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Member postings for Dave S

Here is a list of all the postings Dave S has made in our forums. Click on a thread name to jump to the thread.

Thread: Arduino Gear Hobber
28/11/2020 12:36:23

The facets come from the adjacent teeth on the cutter shaving the flanks / tops of adjacent teeth on the gear blank.

There is a bit of a thread here: Gear cutting with more pictures.

Yes the rolling will ultimately lead to the next tooth, but with a (say) 7 tooth cutter the roll can be completed from entry to exit of the “rack” at the target tooth. The adjacent teeth will also get shaved. Once rolled far enough then index to the next tooth and reset the Z to the start and do it again.

I planned to gear the roll to my TOS spindle somehow as that’s a fully manual machine, but I haven’t got round to it yet, and if I can get my baby cnc to work reliably the I was going to fix up a rotary axis and do it with cnc - but that’s a way off yet - the CNC nearly works, but so far it hasn’t really cut a complete part due to other distractions.


28/11/2020 10:33:57

Yes. It's much like Hobbing in that respect.

All these were cut with the same cutter:

The pinions are profile shifted to avoid tooth undercutting.

There is potential to make 'better' than hobbed gears this way too.

If you don't roll the blank at all you get roughly 5 facets. With a hob you get a number of facets that is equal to the number of teeth on the hob. With coordinated Z and A you can get equivalent to the step resolution number of facets.


27/11/2020 21:58:30

I was thinking of the cutter in the spindle, and rotating, more like this

Where the cutter traverses in x, and the blank rolls on the a (? Think that's x axis roll) axis synchronised with plunge in the z.

Spindle revs are then independent of the cutting of the tooth form.


Thread: Proxxon mf70 spindel/motor coupling?, any good idears?
27/11/2020 19:20:46

I just respindled mine with a complete high speed spindle.

There are a couple of photos on the last page of this thread:



Edited By Dave S on 27/11/2020 19:22:34

Thread: Arduino Gear Hobber
27/11/2020 19:10:55

Coming to this a bit late, but is the aim of the project to cut gears, or to make a hobber?

Bit of a left filed suggestion, but why not dispense with the threaded hob and make a rackform cutter.

With x,a and z axis you could cut whilst also 'rolling' the gear and simultaneously raising the z axis. Like a gear planer, but with a rotary cutter.

That is potentially doable by just plugging in a grbl to the 3 axis and figuring out the g code.


Thread: Traction Engine kits
27/11/2020 18:25:17

D R Mercer are also available from minsteam


Thread: Could a Car A/C pump be converted into a compressor
09/11/2020 14:01:27

Pretty sure American off roasters do something like this (air con pump as compressor).

IIRC they can then lower tyre pressures for certain sections of a trail with the ability to pump them back up as required.


Thread: Help with boring an interior cone
31/10/2020 17:36:55

For a 1 off at that size I would make a 60 degree point on a piece of silver steel, then file away the “top” to make a d bit. Add a little clearance on the none cutting bits. Harden and temper to straw.
To use you could hold in the tailstock and drill, or use like a boring bar in the toolpost.

for a larger cone then setting the cross slide over at 30 degrees (half angle) and feed in with that to bore - which is probably what is meant. The problem with that is the bottom of the bore - if required to be a point will need a boring tool which is very pointy.


Thread: bore measurement
31/10/2020 13:44:07

If they are a cheap set then dismantle them and deburr the bits. A small dab of moly grease on reassembly helps as well.
“this old tony” on YouTube has a video on improving cheap bore gages.

Then using them is a question of practice mostly.
I do it like this:

select a gage where the range is appropriate - if there is an overlap I usually use the larger size gage as the telescoping pieces are less sticking out that way.
with the gage in springy mode plonk into the bore and cant over so the handle touches the side of the bore.
wiggle the gage a little so it’s as extended as it can be in the bore at an angle.

Then tighten the end piece so the gage will move, but is stiff. You may need to figure this out out of the bore until you have done it a few times.

move the handle from the side of the bore through the centre to the other side. Try to sweep in a single movement and along the diameter. As you pass through the centre the gage should tighten and then loosen. This is the bore squashing in the telescopes and then as you pass the centre they become shorter than the diagonal.

fully tighten the lock.

Only sweep once, then carefully remove the gage from the bore without bumping it.

Now you can measure over the ends gently. Be aware that a micrometer is also a g clamp - if you monkey it you will change the measurement.

You should be able to repeat measurement to under a thou without much practice, but it does take some practice.

If you have some ball races then you can practice with those, and know your measurements are correct, as the bores are quite tightly specified.

hope that helps


Thread: CVA 1A series 3 travelling steady
27/10/2020 12:20:02

Does that mean you have a travelling steady for sale then?


26/10/2020 20:55:37

On mine there are a pair of hole on the chuck side and a pair on the tail stock side:

I have no travelling steady, only the fixed one.


Thread: Milling Speeds for end mills
23/10/2020 19:04:28
Posted by Nicholas Wheeler 1 on 23/10/2020 18:26:13:

I wonder how many people are actually using their 12mm cutters at 800rpm?

IIRC I run mine at 560, as it’s the closest speed on my mill...


Thread: What bench drill
23/10/2020 19:00:49

When I had a pillar drill it was a cheap Chinese import - I think this particular one came from B&Q, but they are all quite similar.
I cured the quill slip by pulling the drill to pieces and then, after drilling a hole in the front casting about halfway up, slitting the casting. After bolting on a couple of bits of 1” angle to the sides I made a bolt with a handle so I could “squeeze” the slit.

Made the quill adjustable from “locked” to rattling fit - and so vastly improved the drill.

Then I got a proper sized Mill, with a huge quill and haven’t used a pillar drill since...


Thread: Square block with round steel balls inside
17/10/2020 16:53:41

My father has such an Ivory Puzzle ball. I think it came from China, but my family has some connections with India, so maybe it’s from there.


Thread: piercing saw
17/10/2020 16:51:51

Whilst I have an adjustable frame I have never felt the need to adjust it.

Quality blades do make a difference. I’m currently using Super Pike from Cookson Gold for most things.

Their platinum blades hold up better than normal ones for stainless and shin steel.


Thread: Oouch hot fingers
01/10/2020 12:52:51

For the original question: I hold the blank in mole grips.

As for the dip in water or you’ll ruin it: Rubbish.

The “to hot to hold” temperature is around 50C IIRC ( Had to research this for a product at work) Way less than HSS annealing temps.

If you can get a HSS blank to annealing temps and hold it there on an offhand grinder then I’ll be amazed...

I used to grind slow and dip when I started, but then I gave it some thought.

Try abusing a piece of HSS - I have and it’s still as hard with blue temper colours on it. Most of my HSS tools have some tempering colour on them.

if you want a really sharp tool then grind it hard and fast, then hone it on a diamond bench stone. You’ll be making chips faster than the fussy man (it’s usually a man) who will still be faffing to not over heat his HSS.

One problem is that Starey et al were writing before HSS was commonly used in the home workshop. Sure if you grind a silver steel or carbon steel tool to blue you have drawn the temper and it won’t be as hard.
There is a lot of received wisdom in model engineering which is actually history and no longer accurate IMO


Thread: Making a pinion with a fly cutter
21/09/2020 19:15:51

If you are losing the edge on your cutter rapidly that suggests either the heat treat was not good or you are running it too hard and this drawing the temper, which leads to softening, which then rubs and heats and so on in an unfortunate feedback loop. Are you using cutting oil? How fast are you turning the tool and what feed rate?

My silver steel cutters were a bit hit and miss until I bought an enamelling kiln. I didn’t buy it for heat treating, but it goes hot enough, is pretty well controlled on the temperature and is convenient as it’s in the workshop anyway.
Since I started to use it for heat treat my hardened parts have been much better and more consistent. Not suggesting you need a heat treat oven, but judging temperature by eye on a scaled up piece in a flame is not a thing I ever mastered...

Coventry Grinders sell quality Silver steel at reasonable price.


Thread: Best way to remember Mill movements when turning hand wheels
17/09/2020 07:55:43

It becomes second nature after a period.

Im not sure right now (at work) which way turning does what, but I know if I’m stood in front of my machines I can “just” use them.

This became very obvious when I bought a cheap x-y table to make a cutter grinder.
The cheap table had RH threads on both axis. It only took a couple of oops moments for me to change the Y one to LH to match all proper mills...


Thread: Best way to keep nuts tight (ha ha)
03/09/2020 21:17:14

The quill stop on my TOS just used 2 "nuts", which you lock together using finger pressure.

They are about 1" diameter and knurled, not plain hex nuts.


Thread: Grinding my own external grooving cutter
30/08/2020 13:10:55

You can get away with a whole lot less side relief than shown.
As little as a quick stroke with a Diamond file will be fine.

The front face can be nearly vertical.
If you a smack on center height then a vertical face would still have “relief” by virtue of the cylindrical shape of the bar.


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