I'm going to be installing bushings for the primary throttle shaft on
my Quadrajet carb , and have been pondering on how to accurately ream
the worn bores so there is no binding . I was thinking about lining it
up and boring the holes on the mill . And then tonight I had a thought
.... they sell a piloted reamer for this , so why not make a single flute
piloted reamer like a d-bit drill ? I wouldn't even have to harden a
piece of O1 drill rod to cut the aluminum alloy carb base . I like this
idea enough that I ordered a piece of 3/8" O1 drill rod ...
--
Snag
My rights don't end
where your fear begins .

"Snag" wrote in message news:t165ds$bda$1@dont-email.me...

I'm going to be installing bushings for the primary throttle shaft on
my Quadrajet carb , and have been pondering on how to accurately ream
the worn bores so there is no binding . I was thinking about lining it
up and boring the holes on the mill . And then tonight I had a thought
.... they sell a piloted reamer for this , so why not make a single flute
piloted reamer like a d-bit drill ? I wouldn't even have to harden a
piece of O1 drill rod to cut the aluminum alloy carb base . I like this
idea enough that I ordered a piece of 3/8" O1 drill rod ...

-------------------------

I made one with the pilot half-round, but I think if I made more I'd leave
the pilot full round and mill a narrow slot at the cutting step, with
rounded edges if it would be hardened. It doesn't seem to matter if the
cutting edge is slightly above or below center, and resharpening it will
take the edge below center anyway. I'd test it on scrap the same thickness
as the carb wall to see if it chatters or galls.

My first D bit opened up the U bolt hole in a truck leaf spring without any
back relief, but in aluminum a little cutting edge and shank relief gave a
smoother hole finish. A gear-shaped broach of unhardened O-1 drill rod was
noticeably duller after broaching one hole in a zinc pulley. It bent when
broaching a second pulley.

https://www.colinbinnie.com/workshop-tips.html
I made a tapered venturi reamer as shown, with no back relief. While it
didn't exactly cut freely in aluminum, it did the job.

Pulling the bushings in with nuts on threaded rod would help keep them
straight. I'd use long shaft couplers with the ends faced true to the
threads, and if necessary stepped to center the rod in the bushings.
jsw

On 3/19/2022 8:01 PM, Snag wrote:
>
>   I'm going to be installing bushings for the primary throttle shaft on
> my Quadrajet carb , and have been pondering on how to accurately ream
> the worn bores so there is no binding . I was thinking about lining it
> up and boring the holes on the mill . And then tonight I had a thought
> ... they sell a piloted reamer for this , so why not make a single flute
> piloted reamer like a d-bit drill ? I wouldn't even have to harden a
> piece of O1 drill rod  to cut the aluminum alloy carb base . I like this
> idea enough that I ordered a piece of 3/8" O1 drill rod ...

You "can" cut aluminum with some might soft steel, but I don't think you
will be happy with the results. HSS drill blanks are available and
inspite of the fact that I prefer carbide when possible HSS will work
nicely.

--
Bob La Londe
Proffessional Hack, Hobbyist, Wannabe, Shade Tree, Button Pushing, Not a
real machinist

--
This email has been checked for viruses by AVG.
https://www.avg.com

"Bob La Londe" wrote in message news:t17et7$9ac$2@dont-email.me...

On 3/19/2022 8:01 PM, Snag wrote:
>
> I'm going to be installing bushings for the primary throttle shaft on
> my Quadrajet carb , and have been pondering on how to accurately ream the
> worn bores so there is no binding . I was thinking about lining it up and
> boring the holes on the mill . And then tonight I had a thought ... they
> sell a piloted reamer for this , so why not make a single flute piloted
> reamer like a d-bit drill ? I wouldn't even have to harden a piece of O1
> drill rod to cut the aluminum alloy carb base . I like this idea enough
> that I ordered a piece of 3/8" O1 drill rod ...

You "can" cut aluminum with some might soft steel, but I don't think you
will be happy with the results. HSS drill blanks are available and
inspite of the fact that I prefer carbide when possible HSS will work
nicely.

------------------------

If it doesn't cut the test sample smoothly he can harden and resharpen it.
The finished hole size doesn't matter if he turns the bushings to fit.

I prefer to temper on the softer side initially so the tool is less damaged
if it won't cut. Temper too hard and it may chip. I needed two tries to
drill the neighbor's son's truck springs. The custom U bolts he ordered for
a higher-than-Dad's lift kit came 5/8" instead of 1/2" diameter.

The funny thing is that when they need to haul something too long for their
$$$ trucks they call on me and my 7' bed 1991 Ranger.

An empty tin can lying on its side with some charcoal in the bottom
concentrates and retains the heat of a propane torch. I coat the tool with
Ivory soap to reduce scaling. O-1 is hot enough to harden when a magnet
doesn't stick to it.

Until I bought a Victor oxy-acetylene tote kit (for $50) the white-hot
hardening temperature of HSS was beyond my reach. O-1 is relatively easy to
work with. Keep its cutting speed in steel at 50 feet/min or less.