tapered holes

[firebird]

Hi

On a mates little steam engine the tap/valve that regulates the steam is a tapered piece in a tapered hole. There is a horizontal hole through the two parts that line up for full flow and when turned through 90 degrees closes of the steam. It looks pretty good and would suit the little steam engine I'm building. I can see how to turn a taper, angle the top slide but how do you get a small tapered hole. I have seen small tapered reamers is that the answer????

Cheers

Rich

 

[gilessim]

Rich,
how small are you talking?, probably you can make up a little tapered reamer (of the D-bit type) from some silver steel (drill rod for our friends), I have a couple for violin repair but unfortunately both of my cameras are being fixed, so try googling "tuning peg reamers" and you'll see what they're like, most likely with metal you'll have to step drill a bit but it's quite simple really, one of the ones I have just has one flute, in fact the flute looks like it was done with a ball end mill cutter before the taper was turned,sorry again for the lack of pics, I'll see what I can do!

Giles

 

[Jasonb]

The small reamers you may have seen are probablty for taper pins

When making small valves like drain valves you need to set the top slide over to turn the plug and at the same setting turn a matching taper on a length of silversteel (drill rod). This is then shaped into a D bit by filing to half its thickness. You then harden & temper before touching up the edge on a slip stone and then its ready to use to machine the tapered body of the valve.

Jason

 

[tel]

Spot on Jason - that's how it's done. Also, make plenty of spare plugs while you have the setting, some for future projects, some for spares, some to lose. Pity to let the nice new D bit go to waste and you will never exactly match the setting again.

 

[firebird]

Hi

Thanks for that. Iv'e just done a search on how to harden silver steel but nothings coming up. I'm sure Iv'e seen it here somewhere. If you wouldn't mind run through it again for me. From what I remember you have to temper it as well. What angle would be most suitable do you think.

Cheers

Rich

 

[Maryak]

Kevin,

I would suggest a max included angle of 5 deg, depends on other valve proportions.

Edit: Between 2.4 and 5 degrees which is approx 1/4" per foot to 1/2" per foot taper.

Best Regards
Bob

 

[gmac]

Rich;
for reference,

http://home.att.net/~ShipModelFAQ/ShopNotes/smf-SN-Metals.html

Garry

 

[Bluechip]

Hi Firebird

What you describe is pretty much the same as the petrol (gasoline ) tap as fitted to Velocette m/cycles.

Just measured one, the included angle seems to be 15 deg. or close. Aren't I nice ... going to the garage at the dead of night ...

When you have done one you need to lap the two parts together ( I use pumice/oil ) otherwise it will probably leak.
The petrol taps did after a few years, anyway. Lapped a good few of the b*ggers in my time.

Some folk advocate fine grinding paste, I've never had any luck with it, too coarse, makes the movement stiff.
Hope this is of assistance ..

Dave

 

[gmac]

and another;

http://www.astronomiainumbria.org/a...canica/easyweb.easynet.co.uk/_chrish/t-ht.htm

Garry

 

[tel]

When you have done one you need to lap the two parts together ( I use pumice/oil ) otherwise it will probably leak.

Dave

Brasso is good!

FB - heat your piece to bright red - cooked carrot colour, not the misleading 'cherry, and plunge it vertically into clean water, with perhaps a handful of salt init.

Polish up the flat on the D section and apply gentle heat to the butt end of the tool until the straw colour just reaches the tip, and plunge again.

 

[shred]

http://www.homemodelenginemachinist.com/index.php?topic=4784.0 may be useful too

 

[firebird]

Hi

Thanks Bob. Gary, Dave, Shred and Tel.

Printed out and filed.

Cheers

Rich