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17th May 2021, 11:37 PM #31Member
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update.
So i had a shot at making a tool but need practice.
I found this tool already done in amongst the stuff that came with the lathe, so i gave it a shot at a pass to see whether the finish was better with it.
live centre used as well and you can see the tool in bottom left of the picture
not too bad i think and will come up okay'ish once polished.
187362009_2775981722618833_6369084600986862067_n.jpg
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18th May 2021, 06:50 AM #32
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18th May 2021, 08:18 AM #33Member: Blue and white apron brigade
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18th May 2021, 12:15 PM #34Member
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Thank you.
I'll have to go down and take a look at the speed setup to confirm, but i think it was the fastest setting.
The depth of cut was not really taken down as i just turned the handle until the tool made contact with the face and went with it, so a minimal depth of cut, maybe 0.01mm ?? It was a facing tool so it wasn't cutting from the side and drawn across, just facing
the turning wheels/crontrols for the cross feed and the angle feed have about 20 increments of 'play' before they actually move so is that 20, thousands of an inch ? which is a bit annoying, but i'm unsure of how to fix that.
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18th May 2021, 03:21 PM #35I break stuff...
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As others have said, looks pretty good for black bar. But if your tool is making contact over a large area, as I get the impression from your description, you'll probably find it gets even better than that with a different tool. Incidentally, facing normally refers to taking material off the end of the workpiece, traveling perpendicular to the spindle axis. Working parallel to the spindle is generally just referred to as turning, regardless of what tool you've appropriated to do that. Just might save some confusion as you're asking questions going forward, someone may think you're doing a different operation to what you are.
As to the second part - you don't, is the short answer. The long answer is that this is the backlash I mentioned earlier, and it is present to some degree on all machines that use a screw to create motion. It's just one of the things you need to learn to deal with as a machinist. The good news is for most things it's not much of a problem, as long as you remember to account for it whenever you change directions on the handwheels.
That said, there MAY be some form of adjustment on the bronze nuts for the relevant screws to reduce it somewhat, not sure what South Bends had originally. And in the lifetime of the machine, someone may have replaced them anyway, as is the case with my Graziano which has the same amount of backlash as yours (assuming your cross slide is direct reading) in the cross slide, and the nut is not the original so has no adjustment mechanism. Will most likely require you to remove the cross slide to get at the nut, unless there is some provision made to get at it, and even if it's adjustable it's quite possible it's run out of adjustment, or that the screw itself is badly worn in one section. You can make new parts once you've gotten a bit more proficient on the lathe if this is the case, but for the moment I wouldn't get overly bothered with it other than checking if there is an easy adjustment to be had.
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18th May 2021, 06:33 PM #36Member
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18th May 2021, 07:07 PM #37
Hi Mathu,
Thanks for the video. It looks quite good. Reducing the tool stick out would help with tool holder stability, there is no point in having such a long tool unless you intend to part right through. But you do seem to have the speed about right for that diameter, you will need to increase the speed as you get closer to the centre of the workpiece. Some cutting lubrication would help too. I use a brush and Trefolex when I'm doing that.
Just a mention about the top slide. I have mine set at 6 degrees clockwise from parallel with the lathe axis. The reason is that ten thou on the dial is approximately one thou at the cutting tool. "Pythagoras theorem" About the only time that the top slide angle gets changed is if I want to cut a taper.Best Regards:
Baron J.
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18th May 2021, 08:17 PM #38Member
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Nice
that sop slide is very close to parallel :O but if it works
I finished off the shift knob and my roommate put it in his car for a test.
I was using some degreaser spray as cutting fluid giving it a squirt every 10 seconds or so just couldn't do it while holding the recording device
no idea how to get rid of these marks that are still present. The polish on it is 120 - 180- 240 - 400 - 600 - 800- 1200 - 1500- 2000 grit sand paper Besides the weird tool marks i think it's come up pretty well.
185836073_1215209705561925_3159837671020483781_n.jpg
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18th May 2021, 09:37 PM #39Most Valued Member
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Degreaser is a solvent not a lubricant. I wouldn't use that. Those stop-start scratches are indicative of crappy quality steel. It seems to tear rather than cut. It's almost like galling. A very sharp tool will help. Getting some free-machining steel will help a lot more!
Chris
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18th May 2021, 10:48 PM #40
Are you using the top slide to turn the work ? I hope not !
The top slide is primarily used for turning short tapers, not for moving down a work piece. That is the job of the saddle with the cross slide used to put on the cut. For turning the surface of a bar I use a fine traverse of the saddle under power, about 2 thou per revolution.
In reality it is cutting an extremely fine thread ! The nose radius of the tool bit effectively smooths out the very small thread pattern.
From a beginner point of view it seems that a rounded nose is not very sharp, which is not true ! If I'm grooving a piece of work in the way you show in your video, the bottom of the groove will have sharp corners, because the parting tool is ground that way.
Lathe Tool Shapes.gif
This might help ! The black areas are not intended to be carbide inserts, though they could be like that.Best Regards:
Baron J.
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19th May 2021, 12:33 AM #41Member: Blue and white apron brigade
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19th May 2021, 03:00 AM #42
Hi Mathu, Guys,
Some pictures to show the points that I made earlier:
18-05-2021-003.jpg 18-05-2021-004.JPG 18-05-2021-005.JPG
We discussed grinding lathe tools, so these are pictures of a simple grinding jig that I use to obtain the four and seven degree angles that I want on my lathe tools.
In the first picture is shown the grinding rest which is angled down at the back so that the front of the rest is roughly level with the wheel centre and is sloped down at the back by about ten degrees. Its not critical, anything from five to fifteen degrees will work. I've just used ten. The curve of the wheel will ensure that there is enough clearance on the tool end.
The top and left hand front edges are ground by hand using the slope of the grinding rest to create those angles. Again they are not critical as long as you have some clearance. Unfortunately the photographs don't show the very small radius, maybe half a mm, that I stoned onto the end of the tool bit.
The next two pictures are of the tool that has just been ground. They show the angles seen when looking at the front of the tool and the clearance angles on the top and end. You might notice that the tool has a radius ground at the bottom. This is because I have used this tool bit as a boring bar and needed the radius to clear the bore of the work.
18-05-2021-002.jpg 18-05-2021-001.jpg
Now I also talked about the "Top Slide" this is a picture of mine. you can see in the second picture how the slide is angled away from the axis of the lathe. This creates the hypotenuse of a right angle triangle where the slope increases by one thou for every 10 thou you move up the slope. In this way you can get very fine cuts on your work piece.
HTH.Best Regards:
Baron J.
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19th May 2021, 07:43 AM #43Most Valued Member
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It's a very handy trick. I lost the ability to do it when I replaced my topslide with a solid toolpost. The only downside to it is if you are using a carriage stop to work to a shoulder, you mess up the depth every time you move the topslide. Although if you only use the topslide for the final few passes the error is small.
Chris
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19th May 2021, 09:39 PM #44Member
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I did a thing today
made my own HSS tool
here's how it went in pics/clips
186493218_307583454147039_7164204530357826363_n.jpg
video-1621416090.mp4
video-1621409986.mp4
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20th May 2021, 08:55 PM #45Member
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I made a shift knob for my friends car, got it mirror finish reflections in it, but still get those tool marks, hmmm...
188492314_596252498435869_2676582225737149308_n.jpg
186510000_211177843955357_7402583097527491586_n.jpg
I also made a tool.
round nose, it needs very low speed to run and very slow passes across the workpiece. But the finish wasn't bad Definately better than what i have had before.
video-1621502959.mp4
Sorry i forgot to take a picture of what the pass looked like with the new tool i made. However, i went 120 - 180 - 400 - 600 - 800 - 1200 - 1500 - 2000 grit sand paper afterwards, but didn't get that super nice finish :/
note the comparison between the one on the chuck and the one still in the chuck. They were both done with up to 2000 grit sand paper, but i got a much better finish on the smaller shifter. I need to get a better tool sorted haha.
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