Museum of Obsolete Drafting Technology

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Mr Ron
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Re: Museum of Obsolete Drafting Technology

Post by Mr Ron »

I use a long travel indicator on my lathe when making multiple small parts; they all come out the same length.
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Mr Ron
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Re: Museum of Obsolete Drafting Technology

Post by Mr Ron »

I have a Bruning erasing machine, but it doesn't seem to work on my computer screen.
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Harold_V
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Re: Museum of Obsolete Drafting Technology

Post by Harold_V »

rmac wrote: Thu Mar 04, 2021 8:50 am Thanks, Harold. I was curious because I use dial indicators in a couple of situations and I was wondering if I was missing something.
Judging by your comments, below, I'd say you're right on top of the game. I do have a small issue with one comment, which I'll address.
1. My mill/drill has a ridiculous amount of backlash on the Z axis. Beyond that, sometimes when I think I have the backlash all taken care of, something in the mechanism will get "unstuck" and the spring will pull the quill up by some unknown amount, resulting in a complete loss of position. I put a dial indicator (permanently) on that axis and have been much happier ever since.
With a knee mill, that's generally not a problem, as one works with the quill locked and trusts the knee for making fine adjustments in the Z axis. However, depending on the nature of the work, a long travel indicator can be quite useful. For this tiny part, which I've shown on numerous occasions, I installed a long travel on the quill of my Bridgeport, as the round bosses shown were generated with a boring head and had only a .001" tolerance on both diameter and length. Without an indicator, there would have been too great a chance at creating scrap, as I had to make a couple hundred of them. Note that the spike one sees in this picture is just a common straight pin.

Antenna Latches resized.jpg
2. On my lathe, the markings on the carriage hand wheel dial represent 0.006", which is kind of coarse. Most of the time I can deal with small movements in that direction using the dial on the compound slide, but occasionally need a dial on the carriage like you're talking about.
The relatively coarse markings leave too much to chance, so I'd use an indicator for this feature. As to the compound slide, while it may offer the ability for a better control of linear dimensions, it comes at the cost of the loss of the value of setting dials, a feature that, for more than one-off, should not be lost. Beyond that, on a personal basis, I do NOT like to operate with the compound unlocked (I use the gib to lock the compound slide) unless it is being used. That's due to the loss of the value of setting dials. I also do not like the compound set anywhere except for 29° (5:00), unless it is being used for a specific purpose. Key takeaway here is that that is my choice--it has little to do with proper operation. I'm just more comfortable working that way.

H
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rmac
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Re: Museum of Obsolete Drafting Technology

Post by rmac »

I'm not sure what you mean here by "loss of the value of the setting dials". Maybe that's becuase almost everything I do is one-off, or maybe because I just do things in a different way than you do.

I would like to understand what you're saying, though.

To help clarify, here's how I would cut a shoulder a specific distance from the end of a part:

1. Set the compound at 0 degrees (3:00).
2. Set the compound dial to 0, and lock the compound slide.
3. Move the carriage to bump the tool up against the end of the part. (Or better yet, face off the end of the part.)
4. Set a carriage stop with the carriage in that position.
5. Move the carriage to the right to move the tool away from the part.
6. Unlock the compound slide, advance it by a few thousandths less than the desired distance of the shoulder from the end of the part, and lock it again.
7. Turn the end down to the desired diameter, at each pass running the carriage up against the stop set in Step 4.
8. Before making the very last pass, advance the compound slide by the "few thousandths less" amount in Step 6 so that you can then drag the tool radially outward to clean up the shoulder at the correct distance from the end of the part.

(Man, that sounds complicated! But it really isn't.)

Anyway, I don't see that I am losing any dial settings here. Maybe because I would repeat the entire procedure for a second part?

-- Russell Mac

PS: Without wishing to get myself in big trouble by starting a political discussion, I think that round column mill/drills should be outlawed and that everyone should be issued a high quality knee mill as a matter of birthright. Retroactively, of course, for us old guys.
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Harold_V
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Re: Museum of Obsolete Drafting Technology

Post by Harold_V »

Your procedure isn't necessarily complicated, just not necessary. There's far easier ways to accomplish the same task. No messing with stops, no messing with the compound. All of those steps take time, time you simply can't afford to add to a job when you're working for gain (that was what I did) and are making multiple parts, which wasn't always the case. Tool making often required just one off.

While I was a tool maker, I also ran product. Fact is, tool making was a pleasant surprise, as I had not expected to find myself in that position, but it was the preponderance of the work I did.

That said, the way I operate a lathe is much like a CNC operates, only difference is I was doing it long before CNC's become the norm.
In order for dials to be reliable, you can't move any slide that alters the relative position of the tool as it relates to other slides. That's what happens when you move the compound slide, as it loses registration with both the saddle and cross slide unless it is dialed dead parallel with the spindle. In that case, you lose registration with the carriage only.

Assuming the compound isn't set as I described, dial setting become of no value, and it's no different if you're using a DRO. The tool must remain a constant as far as location is concerned. Said anther way, you know that 0 on the dial represents a given value. If you move the compound, that is no longer true.

When you have multiple parts to make, it's really important to know were the tool is at all times if you hope to make time. That includes using a quick change, or a square tool block, which is my choice (in particular for small work).

I do it like this:

Tool #1 is my turning and facing tool. The stock is set at the required length, then the end faced. Long travel indicator is set @ 0. You now have a reference for the end of the part, which becomes all important for succeeding cuts/operations. Turn the prescribed diameter to the given length, using the dial indicator to determine length. That is recorded on a piece of paper (for the rest of the parts to be made accordingly). The diameter of the part is achieved, with the cross slide dial set to 0, which is also recorded.

I'll assume a second turn is required. You already know where the end is. The second diameter is achieved, both length and diameter, each of which is recorded. Both of them will have a relationship that should be common to you, assuming you're working in inches. If the diameter is a given fraction, the dial setting will be obvious. Lets assume the 0 setting was for a ½" (.500") diameter turn. The second turn is 3/8" (.375"). That automatically results in a dial setting of 125. Length? A no brainer. The end is 0. The long travel counts turns as well as thou. Both of those setting are recorded on paper, along with the first settings.

Maybe you need an undercut, or a snap ring groove. The tool is measured for width, which is important to know (use a micrometer). With the tool properly installed in a holder or square block, the end of the part is picked up with the grooving tool. I use the very corner of the part, which will eventually receive an edge break (usually a small chamfer), so any traces of the pickup are removed. If the dimension is critical, once the corner is picked up, move the tool away a thou and feed it towards the center of the part. It shouldn't touch. If it does, you know you've picked up too deep. You can establish location within a half thou without much effort this way. Once the end is determined, do the math in regards to the tool width and the desired location of the finished groove. Record that location. Go there, then pick up the surface to be grooved. Observe the dial setting, then do the math, adding the amount needed to achieve the required diameter to the dial setting. Record that value.

If other operations are required, simply repeat the above. You can produce parts holding a thou without effort. It likely goes without saying that you must measure diameters, you do NOT trust the dial settings, as when a tool is indexed (or a tool holder is change on a quick change) there is no guarantee that it will register correctly, although they usually do. If your machine is of quality and is known to be reliable, can you see the value in working this way?

Move the compound during any of the above and the system fails. The exception is if the compound is marked, then placed exactly where it was, with backlash in the proper direction. That's necessary when chasing threads, as an example.


My coding when recording cuts is pretty simple. I write something like this:
Tool #1
Face part @ 0 on indicator.
Turn .500 dia. @ 0 on dial to .937 on indicator
Turn .375 dia. @ 125 on dial to 625 on indicator
Tool #2
Cut groove @ 419 on indicator to 266 on dial

Perhaps you can see the value of working like this. Once you have produced a good part, all succeeding parts will be, for all practical purposes, identical. Not only safe, but fast.

Keep your compound locked.

H

Edit:
I agree with you on round column mill/drills. My hat is off to the folks who operate them with success.
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rmac
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Re: Museum of Obsolete Drafting Technology

Post by rmac »

Wow! Thanks, Harold, for yet another post full of invaluable hints. This is all really good stuff and I can definitely see the value in working this way, especially if you're trying to crank out multiple copies of the same part.

I stumbled into my little procedure as a way to get something done in the absence of an indicator on the carriage. And I guess it never seemed that awful to me since I very rarely find myself making more than one or two of something.

Just to stir the pot a little bit, and hypothetically speaking, of course--what if you were routinely making multiple parts longer than the range of your long travel indicator? Would you consider an electronic device with the same function but with greater range, as long as we didn't call it a 1-axis DRO? :D

-- Russell Mac
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tornitore45
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Re: Museum of Obsolete Drafting Technology

Post by tornitore45 »

If the long piece had so many features distributed along the length, then my solution would be to insert a 1-2-3 block to gain 1" or 2" or 3".
Or one can machine all the feature in the right hand side, index a new "Zero" on the leftmost feature and start from there.
I have used alternatives like
Gauge blocks instead of the 1-2-3 blocks
An electronic caliper as a poor man DRO mounted between saddle and a carriage stop after drilling mounting holes on he tines. not much accuracy
But since I installed a Cheap DRO scale I get the accuracy I need. Usually diameters are more important than lengths.
Sometime a 6" scale gets the job done.
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Harold_V
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Re: Museum of Obsolete Drafting Technology

Post by Harold_V »

Mauro offered some excellent advice.
One of the things he mentioned tends to be reality. Large parts typically have large tolerances, so you can adapt methods that offer reliability within the range you'd work.

An example of that is the tiny antenna latch, a picture of which I posted, above. While there's a couple dimensions with open tolerance (± .010"), the block tolerance on that part is specified as being ± .003", with many dimensions held to ± .001", with a few .0002" tolerance dimensions where appropriate. Clearly, small parts are held to a much tighter tolerance, of necessity.

As for long travel indicators, my largest is just a 2", but I specialized in small work. It rarely got used. It would be safe to say that a 1" travel indicator was capable of handling 99% of the work I did, often with lengths exceeding 1".

It is safe to say that I am not against technology, and that I would, indeed, use a DRO, assuming it was necessary. It's just that I never had the need, plus they were not nearly as available in those days as they are now. I have been out of the shop on a commercial basis since 1983.

Notice Mauro making mention of a 6" scale? When I was young, I had exceptional eyesight. I could read a Starrett C305R reliably within ± .003", verified by QC at Sperry Utah (now L-3 Communications), where I worked. Needless to say, that ship sailed long ago, however. With magnification and good light, I fully expect I still can with my 81 year old eyes.

One bit of advice. Do not buy substandard measuring instruments. You can work only as closely as you can measure. That's why I never advise the use of calipers for critical dimensions (I use them regularly, just not for anything critical), be they vernier, dial or electronic. How can one hope to hold a tenth when a thou is difficult to resolve?

H
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James Powell
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Re: Museum of Obsolete Drafting Technology

Post by James Powell »

One thing that was suggested to me by a owner (victim?) of a round column mill was a laser pointer & the wall on the other side of the shop. As long as you use the present values, not the past ones, one can move the column and use the laser to get back to the same horizontal plane position. Be warned, though, that houses & tools both can move... Even if the beam is fairly crap (like a 1/8" dot), if you can go 20' or more, that gives you quite some accuracy (something like 2 tenths).

That came from Harry Boneham, when he was well into his 80's. Shows that a old dog most definitely can come up with new tricks...

Never rely on a caliper- always something better to measure than that if you need to be closer than 5 thou, that's what dad hammered into me. It doesn't mean you can't use them, but don't rely on them to be +/- .001, that's the land of other tools.
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Greg_Lewis
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Re: Museum of Obsolete Drafting Technology

Post by Greg_Lewis »

Harold_V wrote: Fri Mar 05, 2021 3:33 pm ...

One bit of advice. Do not buy substandard measuring instruments. You can work only as closely as you can measure. That's why I never advise the use of calipers for critical dimensions (I use them regularly, just not for anything critical), be they vernier, dial or electronic. How can one hope to hold a tenth when a thou is difficult to resolve?

H

Absolutely. I've found cheapo rules that don't match each other over the 6 inches. I've got a nice Mitutoyo digital caliper that I use almost daily. But I have found it can be off by ±.001. You have to be careful when you turn it on that the jaws are seated and there are no little bits hanging in there. And like Harold, my eyeballs can't detect ±.001 on my Starret vernier calipers. The tenths mics come out when needed.

By the way, I don't know if they still do this, but Starrett used to give tours of their plant on request. I got one many years ago and came out with my brain in a bucket. They have a little museum at the end of the tour where you can see the mechanical dividing machine they used to use for making rules, along with other interesting things. If you are ever near Athol, you should check it out.
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