Member postings for SillyOldDuffer

You may get vibration problems if the stand is on wheels, especially if the wheels have hard tyres or are on castors. Big fat pneumatic tyres might be OK.

I'd try it and see what happens. If the wheels cause vibration, I'd put removable blocks and wedges under the stand to take the weight off the wobbly wheels and provide a firmer platform. Alternatively you might be able to find a suitable "Appliance Trolley" to provide temporary wheels.

Dave

Wow! My inferiority complex has just exploded.

Making it worse, I misread a sentence in the antepenultimate paragraph as 'If I do embark on yet another unfinished project, this will require 28 years...'

Which led me to a genuine query. When looking at plans and project descriptions I find it hard to estimate how much time they will take to build. Any ideas about how long your Jovilabe might take to construct?

Dave

Neil's no youngster if he remembers Prometheus delivering stuff! And that 'de-livering' joke must have been ancient before Pandora got her Box.

Interesting formula. It calls for the Output Power of the motor to be expressed in Cheval Vapeur, which is the first time I've come across that unit since that little Citroen car. (Ah, there's one parked down Memory Lane.)

I expect British Horse Power can be used in the formula without upsetting the result.

Dave

Edited By SillyOldDuffer on 29/09/2016 13:27:33

Me neither, though I wouldn't mind watching someone else trying it!

Anyway, all you need to know about the weight bearing capacity of ice here.

Pure theory where I live of course. In the south of England I have to stay home after a ¼" fall of snow.

Dave

QED? Certainly not. I'm afraid you'll have to lend me your Mitutoyo and Optical Flats so that I can re-run the tests under the same experimental conditions in my secret underground laboratory.

Obviously you can trust me to return your desirable goodies. Eventually ...

Dave

Not at all. The correct caption for this photo is "Don't worry Mr Bond. Apparently there's a fix for this in Service Pack 3."

Interesting pictures of a nice job in progress Damian. Thanks for posting.

I wonder if the quill being made soft is a deliberate feature? An over-stressed quill would bend before anything expensive broke, and then the soft quill would be fairly easy to straighten out again.

I've seen your bricks in Somerset so they're probably not a local brand. Although Yorkshire Tea is popular here I can't imagine there's much demand for Yorkshire Bricks! Possibly the slots provide a key for plastering. Anyone know what they are?

Cheers,

Dave

I agree. Seems to me there are two bad mistakes you can make when spending money:

• Wasting it by buying too cheap
• Wasting it by buying on reputation only or because it's "reassuringly expensive".

Wigglers are a cracking example of something I suspect to be overpriced. Unless I'm doing something wrong a dress-makers pin with a blob of Plasticine out-performs my shop-bought metal example.

How do we know that the £30 calliper isn't just a £5 calliper with good PR? We don't. Unless someone already knows, the only way to find out is to test a lot of them.

Dave

I wonder if a Mitutoyo in practice would comfortably be within spec across the range? It's possible that their ±0.02mm claim is conservative and actual performance is better.

I'm too mean to buy a Mitutoyo out of curiosity. Are there any Mitutoyo owners out there prepared to test their Caliper as I have and share the results?

Thus far I'm concluding that cheap digital calipers are better value for money than dear ones in a home workshop.

But I don't think this means that expensive calipers are a complete waste of money. My £50 example is smooth and comfortable to use. It feels good. I suspect that it, and other quality types, are likely to have longer working lives (David Cambridge apart), and be less likely to inconveniently conk out in a busy industrial setting.

Proving that expensive calipers last longer than cheap ones is too difficult for me.

Looking forward to seeing your ME article.

Dave

I spent time learning just how much thumb-wheel pressure to apply to each Digital Caliper. A bit of practice and careful positioning of the jaws makes quite a difference. Three Calipers work best with the same firm pressure, the fourth (£10 model) works best with a gentle touch.

Unlike the first round of measurements, the Calipers all spent the night in the same room to make sure they were soaked to the same temperature, 18℃.

I took extra care to clean the Calipers generally and also by sliding clean paper between the jaws. Even though the Calipers were cleaned yesterday I was able to remove more dirt. The precision parallel and worktop were cleaned and clean paper was laid on top. I wore new latex gloves and a clean apron.

I took care not to touch the parallel or Calipers more than necessary. As it took 20 seconds to enter the result of each measurement the Calipers had some time to cool off after handling. This is based on Neil's hint that the electronics are temperature sensitive.

I took twelve measurements each of the 24mm dimension and graphed the variation from assumed truth, ie ±24.00mm

• The red line is the most expensive caliper. It is by far the most consistent but it reads 0.01mm high. Mean 24.011.
• The blue line is the cheapest caliper. It reads closest to 24mm but has a tendency to read 0.01mm low. Mean 23.997.
• The yellow line is the £30 caliper. It's not quite as consistent as the blue line and reads slightly lower too. Mean 23.987.
• The green line is the worst performer. It's the £10 DIY store caliper. Mean 24.015 but notice that wavy line which is not good.

The surprise is just how good the £4.99 caliper bought from Lidl is.

I actually took four sets of measurement for each caliper:

1. 24mm measured using half the jaw depth
2. 6mm measured using half the jaw depth
3. 24mm measured with the jaw tips
4. 6mm measured with the jaw tips

Measuring with jaw tips only looks to be less accurate and it also seems as if measurements taken at 6mm are more accurate than those taken 24mm. I haven't done the graphs yet but will post them later if they're interesting enough. It would be nice to see the expensive caliper measuring equally well across the range whilst the cheaper ones don't.

+1 for everyone using micrometers for accurate work!

Cheers,

Dave

Edited By SillyOldDuffer on 27/09/2016 16:19:53

Edited By SillyOldDuffer on 27/09/2016 16:21:05

Good point Richard.

I've just finished collecting data after working with each callper to learn how hard I need to press the thumb-wheel to get consistent results.

Three of the calipers work best with firm pressure, certainly enough to deform a plastic tube. The fourth (the £9.99 model) works best with a much lighter touch and would be much more useful for your needs than the others.

Neil's comment about adjusting gibs could be relevant to the amount of thumb-wheel pressure needed.  More testing to do!

Dave

Edited By SillyOldDuffer on 27/09/2016 14:01:20

It's a fair cop Michael. The sample size is far too small to be more than 'interesting'.

When posting results I try to be open and honest about the data and how it was collected. It's amazing how easy it is to unconsciously mislead oneself, which is why I'm a great believer in peer review even if it's, ahem, robust.

Cheers,

Dave

I didn't even know they have gib screws that can be adjusted!

Ignorance is bliss.

Dave

I have one of those too. It's kept upstairs for rough work when I'm playing electronics.

The main trouble with this one is reading the vernier. The picture demonstrates parallax error very well - the camera must have been off centre. Actually, from directly overhead the reading is closest to 24.05, but it's hard to tell the difference between this and 24.1 or even 24.15. A magnifying glass helps.

Much better than a 6" rule though.

Dave

Yup, I've added the prices.

Average of Five Readings (mm)

'100mm' '6mm' '24mm' Zero at end

Caliper A 99.916 6.012 24.042 -0.01 £9.99
Caliper B 99.922 6.038 24.028 0.02 £4.99
Caliper C 99.952 6.028 24.070 0.00 £50.00
Caliper D 99.880 5.976 23.968 -0.01 £30.00

There's a give away in the numbers about which might be the expensive one. Being an 'absolute' type, it held zero correctly, while the others wandered. That's a useful feature.

As to which was the best deal, on those numbers it's the cheapest.  This is assuming my data is accurate and I'm not just measuring poor technique or dirt etc.

Dave

Edited By SillyOldDuffer on 27/09/2016 11:25:00

I look forward to getting the next ME so I can see what Neil's been up to. The more data the better.

By the way, the cheapest of my sample is also the oldest and it has been well used. Not only that but I dropped it on a concrete floor and then stood on it, cracking the display. It still works as well as the others.

Tomorrow I'm going to pick up on Ajohnw's comment 'Looks like you have a pressure problem to me.' It may be that the biggest cause of error is me.

I'm going to see if I can teach myself to repeatedly get 24.00 readings from the 24mm dimension by experimenting with how hard I push the thumb-wheel.

I suppose it won't be a surprise if I find that careful practice with a tool is necessary to get the best results out of it!

Cheers,

Dave

Curious problem Sam. Sounds like something is loose. Or possibly your 'mild steel' is something much harder.

I expect the machinist will work it out quickly. I guess he'll run some tests to isolate the cause. Does it do the same with something softer like aluminium, or even wood? Does it vibrate in both High and Low gear? Does it drill OK, etc etc.

Please report what happens - I'd love to know how he goes about doing a diagnosis and what the problem turns out to be.

Lots of sympathy though - it's really annoying when you want to get on and something awkward like this gets in the way.

Dave

I thought this would be easy. Melt a tablespoon's worth of glass and pour it from a few feet high into a bucket of cold water. Then carefully retrieve the Drops from the bottom of the bucket and use them to make friends and influence people.

Wrong again. A 'Camping Gaz' blow-lamp doesn't have the heat needed to melt broken bits of a glass Dolmio sauce jar, not even in a firebrick enclosure. It took a lot of welly just to soften the glass.

I have a bigger Seivert and was ready for another go when it ran out of gas. As the spare cartridges are AWOL that was the end of that.

Health and Safety note: broken glass is razor sharp and it may crack and spit when the flame first hits it. Gloves, googles and apron recommended.

Dave

I didn't mention it before but one of the four eats batteries. It's the £30 model.

Otherwise I've had good luck with digital and batteries. The 3 scales on my mill are working fine after about two years and my two cheapest digital calipers are still good after a year. The newest caliper is fine after 3 months - perhaps too early to leap to a conclusion - but the £30 model had a new battery at the same time.

In another experiment I'd found the quality of LR44, SR44 and CR2032 cells to be very variable and had put 'greedy caliper' syndrome down to people being unlucky installing low capacity cheap batteries, old stock, or fakes.

But this Digital Caliper got a new cell from the same pack as the £50 model and must have bit the dust since I last used it a few weeks ago. Therefore 'Greedy caliper' syndrome must be a real thing - shame I don't know of any way of finding out if there's going to be a battery problem other than buying one and trying it.

Dave