Machining metal parts

[3Ts]

I have found that "previously owned" machine tools go pretty cheaply, so I do look for auctions. However, I've also been to auctions where the final bid price is well over the price of a new machine and then the auctioneer's fee on top of that.

I have another machine, a Maho 600P that is a point to point CNC machine, but it's advantage is it has handles! A Universal machine, with horizontal and vertical capabilities, along with a vertical bed, with a horizontal attachment for a horizontal bed. Power for this might be a issue, but I also have a transformer for it to get it to a more available power supply.
Wonder if 3Ts wants to make a trip halfway across the US for a mill that would do most anything he could ever want it to do? Weight in the neighborhood of 5500 pounds, won't be an easy trip home. Probably a lot cheaper than a Bridgeport (which is the one I use)

That would be an interesting trip. I used to live down near the space center but haven't been back there for years. The weight would be an issue. I can handle up to about 3000#, more than that I would have to pass on.

I find the tolerances that can be achieved in machining interesting and challenging. I understand that 0.001 is not that hard to achieve. I'm a reasonably good woodworker and shoot for 0.03 on cabinetry because wood moves more than that with humidity changes so even that is probably more than needed. So, question; When machining do you have to account for changes in size due to temperature changes? I'm aware of compression fits where one part with a hole is heated and the rod to be inserted is cooled, but this is intentional. If I make a part in summer, then try to replicate it in winter is there enough temperature differential to make a difference?

 

[etpm]

I have found that "previously owned" machine tools go pretty cheaply, so I do look for auctions. However, I've also been to auctions where the final bid price is well over the price of a new machine and then the auctioneer's fee on top of that.


That would be an interesting trip. I used to live down near the space center but haven't been back there for years. The weight would be an issue. I can handle up to about 3000#, more than that I would have to pass on.

I find the tolerances that can be achieved in machining interesting and challenging. I understand that 0.001 is not that hard to achieve. I'm a reasonably good woodworker and shoot for 0.03 on cabinetry because wood moves more than that with humidity changes so even that is probably more than needed. So, question; When machining do you have to account for changes in size due to temperature changes? I'm aware of compression fits where one part with a hole is heated and the rod to be inserted is cooled, but this is intentional. If I make a part in summer, then try to replicate it in winter is there enough temperature differential to make a difference?

If you working to tolerances of plus or minus five thousandths of an inch (.005) and the material is steel then it is very unlikely that the temperature of the part will be a problem. The part would need to be several feet in the dimension in question and even then the part must be close to one extreme or the other. And the temperature would need to be a long way from 68 degrees F, which is the standard temp in the US.
However, aluminum moves way more than steel, and a long part sitting in the sun could get hot enough to be out of a .005 tolerance. But the typical home shop metalworker won't run into problems with temperature causing problems with dimensions.
If you are concerned with a particular job then measure the temp, look online for the amount of movement your particular matetial moves per degree per inch or per meter or per cubit and then punch the numbers into your calculator after you have measured the temp.
But let's get real here. You are just getting ready to dip your toe into machining so your first jobs are unlikely to be high precision jobs. The most important thing for you to do is to start machining something. Anything. So get a machine and use it. Make some practice pieces. When you do this you will discover how satisfying machining something can be. And please don't be concerned about making good parts right away. DO NOT listen to folks who discourage your desire to start machining. Especially if they say you shouldn't try because you lack the education. You gotta learn somehow and you might as well learn at your own pace and in the way you learn best. Don't worry, be happy. With the machine you just bought and used to drill a hole into something besides a body part.
Cheers,
Eric