struggles and woes with bushing replacement
Even though the ID's of my old gear bushings were only about 0.005" to 0.009" over the related shaft IDs, they had noticeable slop/wobble so I decided to replace them and get them closer to 0.002" over.
The old bronze bushings came out easily with a 36.2mm diameter bronze rod and the press at work.
Got some new bronze bushings (the kind with the dimples and a seam) from a European supplier.
In order to equally center the new bushings in the gear bores when I pressed them in, I used a small "stop" plug (about 30mm tall) that I fashioned out of some 32mm rod stock. When my 36.2mm diameter bronze rod pressed the bush into the gear bore, it was stopped by the 30mm plug, resulting in the new bushing being about 1.5mm from either gear bore edge.
All good so far except the IDs of the new bushings were about 1.359" to 1.361", and I needed to get them opened up to the 1.3735" and 1.3765" range.
A local precision grind shop was able to hone, broach, or lap the bushes out to a "slip fit" on the shaft ($50 each). When I got them back I measured the bushing IDs and they were between 0.0011" and 0.0014" over the respective shaft ODs. They slipped on, spun freely, and had absolutely no wobble or slop. Looking good I thought, until I pressed on the dog gears. Lordy, why didn't I pay more attention to goats' post #5 in this thread? My perfect fit gears no longer fit onto the shaft!
So back I go to the precision grind shop. I explained how the dog gears had compressed the inner bores at one end, and asked if they could clean up the taper. They said no problem and another $150 later my gears slid on the shaft again and they were still between 0.001" and 0.002" over the shaft ODs. I thought I was in business, but when I rotated the gears on the shaft, I noticed just the slightest bit of wobble. Sure enough all 3 bores seemed to have been cut at a slight angle. First gear was actually 0.017" off from side to side.
Back to square one. Remove synchro pieces (OMG I hate those big snap rings!). Remove dog gears with press. Remove poorly honed bushes with press. Wait for more bushings from Europe. Press new bushings into the bores.
Even though the grind shop hadn't reported a problem with the other bushings moving in the bore as they worked them, I decided to use some green Loctite 620 on this set.
I have now pressed the dogs back onto the gears, and I am ready to have the bushings opened up again (as they all have IDs around 1.359"), but I don't want to go back to the same precision grind shop.
How can I get these things honed, lapped or broached out about 0.015", with a finished diameter accurate to within +/- 0.001", and perfectly centered in, and perpendicular to, the gear?
Is a bushing ID that is only 0.002" over the associated shaft OD correct?
And I am a little confused about "end play" vs. "axial play". I have several different Alfa Shop Manuals. Most of the 105 manuals refer to the "End play" of the gears (which I took to mean the lateral movement of the gear on the shaft), but my 1985-1989 Spider Shop Manual only refers to the "Axial play" of the gears.
In addition, the "axial play" tolerances in my S3 Manual are slightly different from the "end play" specs in the 105 manuals. For example, the 1st gear end play in the 105 manuals is specified to be less than 0.009" (or less than 0.0095") but the 1st gear axial play in my S3 Manual is called out to be between 0.008" to 0.012".
How to open up the bore IDs, and how much of a bigger diameter than the shaft ODs should they be?
'88 Quad - "Claudia"