from the "other" forum several years ago, never found out why, and hasn't shown back up in any of the normal venues that I've seen. Used to look forward to his posts and the wonderful projects that he often shared with us there.
I still treasure my little rocking piston thimble engine that he made in a batch, but each one was still just a little different .... intentionally!
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Yes, Dean is well missed, but at least his website is still up with a whole bunch of useful info available!
It wasn't too long ago, couple of years maybe, that I referenced that while making an ER collet chuck for my lathe.
He's still kickin' yet as I just seen a post from him on the Coleman Collector's forum.
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Success,
The measuring method I came up with proved to be satisfactory. I was able to achieve the 3.250" cut.
I should be able to make some progress this coming three day weekend. It's forecast to be 111 degrees F.
My shop is air conditioned thank goodness.
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Yes, Dean is well missed, but at least his website is still up with a whole bunch of useful info available!
It wasn't too long ago, couple of years maybe, that I referenced that while making an ER collet chuck for my lathe.
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^^^Really miss having Dean around... he was the best at explaining everything and had some of the best build threads.
Looking forward to following this build, take plenty of pics along the way ;)
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This isn't my work, but Dean does a good job of showing how he built the same model steam engine here:
http://www.deansphotographica.com/machining/jobs/pmr7/pmr7.html
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I too will be watching with interest
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I will enjoy following this thread. Please keep the photos coming.
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Looks like really well thought out progress from here!
Remember to always measure thrice and cut once, so that you don't end up like I often do, wherein I've cut something three times and it's still too short!!! ;c)
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Hi all,
I’m really enjoying this so far. My reason for getting into models is because I see the Rapid growth in skills from fellow model builders
I am working on the base, learning how to set up, hold, measure, mill etc.
My skill level has already improved because I’m working off of plans with specific measurements.
In these pics, I am milling the cross head base. I made a tool to determine the center of the crank shaft so I could measure -mill the cylinder mounting surfaces, then I can measure where the cross head tops? Are drilled and tapped.
Is that clear as mud?
Looking forward to the brass!