Author Topic: Video - a skilled machinist shows how to turn small diameters  (Read 4049 times)

Offline Gas_mantle

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Video - a skilled machinist shows how to turn small diameters
« on: December 19, 2017, 03:13:19 AM »
The title says it all.

I came across the video by accident and thought the technique he uses to turn steel from 1/2" to 30 thou dia in one pass may be of interest.


Offline 90LX_Notch

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #1 on: December 19, 2017, 09:15:22 AM »
Joe "Pie" in my opinion has the best machining content videos on YouTube. 

-Bob
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Offline simplyloco

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #2 on: December 19, 2017, 11:33:58 AM »
Interesting stuff, which any competent machinist should be capable of, but I would look in my SS drawer first and find some 30 thou wire .....  :lolb:

Offline kvom

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #3 on: December 19, 2017, 01:00:41 PM »
I wonder what HP the lathe needs for that cut.

Offline Jasonb

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #4 on: December 19, 2017, 02:00:47 PM »
Does not need to be massively powerful really it is no bigger a cut than drilling a 1/2" hole. My far eastern 11x28 will take off a 0.250 depth of cut in steel if I want it to that's 1/2" off dia, would no doubt be a bit more effort in stainless though as this is on 1" bar would probably equal things out.



Offline simplyloco

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #5 on: December 19, 2017, 05:04:52 PM »
I wonder what HP the lathe needs for that cut.

IIRC the man said he was using a 3 to 4 thou feed: this slow rate with a sharp new tool means that even a little lathe made of compressed rice paper would cope!  :mischief:

Online Vixen

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #6 on: December 19, 2017, 05:52:34 PM »
Explain?? :facepalm:
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Offline kvom

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #7 on: December 20, 2017, 01:07:31 AM »
Not so slow.  1200 rpm *.004/rev = 4.8 inches/minute

Offline Jasonb

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #8 on: December 20, 2017, 07:39:27 AM »
Kvom, It can be called a" slow" rate irrispective of spindle speed as whatever the spindle is running at the tool will still advance the same amount per rev. Feed rate is not the distance moved per minute, it is distance /rev. Though I would have said 4thou /rev was a medium/high feed on a hobby lathe.

Interesting thing is that he is not cutting at anything like 0.004" per rev, take another look at the video and it takes him about 30secs to do that first cut which is about the dia of the bar so that is 0.5" per min which means he probably meant to say 0.0004" feed. That video of mine is cutting at my slowest feed of 0.0025" /rev. Wonder how many people have tried doing what he shows at 0.004" and had a big jam up! As they say don't believe all you see on you-tube :ShakeHead:

Mike, if it was Dave's comment you wanted explained than the rule of thumb is that you can remove 1 cu in of metal per minute for each 1HP that you have. So if you only hay an 1/8" HP motor then set the feed rate fine enough so that you are removing less than 0.125cu in of material and your small motored lathe should cope. Don't quite agree with dave's bit about rice paper as you would still want a ridgid machine to do it.

EDIT my feed rate changed.
« Last Edit: December 20, 2017, 09:39:19 AM by Jasonb »

Online Jo

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #9 on: December 20, 2017, 08:18:41 AM »
.....whatever the spindle is running at the tool will still advance the same amount per rev.

Only true for lathes which gear their surfacing fed from the headstock ::)

Jo
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Offline Jasonb

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #10 on: December 20, 2017, 09:13:33 AM »
I know what you are saying Jo but for a feed rate of 0.004" per rev even with your variable speed feed you would still need to reset the speed of the carage to suit a change of the spindle speed if you were to maintain the quoted 0.004" cut per rev. Any change in your spindle speed and you would no longer be cutting at 0.004"

You are also talking about distance moved/time not the usual way feed rate is expressed as distance moved/rev

Online Vixen

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #11 on: December 20, 2017, 09:31:43 AM »
Don't quite agree with dave's bit about rice paper as you would still want a ridgid machine to do it.

That's the bit I wanted Dave to explain. I would not attempt to repeat this trick on anything less than a big, rigid and 'tight' lathe.

Mike
« Last Edit: December 20, 2017, 10:12:32 AM by Vixen »
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Offline Graham Meek

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #12 on: December 20, 2017, 12:36:56 PM »
I well remember visiting the Hardinge stand at one of the Metalworking Exhibitions and seeing 1" Mild Steel being turned down to 0.0625". The cut was taken in one pass. The diameter produced was smooth, spot on size and free from any imperfections. The tool used was a HSS knife tool. While it was a very good party piece the wastage of material just to get some 0.0625" rod is not something I would like to do.

I favour a more systematic approach, the attached photographs give my solution to turning long slender shafts, but with out the wastage. The smallest diameter I have done so far is 0.051 for some 12 BA studs. The maximum turned length is dependent on the stiffness of the original bar stock. The longest 3/32 diameter I have turned in one pass is 3", but I feel this set-up could be used to produce longer turned bar. I have just not had the requirement.

The maximum diameter stock that this attachment will deal with is 10 mm. (I apologise for the mixed measuring systems).

My best regards
Gray,

Offline Bjorn_B

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #13 on: December 20, 2017, 04:09:26 PM »
Wish you had not shown that tool Gray.. Now I must make one :)  :happyreader:

Offline petertha

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Re: Video - a skilled machinist shows how to turn small diameters
« Reply #14 on: December 20, 2017, 05:19:23 PM »
What a brilliant tool, I want to make one! Hopefully understand correctly: The V block is positioned & secured to rub/support the larger stock diameter. Is the purpose of the Delrin washered bolt (green arrow) to allow the cutter to advance with enough friction just by turning the set screw (red arrow)? Under cutting load, the HSS bit cannot back out because of the set screw & it cant rotate out of position because of the washer/bolt & held captive in the slot?

The little pop marks around the set screw I assume are depth graduation reference? What size is the set screw for reference?

I've seen a similar principle used to turn long skinny shafts (but not as compact or elegant). In that case I guess you would have to re-adjust the V slider position to the new diameter each pass? Is the tool intended to be used in this manner too, or it mostly for turning down relatively short sections?