PDA

View Full Version : Newbie question about the mIser engine and reaming...



mofugly13
05-20-2006, 04:28 PM
I bought a Miser engine set of drawings from Jerry Howell, and after looking over them, it looks like I'm gonna have to tool up a bit. I understand that all the parts need to be aligned perfectly and whatnot to get the engine to run properly. My question has to do with reaming some of the holes. There are a few .312" holes as well as as .156" and .062". Is it acceptable to use fractional reamers, 5/16 (.3125), 5/32 (.1562) and 1/16 (.0625)? These are 5 tenths bigger than the drawing shows, but none of the dimensions goes to 1/10000. I looked in the Emco catalog and cannot find a reamer offered in the sizes given, so I am assuming the closest fractional reamer will suffice. But the instructions stress precision for proper operation, so I figured it would be smart to ask here.

SGW
05-20-2006, 04:51 PM
You should be fine with the fractional reamers. You'll end up hand-fitting parts, anyway.

The cylinder bore and crosshead guide should be lapped to size to get a really smooth surface. There have been some pretty good explanations of lapping in past notes, so do a search of the archive if you're in doubt about that. Otherwise, I think alignment is the main thing. I also recommend using bronze for the cylinder and crosshead guide, as I think Jerry recommends. I used cast iron and, while it made a dandy cylinder and crosshead guide, I tried to run my engine a couple of weeks ago, after it had been sitting for months, and the slight trace of rust in the bore -- imperceptible to sight or feel -- was enough to mess up the running of the engine. So use bronze so you won't get any rust when the engine sits for a long time.

CCWKen
05-20-2006, 05:38 PM
I'm not familiar with the plans but if these are for locating or alignment pins, you may want to use undersized reamers. These are available in .001 under the fractional sizes.

JCHannum
05-20-2006, 08:40 PM
Dimensioning sometimes gets trapped by the drawing program used. Many times, a fractional sized hole will end up with a decimal dimension that is either unattainable or unnecessary.

5/16" is a perfectly good dimension, and a 5/16" hole is produced by a 5/16" drill. In most cases, if the drawing calls for a 0.312, 0.3125 or 0.313 hole, it can be drilled wih a 5/16" drill bit and/or reamed with a 5/16" reamer.

When first looking at a part to machine, take a look at all dimensions and how they relate to the other parts. This will give you an idea of how closely you need to adhere to a given dimension.

One other tip to the beginning HSM is that when faced an assembly that is bolted together, rather than laying out the bolt pattern on each part, either clamp the parts together and drill both at one time, or drill the pattern in one part and transfer the pattern to the second part.

Orrin
05-21-2006, 09:44 AM
I built a Miser and it runs very well. I'll make a suggestion, something that I wish I would have thought of, beforehand.

The displacer rod is clamped to the connecting rod assembly with a set-screw. Most commonly available set-screws are of the cup-point variety, so that is what I used.

Well, a cup-point gouges the displacer operating rod. If you have to remove the displacer for any reason, those gouges will hang up in the gland and your precision reamed hole in the gland will be oversized.

To prevent that from happening, again, I held the set-screw on the tip of an Allen wrench and stoned the end to a rounded shape. I suggest you do the same.

Regards,

Orrin

brunneng
05-21-2006, 07:00 PM
I bought a matched graphite piston and glass cylinder for mine from here...
http://www.thestirlingoutlet.com/
They fit together just sweet and no problems for about $10.95. Their already lapped together and you can watch the piston through the clear cylinder.

Kevin

CCWKen
05-21-2006, 07:26 PM
I'd like to see that graphite piston and glass cylinder Kevin but the site you indicated it trying to take WAY too many liberties on MY computer. How about posting a pic here?

brunneng
05-21-2006, 07:50 PM
Their site was running pretty slow today.

Here's the part. It's not installed yet.
http://www.vers5d.com/metal/graphite1.jpg
http://www.vers5d.com/metal/graphite2.jpg

This the spec drawing from their website.
http://www.vers5d.com/metal/graphite3.gif

It slides smooth as glass... (couldn't resist)

lane
05-21-2006, 09:48 PM
Just Remember To Do Your Holes First And Make The Parts That Go Into Them Fit The Way They Are Suppose To On The Drawing Who Cares What Size They Are As Long As They Do What They Are Suppose To. A Thousand One Way Or The Other Wont Hurt On Your Own Building Projects

japcas
05-22-2006, 07:20 AM
Lane makes a real good point. One of the best investments I made for my shop is a couple sets of pin gages. I have the .011 to .061 set and the .061 to .250 set. I'm planning on getting the .251 set to .500 set next. They come in real handy when you need to identify hole sizes that are just to small to measure with standard measuring tools. You drill or ream your hole, then check it with the pin gages to verify the size. They come in .001 increments and +.0002 or -.0002 sizes. I have the -.0002 sizes sets. It's a lot easier to get a precision fit when you know what size you are actually shooting for, not what you think the actual size is. Don't worry if it goes over or under, just always make the mating pin after the hole is made to get the desired fit. One more thing about the pin gages, you may think you wouldn't use them much but since I've bought them they have been used a lot more than I initially thought they would. I wouldn't want to do without them now.

mofugly13
05-24-2006, 01:06 AM
Thanks for all the replies, fellas. I got a new set of reamers on ebay, now I just need to round up the aluminum stock, get my backplate drilled for my 4-jaw chuck, and I oughtta be good to go.