Member postings for Andy_G

Wow, I didn't realise that 2014 was so strong - especially in T651 condition. Question answered.

Is there any problem using 6082 / HE30 for conrods?

(In T6 condition)

Edited By Andy_G on 30/03/2022 11:00:01

Absolutely! A general solution is much more complicated.than my description

FWIW I've sent Dave the spreadsheet I used. It remains to be seen whether anyone other than the author can make head or tail of it!

Andy

With a circular arc and a circular tool, the XY coordinates of the tool centre point wrt the arc centre point are honestly just the XY coordinates of the arc multiplied or divided* by [arc radius] / ([Tool radius] + [arc radius])

The proof / derivation is via similar triangles. These coordinates (relative to the arc centre) then need to be translated into X,Y (or X,Z) tool movements relative to a datum position.

*Depending on whether the cut surface is concave or convex

All the following were cut this way with 0.2mm step in X and a 6mm diameter button tool

8mm external convex radius:

20mm internal convex radius

External concave radius

8mm internal concave radius

17.85 mm internal convex radius

etc...

Edited By Andy_G on 21/03/2022 17:34:14

You can work out the X-Y coordinates of the surface from the formula for a circle (X^2 + Y^2 = R^2) where the origin is the centre of the arc.

It's easiest to work with a round tool (e.g. a pattern following tool or a carbide button).

Translating the surface coordinates of a concave surface to the centre point of a tool of radius r then boils down to scaling the X & Y coordinates by R/(R+r).

You can then choose a known reference position and offset the coordinates wrt this to get your cross slide and feed readings. The devil is in the detail in getting the sign conventions correct!

I used this method to turn some accurate curves in my model jet engine - there's a fairly detailed description part way down this page

https://misterg.org.uk/turbine-html-16/

Link

I find it easiest to set the top slide parallel to the bed and use this for the Z feed, rather than the carriage. I set a stop on the lathe bed where the tool just touches the face of the part and zero the top slide dial. Cross slide dial is zeroed by touching off on the OD. I can then wind the carriage back, increment the cross slide and set the desired Z travel on the top slide without cutting any metal whilst making the adjustment.

I have also sent you a PM

Andy

Edited By Andy_G on 21/03/2022 13:57:13

I would highly recommend using a decent cutting oil instead. It doesn't need much, so shouldn't make additional mess. There are many, many available, but I tend to use CT-90 as it is cheaper than most.

I would also lightly centre punch the hole location. If you're drilling polished stainless tube, the drill point will want to skate off it until it gets going which could result in the drill bit chewing away at the side of your jig.

Otherwise, as above: Decent HSS drill bit; slow speed & apply as much pressure as you need to keep it cutting - it doesn't need huge pressure, but you need enough pressure to get it cutting right from the start. Be bold and keep going! (Bear in mind that you will need to ease off the pressure as the drill breaks through). FWIW, I would go straight for 6mm.

Maybe not for headbangers: Dire Straits "Industrial Disease"

[Verse 1]
Now, warning lights are flashing down at Quality Control
Somebody threw a spanner, and they threw him in the hole
There's rumors in the loading bay and anger in the town
Somebody blew the whistle and the walls came down
There's a meeting in the boardroom
They're trying to trace the smell
There's a leaking in the washroom, there's a sneak in personnel
Somewhere in the corridors, someone was heard to sneeze
Goodness me, could this be industrial disease?

[Verse 2]
The caretaker was crucified for sleeping at his post
They're refusing to be pacified, it's him they blame the most
The watchdog's got rabies, the foreman's got the fleas
Everyone's concerned about industrial disease
There's panic on the switchboard, tongues in knots
Some come out in sympathy, some come out in spots
Some blame the management, some the employees
And everybody knows it's the industrial disease

[Verse 3]
Yeah, now the work force is disgusted, downs tools, walks
Innocence is injured, experience just talks
Everyone seeks damages and everyone agrees
That these are "classic symptoms of a monetary squeeze"
On ITV and BBC they talk about the curse
Philosophy is useless, theology is worse
History boils over, there's an economics freeze
Sociologists invent words that mean "industrial disease"

[Verse 4]
Doctor Parkinson declared "I'm not surprised to see you here
You've got smoker's cough from smoking
Brewer's droop from drinking beer
I don't know how you came to get the Betty Davis' knees
But, worst of all young man you've got industrial disease"
He wrote me a prescription he said "You are depressed
I'm glad you came to see me to get this off your chest
Come back and see me later, next patient please
Send in another victim of industrial disease, ha-ha
Ha, splendid!"

[Verse 5]
And I go down to Speaker's Corner I'm-a thunderstruck
They got free speech, tourists, police in trucks
Two men say they're Jesus, one of them must be wrong
There's a protest singer, he's singing a protest song, he says
"They want to have a war to keep their factories
They want to have a war to keep us on our knees
They want to have a war to stop us buying Japanese
They want to have a war to stop Industrial Disease

[Verse 6]
They're pointing out the enemy to keep you deaf and blind
They want to sap your energy, incarcerate your mind
Give you Rule Brittania, gassy beer, page three
Two weeks in España and Sunday striptease"
Meanwhile the first Jesus says "I'd cure it soon
Abolish Monday mornings and Friday afternoons"
The other one's out on hunger strike, he's dying by degrees
How come Jesus gets industrial disease?

Oh no... I'm sick!

I don't think you're being pedantic, and I would ask Axminster to replace the holder. The ER system is very versatile, and worth persevering with to get a set-up you have confidence in.

This sort of thing does happen, as I found with an ER11 collet holder. (Both the original and the replacement were direct from China, though, not via one of the UK agents.)

Did you check / compare the heights of each piston at TDC?

I don't know the detail of how its put together, but it looks / sounds very much like the pulley/sprocket/whatever is slipping on the motor shaft.

(Looks like part #46 on page 16 of the manual - try tightening #45)

Absolutely!

Congratulations and very well done!

Adiabatic calculator:

**LINK**

The theoretical pressure for adiabatic volume reduction of 16.7:1 is in the region of 800 PSI.

Not sure how standard it is, but could be EN1A (or 304 stainless):

https://www.parkersteel.co.uk/Pages/Engineering-Steel-Colour-Chart

I don't think there'd be a problem cutting a long strip (one would need to produce the artwork somehow though). It might be a bit tricky to get the scaling right to exactly match the table circumference. Maybe not so much of an issue if you were only proposing to etch the numerals, but (I think) quite challenging for the graduations.

The guy in the video below uses a vinyl stencil (7:28 if it doesn't go there on its own). I see that there are plenty of places offering a cutting service, but haven't done it myself, so can't make any personal recommendations.

Actually, the stuff I have could well be engraving brass - if so, it machines very differently to "normal" brass.

What grade of brass is it?

I acquired a sheet of what I thought was brass (it looked like it), but I believe it’s actually aluminium bronze. It produced similar curly chips.

Edited By Andy_G on 20/01/2022 10:41:05

On the topic of epoxy adhesives:

I recently found UHU Endfest 300 which has worked very well for me so far (on aluminium). It has a reasonable datasheet at:

https://media2.supermagnete.de/docs/uhu_plus_endfest_300_eng.pdf Link

Several things are of interest to me:

1) It retains some strength to 140°C

2) It allows the mixing ratio to be varied to optimise its properties (between brittle and flexible).

3) Although a relatively slow curing adhesive, the datasheet gives information on heat curing which dramatically reduces the full cure time (to as little as 5 minutes if the work can withstand 180°C).

4) It is fairly cheap! - Especially compared to other "high temperature" epoxies (whose performance appears similar).

If the OP is prepared / able to heat the parts, it may be an option.

For others, it may be a useful 'high temperature' epoxy (I haven't looked at the Zap products - there may be something similar in their range).

That looks *much* more workmanlike. (I may steal the idea!)

I have added a plunger mechanism to the headstock that engages in indexing holes drilled the chuck backplate:

24 holes works OK for the common 2,3,4,6,8, etc... patterns. For anything else, I get all agricultural:

(Model jet engine that needed 15, 17 & 19 positions!)

Edited By Andy_G on 12/01/2022 11:10:42