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by mrfoo
Fri Jan 03, 2020 12:20 pm
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Re: I see we have a new skin …

How do we stop being automatically subscribed to threads we reply to? I don't want to get an e-mail for every reply... Board preferences > Posting defaults > notify on reply by default It was incredibly painful in the past to change things, as SF has historically had lots of customization. This new...
by mrfoo
Sat Jan 18, 2020 7:22 am
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Re: "In the world of spuds today"

The one I linked to has the benefit of the vise screw claming downwards, preventing the jaw from tilting when it is tightened. It's rather small though, 4"or 6" would be better. I do all my milling on the lathe, which means it's all a bit restricted in terms of space, I clamp onto a plate on the mi...
by mrfoo
Sun Jan 19, 2020 1:31 pm
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Re: "In the world of spuds today"

Yep, that looks about right as far as lever indicators go. You'll probably want a plunge indicator as well, though. And a couple of mag bases. Then you can make up some indicator holders for the lathe toolpost, and maybe one to clamp to the ways. For tramming the mill, all you really need is a piece...
by mrfoo
Sun Feb 16, 2020 1:40 am
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Re: Low-friction/Specialty Ball Valves?

Here's one, for example : https://www.valvesonline.co.uk/manual-v ... l-bkh.html

Relatively cheap, pom / molybdenum disulphide seals, rated for 500 bar.
by mrfoo
Mon Mar 09, 2020 2:12 pm
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Re: JSR's workshop chronicles

It's almost certainly due to burrs or shite geometry, but it could be problems with the handwheel, bent screw, etc. First thing to try would be to remove the handwheel parts entirely, reassemble the rest of the slide, adjust the gibs to "close enough but a bit slack" and see if you can slide it smoo...
by mrfoo
Wed Mar 11, 2020 12:13 pm
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Re: JSR's workshop chronicles

Oh, my. That's shit design. Really shit design. What I'd probably do, if possible, would be to find a way to position and then block #25 exactly where it should be, /temporarily/, then drill and ream for a couple of locating pins to hold everything square. You can then enlarge the bolt holes if nece...
by mrfoo
Fri Feb 21, 2020 12:48 pm
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Re: JSR's workshop chronicles

was pleasantly surprised to find it very clean. That's good news. the deals online were just so much better if one is prepared to wait a little. Personally, I'd rather have second hand quality gear than brand new chinesium, even if it comes in more expensive. But usually, it doesn't, even if it doe...
by mrfoo
Thu Mar 12, 2020 1:32 am
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Re: JSR's workshop chronicles

Nothing wrong with low tech at all. The only real problem with digital caliper DROs apart from the small readout (and that can be taken remote with a bit of work and an arduino) is refresh time; rather than emitting a quadrature signal in real time there's a sample output every x milliseconds, which...
by mrfoo
Mon Mar 16, 2020 2:32 am
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Re: Short question topic

Porting and piston form is going to be important to get air out of a short, squat, cylinder into a long, slender, barrel in a hurry. The big issue is, IMO, going to be changing the direction of the air, as such I'd probably go for a conical piston face mating to a conical cylinder end, with highly r...
by mrfoo
Mon Apr 27, 2020 1:18 am
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Re: Help with making a diy blowback system

Boyle's Law tells us that, for a constant temperature, pressure is inversely related to volume, so for a fixed quantity of gas, if we reduce the volume by a factor of 2, we raise the pressure by a factor of 2. So, if we assume you have a 100mL chamber at atmospheric pressure, and you want to raise i...
by mrfoo
Tue Apr 14, 2020 1:00 am
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Re: "Offtopic-posts-topic" NSFW

Machine tools might possibly be valid reasons for divorce.

Selling my machine tools after a divorce would be a valid reason for "disappearance"
by mrfoo
Fri Jun 12, 2020 6:10 am
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Re: Port size vs performance

Quite. There's going to be a point of diminishing returns where, for a given design and geometry, going bigger will eventually slow the piston down. There's a lot of benefit to be had, for a port that's smaller than the barrel, from profiling the edges of the port, both chamber side *and* barrel side.
by mrfoo
Sun Jun 14, 2020 4:12 am
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Re: Ideas for biodegradable cannon-balls

I'd guess a simple flour / water paste would work. Plain flour, though, not self-raising.
by mrfoo
Tue Jul 14, 2020 12:44 am
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Re: Short question topic

His explanation of how it works is dead wrong, the pressure in the two chambers will always equalise. The principle at work is exactly the same as that of a QEV, the force exerted on the piston at the "bulb" end is gas pressure * piston cross sectional area, and at the strut end it's gas pressure * ...
by mrfoo
Sat Aug 08, 2020 1:07 am
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Re: Cooking up a little something...

Wow, missed that update, came back here from the link you posted elsewhere. 100% success indeed. 1067fps for a golf ball means you're basically being maxed out by the shock wave, i.e you're hitting the sound barrier. This makes me wonder what could be done with a streamlined projectile of the same c...