Metalworking, Machining & More: Peen around the hole, then drill and tap it

The Something Awful Forums > Discussion > Hobbies, Crafts, & Houses > Metalworking, Machining & More: Peen around the hole, then drill and tap it

Punzilupo: Jul 2, 2004

RealKyleH posted:

Lindsay's books has some interesting projects (to say the least) but nothing you cast out of aluminum in your back yard will come close to even an inexpensive made in china or 50 year old American lathe in terms of rigidity, repeatability, precision, etc. It'd made an interesting toy but belt driven lathes can be had for as little as $500 and even if they need a bearing or two, parts are usually cheap. Then theres always the harbor freight lathes.

Having built (along with 2 friends) the Gingery lathe, shaper, and mill, I have to agree with most of what you said, but they aren't toys - though they very obviously aren't production machines either. You can get precise results, if you are willing to take your time and work through the difficulties. Also most of the problems aren't necessarily due to the material (though cast iron would be better), but due to the fact that when building them you are starting from scratch; and the design of the machines is more oriented to that fact than to trying to achieve the core virtues of commercially built machine tools. I've often thought that with the Gingery machines, and a iron-melting furnace, one could build another set of machine tools that would be on par with commercial machines, for the most part. Would it be worth it? Probably not.

# ¿ Jul 20, 2008 06:11

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# ¿ Apr 27, 2024 17:40

Punzilupo: Jul 2, 2004

dv6speed posted:

Well did the 3rd casting. It came out PERFECT... except for yet another steam defect.

Are you sure it's not shrinkage?
How much steam are you seeing rising from the sand?
Are your gates and risers big enough?

# ¿ Aug 23, 2008 05:08

Punzilupo: Jul 2, 2004

dv6speed posted:

Greensand is very very picky about it's moisture content. It is supposed to have enough moisture to hold together, but dry enough that metal can be poured into it right away.

A good test is to take a handful of sand and squeeze it, then break the resulting chunk in half - if the sand breaks cleanly it is wet enough, if it crumbles at the edges of the break it is too dry. Err on the side of too dry, and then moisten just until it passes this test. A small plastic garden sprayer (hand pumped) works well for wetting the sand - spray lightly over the sand, stir, repeat.

Also if you aren't making allowances for small surface defects you should re-consider your pattern, and be willing to spend time filing (or cutting or machining) away the excess.

# ¿ Aug 23, 2008 06:16

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