Finally got a lathe
- Thread starter SkytopBrewster
- Start date
Ok... on the PC now. Where's the reference line on the compound? can't see it in the pic. If its right in line with the cap screw that locks it down(aka perpendicular to the compounds axis of travel). You're 30° the wrong way, needs to be 30° from parallel to the cross slide(where it says 60..). Either way, what I'd do is put that compound perfectly in line with the ways, dial it in, not just by eye or with that plastic protractor thing... Dial it in, then see where is what.
Seeing as it only reads to 60, I'd add another line somewhere so you can go all the way back up to parallel to the cross slide, as it is now I'm pretty sure if you needed to do a 11° taper you got no marks on the compound that read there.
Seeing as it only reads to 60, I'd add another line somewhere so you can go all the way back up to parallel to the cross slide, as it is now I'm pretty sure if you needed to do a 11° taper you got no marks on the compound that read there.
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By golly, I got it. Thanks for posting, after reading it I adjusted compound to the 60 degree mark and tried a few passes, this is the result, I am happy! So I guess this lathe reads true to what the hash marks are, not half. I should have known this cause when I am turning a part, I adjust the crosslide say 20 thou, it removes 20, not 40 thou. Again, thanks a lot, I have been pulling my hair out over this!
That looks quite a bit better. For when you don't have a mating part you'll definitely need a way to check pitch diameter.
I usually finish threads with a quick deburr of the start and end with a V needle file, fine 400 paper when needed and 1 more spring pass if needed, smooth as it gets.
You probably already know this but its always worth mentioning again since everybody does it at some point, be extremely careful with any emery cloth around the lathe. Make sure if it grabs it doesn't pull you in, ideally pieces shorter than the circumference of the part. Same with files, if you have to use them in there for any reason always stand off to the side so if for any reason it hits a chuck jaw or whatever, you don't get stabbed by it. And no long sleeves or loose clothing and all that.
So, when's the mill coming ?
I usually finish threads with a quick deburr of the start and end with a V needle file, fine 400 paper when needed and 1 more spring pass if needed, smooth as it gets.
You probably already know this but its always worth mentioning again since everybody does it at some point, be extremely careful with any emery cloth around the lathe. Make sure if it grabs it doesn't pull you in, ideally pieces shorter than the circumference of the part. Same with files, if you have to use them in there for any reason always stand off to the side so if for any reason it hits a chuck jaw or whatever, you don't get stabbed by it. And no long sleeves or loose clothing and all that.
So, when's the mill coming ?
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.
You have the compound set at the WRONG 29.5 degrees.
Here's a clue. The compound should be aligned (more or less) with one or the other sides of the cutting tool edges, depending on whether you are cutting inside or outside threads.
Point the compound at the work to form a "T", then swing it 29.5 either way as required.
Really a common mistake. Much easier to see on large size threads. Finer threads tend to vanish under the tool when the compound is fed in at the wrong angle.
Cheers
Trev
You use the compound to feed in and control the eventual depth of the threading cut. Once you start, you should not need to back it off.
Use the cross slide to pull the tool away from the work, traverse it to the start point, feed it back to the 'zero' point, add a little feed to the compound, and make the next cut.
I like to set the cross slide handle so it sits at the top or the bottom when setting up the zero points. It allows me to crank back (usually) a full turn, and return a full turn to very near the zero setting.
Cheers
Trev
That's a good reminder about emery cloth safety, use small pieces, I've almost got caught a few times and learned my lesson, probable most dangerous part is polishing a part with emery cloth and getting fingers caught, have fun but be safe , serious injury is just a blink of an eye away
By golly, I got it. Thanks for posting, after reading it I adjusted compound to the 60 degree mark and tried a few passes, this is the result, I am happy! So I guess this lathe reads true to what the hash marks are, not half. I should have known this cause when I am turning a part, I adjust the crosslide say 20 thou, it removes 20, not 40 thou. Again, thanks a lot, I have been pulling my hair out over this!
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i dont know if it is a trick of the light. but that doesent look like a proper 60deg thread. one side looks longer than the other. (the back side facing the left)
fingers284
CGN Ultra frequent flyer
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Re: files at the lathe. Every file that I have that comess anywheres close to my lathe has a golf ball pounded onto the tail. I just drill a small hole about 1/4 " deep and pound it on as far as it will go. Dont drill all the way into into the center, most balls have a fluid center and it is under considerable pressure and will produce a considerable mess on your drill press (dont ask me how I know).
I even remove the wooden handled ones that come that way... shattered wood can become a very sharp spear in an instant around a machine.
I even remove the wooden handled ones that come that way... shattered wood can become a very sharp spear in an instant around a machine.
Golf ball handles are a cheap handy, and a good use for golf balls. If you are drilling holes in them, be aware that there are some out there that have mineral oil in the middle. They squirt pretty good when punctured, and make a mess, as well as being some risk to eyes, etc.
If using a file in the lathe, I usually try to file on the underside of the work. This accomplishes two things. When you are standing in front of the lathe, as a right handed person, your tendency is to swing an arm over the spinning chuck. If your chuck jaws are extended at all, there is a risk of hanging up on clothing or whacking a chunk off yourself. You also cannot see what is actually happening to the work as you file.
Hold the file under the work with the handle facing the back of the chip tray or the back of the lathe.
Running the file below the work also causes the file to be launched AWAY from yourself, if it hangs up.
So, i guess that's three things, eh.
Get a couple lathe files for use on the lathe. The angle the teeth are cut at, is much steeper, and the chips do not bung up as quickly.
Cheers
Trev
If using a file in the lathe, I usually try to file on the underside of the work. This accomplishes two things. When you are standing in front of the lathe, as a right handed person, your tendency is to swing an arm over the spinning chuck. If your chuck jaws are extended at all, there is a risk of hanging up on clothing or whacking a chunk off yourself. You also cannot see what is actually happening to the work as you file.
Hold the file under the work with the handle facing the back of the chip tray or the back of the lathe.
Running the file below the work also causes the file to be launched AWAY from yourself, if it hangs up.
So, i guess that's three things, eh.
Get a couple lathe files for use on the lathe. The angle the teeth are cut at, is much steeper, and the chips do not bung up as quickly.
Cheers
Trev
Yes, I was looking but not seeing, now it is so obvious it's retarded, thanks
colt45cz75
CGN Ultra frequent flyer
You ain't the only one to have made this mistake. I am ashamed to admit I myself did it twice, with two different lathes. Bought a used one, tried threading, made a complete hash of it. Watched all the videos again, tried a few more times, made a mess, got pissed off and ordered a new 16x40 met tech.Took 7 months to get it due to Japan's recent troubles, then set it up and did the same goddamn thing. Finally thought of using my digital angle gauge and voila! The mists of confusion parted and a deep sense of thick headed embarrassment set in for a couple months.
Boring Bars
Need to order a set, was going to order these just because they will fit in the tool-holders I have already. Good choice?
http://www.kbctools.com/can/Navigation/NavPDF.cfm?PDFPage=58
Need to order a set, was going to order these just because they will fit in the tool-holders I have already. Good choice?
http://www.kbctools.com/can/Navigation/NavPDF.cfm?PDFPage=58
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$226
Brewster, by now you've figured out that it was the wrong 29.5. And your experience matches mine on the lack of hack marks to use for setting the angles. Which is why I was suggesting adding some.
What I do when cutting threads is that I set the compound up and set the cross slide dial to "0". To cut the thread I move the compound in for the amount of the cut. As the cutter reaches the end of the thread portion I use the cross slide to suddenly pull back out. Because it was set to "0" it is then easy to put back right on the money. The compound is then set in by the amount for the next cut.
There's often quite a bit of flex in thread cutting. So every couple of passes I do a pass with no added cut on the compound. These clean up cuts typically remove a couple of thou despite not adding anything to the compound. It's also a wake up call as to how much even a good setup flexes and why it's so important to do light clean up cuts when working to specific sizes.
What I do when cutting threads is that I set the compound up and set the cross slide dial to "0". To cut the thread I move the compound in for the amount of the cut. As the cutter reaches the end of the thread portion I use the cross slide to suddenly pull back out. Because it was set to "0" it is then easy to put back right on the money. The compound is then set in by the amount for the next cut.
There's often quite a bit of flex in thread cutting. So every couple of passes I do a pass with no added cut on the compound. These clean up cuts typically remove a couple of thou despite not adding anything to the compound. It's also a wake up call as to how much even a good setup flexes and why it's so important to do light clean up cuts when working to specific sizes.
Yeah. A spring pass once in a while is a good thing, and can save yer butt when you are 'almost' in spec for a thread when measuring across the wires, but not quite...
I have resorted to planting my thumb on the back of the tool post to add just that tiny wee bit of a cut on a spring pass...
Which is a bit of an eye opener to the FNG when they see how much material can be taken off from such, after the spring passes have stopped removing material!
Brewster, you now know what lots before you know. That the lathe makers will carve degree marks just about anywhere on the slide, and that they are not really much good to you unless you ignore the numbers they engraved beside the scales.To be truly useful, the scale really does need to be around the half on the compound that faces the chuck, with a couple extra reference marks thrown in, IMO.
I would second the idea of adding a couple extra zero marks onto the compound. I should think, with the location of that scale, that every 45 degrees might be a good choice. Whether you scribe a line, center punch a dot, or draw it on with a Sharpie marker, I leave up to you to choose.
Really, really common 'new guy' mistake, at maybe 50 percent of the guys that came onto the shop for training, doing exactly the same, even with a picture in front of them.
Cheers
Trev
I have resorted to planting my thumb on the back of the tool post to add just that tiny wee bit of a cut on a spring pass...
Which is a bit of an eye opener to the FNG when they see how much material can be taken off from such, after the spring passes have stopped removing material!
Brewster, you now know what lots before you know. That the lathe makers will carve degree marks just about anywhere on the slide, and that they are not really much good to you unless you ignore the numbers they engraved beside the scales.To be truly useful, the scale really does need to be around the half on the compound that faces the chuck, with a couple extra reference marks thrown in, IMO.
I would second the idea of adding a couple extra zero marks onto the compound. I should think, with the location of that scale, that every 45 degrees might be a good choice. Whether you scribe a line, center punch a dot, or draw it on with a Sharpie marker, I leave up to you to choose.
Really, really common 'new guy' mistake, at maybe 50 percent of the guys that came onto the shop for training, doing exactly the same, even with a picture in front of them.
Cheers
Trev
