update on lathe chuck

Found a 4 jaw chuck on amazon-running a lot better now- turned a piece of 4140 steel -is a little rough-how do you finish it - a file won't touch it?? Had to use a 3/4 impact to get off old faceplate-was tight almost all the way off.

Depending on the Finish roughnessdesired, and its intended size, 220 grit silicon Carbide paper (polished in the lathe) followed by 400 grit Etc. till happy. Jim

I like working 4140.

You are using carbide tooling?

If you are not going to an exact size, it cuts better when taking a deeper cut, say over .010.

If you need to make a drag pass, it will fuzz up a little, but polishes out nice at high RPM.

4140 and 4150 are HCHC steels and are good for toughness and can be heat treated. If you're using HS steel tool bits you need to slow the spindle RPM for light cuts.

(quoted from post at 18:08:51 03/02/17) 4140 and 4150 are HCHC steels and are good for toughness and can be heat treated. If you're using HS steel tool bits you need to slow the spindle RPM for light cuts.

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Also, an clean small radius ground on tool tip, will give a much better finish then a sharp point.

When you get down to the last few cuts, especially if you have done a lot of work with the tool, you might to want to touch up the tool. With a small radius and a good sharp edge it should cut and leave a decent finish. After grinding you want to stone it with a fine stone, by hand, until all the grinder marks are gone and it looks smooth with a 5x to 10x loupe. It is surprising how rough a smooth looking surface can look when you look at it with a loupe. McMaster has them for not too much, I think around $12 or so depending on the power maybe or the quality. I have both a 5 and 10x and often use them. But you can often see the edge looks a little shinny and not sharp when you need to touch it up. Another trick you can use to improve the finish or to remove just a little is a file. First get a new fine cut one. Then take a good flat/true small stone and just rub it over the surface of the file lightly two or three times. This cuts off the top/tips of high teeth and it will make a smoother surface. It will not cut as well on a flat surface so save that file just for the lathe. Then polish with Scotchbrite. If you get the tool cutting good you may not need these other two methods especially if it isn't an appearance thing.

What tom and jiles said is good advice. In addition to my first comment, slow it down to where the chips don't even turn yellow. Even with carbide tools I would go that slow on finish cuts.

(quoted from post at 16:46:39 03/02/17) When you get down to the last few cuts, especially if you have done a lot of work with the tool, you might to want to touch up the tool. With a small radius and a good sharp edge it should cut and leave a decent finish. After grinding you want to stone it with a fine stone, by hand, until all the grinder marks are gone and it looks smooth with a 5x to 10x loupe. It is surprising how rough a smooth looking surface can look when you look at it with a loupe. McMaster has them for not too much, I think around $12 or so depending on the power maybe or the quality. I have both a 5 and 10x and often use them. But you can often see the edge looks a little shinny and not sharp when you need to touch it up. Another trick you can use to improve the finish or to remove just a little is a file. First get a new fine cut one. Then take a good flat/true small stone and just rub it over the surface of the file lightly two or three times. This cuts off the top/tips of high teeth and it will make a smoother surface. It will not cut as well on a flat surface so save that file just for the lathe. Then polish with Scotchbrite. If you get the tool cutting good you may not need these other two methods especially if it isn't an appearance thing.

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If you're going to use a file on a lathe, make dam site it's got a handle on the tang. You don't want to catch the jaws and have that file shoved down into your wrist. You'll be on injured reserve for quite a while.

Donovan from Wisconsin

The answer to achieving surface finishes without undo hand work is to NOT take what Steve properly called "drag cuts"
After just a little bit of handle time observant operator wannabes find that they can have a real nice finish as they are approaching size.(assuming they have learned speeds and feeds, proper tooling and set ups) until they chicken out as they get close and drop the in feed to near nothing or neglect to speed up the spindle as the diameter is reduced to keep surface speeds at spec. . Just throwing in the discussion that there are TWO ways to do it. While other responders here are not incorrect that you can drop back the in feed and or speed and then file and emery cloth your way to size and finish, you can come to size with proper in feeds and speeds which in turn allows for good surface finishes. You learn this while making parts from bar, not while turning some $$$ part, that's for sure!! The fellow I apprenticed under taught me that sloppy habits make sloppy parts. Make every cut on every part as if it was the last pass on a tight tolerance job. Have a size expectation on every pass and learn to meet it. You will also then know if flex in the part is going to cause problems and fix that prior to coming to finish size. As it applies to this question you also have a surface finish expectation on each cut and fix problems prior to coming to size. I realize that this is not advise for the those in the early stages but following it will allow a person to learn how to come to size while making cuts at speeds and feeds that allows for good surface finish. Bottom line is you learn to fix ALL issues while making your approach cuts, not saving them for last one. Once learned you will nice parts that are to size and have good finish without any hand work other than breaking the corners with a file and be using the file.

I agree with everything you just said Butch.