BARE essentials

This topic has 22 replies, 8 voices, and was last updated 18 January 2015 at 13:53 by Neil Wyatt.

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12 January 2015 at 00:13 #7434
Martin Botting 2
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@martinbotting2
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12 January 2015 at 00:13 #175689
Martin Botting 2
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@martinbotting2
Would someone give me a clue as to the meanings of legends on some drawings I am reading:

⅜ bare.

3/16th FULL.

.240 = N.S.

I am sure i will come upon many more terms that will need explaining.

Many thanks

Martin
12 January 2015 at 07:26 #175696
john kennedy 1
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@johnkennedy1
I've only heard those terms used in American woodworking programs by people like Norm in New Yankee Workshop. Another term he uses is "Strong".

Never heard them used in engineering.
12 January 2015 at 07:42 #175697
JasonB
Moderator
@jasonb
Often used on the older ME drawings.

Bare would be +0, -0.002" eg just undersize and definately not oversize.

Full would be +.0005, -0

NS probably non standard but if you can say what the part is and what it fits to could then be sure.

The best thing to do with these references is look at what the part mates with. If its a press fit in a hole then it will need to be full, is a running fit then it will need to be bare. But just make one part to fit the other as the mating hole may be under/over size.

Edited By JasonB on 12/01/2015 07:50:04
12 January 2015 at 09:11 #175699
Circlip
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@circlip
Posted by john kennedy 1 on 12/01/2015 07:26:32:

I've only heard those terms used in American woodworking programs by people like Norm in New Yankee Workshop. Another term he uses is "Strong".

Never heard them used in engineering.

Obviously too young to have been taught by old school Ingineers.

Never heard of a "Proud" sixteenth or a "Shy" sixtyfourth.?

Regards Ian.
12 January 2015 at 09:35 #175702
colin hawes
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@colinhawes85982
These terms were used frequently in UK many years ago when precision measuring was not at everybody's disposal. Bare being as near to size as possible Full tending towards oversize and Free for a loose fit. Colin
12 January 2015 at 10:09 #175706
Neil Wyatt
Moderator
@neilwyatt
I'd guess that N.S. = nominal size (i.e. just like an M6 bolt is actually rather smaller) so probably referencing a bought in part or a thread.

Neil
12 January 2015 at 11:12 #175720
Martin Botting 2
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@martinbotting2
The legend 3/16 Bare is attached to a gudgeon pin for a cross head so would I be guessing right that you make the shoulder the exact size as the con rod small end's width so allowing the nut to tighten but leave little slop, maybe see if I can grab a shot of what I am talking about and post it here. also on the horns and axel boxes.
12 January 2015 at 11:21 #175721
Martin Botting 2
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@martinbotting2
I bought a set of castings for a robroy from the well known auctions site and among the bits were no horn guides of the gunmetal type but honking great cast iron ones so I have ordered some from Messrs Blackgates to pick up at the show next weekend. In the box of tricks I found what I think are the crossheads but they are gunmetal not MS as per the drawing. WHEN I get round to butchering this part would you advise making MS ones as they have to run on case hardened steel slide bars.

Many thanks as always.

Martin
12 January 2015 at 11:22 #175723
john kennedy 1
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@johnkennedy1
Posted by Circlip on 12/01/2015 09:11:43:

Posted by john kennedy 1 on 12/01/2015 07:26:32:

Obviously too young to have been taught by old school Ingineers.

Regards Ian.

Obviously.

Sounds a load of old tosh used by amateurs to me.

What's wrong with dimensions with tolerances.?
12 January 2015 at 13:19 #175740
JasonB
Moderator
@jasonb
The 3/32" bare is so that the nut will tighten down without bottoming on the 5/32" dia

The 3/16" full is so that teh part is not trapped between teh screw head and the part with the 5/32"" hole

John not much point in giving a H7 tollerance when the chap making the part back in the day is using a pair of callipers set with a ruler. As I said at the start look at the parts and fit one to the other.

J

Edited By JasonB on 12/01/2015 13:20:28
12 January 2015 at 13:45 #175743
Martin Botting 2
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@martinbotting2
Jason.

You are right about looking at the bits it connects too. Thats cleared that one up. The axle boxes would need a bit of slop in the horns I am guessing.

The real fun is going to start when it comes to machining the axle's to fit the wheels the drawings call for a 7/16 reamed hole and press fit on the axel as this will be a first time I am thinking down the bottled fitting solution lines, Locktite.

Hope I can get back down the workshop soon as I have a half finished Voith propellor to finish and this sitting around sick is getting on my nerves now, so back to the drawings.

Thanks to everyone for the pointers
12 January 2015 at 16:26 #175760
Neil Wyatt
Moderator
@neilwyatt
Hi Martin

Ream the holes first.

Make a test bar and turn it down slightly bigger than the reamed holes. Put a shallow taper on the end of the bar, and poking it into the reamed holes you can see how far you are away from a dead fit in he holes.

Carefully skim the test bar until its a tight push fit in the wheels and note the cross–slide reading.

Use this setting to turn the ends of the axles for loctiting, or if you want a press fit, leave them slightly oversize.

Don't pay any attention to suggestions of leaving space for the loctite, it works best when the two surfaces have a shearing fit and a pin tight in a hole is what its designed to work with, though it will forgive you if you make the axles slightly undersize.

Neil
13 January 2015 at 19:43 #175920
Martin Botting 2
Participant
@martinbotting2
Thanks Neil. I will try that out when I get round to the axles and for other bits. All this info is being stored away in the grey filing cabinet.

I will say it again this forum is like having a club night 24/7 365! many thanks to everyone.

Martin
15 January 2015 at 12:19 #176108
Circlip
Participant
@circlip
Posted by john kennedy 1 on 12/01/2015 11:22:13:

Posted by Circlip on 12/01/2015 09:11:43:

Posted by john kennedy 1 on 12/01/2015 07:26:32:

Obviously too young to have been taught by old school Ingineers.

Regards Ian.

Obviously.

Sounds a load of old tosh used by amateurs to me.

What's wrong with dimensions with tolerances.?

Nothing, but those that taught me were used to actually building things that worked in industry. Surprising how many general usage components were/are made on tooling that never saw tolerances in their manufacture. Self proclaimed Muddle Ingineers who constantly witter about "Why are there no tolerances on toy drawings?" show a total ignorance of the job in hand and have no concept in the term "Fitting". Likewise "Why isn't it dimensioned in Metric?"

We proper ingineers had a joke circulating in the distant past, "Six munce ago I cutan't even spell Ingineer, now I are one.

Never seen yarn tension mentioned on knitting patterns.

Wonder how all the engineering marvels were made without the use of Digital electronics and CAD/CAM?

Regards Ian
17 January 2015 at 14:01 #176322
Mark C
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@markc
"Wonder how all the engineering marvels were made without the use of Digital electronics and CAD/CAM?"

Generally, over engineered and without much concern for cost!

Mark
17 January 2015 at 16:25 #176333
Gordon W
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@gordonw
Marc- Over engineered and without concern for cost- you never owned a Metro..
17 January 2015 at 16:34 #176335
Mark C
Participant
@markc
Gordon,

I was not in their design department but I belive they had adopted CAD by the time of the Metro! It was certainly an innovative design utilising modern materials and concepts.

Mark
17 January 2015 at 16:42 #176337
Gordon W
Participant
@gordonw
Adopted CAD, yes that's the point. Even I was using CAD then. Are you thinking about the same Metro ? ex BMC ?. Innovative? Bits of the Mini. More bits of the M1000? Second quickest chassis self -destuct. Let's not get any further into this.
17 January 2015 at 19:07 #176354
Mark C
Participant
@markc
Gordon, do you really think the design was to blame for build quality? There are always exceptions, I think they got Concord into the air without CAD but I may be mistaken.

Mark
18 January 2015 at 10:15 #176413
Gordon W
Participant
@gordonw
My last word on this- No, design not to blame for the build quality, BUT the design ( for anything) should take the expected build quality into account and allow for it.
18 January 2015 at 11:50 #176438
Mark C
Participant
@markc
Gordon,

OK. The point I was making was the advances in design tools have allowed us to get from having to make stuff that "looks" about right which generally involves more material than necessary and adding strength "just to make certain" to being able to "look" at the design in ways that allow you to see the stress and deformation and easily know the exact attributes without days and weeks of manual long hand calculations (that would have been done on a slide rule?).

"Wonder how all the engineering marvels were made without the use of Digital electronics and CAD/CAM?"

Generally, over engineered and without much concern for cost!

You responded to the second part of that quote but the first bit is the interesting part for the reasons given. I think the Metro might have been a poor example and given the advances in the later engines (K series – i know they are Japanese) from my point of view, they were fairly advanced engineering, as for the Metro – A quick look on the internet suggests it was only second in popularity to the Escort here in the UK!

Mark
18 January 2015 at 13:53 #176461
Neil Wyatt
Moderator
@neilwyatt
I once saw a Metro 6R4 up close on display at the start line for the RAC Rally. I asked the engineer who was with it how much of it was 'real Metro'. He thought for a bit and said 'the dashboard'.

Neil
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