Installing over sized throttle shaft?

[Gino]

Morning, I purchased an over sized throttle shaft but I can't find the correct drill bit. I think it calls for .294. Anyone conquer this problem. Or should I order bushings? And there again will I need a hard to find drill bit for those? Thanks for the help.

[BRENT in 10-uh-C]

You need a fluted reamer, -not a drill bit.

[Ron/IA]

While a fluted reamer will work, so will a drill bit. I used a letter M drill bit to drill out the throttle shaft hole in my carburetor body 4-years ago, and it has worked fine ever since.

Our club librarian made a fixture to hold the carburetor body so it could be done in a drill press. I think this is the reason using the drill bit worked. I would not recommend doing this operation with a hand drill.

[Ed in Maine]

I would go the bushing route rather than installing a non-standard throttle shaft. In the future, you can always change the bushings and continue to use standard shafts. Ed

[Mitch//pa]

i install the oversize shafts with a drill bit on a hand drill and never had a problem doing so.
thanks rusty on the size correction

[wrndln]

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Gino,
If the oversized throttle instructions say to use a .0294" drill bit, a 19/64" is .0297. I would sure think that would be close enough for a model A. A bushing would also work if you can find one the correct size, which could be a problem.
Rusty Nelson

[redmodelt]

The dealers sell bushings as well as standard and over sized throttle shafts.

[ericr]

Originally Posted by BRENT in 10-uh-C

You need a fluted reamer, -not a drill bit.

where do you get such a tool?

[Bob C]

Originally Posted by ericr

where do you get such a tool?

Here http://www.mscdirect.com/browse/tn/?...er&hdrsrh=true
or here http://www.amazon.com/s/ref=nb_sb_no...ds=.294+reamer

Bob

[Gino]

Well thanks everyone, I will look into the bushings first and if they should become problematic I'll go with the 19/64 drill bit. Should get it done this week I'll post with the outcome.

[BRENT in 10-uh-C]

Originally Posted by wrndln

Gino,
If the oversized throttle instructions say to use a .0294" drill bit, a 19/64" is .0297. I would sure think that would be close enough for a model A. A bushing would also work if you can find one the correct size, which could be a problem.
Rusty Nelson

Better drop the zero ( .Ø294 ) or the hole will be WAY too small!!

Originally Posted by ericr

where do you get such a tool?

Fastenal is where I get mine. Many industrial tooling suppliers have them. They will have them in .294 or .297.

Originally Posted by Gino

Well thanks everyone, I will look into the bushings first and if they should become problematic I'll go with the 19/64 drill bit. Should get it done this week I'll post with the outcome.

Now there is a couple of things that need to be thought thru on this.
* A drill bit often does not drill a round hole.
* Also a drill bit does NOT always drill in a straight line. (The spirals tend to move it off-center unless it is piloting off of something)

These are two critical keys in making a carburetor operate correctly. The idle speed of an engine is controlled by shutting off the air to the engine (not fuel per se'). When you have a poor fitting throttle shaft, air leaks around the shaft. Air signals (vacuum) also are important to have a carburetor that performs linear throughout the entire RPM band. Vacuum leaks around the shaft do not allow for this.

A reamer (especially the ones I purchase which are about 3½ inches long) allow for a straight bore all the way thru but not drill thru the back side of the housing. The housing bore is smooth which allows the shaft to move without binding or leaking. So, do you really need a reamer? I guess it all depends on the quality of work you are desiring. Just my thoughts......

[Tom Endy]

The installation of bushings with a new standard size shaft has always been my choice. for repair. I have done countless numbers just using my drill press and two different size drill bits. Bratton's sell the bushings and the standard shafts. The bushings have to be reamed once installed to accommodate the new standard shaft.

For a complete description of the task go to the web site of the Santa Anita A's of Arcadia, California at santaanitaas.org. On the home page put your cursor on "Technical Reference", my name will appear below, click on it. On the menu list go to Zenith Restoration Tips. There is a section with photos showing the throttle shaft repair task and the drill and reamer sizes are indicated.

Tom Endy

[Bob C]

Originally Posted by Gino

Well thanks everyone, I will look into the bushings first and if they should become problematic I'll go with the 19/64 drill bit. Should get it done this week I'll post with the outcome.

Something to think about, the 5/16" hole for the bushing
is bigger than the 19/64" oversize shaft.

Bob