D-drill bit??

[Generatorgus]

I'm building a new carb for my Wyvern engine using my own version of George Britnell's air bleed carb plans. I'm hoping to successfully make a usable carb that will look similar in size and shape to the original Wyvern carb. I have it almost completed.
The original is brass, but I was inspired to use SS by River Gypsy's use of SS to build his work of art Entablature steam pumping engine. I like the look of SS as well as it's maintenance free character.


It's a weldment and still needs some clean up, but I don't have Dave's enthusiasm/fortitude to do any polishing.

I've gotten to the point of drilling the tapers to form the venturi.
I'm thinking a D-bit will do the job.

I tried searching this site a bit but haven't come up with any info on making a d-bit, but I'm sure I saw it here.
I remember that the flat has to be cut a little off center, but can't remember the details. I'm sure someone here lead me there.

Thanks
GUS

 

[enfieldbullet]

actually you turn the outside diameter to the final diameter or taper in this case, then harden and finally grind away to 1/2 diameter.

some people leave a thou over 1/2 diameter.

you could also make a reamer with just a little more effort for a given taper.

 

[kspringer80]

I've made quite a few of these as well using O1 tool steel. I cut the desired profile on the lathe, polish it then set it up in my mill on a parallel. I then machine away 0.001 to 0.002 less than half the thickness with a carbide end mill. After that's done I harden it then throw it in a "carefully calibrated" barbecue grill to temper. Many temper by color change, but I always find myself getting to this point after dark. Once tempered I use some 0000 steel wool to clean up the surface and hone the remaining flat on one of those little pocket diamond hones. If you're doing a taper I've found it easier to leave a reference diameter that I also cut into at the back of the cutter to measure the depth of your facing cut.

 

[Generatorgus]

Guys Thanks for the replies.

I don't have any accurate grinding equipment so I will have to do my best on the mill.

GUS

 

[kquiggle]

Gus - look here for a number of links on D-bits (scroll down to "D Drills"):

https://sites.google.com/site/lagadoacademy/useful-links#lathetools

 

[Generatorgus]

Hey KQ Thanks, Lots of good stuff there, it will come in handy.

I made a fairly crude looking bit yesterday, crude or not it did the job.

GUS

 

[gus]

Hi Gus,


Another Gus from Singapore.

 

[Generatorgus]

Hi, other Gus.

I've been watching your build, great job. I'm hoping to see that governor in action.

I haven't been very active replying to much that's going on here at HMEM, I guess I've got a case of writers cramp, but I'm think I'm getting over it.

GUS

 

[kspringer80]

KQ, I checked out that link....WOW! That's an incredible amount of information packed into one place. My fiance already knows what that page looks like and I just got a great eye-roll 15 minutes ago! She will be happier once I finish fabricating our wedding bands and I can get to a little engine building!

 

[gus]

Hi, other Gus.

I've been watching your build, great job. I'm hoping to see that governor in action.

I haven't been very active replying to much that's going on here at HMEM, I guess I've got a case of writers cramp, but I'm think I'm getting over it.

GUS

Hi Gus,

Hopefully will get it up and going. Been doing test spin with hand held starter.There is a tight fit some where.

Christmas is around the corner.