Vise Abuse

[SteveM]

You need a hole that is round, on size and properly located? Bore.

There's a reason Moore Tools made a Jig Bore and not a Jig Drill

Steve

[rmac]

Somehow I missed seeing the last part of this thread until just now. Thanks to all for all the hints. Based on them, I think I need to stop kidding myself about measuring tenths and worry more about some of the fundamentals like getting a decent surface finish, and measuring technique in general.

-- Russell Mac

[Harold_V]

Harsh reality is if your surface finish is lacking, you can't really work to tenths. Those who think they can are living in a dream world.

I spent several years in precision grinding. It's a whole different world----a world where working close is actually quite easy, in part because the surface finishes one creates are exceptionally good, and a mention that grinding machines are built accordingly. They make it easy.

Don't ignore working in tenths. it's a wonderful way to improve your capability and will save you when the day comes when it's mandatory. All too many think they have no need, but if you have to fit a bearing, you must be able to work to tenths.

H

[SteveM]

Don't ignore working in tenths. it's a wonderful way to improve your capability and will save you when the day comes when it's mandatory.

If you can't work to tenths when it doesn't matter, you cant when it does.

Steve

[rmac]

Don't ignore working in tenths. it's a wonderful way to improve your capability and will save you when the day comes when it's mandatory.

I don't intend to ignore it forever. But I gotta get the surface finish issue resolved first. As a wise man once said (very recently) ...

-- Russell Mac

[Harold_V]

One tip. If you work dry, you will have a lot more trouble creating nice surfaces. That's attributed to welding of the material being machined to the cutting tool. You can avoid that by simply brush applying a trace of cutting fluid, properly selected for the material being machined.

For aluminum, kerosene is recommended. You can use WD-40 and achieve quite good results, or even used solvent that contains traces of oil.

For steel, as much as I don't care for the smell, sulfur based cutting oil serves quite nicely.

Keep the cut damp with cutting fluid. I do that by using an acid brush. Flood, while better, isn't necessary for good results. It is necessary if you're relying on the fluid for cooling.

H

[rmac]

One tip. If you work dry, you will have a lot more trouble creating nice surfaces.

Thanks for the tip. I have been using WD-40 for aluminum and stinky cutting oil for steel ... applied with an acid brush, even! I've never paid much attention to the nose radius when grinding my tools, so that's probably the first thing to correct, followed by more careful attention to rigidity, especially when boring.

But back to cutting fluids ... what about brass and/or bronze? I never hear anybody talking about cutting fluids for them.

-- Russell Mac

[Harold_V]

I've never paid much attention to the nose radius when grinding my tools, so that's probably the first thing to correct,

Indeed! Nose radius coupled with feed rate spell the difference between rough and fine finishes.

For roughing, assuming you have the power and spindle speed to justify insert tooling, negative rake beats positive rake hands down. With a powerful enough machine, it also yields a respectable finish, although it may be coarse due to the heavy feed rate. The tearing that is so characteristic of mild steel and many of the steel alloys isn't a problem in those circumstances. However, once stock has been removed and it's down to finish cuts, positive rake tends to win the battle. For one, it lowers cutting pressure by a huge margin. Negative rake doesn't really cut at the tip (when it's applied properly). If it is cutting at the tip, depth of cut and feed rate are not appropriate. In either case, cutting resistance is extreme because the material is being plowed (pushed) off instead of being cut off. Positive rake doesn't do that.

So then, reduce feed rate and offer a reasonable radius, so the peaks of the cut are not as pronounced. The larger the radius and finer the feed, the lower the peaks. What's left, then, is to avoid tearing. Stainless steel usually cuts without tearing, much like free machining materials. Mild and medium carbon steel are notorious for tearing. I like to avoid them when possible and finish is important. If not, grinding is an acceptable alternative to establish a respectable finish, assuming the added operations and cost can be justified.

But back to cutting fluids ... what about brass and/or bronze? I never hear anybody talking about cutting fluids for them.

Many are best machined dry, but it's always a good idea to avoid anything with sulfur, which readily discolors many of the copper alloys.
If you like machining those alloys, there's one that's heads and shoulders better that almost all others. It's leaded phosphor bronze. Best machining material I've ever encountered. Machines perfectly well dry, but I'd likely suggest a lubricant suitable for aluminum if you must use some cutting fluid.

I don't have a lot of experience with the copper alloys, although I've experienced a large variety of them through the years. Just never a lot of the same one.

H