The Radial Five (Rudy Kouhoupt)

[Kim]

Having finally completed my Marine Twin build, I am now excited to get on with my next build!  I've been contemplating what to do next for over a year, but about two months ago, I finally made the decision to do Rudy Kouhoupt's Radial Five as my next project.

I'm sure most of you are familiar with it, but just in case, I added a photo, scanned from page 47 of "The Shop Wisdom of Rudy Kouhoupt, Volume Four: The Micro Machinist's Legacy".


I chose this engine because it is very different than any other that I've built.  This one has five cylinders, uses a rotary valve, and of course, is a radial!   It actually looks like it has fewer unique parts than the twin that I just built, but with it being five cylinders, it's probably pretty close to the same in total parts count.

The plans contained in the book are accompanied by copious instructions on how to perform each step, and what order to do things in.  I've never had this much information about a build before!  So, I don't know if I'll follow his step-by-step instructions, or do my own thing.  Likely some of both.

Anyway, the first part of any build is studying the plans, pulling together a BOM, and getting all the raw materials in house.  I'm starting to get a collection of left-over pieces of metal, but I still don't have a ton.  Especially when it came to the bigger chunks that were needed.   So I made a trip to the local Metal Supermarket and picked up some of my missing pieces.  I've never used them before - I've always ordered from Metals On Line in the past - they seem to have better prices.  But I wanted to be able to get started right away, and didn't want to wait for the shipping.  So I drove all the across town and picked up these hunks of aluminum:


I still have a few things I need to collect (like some bronze for the bearings - Metal Superstore apparently doesn't carry bronze).  But I think I'mready to start making swarf!
Kim

[Don1966]

That should be a very interesting built Kim also a great learning curve to go with it. Good luck buddy and I believe you will do good on this one also.

Regards Don

[Dave Otto]

Oh boy

Way to jump into the next project; I for sure will be following along with your next build.

Dave

[Johnmcc69]

Nice project!

[zeeprogrammer]

Way to jump into the next project; I for sure will be following along with your next build.

  What Dave said.

[b.lindsey]

Nice looking engine Kim...I'll be along for the ride as well and looking forward to your progress.

Bill

[Kim]

Thanks guys!

So, I spent a couple of hours tonight trying to figure out how to adapt some of Rudy's fixtures to my equipment.  The way I came up with required me to cut some threads using my new lathe this is a new experience for me   So tonight I just tried an experiment.  It came out kind-a OK.  Good thing it was just practice.  I remembered lots of things I've seen other do as I was executing my experiment.  And its amazing how much sense it makes when you are trying it for yourself.

me... "Oh, THAT'S why people cut a relief behind the  last threads!"
Me again... "Oh, THAT's what it looks like when you cross thread cause you didn't start on the right number."
And again... "Oh, THAT's what people mean by 'cutting on the leading edge' and why they say you should feed in with the compound slide set to 59.5 degrees.

But I've never heard people talk about how you have to divide the thread depth by Sin(60) in order to get how far you have to feed the compound slide in when cutting the threads.  Do others do this and I just don't remember it?  Or did I do something unnecessarily complex?  (and potentially make my test threads too loose?)

What a neat learning experience for me this was!  I'll take pictures when I do it for real to show you all the cool fixture I'm making.

What fun!
Kim

[fumopuc]

Hi Kim, it is always a good learnig curve if you have to make some equal parts for one project. That  will show you, how repeatable are your skills in accurateness. I have learned this at my 16 valve build and have recognized  there is a lot of space for improvement.

[Mike OConnor]

Hi Kim,

The compound rest infeed for 60 degree American National Threads for the various angles are:

External Threads:

Depth of Cut @ 30 deg. = .75/ N, where N = No. of Threads Per Inch (TPI)

D.O.C. @ 29.5 deg. = .746/ N

D.O.C. @ 29 deg. = .743/ N

Internal Threads:

D.O.C. @ 30 deg. = .625/ N

D.O.C. @ 29.5 deg. = .622/ N

D.O.C. @ 29 deg. = .619/ N

These formulas are based on the tool having the proper flat on the threading tool. For External Threads that is W = P/ 8 and for Internal Threads W= P/ 4, where W = Width of Flat and P = Pitch = 1/ N, N = Number of TPI.

Remember to double this result if your compound rest reads Diameter Reduction directly. Fortunately, if you dial in the total compound rest infeed and your thread looks incomplete, you have direct reading dials and the number must be doubled.

My preference when single point threading is to infeed with the compound rest at 29.5 degrees and stop .003"- .005" short of the total infeed depending on how coarse the thread is. I then check the pitch diameter with a set of thread wires, which are not expensive or a thread micrometer. To finish the thread, I feed the remainder with the cross slide .001" at a time taking free passes along the way to bring the thread to the correct pitch diameter.

By in feeding the threading tool with the compound rest at an angle slightly less than one-half of the included angle, transfers 7- 11% of the total depth of cut to the trailing flank of the tool. Sorry, too tired to get up and find my notebook at this time! Sometimes, if you infeed at 30 degrees (or 1/2 of the included angle of the thread) the trailing flank of the thread can be scarred when you are taking the first passes and that damage will appear on the finished thread because the tool follows that same path along the trailing flank. By in feeding at 1/2- 1 degree less, you are taking a bit off that trailing flank with each cut. By taking the last finishing cuts with the cross slide straight-in, you are also taking a finish pass on all three surfaces of the thread: leading flank, trailing flank and the root.

Enjoy your next build. I will be following along.

Mike

[Maryak]

Hi Kim,

The 2 ways of cutting a thread on a lathe.




Hope it's useful.

Best Regards
Bob

[Stuart]

why not set over the topside to the position you require 27.5 29.5 or WHY
then put a dial indicator on the saddle bearing on the tool post that will then read your in feed with no maths used during the machining

look up Keith Fenner on youtube he has a lot of vids and a flip though will show you how to sett it up and a demo of it in action


Stuart

[Mike OConnor]

Hi Kim,

With regard to Bob's post above, I find that feeding the tool at an angle with the compound rest is only absolutely necessary when cutting coarse pitch threads. With threads 24 TPI or finer, feeding straight-in with the cross slide should work just fine as long as there is proper clearance on both flanks and under the flat on the tip. In this case the infeed is the Depth of Thread (DOT). For American National External Threads, DOT= .64952/ N, where N = Number of TPI. Internal DOT = .541/ N

You will find what works best for you. Ultimately, the finish on the thread is what matters and if in doubt I choose the angled infeed to avoid trouble. If machining tougher materials, the angled infeed will avoid the tearing problem on the trailing flank.

Single point threading on the lathe isn't difficult, it just takes practice like anything else. A good practice exercise is to take a 1" diameter bar of CRS, use 12L14 if you have some about 6"- 8" long and put it between centers. Scrounge up some nuts or buy some singles from the hardware store like 1"-12NF, 1"-8NC, 3/4-16NF, 3/4-10NC, 5/8-18NF, 5/8-11NC, 1/2-20NF and 1/2-13NC to use as mating parts. Then turn the bar to the proper Major Diameter and choose a particular length for your thread and just start practicing. Protect the diameter of the bar with a piece of brass under the dog's set screw. You can take a nut and split it with a hacksaw to use to dog on a finished thread if you want to protect it, just make sure you squeeze the split-nut with the dog's set screw so it clamps the work. Just keep turning off the threads as you go to the next smaller size. Placing the bar between centers will allow you to remove it from the lathe to check the threads with the nuts. Just remember to put the tail of the dog against the same chuck jaw or driving pin when you put it back between centers or you lose the synchronization with the thread. It is common practice to drive the lathe dog with the No.1 jaw if using the chuck jaw to drive the dog.

The formulas are simple and if you complete such an exercise, many will be committed to memory by the time you are finished.

This was the first lathe project for my students and it introduced them to all of the basic lathe operations. I will start another thread later and post the step-by-step drawings for that project. I have to dig them out and scan them. I think this would be useful for beginners to practice their thread cutting.

Mike

[Kim]

Thanks Achim,
Yes, this project should let me practice my repeatability, that's for sure!

Thanks Mike, Bob, and Stewart,
I am reviewing several YouTube thread cutting tutorials now and as I said, its amazing how much more you pickup when you've tried something yourself and are actually implementing it!

I was worried that I was off by a significant amount when Mike started talking about 29.5 there.  But Bob, your picture helped out a ton!  I see that my compound is numbered the other way so that my 60 is other people's 30 I remember hearing others talk about this, but NOW it makes sense!

But I should be using 60.5 degrees, which is the complement to 29.5.  I knew there was a half a degree in there somewhere, I just went the wrong way. But with Mike's explanation, it makes sense which way it should be, and WHY its 1/2 a degree different than the slope of the thread.

I will practice this a little more!  I'm really quite enjoying the single pointing threads thing

BTW, for my fixture, I'm cutting 3/4" 16 TPI threads.

Thanks for all the suggestions and help!
Kim

[Dreeves]

Kim, I have some fixtures for making the cylinders and one to solder the tubes. Let me know if you want them. I have made 3 of the 5 cylinder and a modified 10 cylinder.

Dave

[Kim]

Thanks for the kind offer Dave (Dreeves).  That's very thoughtful!  I'll let you know if I need anything, but for now I think be making the fixtures that I need.  All part of the fun, right?

Thanks everyone for all the help with threading!  I read everyone's advice, reviewed several tutorial videos, did a few practice runs, and then launched in to making my fixture!

Unfortunately (or maybe fortunately, for you all ) I didn't take pictures during the operation.  However, it was just pretty basic turning & threading.  Fun and new for me, but old hat to most of you all.

Here's the part after I finished the threads.   I don't have a set of thread depth measuring wire (another thing I need to put on my NEED list ) so I just crept up on the depth carefully till a 3/4-16 nut fit on it nicely.  Maybe not ideal, but it'll work for me this time. And I didn't want to wait for a shipment to come in (how impatient can he be?  )


This is what the whole gizmo looks like out of the chuck.


What is it, you might ask?  It's simply an adaptor for my Taig accessories.  Now I can use my 1" 5C collet to hold this little adaptor, and then I can screw in any of my Taig chucks or faceplates.    And this means that I can move a part between my Grizzly lathe and my Taig mill (and Sherline rotary table) without removing it from its mounting.  Pretty ingenious eh?  Well, I'm sure its old hat.  But I thought it was cool!

This is how it will look when in use - almost nothing but the business end showing.


And here it is with the Taig 3.25" face plate mounted on it.


I even got the registration part that fits tightly on the very back of the chuck or face plate.  It seems to be a pretty good fit.  I'm measuring about +/- 0.0005" TIR on the face plate when mounted like this.  Hopefully that'll be good enough accuracy for anything I do in my shop!

You know I had so much fun single pointing these threads that I'm going to have to find another project that uses more threads!

Thanks for looking at this first itty bitty baby step on my new build.
Kim