What are you machining?

Brad93 · May 12, 2020

pressbrake1 said:
Lump of 200mm chrome round in the dsg being made into something else round..
Machine must be 65 years old and still produces finish close to ground View attachment 229650 View attachment 229651 View attachment 229652

Great finish. HSS?

slim_boy_fat · May 12, 2020

pressbrake1 said:
Machine must be 65 years old and still produces finish close to ground

Won't that be more to do with the cutting tools than the age of the machine? :dontknow:

pressbrake1 · May 12, 2020

slim_boy_fat said:
Won't that be more to do with the cutting tools than the age of the machine?

No

pressbrake1 · May 12, 2020

Brad93 said:
Great finish. HSS?

Knux , hss wouldn’t survive chrome.
Big mass and rigidity exceptional design and overall quality equals finish

grim_d · May 12, 2020

Pulley finished.

Ground up a tool for cutting @qwakers thread when the material arrives, discovered it is a M16 X 4mm trapezoidal, just aswell I ordered 16mm stock!!

Seadog · May 12, 2020

Does that have top rake? It's bad practice, surely, because it will alter the geometry of the thread. Or have you been really clever and compensated for the error?

grim_d · May 13, 2020

Yeah it does because I ground it from something that already did. I've certainly not been clever...

I can remove it easy enough, having trouble visualising why it's no good but it's late and I'm stupid.

Edit: it just clicked. Idiot. I shall make another.

minimutly · May 13, 2020

Please explain for idiots like me?

Hood · May 13, 2020

Ok simple quick drawing, just cut side relief angle on a block.

You get this if looking down from the top.

Now cut some top rake.

And now looking from the top.

Hood · May 13, 2020

Here it is with a threading style tool
Side clearance only.

From top

Add some top rake

View from the top, dotted lines showing original angle.

fizzy · May 13, 2020

pressbrake1 said:
Knux , hss wouldn’t survive chrome.
Big mass and rigidity exceptional design and overall quality equals finish

They definitely help but plenty of people get very nice finishes on tiny little lathes.
Perhaps not on chrome though?

Agroshield · May 13, 2020

Hood said:
View from the top, dotted lines showing original angle.

So can you do it the other way with the 3D model? Start with say 5 degrees top rake and a bit of side rake and determine what angle you would need to grind at to achieve a true 60 degrees plan view.

pressbrake1 · May 13, 2020

fizzy said:
They definitely help but plenty of people get very nice finishes on tiny little lathes.
Perhaps not on chrome though?

Naturally but when you’ve got half a ton of knarly old poop swinging and a damaged used insert and get good finish it takes a good lathe.
I should re state it as ‘ dsg that’s done 65 years of work still gets exceptional finish no matter the material or condition of the tool’

Hood · May 13, 2020

Agroshield said:
So can you do it the other way with the 3D model? Start with say 5 degrees top rake and a bit of side rake and determine what angle you would need to grind at to achieve a true 60 degrees plan view.

I would imagine so but you could just as easily regrind the tool as is until it just kisses the back edge, assuming that you can accurately set the angle of the grinder you are using.
In reality the tool above is likely very close to the required angle anyway.

Brad93 · May 13, 2020

pressbrake1 said:
Naturally but when you’ve got half a ton of knarly old poop swinging and a damaged used insert and get good finish it takes a good lathe.
I should re state it as ‘ dsg that’s done 65 years of work still gets exceptional finish no matter the material or condition of the tool’

I imagine all the mass of a DSG absorbs a lot of vibration, plus the quality/tightness of the ways and the rigidity all plays a part in a finish like that.

grim_d · May 13, 2020

Hood said:
I would imagine so but you could just as easily regrind the tool as is until it just kisses the back edge, assuming that you can accurately set the angle of the grinder you are using.
In reality the tool above is likely very close to the required angle anyway.

For a vice screw that looks like it was rolled using some very worn tooling I'd imagine it will be so Insignificant as to make zero difference, still it's good to know that, every day is a school day.

slim_boy_fat · May 13, 2020

fizzy said:
but plenty of people get very nice finishes on tiny little lathes.

Kinda my thinking in my question re the tooling, but it got shot down. :rolleyes:

zx9 · May 13, 2020

Up date on my hammer.

Today was maths to work out the offset of the tailstock and I hit the length of taper to within 1/2 a mm and actually turning between centres with a lathe dog. The finish of taper is straight from the tool, I could have run some emery tape over it but what is the point in that, this is supposed to be a learning project that I can will look back on and judge my progress.

mtt.tr · May 13, 2020

Had enough for one day pretty productive as im leaving mrs calls, "dont forget the transformer oh and the knob"

Very quick rummage for some ali, very quickly centre punch the holes and drill then onto the lathe

Not overly pleased but will do what swmbo wants.

Couldn't remember the thread diameter mind grrrhhh! Will finish of and deburr when threaded

Hood · May 13, 2020

mtt.tr said:
Had enough for one day pretty productive as im leaving mrs calls, "dont forget the transformer oh and the knob"

I was thinking maybe that had something to do with the ripped jeans the last day.

What are you machining?

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