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Trouble Cutting Silver steel

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Chris TickTock25/08/2019 12:52:52
163 forum posts
1 photos

Hi, I have machined EN1A with no problem. The project I am undertaking needs to finish it a 1 and 1/4 inch long by 1/8th piece of round silver steel to be machined. I have now twice bent 2 pieces of metal in my attempts.

There are obvious possibilities like the HSS not being sharp enough and possibly the wrong speed chose. I am using a Sherline lathe with a 3 jaw self centering chuck which is not part of the problem.

to machine a thin piece of Silver steel only held by one end means the cutter has to be spot on.

Any thoughts or tips appreciated.

Regards

Chris

Tony Pratt 125/08/2019 12:59:30
882 forum posts
2 photos

So the silver steel is 'as standard' 1/8th " diameter & you are just facing to length, is that correct? Obviously cutting speed needs to be correct[at that dia. what is the fastest you can run?], cutter sharp & on centre line & maybe some coolant [soluble oil/cutting oil]

Tony

Nicholas Farr25/08/2019 13:01:35
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1940 forum posts
922 photos

Hi Chris, you could try drilling a clearance hole into a larger piece of mild steel bar and hold that in the chuck in your tailstock and let the free end of your Silver steel rotate in it with a squirt or two of oil when you are parting it off.

Regards Nick.

Howard Lewis25/08/2019 13:06:50
2207 forum posts
2 photos

Suggestion

1 ) Set a sharp tool, exactly on centre height

2 ) With as little as possible protruding from chuck, face the end.

3 ) Remove chuck and hacksw to a little over length.

4 ) With as little possible protruding from chuck, face the raw end.

5 ) Remove and measure length, so that you know how much needs to be removed to bring it to 1.25" long.j.

6 ) Face to length

7 ) Deburr both ends.

Howard

Bob Stevenson25/08/2019 13:07:00
295 forum posts
6 photos

Being a clock maker you have, of course, made yourself some female centres.....

....Put metal in 3-jaw with enough showing to turn a nice point......Extend workpiece to required distance, place point in female centre held in tailstock, machine workpiece to satisfation, finish the ends ....Done.

Andrew Johnston25/08/2019 13:19:52
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4773 forum posts
538 photos

The most likely solution is that too much of the work is sticking out of the chuck. If that is the case then everything else is secondary. What are you trying to do? Even a light cut will be enough to bend 1/8" silver steel if too much is unsupported.

Andrew

JasonB25/08/2019 13:27:28
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As Andrew says if you have as much sticking out as you did with that hex stock yesterday then that is the problem. Have less than 1/8" sticking out assuming you are facing to length.

Edited By JasonB on 25/08/2019 13:28:58

Bob Stevenson25/08/2019 13:33:53
295 forum posts
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Great idea to only have 1/8'' sticking out of the chuck!........................................................But wait, how do you machine the other inch and an eigth?

JasonB25/08/2019 13:42:20
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I did say "assuming he is facing off which you omitted to quote

He says he needs to finish it at 1 1/4" long. Face one end with approx 1/8" sticking out, then flip it around and face the other end, remove measuer and then face off what is left. Simples.

Though I wonder if this is a tapered point for the scriber being made, lack of detail again. Would help if we knew if it were 1/8" to start with or something else?

Edited By JasonB on 25/08/2019 13:43:01

Edited By JasonB on 25/08/2019 13:43:56

Chris TickTock25/08/2019 13:57:34
163 forum posts
1 photos

OK More detail but not sure I haven't given enough already as it all comes down to a piece of 1/8th dia eound silver steel that approx half is turned down to fit in the punch I have made from EN!A. So one half of the S>Steel needs to fit in the 2.5mm hole drilled in end of hex mild steel and the other half of the S. steel needs tapering then finishing to a point.

problem is with approx 5/8th sticking out the 3 jaw chuck the S.steel is very keen to bend. On the Sherline there is variable speed the max being 2800.

Chris

Neil Wyatt25/08/2019 14:31:27
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Why not make the hole 1/8"?

Very sharp tool, and very gradual feed.

Neil

Andrew Johnston25/08/2019 14:45:54
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Posted by Chris TickTock on 25/08/2019 13:57:34:

OK More detail but not sure I haven't given enough already,,,,,,,,,,,,,,,,,,

Not really, you missed the key point, which is trying to turn 1/8" silver steel with 5/8" stick out. sad

I'd go with Neil, make the hole 1/8". Or even better just make the whole thing from one bit of silver steel. If you must turn the end down, start with about 3/16" sticking out. Turn it down to the correct size and note the cross slide reading, Move the material out another 3/16" and starting at the un cut point wind the cross slide handle in to the previously noted reading. Machine down another 3/16" and so on until you get the required length. It's not a pretty solution but perfectly acceptable in this application. If the finished shaft doesn't quite fit you can always do some gentle "mods" with a needle file on the high points.

Andrew

Michael Gilligan25/08/2019 15:08:18
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13780 forum posts
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Chris,

I can only assume that this is a turning exercise, and that you are therefore 'following the book' meticulously.

... In which case, I would recommend that you find a different book.

It seems ludicrous to turn 1/8" Silver Steel down to 2.5mm just to fit the hole in a badly designed punch.

The alternative designs already suggested are much better from a 'production engineering' perspective, and if what you really want is to to learn to turn 'difficult' steel to make clock pivots then the Saunier book [that I recommended on another thread] is one of many that would be much more useful.

MichaelG.

JasonB25/08/2019 15:16:51
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So staying with my approx 1/8" sticking out this is one way to do it without having to bother making tools to make things which is an ever decreasing spiral.

Saw off a bit of rod just over 1 1/4" long and face off

20190825_144924.jpg

Now turn what is still sticking out to 2.5mm dia I did it in one pass

20190825_145042.jpg

Slide the work out another 1/8" so total 1/4" sticking out and reduce the next bit to 2.5mm

20190825_145126.jpg

And again

20190825_145232.jpg

And again

20190825_145327.jpg

One more tine and you should have 5/8" now at 2.5mm dia

20190825_145421.jpg

20190825_145440.jpg

Now reverse in the chuck again with 1/8" sticking out, set topslide over to 45deg to give the 90deg included angle for your punch and turn a point

20190825_145633.jpg

20190825_145625.jpg

Set topslide to taper angle about 4deg and with 1/4" sticking out turn the taper on that bit

20190825_145826.jpg

another 1/8" etc

20190825_150003.jpg

last bit will be cut while holding by the 2.5mm dia

20190825_150202.jpg

Job done

20190825_150249.jpg

Chris TickTock25/08/2019 15:20:34
163 forum posts
1 photos

Thanks Guys I agree the easiest solution would be to increase hole size to accommodate 1/8th S. Steel. however this is a learning project for me to get me more familiar with thev lathe having done little before on it. My objective is to gradually improve so I can undertake more precision machining on the Sherline. With that in mind holding delicate small items whilst machining is critical so solving this immediate problem with a bigger hole will only defer the day I have to solve the issue.

That said machining shorter lengths sticking out the chuck is definitely one way forward. Obviously if I manage to improve enough to machine very small items then i would invariably be using a collet and not the 3 jaw chuck.

Can anyone give me a pointer as to appropriate speeds for such small dia S.Steel baring in mind max is 2800.

I also appreciate I could use a steady rest but for precision work that as likely to be inappropriate as would likely get in the way.

Chris

SillyOldDuffer25/08/2019 15:22:01
4587 forum posts
980 photos
Posted by Chris TickTock on 25/08/2019 13:57:34:

OK More detail but not sure I haven't given enough already...

...

Chris

Don't worry Chris, engineers like to have all the details. Long painful experience has taught us that even carefully drawn and double-checked drawings can mislead. As we haven't read your project book and don't have access what's in your mind's eye it's really easy for chaps to get confused and give misleading answers! A picture is worth a thousand words; I reckon you mean one of these:

scribe.jpg

This object's a difficult challenge because long thin rods bend easily. You have to plan how the rod will be supported whilst being cut to shape : it's not as simple as gripping one end in a chuck and shouting 'tally-ho'. At least on a Sherline there's no risk of the rod kinking and whipping into the operator at high-speed. Many nasty accidents on big machines where several horse-power at high rpm can instantly convert a long steel rod into a lethal flail.

The answer is to plan some way of supporting the job during the cut. A fixed or travelling steady will be too big. Bob's suggestion of making a female centre is a good one. The idea is to put a short section of taper on one end whilst most of the rod is safely held by the chuck, then to extend the job out so the point runs in a female centre held by the tail-stock. A rod supported at both ends is much stiffer. Still needs a sharp HSS tool running at high rpm exactly at centre height (See Howard.)

Another method might be to support the rod with a block of wood opposite to the cutting edge.

Planning is an important skill because the order of operations can make life easy or impossible. I often rehearse various methods and sleep on ideas to make sure they're sound before trying it. Being self-taught is a disadvantage; apprentices get told stuff and lots of on-the-job training. The rest of us bumble about! A good trick is to delay cutting objects to final size for as long as possible because the base stock can often be used for gripping and support during manufacture. In other words don't start by cutting 1.25" of silver-steel off and then struggling to hold a small bit of metal. For the same reason, finishing the taper should be left late because a taper is much harder to hold than a cylinder. Also, avoid weakening the job until the last moment.

As Neil suggests, a good plan should look for ways for simplifying the job, in this example avoiding turning down to 2.5mm by drilling a 1/8" hole instead. Don't do that - at this stage of the game it's more useful to learn how to make the difficult object. Cheating comes later in the curriculum!

Dave

PS Must learn to type faster.  Jason made one and posted photos while I was dithering.  My work-rate is  depressing...

 

 

 

 

Edited By SillyOldDuffer on 25/08/2019 15:29:14

Chris TickTock25/08/2019 15:25:59
163 forum posts
1 photos
Posted by JasonB on 25/08/2019 15:16:51:

So staying with my approx 1/8" sticking out this is one way to do it without having to bother making tools to make things which is an ever decreasing spiral.

Saw off a bit of rod just over 1 1/4" long and face off

 

Great post Jason and very helpful. I too manage to reduce to 2.5mm in one go (several light goes) but foul up by having too much sticking out for the taper. I think the 1/8th at a time on the taper will sort it. Question: what insert are you using Aluminium with 0.02 nose radius?

Regards

Chris

Edited By JasonB on 25/08/2019 16:31:09

Chris TickTock25/08/2019 15:32:23
163 forum posts
1 photos
Posted by SillyOldDuffer on 25/08/2019 15:22:01:
Posted by Chris TickTock on 25/08/2019 13:57:34:

OK More detail but not sure I haven't given enough already...

...

Chris

Don't worry Chris, engineers like to have all the details. Long painful experience has taught us that even carefully drawn and double-checked drawings can mislead. As we haven't read your project book and don't have access what's in your mind's eye it's really easy for chaps to get confused and give misleading answers! A picture is worth a thousand words; I reckon you mean one of these:

scribe.jpg

This object's a difficult challenge because long thin rods bend easily. You have to plan how the rod will be supported whilst being cut to shape : it's not as simple as gripping one end in a chuck and shouting 'tally-ho'. At least on a Sherline there's no risk of the rod kinking and whipping into the operator at high-speed. Many nasty accidents on big machines where several horse-power at high rpm can instantly convert a long steel rod into a lethal flail.

The answer is to plan some way of supporting the job during the cut. A fixed or travelling steady will be too big. Bob's suggestion of making a female centre is a good one. The idea is to put a short section of taper on one end whilst most of the rod is safely held by the chuck, then to extend the job out so the point runs in a female centre held by the tail-stock. A rod supported at both ends is much stiffer. Still needs a sharp HSS tool running at high rpm exactly at centre height (See Howard.)

Another method might be to support the rod with a block of wood opposite to the cutting edge.

Planning is an important skill because the order of operations can make life easy or impossible. I often rehearse various methods and sleep on ideas to make sure they're sound before trying it. Being self-taught is a disadvantage; apprentices get told stuff and lots of on-the-job training. The rest of us bumble about! A good trick is to delay cutting objects to final size for as long as possible because the base stock can often be used for gripping and support during manufacture. In other words don't start by cutting 1.25" of silver-steel off and then struggling to hold a small bit of metal. For the same reason, finishing the taper should be left late because a taper is much harder to hold than a cylinder. Also, avoid weakening the job until the last moment.

As Neil suggests, a good plan should look for ways for simplifying the job, in this example avoiding turning down to 2.5mm by drilling a 1/8" hole instead. Don't do that - at this stage of the game it's more useful to learn how to make the difficult object. Cheating comes later in the curriculum!

Dave

PS Must learn to type faster. Jason made one and posted photos while I was dithering. My work-rate is depressing...

Edited By SillyOldDuffer on 25/08/2019 15:29:14

Great Post all points noted and appreciated. Unfortunately by my mistakes I learn some good lessons.

Chris

ChrisB25/08/2019 16:14:12
392 forum posts
162 photos

Your will to help others is impressive Jason!

I mean to post suggestions etc is one thing, but to take the worry and go down the workshop (on a Sunday) and phisically knock out the actual item in subject (complete with illustrated step by step guide) is beyond what one could hope for!

 

Edited By ChrisB on 25/08/2019 16:15:54

Chris TickTock25/08/2019 16:34:20
163 forum posts
1 photos
Posted by ChrisB on 25/08/2019 16:14:12:

Your will to help others is impressive Jason!

I mean to post suggestions etc is one thing, but to take the worry and go down the workshop (on a Sunday) and phisically knock out the actual item in subject (complete with illustrated step by step guide) is beyond what one could hope for!

Edited By ChrisB on 25/08/2019 16:15:54

But hos help is greatly appreciated and at last flaws and all I did it.

Chris

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