Another Tiny IC Engine

[gbritnell]

Hi Bill and others,
Here's two ways to thread up to a shoulder, well almost. First I have several threading tools that are first ground with the 60 degree tip. I then grind away material until I only have enough to go to the proper depth for the thread I'm cutting. It's actually a little longer but it's close to depth. Now I'm using a Craftsman/Atlas for my small stuff so I made up a handle to turn the spindle over by hand. It has a bushing turned up that is about .010 smaller than the bore of my spindle. The bushing is split at an angle, 20-30 degrees. When the through bolt is tightened it draws the 2 pieces together which ramp out and lock up inside the spindle. I set up for threading, gears and dials just like you would do if you were threading under power but instead I use the crank. For a spark plug you should use a washer so the last little bit of unthreaded area is taken up by the washer.
gbritnell

[gbritnell]

The other way to get up to the shoulder is to grind up the tool as I mentioned but mount it upside down. This only works if you have a lathe with a toolholder that will give you enough room to do it. I have a special block made up for my Craftman/Atlas lathe that will allow me to turn the tool upside down and still get it on center. Now set up for threading, gears, dials etc. Run the spindle backwards and reverse the feed. Come into the shoulder, touch the stock, advance the tool, engage the half nut and cut toward the tailstock.
gbritnell

[zeeprogrammer]

I don't know if this helps anyone...

I took a piece of hacksaw blade (very thin), grounded the end, and used it as a kind of parting tool to make the undercut.
But I've (so far) cut mostly brass and aluminum. Not much steel.

[gldavison]

Hi Bill

Ive been following since the beginning. Excellent work you are doing.  John posted a picture of my Tiny at NAMES. Here is a short video:

http://www.gldpages.com/Video/Tiny%20IC.mp4

[b.lindsey]

Many thanks GL for the video. Very nice runner indeed. I hope mine will run half as good!!

Bill

[b.lindsey]

This evening I finished up the few parts for the spark plug but before finally assembling it I have a few questions for those of you that have made them. I will show where I am first. Photo one is the cap, threaded 0-80 to secure it in the top of the insulator. It looks awful but its just a bit of filing dust, it does look better I promise. Photo 2 shows the finished insulator and metal base. Photo 3 shows things loosely fitted together, with the electrode already soldered into the cap but left long on purpose for the moment. Now for the question(s). Photo 4 shows the bottom of the plug. How much recess should there be for the insulator between its bottom and the bottom of the metal part? Secondly what should the final length of the electrode be? Should it be flush with the bottom of the metal base? Or should there be an bar from the base extending out over the tip of the electrode as in a conventional spark plug? Thanks for any help or guidance here.

Bill

[90LX_Notch]

Looks good Bill.

Arv's site has pictures of his plug.  He also has notes  in a pdf file.


http://putputman-001-site1.htempurl.com/?folderKey=TPlIAV5lTUmr-dGEyAaOvQ


-Bob

[b.lindsey]

Bob, yes I have looked at Arv's drawings and notes and that helps, but George's design is somewhat different. Just want to be sure before I lock things down and can't change them. Many thanks for the input!!

Bill

[Flyboy Jim]

May I? Threading to a shoulder is in my opinion, a passage into the world of being a real "machinist". It requires nerves of steel or a super nice "old iron" lathe with features that allowed it. However, in darn near every real world incidence that required a part to be "screwed to a flat", there is an undercut, and usually a radiused one at that. I usually do the the "die flipping" and then take one of the Warner grooving tools and cut a undercut if ithe part has to be tightened flat. With a small enough grooving tool, one shouldn't have to stress over those last threads or two. Now that's the views and opinions from beautiful Springbucket Tennessee

Eric, My life definitely got easier after I got my Warner Groover set.

Bill, don't know much about making spark plugs, but yours sure looks the part.

Jim

[zeeprogrammer]

Bill, don't know much about making spark plugs, but yours sure looks the part.

What Jim said. 

[gbritnell]

Gents,
Although I have cleared the threads up against the shoulder in the past I found that when using a washer if would float in the undercut thereby not staying centered. I would say to use the undercut if you don't plan on using a washer but just thread as close as you can and let the washer take up that unthreaded distance.
Arv's plug is larger than the one that I drew up. I made mine to give a little more room between the top of the plug and the rocker arm to try and eliminate the spark from jumping when the plug gets fouled. I also changed the plug angle in the head. The entry point in the combustion chamber is the same but it angles more steeply on the outside.
I make the insulator flush with the bottom of the plug with no reduction in diameter. The reason a full sized plug has a reduced diameter at the tip is for heat transfer. This is how different heat ranges are created.
I also make the center electrode flush with the bottom. As long as the tip is exposed the spark will jump to ground.
When I first started making plugs many years ago I didn't even have a ground strap on the plug. I would just let the center electrode extend beyond the body and let it arc over to it.
gbritnell

[b.lindsey]

Thanks George, that clears things up nicely!!

Bill

[rudydubya]

Really nice work on the plug, Bill.

Regards,
Rudy

[b.lindsey]

Many thanks Rudy, and to Jim and Zee as well for your support.

Bill

[Kim]

Nice spark plug Bill. I'm learning a ton from your guys discussions here. 

Looks very interesting - makes me want to build an IC engine now... 
Kim