paul
Member
Posts: 8
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Post by paul on Dec 4, 2006 13:50:42 GMT
How do I make a nice square shoulder when turning a substantial amount off a rod (I'm making a small flywheel)? Ideally I suppose I need a 'stop' which will prevent the tool advancing any further. I don't want to end up with a shoulder like the one on the right of this picture! Thought: I suppose I could make turning cuts up to a point slightly short of where I want the shoulder to be and then use facing cuts.... (I did say there'd be lots of silly questions once I bought a lathe)  |
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Post by ron on Dec 4, 2006 14:16:48 GMT
Paul
That will work quite well, or you can do a combination of turning and facing till you are nearly at size and finish off with one cut both ways.
Ron
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Post by chris vine on Dec 4, 2006 14:21:44 GMT
Hi Paul,
Does your leadscrew have a graduated handwheel? if so, when you are turning the diameter, IE moving the tool to the left, can you use the leadscrew and stop each cut about or 10 thou' short of the shoulder. Then you can face off the last bit as you suggested or even just run the tool the last few thou and then face the end, moving the tool outwards.
If you are working on the end of a piece of bar, if you go a bit too far, you can always face a bit off the right hand end to fix up any mistakes!!
If your leadscrew does not have a graduated handwheel then you can do the first rough bit by eye and a ruler on the first cut, working subsequent cuts up to approx the same shoulder. Then, clean up with a wee facing cut and measure with either a ruler and looking carefully, or use the depthing rod on a vernier caliper. When you know how much more to take off you could use the top slide (assuming there is a calibrated thimble on this) to set the last facing cut.....
Chris.
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paul
Member
Posts: 8
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Post by paul on Dec 4, 2006 15:11:11 GMT
Cheers Ron, that sounds reasonable. Chris, no there's no graduations on the handwheel (is it just me or are these handwheels usually annoying, I keep catching the cross slide handle with the back of my hand so I end up using the lead screw wheel like a steering wheel!!). Thanks for the reply, most helpful as ever  |
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Post by Jo on Dec 4, 2006 16:08:13 GMT
Paul,
If you do not have graduations: May I suggest that you position a dial gauge against the right hand side of the saddle mounted on the lathe bed. This way you can read directly off the dial gauge the longditudinal movement of the tool.
Jo
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Post by Richardw on Dec 4, 2006 16:43:00 GMT
Paul
I am also quite new to lathe work but one method I have read for doing this is to use a parting off tool to cut the shoulder square to depth and then turn down the remaining diameter to size that way you are not cutting all the way to the shoulder each time.
Alternatively take a cut to the shoulder position and then without moving anything clamp a bit of bar to the lathe bed up tight to the chuck side of the saddle that way the saddle should stop in the same place every time although I haven't actually tried this yet either.
As I said, I have had both ideas suggested to me but haven't tried them yet. If you try them and they work please let us know.
Richard
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paul
Member
Posts: 8
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Post by paul on Dec 4, 2006 17:48:37 GMT
Richard, that first idea sounds good - trouble is I haven't got a parting-off tool yet. The second idea is really what I mentioend at the top of the thread i.e. a 'stop'. Jo, yes I've seen a picture of that on the net but as a newcomer I don't possess the equipment (yet). Thanks for the suggestion though |
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John Lee
Part of the e-furniture
Posts: 375
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Post by John Lee on Dec 4, 2006 17:49:20 GMT
Not sure what lathe you using, but set it up so you can lock the gibs of the axis that you DON'T want to move with a little soldered in handle.. the middle gib screw (I assume 3) will do. No "knocking the handles" problems. A soldered handle can be the hexacon key, cut short, that you can buy from B&Q or elsewhere for next to nothing.. or glue it in.
Next, as advised above, face it slightly short, then retract once, near to final length .. and then a skimming cut with lots of oil to get exact... due to the flex of tools and movement on your crosslide. If still not there advance "left" a thou or two and try again.
John
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Post by havoc on Dec 4, 2006 21:47:12 GMT
Since I have the creeps having to use the parting tool, I prefer the method of first making something like your right drawing, then in one go, bring the small diameter to size and from the inside, face the shoulder. Then bring the lenght of the small diameter to size by facing the right side.
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paul
Member
Posts: 8
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Post by paul on Dec 4, 2006 21:56:32 GMT
Hey Havoc - what's the problem with the parting tool? I need to know before I buy/use one!
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paul
Member
Posts: 8
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Post by paul on Dec 4, 2006 22:17:31 GMT
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Post by baggo on Dec 4, 2006 22:47:07 GMT
Aah, you've yet to learn the horrors of parting off! ;D ;D
There is actually a carriage stop available for the CL300/C3 but it will be more fun (and practice) making one for yourself. I keep meaning to make one for my ML7. I've got the graduated leadscrew dial though so I tend to use that to get all the cuts the same depth. Then just a slight facing cut to clean it up.
John
PS just a thought but it may be better if you can make a stop to fit to the front of the bed rather than the back. There will be less chance of the saddle 'twisting' then when you wind it up against the stop.
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John Lee
Part of the e-furniture
Posts: 375
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Post by John Lee on Dec 5, 2006 6:48:22 GMT
Hey Havoc - what's the problem with the parting tool? I need to know before I buy/use one! See above from Havoc.. The problem is that on "our" size lathes, unless they are locked up really tight, again as I describe above, it will snatch at the last minute, and ruin the job or the tool, often both. Not a problem on a big lathe as they are master of the tool, rather than the other way around. If you are going to buy, and you really do need one rather than hacksawing off and facing again, then the ideal answer is a back tool post to hold it. I don't have one, but as before I can lock all the axis except the crosslide I am using to do the parting off. And I use one of the blade type tools. Even so its lots of oil and hold my breath. Usually works.. John |
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Post by chameleonrob on Dec 5, 2006 9:20:51 GMT
And I use one of the blade type tools. Even so its lots of oil and hold my breath. Usually works.. and slow the lathe down to at least half the speed used for normal turning and as close to the chuck as you can. parting off for me isn't difficult as my lathe is driven from a flat belt that slips before I can ruin the tool and workpiece. I made a carriage stop for my lathe by drilling and tapping two M6 holes in a meaty part of the headstock and use them to clamp a piece of 10mm square, easy to adjust, can be as long or as short as I want and as long as I don't over tighten the nuts the stop can be push along rather than causing damage. rob |
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Post by davidimurray on Dec 5, 2006 10:11:50 GMT
And when parting you must not hesitiate or pause - if you do then back the tool out and start a new cut. I've recently been doing a lot of CNC parting and the benefits of a continuous feed are amazing!
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Post by districtgrandmaste on Dec 5, 2006 11:48:30 GMT
Hi - This thread started off about making a sharp shoulder but has now got onto parting off!
On that subject nobody has mentioned the value of Tailstock Support when parting off.
I use a Super 7 and always plan to drill a small centre on the end of the bar being parted off. Also lock everything tight - and use plenty of lubricant when parting off mild steel. If you have a revolving centre that is useful but not essential.
When I'm feeling really daring I put on autofeed - but that can be very scary!
Always make sure your parting tool is sharp.
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Post by spurley on Dec 5, 2006 13:34:40 GMT
Rigidity, good lubrication and a slow speed are the key things to be aware of when parting off. Can be pretty scary I agree but I've found a good parting tool and have finally got a 'feel' for feeding the tool into the job.
Cheers
Brian
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Post by davidimurray on Dec 5, 2006 13:54:50 GMT
Speeds - that is where things get interesting. Some say slow, others say fast.
To be honest try both and see what you are happy with - I'm a fast man myself - anything between 500-1000RPM!
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Post by havoc on Dec 5, 2006 20:26:29 GMT
I had only parted some small brass rod/hex. And that worked reasonably well. But then I tried it on 25mm C45 bar. This rattled the foundations of the house. The tool (a separate blade in a holder) looked blue with the sides scored beyond salvation. Since that experience I use a hacksaw and face afterwards. I'll try to get a pic of the tool, it still is somewhere in the shop.
I'll give it another try one day.
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Post by chameleonrob on Dec 5, 2006 20:32:48 GMT
I find that a slow spindle speed keeps the heat down, remember you are cutting on a wide front with little in the way tool to conduct the heat away, and a hot tool goes blunt very quickly, thats why the angles on a knife tool are all close to 90o, more metal to take the heat away. the same goes for form tools and roughing cuts.
rob
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