Author Topic: Thoughts on Mem Corliss build on Sherline equipment  (Read 2650 times)

Offline Jasonb

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #15 on: March 13, 2016, 03:50:03 PM »
I use the method quite often on cylinders and bearing housings. It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut











Online sco

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #16 on: March 13, 2016, 04:17:40 PM »
It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon
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Offline Captain Jerry

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #17 on: March 13, 2016, 05:46:01 PM »
It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon

The deflection of the unsupported end of the boring bar is of course the same throughout the cut, as long as the hardness of the material being cut is the same.  Hard spot, more deflection, soft spot, more chatter.  Supporting both ends of the boring bar is more rigid. In addition, better ful length support of the part helps greatly, after you get it set up and dialed in.  Hitting the target for bore radius can be a PITA.

Just my thoughts. only did it once.
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Online crueby

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #18 on: March 13, 2016, 05:47:53 PM »
It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon
I've had same question. As long as I finish with light cuts and even feed rates to avoid any waviness, I've always gotten very straight bores. If the part itself was deflecting from the chuck or the headstock was not square to the ways I could see the reason for a taper.

For my setup on this project I am not sure the centers method would work best, would have to get a larger hole drilled to start, and would need new tooling. Very interesting to see the different methods though!

Offline sssfox

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #19 on: March 13, 2016, 06:01:26 PM »
It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon

You would use this method for the same reason that you would use a tailstock to support the end of a rod that you are turning.  As the diameter of the rod gets smaller and the length increases, the deflection increases.  At some point, a tailstock is a necessity.  The smaller the boring bar, the more deflection.  Depending on the size and depth of the hole that you are boring, there may not be a boring bar that can support itself without flexing more than an acceptable amount.

Offline Jasonb

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #20 on: March 13, 2016, 06:22:54 PM »
I suggested this method as it would save having to use several pieces of metal as you could easily get a single block of metal on the cross slide rather than another method of boring the cylinder for your setup. Tooling is easily made, I teh smaller dia bar I show is just a long 5/8" bolt with teh head and thread cut off, ctr drilled each end and a cross hole drilled

I see Jerry mentioned a built up cylinder, that works too provided you have enough heat to silver solder the parts or can use epoxy with fixings.





Though I still like to turn the final bore after assembly and skim the cylinder cover flange at te same setting to ensure everything is true and concentric as things can distort with the heat.


Online crueby

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Re: Thoughts on Mem Corliss build on Sherline equipment
« Reply #21 on: March 14, 2016, 05:55:48 PM »
Thanks for some great ideas everyone, lot to think about.

Currently I am leaning towards the built-up approach like Capt. Jerry suggested, think it will fit my tools and materials best, while giving me leeway to redo parts of it if needed (which means it will all go perfect, according to Murphy, but thats okay too!). I did some drafting on it, and in order to get the fastener holes around the shaft holes and cylinder ends, plus to leave a reasonable thickness on the end of the cylinder core where the end plates go on, I am going to make one tiny change - moving the valve bores out from the cylinder just a bit, which also means the height of the block is slightly taller.

In doing more research on this type of engine, I did see some diagrams of the engine blocks without all the insulation and covers, and as Jerry said, this is about what they looked like. Mine will get plates to cover the sides/top so end result will look like the MEM plans.

Below is a sketch of where I am so far - the cylinder core piece will be 1.5" round (which is the limit of how big I can hold in the 4-jaw with the jaws normal way, which gives most surface to the jaws), stepped down at the ends to form a shoulder the end plates can seat against and also give clearance for the valve bore. The end plates are thick enough to take the bolt holes for the outer valve plates. I did not show the steam/exhaust tubes like Jerry did, but will put them in like he showed. Only functional difference from the original MEM plans is the distance from the valve bores to the cylinder is longer, but that is a fair tradeoff for keeping the cylinder core ends thick enough to be strong. The difference is small enough not to effect performance at all.

Again, thanks all for your help, build will probably start in the next couple weeks once some other projects are out of the way.