DRO uses with conventional drawings

[Jonathan Coates]

I've been looking at the drawings for a Stuart engine that I'm about to attempt and realised that I'm probably going to have to calculate the hole positions relative to a fixed datum zero point so that the DRO can do all the heavy lifting. Just wondering what the concensus is on posting a chart for the positions relative to a fixed point and what the copyright infringements might be if I redid the drawing showing the X,Y positions of the various holes?
The drawing is in fractional inches and at the very least I'm going to have to cope with translating these to decimal. It might be easier to do this in the warm office rather than the draughty shed, and I'll need coffee on hand.
Your opinions please gentlemen and ladies.

 

[danallen]

Do you mean just for your own use or posted online for others? I can't imagine a problem if you do it just for yourself.

 

[Jonathan Coates]

To share, if the drawings are used a lot. I'm sure there are many builders of the entry level Stuart S50 I'm pondering at the moment for example. A rarer beast may have little or no use to anybody else.

 

[Jonathan Coates]

This is the kind of thing I'm working on at the moment. A DRO cheat sheet for each drill size so I can hit them all in one go, then change drill size and do another sheet.

 

[f2cf1g]

Working in 29/64s and suchlike is beyond me so I redraw parts in metric with dimensions from what i think will be DRO reference edges. Less scope for mistakes too.

 

[timo_gross]

I did redraw most times in my computer, then I use the CAM software to give me the references.

Now that I think of it? Without a CNC and just the DRO a posted G-code can still be very helpful and sufficient.
You can be your HNC (human numerical control).

The Code is not really complicated to read! The work for the DRO user would start with edge finding the zero postion and zeroing x and y on the DRO.
(x and y can freely be decided based on preference in the computer. In the example the lower left corner of my flat stock seemed a good startpoint)
Then in line 17 of the G-code the first point. X86/Y104.5 can be found. Next X147.0 Y88.0 and so on.
In line 23 there is only x25.5 no value for y; it means do not touch y and just move x.
Usual model parts with only a few hole locations should fit on a single printed page, that you can take to the shed and cross out the holes that you have finished.

Greetings Timo

 

[Steamchick]

Wow! I didn't understand a thing after the 41/64ths. Which are OK for me as my vernier caliper does 128ths!
Why does anyone need decimal when binary is so simple?
K2

 

[Jonathan Coates]

There are 10 kinds of people, those who understand binary and those that don't.
Looks like this is a common issue and people have found ways round it as I'm trying to do, so I feel I'm among good company.
No I've got to wrestle with the two options. 1st is to just sand the bottom flat as many on the YouTube seem to do and then reference everything off that, or 2nd is to try to fix the thing upside down and flycut the base flat to get the base to crank centre correct. The casting hints at where the crank centre is supposed to be so next step is, after this coffee, measure the current height of the lump in the casting and see what's what.
I think drilling the crank bore will be a first operation as this then gives me one half of the datum when the centreline is defined. I've ordered some oilite bushes so I must remember to ream the holes for these.

 

[Jasonb]

My only comment on your PDF would be to put the 9/32" above the ctr line for consistency that way all the fractions are above and the decimals below.

It may also be easier for beginners to follow if the dimensions could be related to the actual casting, something along the lines of these corrections I've published in a few places for the Stuart Victoria.

 

[Jonathan Coates]

My only comment on your PDF would be to put the 9/32" above the ctr line for consistency that way all the fractions are above and the decimals below.

It may also be easier for beginners to follow if the dimensions could be related to the actual casting, something along the lines of these corrections I've published in a few places for the Stuart Victoria.

Moving the 9/32" up still leaves the pesky 0.2813 at the right hand side above the centre line so I'll have to put up with it I think. I didn't want to publish the actual drawings as there might be copyright issues. Granted, without the casting the drawing is pretty useless, but anyway. I intended to use the crib sheet alongside the actual drawing, only leaving the fractions in to allow the hole pattern to be cross referenced to the drawing. I'm sure there's lots of ways to do this and some methods will suit some models more than others and vice versa. Good to have more input as its all food for thought.

 

[Jasonb]

You could put a note that holes are symmetrical about the ctr line and that would do away with the other 0.281". Often a note is not even needed as the symmetry is assumed as in my example. If you do keep it then I would go with the two decimal dimensions at the same end of the drawing

You would not need to do an exact copy of the drawings, just a basic shape to help with orientation. On mine I modelled the whole engine in CAD anyway so it was easy just to pull an elevation and add the dimensions to that.

There are certainly different ways to lay out dimensions particularly depending on how they are being positioned. With the DRO I generally work to ctr lines but if someone were using handwheels which would still benefit from decimals then it can help to use a corner so that all dimensions are in one usually positive direction to make it easier to compensate for backlash.

This is an example I did some time ago to illustrate how it can vary depending on what is being used. The left hand side suites a DRO where you touch off on opposite sides and use the 1/2 function to locate the ctr line. The one on the right you would find top and left edge and work from the corner with the handwheels

 

[Steamchick]

Hmm.
Back in the 60's I was taught to ONLY work from one direction for setting from the dimension rings on the machine. = Wind through and back if coming from the wrong direction.
But I was taught on all WW2 ex-US (well-worn) machinery, the stuff that didn't get sunk by Herr Hitler's Uboats. As machines were so worn, we had to Measure, measure measure to be sure we had correctly adjusted for wear. The machines were robust, if not accurate. I still follow exactly the same philosophy with my relatively new and hardly worn Chinese lathe...
But maybe that isn't taught when people learn about machining nowadays (via Utube?)?

 

[danallen]

Hmm.
Back in the 60's I was taught to ONLY work from one direction for setting from the dimension rings on the machine. = Wind through and back if coming from the wrong direction.
But I was taught on all WW2 ex-US (well-worn) machinery, the stuff that didn't get sunk by Herr Hitler's Uboats. As machines were so worn, we had to Measure, measure measure to be sure we had correctly adjusted for wear. The machines were robust, if not accurate. I still follow exactly the same philosophy with my relatively new and hardly worn Chinese lathe...
But maybe that isn't taught when people learn about machining nowadays (via Utube?)?

I agree. I also learned in a shop full of old worn machinery. I call my method sneaking up on the final dimensions. Measure cut measure cut until you are close and then go for it with fingers crossed.

 

[Jonathan Coates]

I started on metric machines which had been recovered from Germany as War Reparations. These were worn out by 1979 so we did the same stuff. Oddly they were OK made Ward lathes, full capstan things. I found that piece work went better if half a day was spent setting up all the tooling and using it correctly. The times alloted, and therefore money, was calculated by a Time And Motion Consultant off site.
The creeping up idea, I've found, doesn't work with insert tooling. Try a slight cut and nothing happens, until you've added several increments then you get them all at once.

 

[ShopShoe]

Random Thoughts .............

For an individual working with that individual's own set of tools and own usual techniques everything is undrstood by that individual and precision and repeatability is pretty much, well..., repeatable.

Standards for communication and practice come into play when person one needs to explain or demonstrate to persons two, three, etc. what is called for. This is even worse when Two makes Part A and Three makes Part B and everything is supposed to work well together.

This is both bad and good. As far as this forum and home shop production goes , the Good part of this series of events gets back to the posting of interesting work that can explain to the follower what the builder is doing and how well each step works so that the follower can learn and practice new skills.

AHEM........ The use of regular (standard?) conventions makes things understandable for more followers and saves time with fewer errors. If a standard is not known or does not exist then the originator needs to explain or illustrate more to be clear. This is itself illustrated in the repeated calls to explain Elmer Verburg's drawing notations (The little letters inside circles on some of the plans)

What makes standardizing difficult is what is done in different industries and different parts of the world and in different training environments also changes a lot from one situation to another.

SO.....: explain things, even if it seems simple and even if it seems redundant. Attempt to make clear the source of things that might seem "foreign". "Consider the Audience," maybe even explain some context so that followers can adjust their thinking.

And So and So On .....: This is a rambling post but I wanted to add to the discussion and I am attempting to be clear with explanations and examples. Perhaps I did not succeed in this, but I am pretty sure if I unleashed some angry words and told readers to (censored) I would succeed even less.

Emphasis....: If I ramble too much, my main point is in paragraph three, sentence two.

--ShopShoe

 

[comstock-friend]

I always convert the Stuart drawings to decimal and I'll find the most useful datum for the part and machine it from there. If the drawings were metric, I would convert them to decimal inches. All one needs to know is 1.000 inch equals 25.4 mm EXACTLY. My machines are inch screws and handwheels. The Tormach PCNC1100 can swing from either side but my brain at 73 years is in inches.

 

[Steamchick]

As I have many old drills that are factional inches, and many threads use number drills, as well as fractional inches for the pilot holes, I find I use "whatever the table says" is needed for the drill sizes. Metric, fractional inch, Number, etc. I.E. I use all the "tool sizes" required without worrying about Imperial or metric units.
Similarly, I have metric dials on the milling machine, and imperial on the lathe, so simply convert whatever needs converting on the drawing to "machine sizes".
I think in whatever dimensions "suit the job".
I grew-up as a teenager in an "imperial" school, that was converting to Metric, so we had new text books in the "new units". - Same sums, just expensive conversions!
Yet I then experienced piston sizes for various car and truck engines, at a machine shop where I worked part-time, and found that most pistons were in fractional inch sizes - but not simple sizes - just converted from round-numbered mm sizes!
e.g.
Millimeters to inches conversion table

Millimeters (mm)	Inches (") (decimal)	Inches (") (fraction)
60 mm	2.3622 ″	2 23/64 ″
70 mm	2.7559 ″	2 3/4 ″
80 mm	3.1496 ″	3 5/32 ″
90 mm	3.5433 ″	3 35/64 ″

But re-boring and honing the cylinders was in Imperial over-sizes, so the decimal inch was quoted in the books next to the "standard" (fractional inch, or sometime cm!) bore size, with the part size in decimal inches.
Hence I am ambidextrous-ish in these units. I never realised it was such a problem until this thread.
"Fortunately" we all live with our own histories, and manage whatever way we can. I think the only real "standard method" to propose is "work to the drawing sizes, converted to our own machine/tool sizes as appropriate". After all, we make parts using the available tools and scales on the machines, so need clear instructions when doing that.

Hi SHop SHoe,
I hope this suggestion doesn't contradict your message (I got confused a bit by your ramblings... But I am sure my ramblings are more difficult to follow! PLEASE correct me when I ramble too much, or am unclear.).

ENJOY,
K2

 

[timo_gross]

As I have many old drills that are factional inches, and many threads use number drills, as well as fractional inches for the pilot holes, I find I use "whatever the table says" is needed for the drill sizes. Metric, fractional inch, Number, etc. I.E. I use all the "tool sizes" required without worrying about Imperial or metric units.
Similarly, I have metric dials on the milling machine, and imperial on the lathe, so simply convert whatever needs converting on the drawing to "machine sizes".
I think in whatever dimensions "suit the job".
I grew-up as a teenager in an "imperial" school, that was converting to Metric, so we had new text books in the "new units". - Same sums, just expensive conversions!
Yet I then experienced piston sizes for various car and truck engines, at a machine shop where I worked part-time, and found that most pistons were in fractional inch sizes - but not simple sizes - just converted from round-numbered mm sizes!
e.g.
Millimeters to inches conversion table

Millimeters (mm)	Inches (") (decimal)	Inches (") (fraction)
60 mm	2.3622 ″	2 23/64 ″
70 mm	2.7559 ″	2 3/4 ″
80 mm	3.1496 ″	3 5/32 ″
90 mm	3.5433 ″	3 35/64 ″

But re-boring and honing the cylinders was in Imperial over-sizes, so the decimal inch was quoted in the books next to the "standard" (fractional inch, or sometime cm!) bore size, with the part size in decimal inches.
Hence I am ambidextrous-ish in these units. I never realised it was such a problem until this thread.
"Fortunately" we all live with our own histories, and manage whatever way we can. I think the only real "standard method" to propose is "work to the drawing sizes, converted to our own machine/tool sizes as appropriate". After all, we make parts using the available tools and scales on the machines, so need clear instructions when doing that.

Hi SHop SHoe,
I hope this suggestion doesn't contradict your message (I got confused a bit by your ramblings... But I am sure my ramblings are more difficult to follow! PLEASE correct me when I ramble too much, or am unclear.).

ENJOY,
K2

What a mess.

I use 5/127" or decimal fractions of it .
Found a drill with an F in my workshop yesterday. No idea why I have it or who gave it to me?

 

[Steamchick]

How can I reply to that? mm - let me think....

"F-in-Workshop?" - mind your language please...

Or did you mean 0.2570inches? (6.5278mm for the pedantic). - I call it " 1/4in. clearance"...
K2

 

[Steamchick]

Back to the thread...
A sequence I should use, may not be the best, just how I did it recently:

1. Mount casting in the mill to make a cylinder-end flat surface. This face becomes the primary datum surface. (perpendicular to the bore in 2 directions).
2. In the same setting, determine optimum centre for the bore, drill and bore (in the milling machine).
3. Set-up the angle plate (or fixed jaw of the machine vice) to be in line with the travel for the long axis of the table (DTI checked!).
4. Mount the cylinder datum face on the angle plate surface and skim the valve face as the second datum face.
5. Skim one edge of the valve face to give the 3rd datum face, before removing from the set-up in "4" above.
6. From those 3 datums (dati? Datum faces?) you can machine all the other features.

The primary datum face is the one used to mount the cylinder block relative to the crank axis.
Any better ideas? - I'd like to learn from the experts...
Perhaps the second datum should be skimmed before removing from the first setting? - and possibly the 3rd?
K2