What tool do I need? I need to measure the radius of a tiny fillet on a 90° edge.

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What tool do I need? I need to measure the radius of a tiny fillet on a 90° edge.

This topic has 97 replies, 31 voices, and was last updated 6 January 2022 at 14:43 by John Smith 47.

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30 December 2021 at 13:08 #577505
John Smith 47
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@johnsmith47
Hello

I need a tool to enable me to measure the radius of a small convex fillet where two flat faces meet at 90 degrees.

The radius will be very small – somewhere between 0.1 and 0.5mm.

What tool do I need?

J
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30 December 2021 at 13:08 #20551
John Smith 47
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@johnsmith47
30 December 2021 at 13:45 #577516
Robert Butler
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@robertbutler92161
A very small radius gauge!

Robert Butler
30 December 2021 at 13:59 #577520
Nigel Graham 2
Participant
@nigelgraham2
"Fillet " normally means an internal (concave) radius, as the root of hot-rolled steel angle, and if its end is accessible it can be gauged with a twist-drill shank.

For a radius along an edge, you'd need a radius-gauge – but lacking a set, you could make one by drilling the right-size hole through a slip of sheet-metal, near one corner, and carefully cutting a 90º sector from it.
30 December 2021 at 14:10 #577522
David George 1
Participant
@davidgeorge1
Hi John where are you as it may be possible to borrow or use some ones gauges. I personally have sets of Starrett radius gauges in meteoric and imperial from when I did toolmaking at work before retirement.

David
30 December 2021 at 14:14 #577525
John Smith 47
Participant
@johnsmith47
> "Fillet " normally means an internal (concave) radius

1. This appears to be out-of-date.
As Wikipedia says: "Autodesk Inventor, AutoCAD, CATIA, FreeCAD, Solidworks and Vectorworks refer to both concave and convex rounded edges as fillets"

2. I have been very explicit that I only wish to measure convex radiuses.

3. I do not wish to make a tool, I wish to purchase a precision tool.

4. In particular I need something that is designed to work on 90° convex edges…

OK, I shall further research "radius gauges". However their sets seem to come in various flavours, many of which are measuring concave rather than convex radiuses.. or both!

Thanks

PS I am trying to avoid the dreaded Amazon. Who else would you recommend trying? (But must do a rapid delivery service!)

Edited By John Smith 47 on 30/12/2021 14:19:30
30 December 2021 at 14:30 #577530
peak4
Participant
@peak4
Most radius gauge sets seem to include blades with measure convex and concave.
For the larger radii, it tends to be on the same blade, but smaller ones use separate blades.
The smallest I've seen, start at 0.3mm, but that doesn't mean they are the smallest available.
I include this link to Amazon, though they are available via eBay from foreign shores.
https://www.amazon.co.uk/R0-3-1-5mm-Measure-Leaves-Metal-Radius/dp/B008MJTJWQ

I suspect higher quality tool merchants may also sell them, but at a price.
RS do a set, but it starts at 0.75mm and goes up in o.25mm steps, so too large and too coarse.
Mitutoyo only seem to start at 0.4mm

For smaller, maybe you would need access to a shadowgraph/Profile projector, but that certainly won't come cheap, even for second hand.

There are certainly vintage magnifying overhead projectors available, but I'm not sure they would suit your needs.
https://www.etsy.com/uk/listing/230507873/vintage-magnajector-enlarging-projector

I wonder if a conventional overhead projector may work.
i.e. use a measured disk of say 1cm next to your workpiece; project both adjacent images onto a wall simultaneously and scale the measurement from the known calibrated size.

Another possibility, I've not fully though through, would be a magnifying loupe, with an appropriate reticle.
I'll include this link, to give you some idea, even though it's from over the water.
I'm sure similar things will be available from UP suppliers
https://www.peakoptics.com/index.php?main_page=product_info&cPath=66&products_id=10

Just found a UK supplier, so maybe worth investigating, but reading increments of 0.1mm might be tricky
https://www.theloupestore.co.uk/Scale-Measuring-Magnifiers/

Bill

Edited By peak4 on 30/12/2021 14:51:57
30 December 2021 at 14:59 #577534
Chris Evans 6
Participant
@chrisevans6
When |I was working (toolmaker) this was a daily task. Made easy with a shadograph with resolutions from 10 to 1 up to 100 to 1. Where are you located ? There may be a local company willing to let you use their kit or measure for you for a tea fund donation.
30 December 2021 at 15:07 #577535
John Smith 47
Participant
@johnsmith47
Yes, unfortunately it seems hard to find anything smaller than 0.3mm.
e.g. Starrett only seem to go down ton 0.5mm.

To get clear, what I am planning on is to find a gauge that has two 90 degree edges that make a concave space, and that has known radius whether they meet.

My plan would be to start with smaller radius gauges, and then work my way up in sizes. ==> And at some point the square edges would no longer fit around the square faces of my part, and the gauge start to 'rattle'.

i.e. This would happen once the rounded 'fillet' on the my part starts to interfere with the radius in the corner of the gauge.

So in this way, by measuring at what size of gauge the 90 degree edges no longer fit snugly, I would not need to visually see exactly what is going on in the corner with any accuracy. Instead I would 'feel' the fit.

==> i.e. In effect used a bit like a feeler gauge!

(If I did need to see what is really going on, then I have various high-powered clip-on reading glasses and if necessary I could even use my dissection microscope!)

Edited By John Smith 47 on 30/12/2021 15:12:20
30 December 2021 at 15:11 #577536
peak4
Participant
@peak4
To follow on from my last post, amateur and professional mycologists have the need to measure fungi dimensions under the microscope, and are often working out the sizes of individual spores.
There is software available which allows a USB camera image to be measured when it's imported to a computer.

For spore sized, you're looking at a specialist 100x oil immersion lens, but for larger measurements, such as gills etc, a cheap microscope with USB-camera might just do the job.
They come up for sale via Lidl/Aldi and thus appear in eBay when the owners get bored, often made by Bresser.
Just make sure the USB camera is supported by your operating system.

I'll include this page out of general interest, but mainly because of a link to Mycocam4 contained within.
https://www.first-nature.com/fungi/~microscopy.php

Bill

Edited By peak4 on 30/12/2021 15:15:40
30 December 2021 at 15:14 #577537
Peter H
Participant
@peterh38181
This tool looks like it will measure the radius from 0-10mm in 0.1mm increments across right angles.

Radius gauge 0 – 10 mm, 0,1 mm (0597305)

**LINK**
30 December 2021 at 15:17 #577538
John Smith 47
Participant
@johnsmith47
Nice thinking Bill… however it seems to me that measuring along length of an edge that might be say 2 or 3 cm long, and have a variable (hand made) radius, would be best 'felt' (if technically possible) rather than inspected visually.
30 December 2021 at 15:18 #577539
peak4
Participant
@peak4
Posted by Peter H on 30/12/2021 15:14:02:

This tool looks like it will measure the radius from 0-10mm in 0.1mm increments across right angles.

Radius gauge 0 – 10 mm, 0,1 mm (0597305)

**LINK**

I think your link maybe broken, Is it this?
https://shop.kinexmeasuring.com/en/radius-gauge-0-10-mm-0-1-mm-0597305-p8900618c30c237/

Bill
30 December 2021 at 15:18 #577540
John Smith 47
Participant
@johnsmith47
Posted by Peter H on 30/12/2021 15:14:02:

This tool looks like it will measure the radius from 0-10mm in 0.1mm increments across right angles.

Radius gauge 0 – 10 mm, 0,1 mm (0597305)

**LINK**

Peter I can't get that link to work.
30 December 2021 at 15:22 #577544
Peter H
Participant
@peterh38181
Bill has posted the correct link.
30 December 2021 at 15:29 #577545
John Smith 47
Participant
@johnsmith47
Posted by peak4 on 30/12/2021 15:18:06:

Posted by Peter H on 30/12/2021 15:14:02:

This tool looks like it will measure the radius from 0-10mm in 0.1mm increments across right angles.

Radius gauge 0 – 10 mm, 0,1 mm (0597305)

**LINK**

I think your link maybe broken, Is it this?
https://shop.kinexmeasuring.com/en/radius-gauge-0-10-mm-0-1-mm-0597305-p8900618c30c237/

Bill

Looks cunning, but do any of you know how to use it? I can't work it out!

PS Also rather expensive at c. 211 Euros!

Edited By John Smith 47 on 30/12/2021 15:31:51
30 December 2021 at 15:48 #577549
SillyOldDuffer
Moderator
@sillyoldduffer
Posted by John Smith 47 on 30/12/2021 13:08:08:

I need a tool to enable me to measure the radius of a small convex fillet where two flat faces meet at 90 degrees.

The radius will be very small – somewhere between 0.1 and 0.5mm.

Can you clarify please John?

Do you want to:
1. measure arbitrary radii to know what they all are to some level of accuracy, or
2. to indicate that one radius is more-or-less correct?
The first finds out what a radius is, the second confirms a radius is within acceptable limits – perhaps a GO/NO GO Gauge.

Checking radii in the range 0.1 to 0.3mm is a tough requirement, especially if it has to be done accurately! You can look for light leaking around the corner of a thin plate placed into a gauge, but much harder to detect if a radius is correct along a lengthy edge.

Easy:

Gets harder with increasing length:

Radius gauges are easy enough to buy in larger sizes, but not many tiny ones about. Could be you need a loupe, shadowgraph or microscope.

Dave
30 December 2021 at 16:03 #577552
peak4
Participant
@peak4
Posted by John Smith 47 on 30/12/2021 15:29:11:

Looks cunning, but do any of you know how to use it? I can't work it out!

Edited By John Smith 47 on 30/12/2021 15:31:51

Here you go, shown in use on P53 of their catalogue
https://metrology.mahr.com/fileadmin/catalogs/OnlineCatalogs/Helios-Preisser/index.php?catalog=HP-Metrology-EN&lang=en

Essentially, it requires knowing that your radius is actually a section of a circle.
It relies on three point contact of the two sizes and the circle radius>
The sliding vernier scale gives the radius measurement.
As you can see a 45° flat would also give a reading, but an erroneous one; compare it with the chamfer gauge at the top of the same page.

Bill

Edited By peak4 on 30/12/2021 16:05:15
30 December 2021 at 16:09 #577555
Robert Butler
Participant
@robertbutler92161
The Helios Preisser H0597305 radius gauge works by offering the test piece to the gauge with the two relevant edges containing the radius against the gauge and the calibrated angular slide advanced until it touches the radius. A reading is then taken from the Vernier scale and compared to tables supplied? or calculated? I know not which. It all depends on the accuracy of the radius.

Robert Butler

Edited By Robert Butler on 30/12/2021 16:11:54
30 December 2021 at 17:25 #577576
Tony Pratt 1
Participant
@tonypratt1
Some sort of shadowgraph would be my tool of choice. Watching this thread with interest to see where it leads. Are we to assume this radius will be machined rather than filed?

Tony

Edited By Tony Pratt 1 on 30/12/2021 17:26:15
30 December 2021 at 18:31 #577595
Tim Stevens
Participant
@timstevens64731
the link sent by Peter H was caught by an oddity in the software used by ME* – it came out like this:

radius%20gauge%200%20-%2010%20mm%2C%200%2C1%20mm%20%280597305%29

Some typesetting and word processing programs use an extra 'hidden' symbol or two to tell the computer what it intended. Here the extra symbols include %, followed by a number, calling up a letter or symbol not in the 'standard alphabet' used in the days of 8-bit and 16-bit computers. I'm not sure what you or I can do about it, except wait for ME to update – or, * perhaps the fault lies within the computer used by Peter H. I wonder …

Cheers, Tim

Edited By Tim Stevens on 30/12/2021 18:33:09
30 December 2021 at 18:52 #577602
Brian G
Participant
@briang
To measure the radius in the same way as the gauge Bill described you could use a square without a notch in the corner and try putting different thicknesses of wire in the corner of the square to find the largest that doesn't make the square rock against the test piece, then draw it up in a large scale (or in CAD) to determine the radius. The catch is that for radii between 0.1mm and 0.5mm you would need to source a selection of wires between 0.0344mm and 0.176mm.

Sorry about the rotten drawing, I have only just switched to 4M CAD and haven't worked out how to add diameter to the dimensioning toolbar (or how to dimension manually)

Brian G
30 December 2021 at 19:01 #577605
Robert Butler
Participant
@robertbutler92161
As the OP has advised the component has a variable (hand made) radius, what exactly is being measured? A simple set of radius gauges viewed against a light source will produce an indication of the radius and allow acceptance or rejection of the component. Anything else appears to be a waste of time and money.

I hope we will all be able to retire on our share of the Royalties from this device when it comes to market.

Robert Butler
30 December 2021 at 19:33 #577612
Tony Pratt 1
Participant
@tonypratt1
Just stone the edge with a fine oilstone, that is bound to be within 'limits'

Tony
30 December 2021 at 19:41 #577615
martin haysom
Participant
@martinhaysom48469
am i missing something ? if i read this right this is a handmade radius , file ? than i would check it by eye
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