Webster build questions

[Brian Rupnow]

Yes Chuck, you have it right.---Brian

[chucketn]

Thanks again, Brian. It's great having someone to ask the questions we need answered. I am no way an engineer, just putzing in the shop. I would have made the O-ring groove as I described, but it's nice to be able to confirm my thinking.
And a big thanks also to everyone that has contributed to this thread. I feel like we're all here together in my little shop...
Pics tomorrow of the progress thus far, probably best to put them in my build thread.

Chuck

[Brian Rupnow]

Got the cast iron cylinder profiled and today, I bored it out. I was sneaking up on the bore dia. of .873 and measuring on the lathe it was .872. Took it off the lathe and it measured .904! I have no idea what happened there! Good thing is, it measured the same on both ends of the bore.
2 more questions, what do/can I use to hone the bore, and will the 7/8 Viton 0-ring still work. I see our(US) Horrible Freight now carries an assortment of Viton O-rings.
Finish on the cylinder isn't my best, but I'm happy with it. Seems the barbell cast iron is quite porous, has tiny pits on all surfaces. Pictures to come, camera batteries are flat, as seems is always the case when I want to take pictures.

Chuck

Somehow, I missed this post. The "notification by email" part of this forum could stand some improvement!!! How were you measuring the inside of the cylinder in the lathe? I have completely given up on measuring inside diameters with Vernier calipers. I have been bitten on the bum too many times to use that method anymore. I bought a cheap set of those spring loaded measuring devices that look like a capital T---the long part (handle) has a "twist lock" feature and the short arms are spring loaded.--You slide the short ends into the thing you want to measure, wiggle the handle around a bit (this is a developed art), lock the handle and then withdraw the instrument and measure it with a micrometer or Vernier. This gets you much closer to where you want to be.

[10KPete]

Telescoping hole gauges....

Pete

[Brian Rupnow]

Thank you Pete---I knew that.---Well, I think I knew that---I was too lazy to get off my computer chair and walk eight feet to where my "telescoping hole gauges" are to read what they were actually called. Damn, I hate getting old---

[chucketn]

Brian, I was using a digital Vernier caliper. I don't have telescoping gages.

Chuck

[Ian S C]

Chuck, you at least need a pair of inside, and a pair of outside calipers, with practice you'll be able to get a fair indication of the measurements, but for best, the telescope gauges are what you need, best used with a micrometer.  Calipers, digital or Vernier will only measure the bore at the ends, but not in the middle.
Ian S C

[Brian Rupnow]

This is the set I bought, from Littlemachineshop.com  they are not the worlds best quality, but the price is right and they certainly get the job done for less than $100 for the full set.--Just be warned--There is a set of 6 gages on their site for $14.95, but the quality and repeatability of those super cheap gages is very poor. In the case of gages, you really do "get what you pay for".---Brian
http://littlemachineshop.com/products/product_view.php?ProductID=3185&category=

[chucketn]

Next question. I will be using a weedeater flywheel and coil for ignition with a NGK CM-6 plug(finally found that plug locally). Problem is, the connection point on the CM-6 is smaller than the usual plugs used in a weedeater. What do you guys use to make the plug connection? Home made or store bought?
I am working on a mock up test stand to make sure the ignition will work before I adapt it to the Webster.

Chuck

[chucketn]

I think I've answered my latest question. I looked through my spring collection and found one that fits the CM-6 plug. That spring also fit the connector on the first ignition coil I'm going to test.

Chuck

[Brian Rupnow]

I generally buy silicone boots with about 16" of attached wire from Roy Scholl at S and S engineering. They are custom made to fit tight on a cm6 plug.

[chucketn]

I'm back on the Webster after a hiatus. Next issue is the piston. I've turned it, cut an o-ring grove, and honed it to the cylinder. I put it back in the lathe and bored the .750 x .250 pocket. Now, what order of ops and what tricks/jigs did you folks use to mill the con rod pocket, the wrist pin hole and the oil hole. These steps have me scratching my head.

Chuck

[Hugh Currin]

Chuck:

When I built mine I chucked up some 1" aluminium in a 5C collet in the lathe. There I cut the outside and inside pocket, as you did. I then moved the part, still in the 5C, to a collet block in the mill. Vertically was able to cut the 3/8 slot and tap the two internal holes. Then turned the collet block horizontal for the wrist pin holes and oil hole. Back to the lathe to part off. And finally turned around in a 7/8 collet to face the parted off end.

Here's the description with pictures, post 111. I didn't lap the pitson since I used cast iron rings.

Hugh

[gbritnell]

Hi Chuck,
I can't speak for the Webster by my normal machining process for pistons is this. The first operation is to put the wrist pin hole in. By doing it first you have metal support and the hole goes through straight. I put the piston in my mill vise with the head end toward the fixed jaw. I then bump the piston with my edge finder to locate center. I drill and ream the wrist pin hole. Now I take the piston and using a pair of small V-blocks for support, clamp it in the mill vise. I put a piece of rod into the wrist pin hole to align the piston square with the vise then clamp tight. Remove rod and center drill and drill the piston to remove the extra stock. Now using an end mill I cut the pocket to the required dimensions.
The oil hole can be done by just drilling after the other operations are finished.
gbritnell

[chucketn]

I have neither collets large enough for the piston, nor V-blocks. I will start with the wrist pin hole. At least I do have a reamer for that. I have an 8" piece of, I think stainless(only slight magnetic attraction to a hard drive magnet) that I will use for the wrist pin.
The only other option I can think of is my 3" chuck on my Rotary Table. Set the table up with chuck, chuck the piston, align the table to 0 deg, mill the con rod slot while table is vertical. Set the table up horizontal, drill oil hole, rotate 90 deg and drill/ream wrist pin.
What about that? See any easier way?

Chuck