Bush reaming AMC gearbox?

I've done a few transmission restores this last decade and pretty much got it down but for the correct/easy way to get bushes to fit well. I don't want to spend the hours of hand reaming/working bushes free no more. What procedure/tools &/or who can do this for me, us in general?

Poor man's way is a drill powered 3-stone hone. I have a small one intended for brake cylinder refurb that works well. Take a little at a time and test fit often with oil.

I'm fortunate enough to have an old wood lathe with a 3 jaw chuck. I chuck the gear/bush in the lathe and spin it at 600 rpm while holding the hone in the tailstock (drill chuck). Works for me.

Hobot, thanks for asking this question. This will be coming up soon on my gearbox rebuild and I am trying to decide if I should take the time or try to find a local machinist to do the work. I would prefer to do it myself, but I don't want to make a large investment in tooling that I may never use again.

My ears are open to creative home techniques that will deliver a quality product.

Thanks for the feedback Dave. My down/dirty desire is sand paper on a dowel in a hand drill, yet I've been constantly warned not to use any sand paper or stones to ream various non ferric items in Norton d/t risk of emedded grit. I've seen and used stone hone on brake cylinders and such but they weren't picky Norton and were steel bores not soft brass or Al. So I"m confused as usual. I'm pensive to hand ream any more d/t risk of off centering bore and non true straightness from hand wobble. Also strains my neck spinal cord to stay head down under tension so long, to suffer later as inflammation sets in with some delay.

My pure stock Trixie has her current tranny done the hard hick way and worked a treat but she is just ordinary 13 sec 1/4 mile bike never intended to test 13 sec times against angry squids , but Ms Peel will be tested hard hi rpm in lower gears and lugging chugging with heavy cargo and then spinning tire air borne till harsh landings off road jerk new loads on drive train.

Best plan now is take pieces to machinist to open up to just accept a slick slide on fit and expect the heat to make it loose enough to get by a while with ATF.
I've never seen what clearance to shoot for in the various bushes either. I hope the machinist will have idea of what tool to use and how tight to stop at.

I generally use the shafts themselves, since the splines make a nice reaming tool of the correct diameter if you clamp the shaft in a vise and hold the gear with the new bush already pressed in place in a rag, us plenty of WD 40 and it doesn't generally take too long to get the correct fit. This has worked well for me on quite a few gearbox rebuilds, although recently I helped a friend with one where the bushes were too tight to use this method - I'm not sure where his overhaul kit came from but I generally get mine from Norvil in the UK and have had no problems.

When you say use the shafts themselves with WD40 are you just twisting the shafts in the bushing or are you using something like valve grinding compound? I'm not seeing how just turning the shafts in the bushing will actually "ream" anything but OTOH, I've never tried it.

There are splines on the shafts, these can act like cutting blades, broaches so no cutting paste is required. Not sure if all the diameters required are covered by the splined areas.

On my gearbox build last year, I used a combination of;

1.The splines on the shaft as mentioned by DaveM and Kommando,
2.Purchased 1 X appropriate sized reamer costing about £17 GBP. (I think it was first gear layshaft bush but can't remember now without referring to the old shaft in my garage?)
3.For the kickstart axle bush, as it was "blind" I was unable to ream this with my reamer, and I had to take this to my local machine shop.
4.As I bought a new sleeve gear from A/N, that came with the bushes in machined to correct tolerances.

Ok glad to learn about the spline as cutter method, but duh don't ya think I'd of thunk of that if the bush even allowed some starting entry w/o just binding right up. I'm so pleased with myself on doing it ok the hard way prior, I've no desire to ever do it again : (

Another reason I think I don't work to hand ream again is I think I'm compacting and burnishing over the porous brass/bronze [?] nullifying its self lube property when oil flow ain't reaching inside d/t the hi rpm oil spin out under shaft bowing loads. Any thot's on this issue?

Since kicker bush ain't spinning up fast constantly I used dowel wrap sand paper after grooving an oil spiral with Dremel - embedded grit be damned.

So going by feedback, the best way is a proper ream or lathe milling, not knowing what that means and so rarely needing it, my best bet is to take the pieces to tool/die maker to fit. I owe him some beer and ammo anyway and want to stay in favor as he's got the best/worse trial course around.

Now just need idea of how tight or not to fit this and that bush/shaft.

Ouch, from a lifelong machinist. Using splines to bludgeon material off is just that, use of force. Doing this, you are only using something hard over something soft to achieve questionable aims. Nor is sanding with any paper or media the way to go. Bellmouth shape, barrel shape or taper is almost guaranteed. If you had the means to measure your bushings size, profile and surface finish, rather than just checking if the fit was "OK", you would be amazed. Finesse and exacting machining is what we need here. The shaft is hardened, ground and, presumably, straight as an arrow. You need your bushings, and not just at this application but everywhere, to have as near to an exact match of profile as possible. Proper clearances must be factored in, of course. Your best bet is to take your bushing to a small machine shop (small because the bigger ones are only interested in big $$ customers) and tell them what size you need the bushing bored to. If they're worth a @#$!* they can hold .0005 of your stated size. They are in no position to tell you what these clearances should be. You're going to have to research that and tell them what you want. Exactly what you want.

Could not have stated the case better myself Dan : )
Ok so what would you think fit should be considering the bowing and heating factors?
I would of though this well know like crank end float, but its a blank page on my learning curve to fill in right.

Dan, I agree 100% that the best way to do this is with the correct reamers or at a machine shop, however as with many of the designated workshop procedures required to repair our bikes, so many of us don't have access to all of the options and so need some other way to get us back on the road. The spline method is not quite as coarse as you suggest as long as the bush isn't too much undersize (if it is or the shaft diameter is unsuitable for a particular bush I send it away and wait), a reamer is after all simply a shaft with 3 or 4 parallel hard blades gouging material off a softer component. A gear shaft is the right size, the right material, it's parallel and doesn't deposit abrasives in the bushes. I haven't experienced any problems with this method and have done quite a number of AMC boxes. I get a nice sliding fit with no perceptible side play and no subsequent problems in operation.

I guess this is one of those things the Norton engineers didn't tell us much about. We have three different materials involved here. (Right?) Shaft is probably something like 4340 hardened to 80 Rc. Bushing is AlBronze (oil impregnated?). Gears similar to shaft but maybe just case hardened. All fitting into aluminum cases. Different materials, different rates of expansion when heated. My best guess would be .002 a side clearance, or .004 total. Not too loose, and not too tight to bind up when under running conditions. Similar to rocker clearances. I'd be very interested to see what original Norton specs are, if they exist at all that is.

I'm glad it's working for you, Dave. You're right, we don't all have the same equipment at our disposal, and if it works? It works !! I'm just used to splitting hairs with everything due to my line of work, and this has worked well for me.

hobot said:

Another reason I think I don't work to hand ream again is I think I'm compacting and burnishing over the porous brass/bronze [?] nullifying its self lube property when oil flow ain't reaching inside d/t the hi rpm oil spin out under shaft bowing loads. Any thot's on this issue?

Now just need idea of how tight or not to fit this and that bush/shaft.

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That is highly possible. I think you're on to something there. Today we can buy adjustable reamers (sets or 8 or 9) for $150.00. Probably not that great a quality but for this type of work they will work. A slow speed drill press would be the cheap way into it from there.

From my memory all the bushings should fit the shafts and the gears by hand fitting. Just those that anchor in the cases require shrink fitting. I think the manual goes into this so it would be good to check.

Adjustable reamer would be a good method. These have a set screw in the end that spreads the blades very slightly as you tighten it. Try somewhere like MSC.com. Drill press good too, run slow and use lots of oil.