Farm Boy – Drawing 11

[Speedy Builder5Participant @speedybuilder5]

Looking at Drawing 11 of Jerry Howell’s Hit and Miss engine,  The Primary exhaust valve pushrod has a ball bearing race on the end of the lever.  The race has an Id of 0.125″ and the drawing states its held in place by a 2-56unc screw through it centre.

2-56 unc îs 0.88″ diameter (a bit slack ?)

The best fit would be a 5-40unc or 5Ba 0.126″ dia shaved down a little ?

Or am I missing something here??

Bob

[JasonBModerator @jasonb]

Not done a farmboy but a couple of engines that have used a bearing as the cam follower use a stepped screw or stud, shank to suit the bearing and then a smaller size thread on the end.

[DalboyParticipant @dalboy]

For those that don’t know here is a section of the page (did not want to publish the whole sheet)

I did not use a bearing but turned from Silver steel it seems to rotate on the shaft

[John PurdyParticipant @johnpurdy78347]

The Red Wing uses a similar bearing and it is held by a stepped shaft. In your case what I would do is, as Jason suggests, use a stepped screw, or a normal screw with a spacer .125″OD x .145-.150 wide x an ID to suit the mounting screw, #2,3,4 or BA, with a washer under the head as appropriate.

John

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