More mini lathe issues

Hold your 6" steel scale vertically between the tool bit and the work. Advance the cross feed until the tool bit holds the scale against the work piece. Is the scale vertical or tilted forward or back? Figure out whether the tool is center height, above or below center?

Center it!

Learn to sharpen a HHS tool and use them! Save the carbide for hard stuff and production. Self ground HSS tool bits allow you considerable more flexibility in tooling then pre-ground carbide tools.

As far as speed goes, learn to calculate cutting speeds. Make up a chart of "recommended cutting speeds" and use it until you get a feel for the material (then use it anyway :-)

Regards,

J.B.

When I took a night school machinging course years ago, the instructor said that you should be getting chips that come off shiny but turn light blue as they cool. He also said that HSS tools should last about an hour before you need to resharpen them. He was talking about using bigger machines and optimizing the time machining versus the time sharpening tools. I usually do not try to remove metal that fast, but I am not trying to make a living doing machining.

Dan

Hi, Bob. I see that you have already gotten a ton of great input on this topic. I read all the first level posts, but not all of the deeper ones, so I hope I'm not wasting your time, but here's my 2 cents:

The work should never stick out of the chuck more than 3 times the diameter. This means that you really need to get some center drills and get used to turning between centers. In case it didn't come clear already, the reason that carbide cutting tools aren't good for you is that carbide chips easily and therefore they have to make the cutting edge very strong, which means, essentially, dull. The posts that say to switch to HSS are "right on". But, here's a thought about the carbide tools, just don't tell anyone I told you this: Suppose you have a chipped carbide cutter. You may be able to actually use the chipped part as a sharper-than-normal cutting edge.

Last point: To get the final finish, you may be able to mount a Dremel tool on the tool post and use that as a tool post grinder to get that last tenth or two off. Just make sure to cover EVERYTHING around the lathe to keep abrasive dust off important surfaces.

Pete Stanaitis

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One of the jobs I had as an apprentice boy was making planer heads from old line shafting that was removed from a large woolen mill. these were 8 inch shafts and we were machining them into a two inch shaft about 4 feet long incorporating an approximately 3 foot long cutting head.

At the time I was working approximately 3-1/4 hours a day in the shop and going to school the rest of the day.

We were (as best I remember it) taking approximately a 3/8th deep cut and the chips were coming off hot - brown and blue. No one ever started and finished a cut during his approximately 3 hour shift. We sharpened the bit once a day.

I can't say that this was the best speed and feed but it certainly typified the usual shop practice before carbide became commonly used.

Regards,

J.B.

When you say sharpening once a day, is that once per 3 hour shift?

Dan

Perhaps I should have said "approximately once a day" as I know the bit must have got sharpened but I don't remember ever doing it. It seemed to me that I either took over just before or just after a new cut was started. One day I got to start a new cut; the next day I sat there and watched the chips fall in the pan.

Regards,

J.B.

Another way to check is to run your bit across in a facing cut. If the tool is low, you will leave a nub. If on center, the nub will disappear when you reach the center. If the bit is high, there will be some tool distress when you get to center, so start low, which is what sounds like is happening.

LOL! I thought I was the only one who did that!

A lot of the advice in this thread was right on, and I see Bob has already machined his pivot, so there's no use adding to the confusion except to say I make knife pivot pins like this on my mini-lathe all the time and have finally learned what works, after wasting yards and yards of good A2 pin stock.

-Frank

Verrry nice!

For work that isn't worth $100 an ounce, does A2 hold up well enough without hardening?

jsw