Custom Pilot Bushing

[ronzi]

Has anyone out there had any experience making/machining a custom transmission input shaft pilot bushing?
If so, what material did you use?

From what info I can find, the typical pilot bushing is cast sintered bronze, not regular bronze and is not a machined piece. Normal machining apparently can cause problems with the oil in the bushing not getting to the input shaft surface.

 

[David_DuBois]

If you can find a busing with a correct ID and an OD that is oversized, you could have it cut down without any problems. The problem involved with machining a sintered bronze bushing is that it smears (for lack of a better word) the material into the open pores of the material, inhibiting the filling with oil.

On the subject of sintered bronze bushings, the instructions always state that the bushing should be soaked in oil for 24 hours before installing. If you are like me, you get up to the moment of installing the bushing, only to find that you forgot to soak the thing. If that happens (or for that matter, just forget about the 24 hour soak), just place one of the open ends of the bushing on your thumb, fill the bushing with oil until it brims over the end, place the other thumb over the open end (it helps to be double jointed here) and press your two thumbs together. In a few seconds you will see oil oozing out of the pores of the bushing - Viola! a 24 hour soak in 10 seconds.
Cheers,

 

[vping]

I never knew that bushings were porus and Dave, the description of teh "Smear" and a 10 minute soak are excellent.

 

[Bugeye58]

I keep a selection of Oilite bushings on hand, and store them in a small covered jar full of oil.
You <u>can</u> bore the ID, but you have to use an <span style="color: #FF0000">extremely</span> sharp tool to do it to prevent smearing.
It would be best to not have to do it.
Jeff

 

[PAUL161]

Sorry, I don't mean to interrupt your thread Ron, but it made me think of something I never thought of before, would the MG flywheel lend it's self to a sealed roller or ball bearing pilot? Could it be bored out enough to fit one? Also, does anyone make a roller type throw out bearing for an MG setup? PJ

 

[Steve_S]

They used to make roller throwout bearings but they were problematic. I don't know if they still sell them.

 

[ronzi]

Much obliged for the responses.

One of the possible options for this application is using a trans that has an available sintered bronze bushing that would need to have the OD massaged a little. Sounds like the way to go.

 

[Hap Waldrop]

Oillite bronze is for sure the material you would want to use, I recommend machining it dry, bronze doesn't respond well to being machined lubricated, as mentioned by Jeff you need a really sharp cutting tool. Check McMaster Carr they offer in both bushing stock, and bar stock.

 

[vping]

I was curious as to what "Sintering" was, and for all who were just as curious:

Sintering is a method for making objects from powder, by heating the material (below its melting point) until its particles adhere to each other. Sintering is traditionally used for manufacturing ceramic objects, and has also found uses in such fields as powder metallurgy.

The word "sinter" comes from the Middle High German Sinter, a cognate of English "cinder".

Sintered bronze in particular is frequently used as a material for bearings, since its porosity allows lubricants to flow through it or remain captured within it. In the case of materials with high melting points such as Teflon and tungsten, sintering is used when there is no alternative manufacturing technique. In these cases very low porosity is desirable and can often be achieved.

 

[ronzi]

One other little bit of info I gained while investigating the pilot bushing issue ... the bushing that will probably be used is magnetic. Lay a magnet on it and it sticks.
Other bronze bushings, for example, MG rocker shaft bushings, are not magnetic.
Apparently the bronze alloy in the pilot bushing contains an iron component.

 

[ronzi]

Sorry, I don't mean to interrupt your thread Ron, but it made me think of something I never thought of before, would the MG flywheel lend it's self to a sealed roller or ball bearing pilot? Could it be bored out enough to fit one? Also, does anyone make a roller type throw out bearing for an MG setup? PJ

PJ
Opinions on roller bearing (actually caged needle bearing, I think) pilot bearings seem to vary. Some say they have had nothing but trouble with them, bearings seizing up and breaking up at very short mileages, etc. Others say their experience is just the opposite. One opinion I have read says they are reliable IF they are installed properly. Alignment is very critical, moreso perhaps than with a bronze bushing.
In any event, the sintered bronze bushing seems to be hard to beat for most applications.

 

[David_DuBois]

To expand on what Vince wrote (thank you Vince for the very comprehensive explanation of what sintered items are and how they are made), the sintered busings was a high tech (strange to use the term, high tech for something that has been around for so many years) adaptation of some of the original bearings used at the start of the mechanical age. Bearing material used at the very beginning were turned from iron wood. This material had the unique property of being able to absorb oil when it was cool. As it heated up from the shaft turning in it, the oil would seep out to lubricate the shaft. When the machine in use was shut down and the shaft and bearings cooled, the oil that had seeped out was absorbed back into the iron wood busing, providing what was called a self lubricating bearing.
Cheers,

Note: this is just a historical note. I am not advocating running out and having pilot bushing made from iron wood.