Finally got a lathe

SkytopBrewster said:
Please have a look and see if I did anything wrong. Having problems getting nice threads, can't really see in photo but I keep getting very slight galling. Have been using Vipers Venom sulphur based cutting fluid and another type of aerosol cutting fluid called S00208 by sprayon,also just tried Rigid Dark thred cutting oil all with the same results. Last couple threads I cut I only took like .0002 per pass (it took a while). I redid my practice piece for muzzle brake (1'' 4140).

It's 24tpi, made the relief cut with part off blade.

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Did the crown with the tip of an inside 60 deg threader, then did 11 degree recess with PTG piloted crowning tool.

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Just chucked it up in the 3 jaw and checked run out was .0005, I know not proper for barrel work but this was just cutting practice.
All advice and help much appreciated. I have only been running lathe for 3 days and I know I am hooked.
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not to bad for your third day on a lathe :) try playing with your speeds. sometimes the machisist handbook is better used as a guide rather than exacting speeds and feeds. also 4140 isn't always easy to machine. the first thing I ever threaded was and inside thread on hole measuring .492 for a flash suppressor I built for my ar-15. I built it out of aluminum and had similar results. seeing how It was my first thread job I used slow spindle speeds, I was a lil nervous about crashing it into the chuck. I found slow speeds weren't ideal for aluminum.
 
Yep, you right, brazed carbide. Was turning at only 70rpm on that one. Tried 300rpm on a 1'' thread and same result. Did another 1'' thread at 200rpm and it turned out a lot better. and yes, compound set at 29.5. I have a carbide insert cutter, will try that at 200 and see how that one goes. Thanks for your advice. Gotta head North in a couple for 20 days, will be ordering some more tooling and thread gauges when I'm at my real job.
 
SkytopBrewster said:
Yep, you right, brazed carbide. Was turning at only 70rpm on that one. Tried 300rpm on a 1'' thread and same result. Did another 1'' thread at 200rpm and it turned out a lot better. and yes, compound set at 29.5. I have a carbide insert cutter, will try that at 200 and see how that one goes. Thanks for your advice. Gotta head North in a couple for 20 days, will be ordering some more tooling and thread gauges when I'm at my real job.
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Take a good look at the diagrams showing the tooth form for the thread shape.

Look in particular, at the tip profile. There should be a flat there, width dependent on the thread's pitch.

The brazed carbide tools come with a sharp point. Which, like as not, is now chipped pretty well. The points are quite fragile, and are part of the reason that the shape of the thread is the way it is.

Look at your tool with some magnification.

The good news. An Eze-Lap diamond file can, with some care and attention to detail, be used to file off the tip and with same care, resharpen the carbide tip sides. A cast iron lap with diamond grit, or a diamond wheel on a grinder can work to advantage too. If you wish to try.

I like my Eze-Lap files Medium and fine get most use. Extra Fine, not as much. I don't find much use for the coarse one. YMMV.

Good start on the thread. As you gain experience, you will find that you will run higher revs, and will work out what works for you, wrt tools and techniques. Try some cutting oil or coolant. The threading oil from the big box stores is stinky vile smelling stuff, but it works. Some animal fats work well for cutting oils too. Mmmm. Bacon! :) Bacon fat can be used, eh. Lard or lard oil, was a common cutting lube.

A small bottle of soluble oil is a couple bucks. I had some Cutswell 45, IIRC, and it worked well. A couple cc's into a relatively large volume of water, in a soup can with a brush in it, sat behind my lathe for quite a while. When it dried, a dribble of water and a stir, and it was useable again. For threading, it was get set up, dab the brush onto the part, then engage the half nuts, take the cut. Repeat as required.

Whatever tooling you use, a dribble of cutting fluid of one sort or another, is going to be helpful. Esp. if turning at low revs.

Cheers
Trev
 
WooHoo! I finally did it too!!! After many deals on KIJIJI falling through over the last 8 months including last night. I happened to check this morning and wouldn't you know it, an old Southbend 9" with change gears and a whack of tooling just $250 and 45 min. away! Fantastic shape and 3/4" through spindle bore. It's not super slick and easy to use but boy is she purdy!!! Will post pics when all set up.......at least a week! Cheers!
 
The B and C model South Bends are OK light machines.

Changing gears gets to be pretty quick, and once you figure out how it works, you can pretty much sort out what you will want for the power feed set-up, for when you are not cutting threads.

Sounds like a bloody good deal, too. I sold a half stripped off carcass of a SB9 for a bunch more than that a few years back.

Cheers
Trev
 
As a person who has been a ticketed machinist and working full time with that ticket (both manual and cnc) for the past 15 years, I have cringed a fair bit over some of the setup "advice". OP that is a perfect hobby size lathe, enjoy it to the fullest!
 
I agree TN13, it is the operator who knows the limitations and strengths of his skills and equipment who can make the most of both, often to very fine results bordering on perfect.

Ingenuity is the Mother of Invention!

:cheers:
 
I am also reading every post in this thread with relish, because learning never stops and knowledge always grows.


Among thinking beings of course, antis and Lieberals need not apply again.
 
trevj said:
The B and C model South Bends are OK light machines.

Changing gears gets to be pretty quick, and once you figure out how it works, you can pretty much sort out what you will want for the power feed set-up, for when you are not cutting threads.

Sounds like a bloody good deal, too. I sold a half stripped off carcass of a SB9 for a bunch more than that a few years back.

Cheers
Trev
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x2 on the good deal! I've checked all the gears and no missing teeth, also began a minor teardown looking for play and anything that I wouldn't want to deal with on a fully assembled machine. I'm so glad this popped up as I almost forked out twice as much for an ATLAS last year and still cringe when thinking about the ZAMAK parts.
 
Threads turning out better now, something to do with my compound being set at 29.5, I left it at zero and just used an indicator up against the cross-slide and now they are turning out near perfect, I think I'll just stick to that method. Heres another practice piece from today, chambered and everything.

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Pretty pleased with myself, been running it less than a week.
 
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This thread makes me want to put my lathe back together. I took it apart years ago and never put it back together. I doubt I'll remember where any of the gears go.
 
Um, when you set the compound to 29.5 what are you using as the reference? The "0" for this is when the dial for the compound is laid back along the cross slide, not in line with the longitudinal axis. You then set it over towards the tail stock by the 29.5 degrees. You want to be sure you're using the right "0" hack mark for this too.

Sorry if this seems so basic and obvious. But it's been proven a few times before that apparently it's not as basic and obvious as it may seem. If your previous threading was badly distorted and seemed like it was "leaning" then setting the angle from the wrong zero point could be the problem.

I've found that I got my best ever thread cuts once I began working with the compound set to the 29.5 angle instead of straight in plunging which sounds like you are using now. So I suspect you have simply gotten caught by this source of confusion over the starting point of the angles.

It helps a lot if the top surface of your cross slide has multiple hack marks to use for setting the zero to either in line with the cross slide or in line with the bed axis. It aids in avoiding a lot of adding and subtracting for different setups. If your cross slide doesn't have these multiple zeros it's not hard at all to use a small and narrow cold chisel to make them. Or even a little center punch mark.
 
I used a Chinese 14 X 40 lathe for years to learn DIY gunsmithing. Since I had zero experience I did a night course at NAIT in Edmonton. I think it cost about $600 in 2002 and eventually saved me money as I didn't buy a lot of tooling I didn't need and it gave me the confidence to start on the "big" stuff. I started chambering and rebarrelling rifles for friends involved in TR and F-class shooting. Action trueing and other advanced skills can be learned and mastered with the right attitude and patience.

One of the best things I did on my "cheap" Chinese lathe was completely level and alighn it, then bought a high quality chuck. In my case an 8 inch 6 jaw Bison Set-Tru chuck. That made everything so much easier. Even the greater weight of the Bison smoothed things out. Once you've used a 6 jaw Set-Tru you'll never go back.
 
Yeah, the idea is to advance into the material for each cut with the compound slide (at the 29 or 29 1/2 degree angle) so that most material is removed from the left side of the tool and the right side just smoothes up the cut a bit.
 
BCRider said:
Um, when you set the compound to 29.5 what are you using as the reference? The "0" for this is when the dial for the compound is laid back along the cross slide, not in line with the longitudinal axis. You then set it over towards the tail stock by the 29.5 degrees. You want to be sure you're using the right "0" hack mark for this too.

Sorry if this seems so basic and obvious. But it's been proven a few times before that apparently it's not as basic and obvious as it may seem. If your previous threading was badly distorted and seemed like it was "leaning" then setting the angle from the wrong zero point could be the problem.

I've found that I got my best ever thread cuts once I began working with the compound set to the 29.5 angle instead of straight in plunging which sounds like you are using now. So I suspect you have simply gotten caught by this source of confusion over the starting point of the angles.

It helps a lot if the top surface of your cross slide has multiple hack marks to use for setting the zero to either in line with the cross slide or in line with the bed axis. It aids in avoiding a lot of adding and subtracting for different setups. If your cross slide doesn't have these multiple zeros it's not hard at all to use a small and narrow cold chisel to make them. Or even a little center punch mark.
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Ok, I guess I'm one of the slow guys that doesn't quite get it. Here is a pic of my setup, compound at 29.5, bit squared up with the work, set compound to zero, contacted work with bit until touching, set crosslide to 0, back out crosslide, move to the right, set cross back to 0, advance compound, make cut, back out cross, move back, set cross back to 0, advance compound 2-5 thou, make next pass and repeat. Results were not geat.

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I thought the point of using the compound was just to get finer adjustments, guess I was wrong.
 
I'm just on the iPhone here but the pic of that compound def ain't 30. Looks 45 Ish. Those lathes tend to have ref line at 15 or where ever. Usually gotta add a new proper and usable one.
 
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