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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: Being nice to a vise
08/10/2021 15:38:25

Never worried about it with my metalworking vices.

A none issue in a workmate - there are 2 screws just balance the loading.

Dave

Thread: cutting spur gears on a mill
07/10/2021 19:23:43

Over on homeshopmachinist there is a thread where a chaps leadscrew appears to be the wrong pitch.

In the middle of that is :Plastic gear making

Spur gears free moulded install a lathe…

[Nomex Donned]
Dave

Edited By Dave S on 07/10/2021 19:25:29

Thread: Brazing/high temp silver soldering with 999 Ag wire?
07/10/2021 13:56:21

Copper to copper is certainly possible with fine silver - that's how I attach things I'm going to enamel together.

I use plain borax for the flux.

I suspect brass will be 'tricky' as IIRC the melting point of silver is above the melting point of brass.

Can't say about the price comparison for sure, but a reel of fine sliver wire I bought was about £30 and I expect it to last me for a good few years yet.

Dave

Thread: gr 8.8 ht bolt steel which carbide tip
06/10/2021 18:52:08

For what it’s worth I don’t think these are made of chinesium or cheese, but the modified quite easily with a quality HSS endmill

Tools1.jpeg

Tools2.jpeg

Dave

06/10/2021 17:38:52

Don’t forget that tool holders are just metal, and can be modified.

My 2 mainly used ones are both larger than ideal for my tool holders, so I chucked them in the mill and removed a chunk from the underside.

Dave

Thread: Shim stock
03/10/2021 16:25:14

I have used razor blades for small shim stock - the double edge type, not the ones moulded into plastic.

Dave

Thread: I need to cut chamfers into x64 pieces of mild steel - any advice?
29/09/2021 15:59:18

“Coolant” with carbide is mostly to flush the chips away.
The need to cool the tool, especially with the limited power of your Proxxon is minimal.

Intermittent coolant on carbide tends to thermally shock the tool, and is more likely to lead to poor tool life.
Carbide coatings have been developed to increase tool life without coolant.

I mostly use coolant when I want to be able to measure a part soon after cutting - it helps to keep the part at near to ambient temp - so my measurements are more likely to be accurate…

I would trust MSC and Ketan for info more that Axminister.

Dave

28/09/2021 18:44:10

Coated carbide on mild steel and a machine that isn’t setup for full flood I would try no coolant at all.

Also go look at MSC direct for *much* better choice and prices.

Dave

Thread: PM Research#1 Cylinder Can it be saved ?
26/09/2021 13:05:45

I would bore slightly oversized and sleeve the cylinder.

If you haven’t made the valve yet you can make it oversized to cover your ports.
The limit on flow will be the (presumably to do) drilled holes from the ports to the ends of the cylinder, so the imbalance in slot sizes shouldn’t affect the running much.

Dave

Thread: cutting spur gears on a mill
24/09/2021 17:30:05

Pretty sure you can calculate PCD from Mod and tooth count, and can do Mod from tooth count and outer diameter.

From that you can layout the centre distances of a pair of gears.

PCD for a single gear is not a very useful number anyway

Dave

Thread: Buying advice sought re Milling Machines: e.g. Proxxon: FF230 vs. BFW40/E vs. MF70
24/09/2021 12:38:15

John - What is so bad about your MF-70?

Dave

Thread: Cylinder Head Combustion Chamber Template
24/09/2021 12:35:09

If you have some gash vales you could use them?

Clean the faces, place in the valve guides, add glue to the faces.

Position your template and then turn the head over so the valves sit on the template whilst the glue sets

Dave

Thread: cutting spur gears on a mill
22/09/2021 12:18:27

I’ve gone involute for the clock because I wanted to explore the use of the “rotary Sunderland rack method” as a way to make gears.
That plus many naysayers telling me that a clock couldn’t possibly work with involute gearing as it’s not possible to gear up with involutes… I’m not sure how the gear knows

Dave

22/09/2021 11:00:41

Yes it’s a clock, and no I’m not sure.

These are the first gears I’ve ever cut, and I suspect that I should have profile shifted the wheels the opposite way to thin the teeth.

Still it’s all learning, and if they are depthed ok then they mesh ok - even if it’s not quite correct…

Will do better next time

Dave

22/09/2021 08:08:50

Not really. Design pressure angle stays the same - hence the gear can be cut wit the same cutter, and mesh with gears cut with that same cutter. I believe the actual pressure angle where the teeth meet changes, as a result of being at a different point in the curve.

Read here: Gear Profile Shift | KHK Gears for an explanation of profile shifting. It is fairly common in industry to match the tooth form to the required result.

Edit to add: Introduction to Gears | KHK Gears is a fairly good primer on all things gear related.

Dave

Edited By Dave S on 22/09/2021 08:10:33

22/09/2021 07:20:18

The undercut is an unfortunate artefact of the process of making an involute gear. It limits the strength of the root of the tooth, which can be a bit of an issue. Profile shifting just uses a different part of the involute curve, and so can avoid the undercut. It’s trivial to do in practice - using the same rack form cutter you just move it out a bit (simplification but essentially the process)

I have made some 12 tooth pinions without undercutting by doing just that and they roll against the 144,96 and 90 tooth gears made with the exact same cutter perfectly.

Dave

Thread: A straight line engine
21/09/2021 17:50:07

The complexity isn’t actually the most off putting thing.
It’s the total perfection required in the rigidity and guiding of both the tool and the workpiece.

Rose engines benefit somewhat from a mechanical reduction in the pattern to the work - especially at watch sizes.

That isn’t true for a straight line engine.
It’s a bit like how a cheap light surface grinder will make nice looking ground parts, but it takes a rigid heavy one to hit tiny tolerances and be flat to bugger all. The cut is smaller, but the rigidity and perfection to guide it is much higher.

Still one might turn up, or I might revise my build plans and make one.
still hoping for the simpler solution…

Dave

21/09/2021 17:28:38

I posted a want to buy for a straight line machine recently. I have thought about building one, but having had discussions with Chris Manning about what it takes to have a successful machine I am reconsidering, hence looking for one.

Dave

Thread: cutting spur gears on a mill
20/09/2021 15:30:51

What you are describing is using the cutter “vertically” I think. With a standard end mill.

what I was envisaging was the cutter “horizontally” more like a slitting saw.

so as the blank rolls the gearotic code rolls A and moves Y. I was thinking roll A and move Z

This would mean the “stick out” issue of a long thin cutter is now a diameter issue of a thin slitting saw like cutter.

I have experience with Gearotic, and knew John quite well. Clumsy Bstard lived 5 mins up the road.

Dave

20/09/2021 14:39:54

You can always profile shift if you want to avoid undercutting on low number tooth pinions.
I suspect with appropriate CNC magic and a pointed V cutter you could actually cut a number of mod sizes and any tooth count with just one cutter - you would do offset passes without the rotation to clear the bottom of the tooth gap appropriately. Needs a bit more thought, but imagine cutting an acme thread but using a pointed tool and moving the top slide parallel with the cut to clear the root.

Dave

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