Topic: DIY back-cut tranny questions.

[iron_worker]

Are the factory dogs cast in place? I would have presumed they were machined and pressed in place like I'm describing.

You guys are probably right on the difficulties of drilling the hardened material. Would likely have to anneal first and reharden to do a proper job.

IW

[iron_worker]

Also note I used the word PREsume and not ASSume. ha

IW

[70CB750]

Gear wheels are typically forged and machined. Same for the dogs.

[alancop]

Couldn't you press them in then have them TIG welded and grind down the welds to flush? That would hold your new pressed in dog well enough to hold up to the shear forces of riding on the street. I probably wouldn't go that rout for drag racing though...

[strynboen]

welding vill thange the hardness of the steel..it vill break klean off...

[vfourfreak]

Hi Guys on this thread, Happy Christmas !!!!
Specifically to Fang about gear modifications, especially the undercutting you propose.
I have seen reasonably balanced arguments from all sides as to the practicality of the approach you might take to achieve your goal.
Not to put a dampener on a Christmas day, but can I please put in my €0.02 ?
As a former roadracer, on both 2 and 4 strokes, I always handled the issue of motor failure carefully, and my preparation reflected that  concern. Amongst my mates we were well used on the Yam TZs to seizures  (we used to call it an "engine sneeze") and so ALWAYS had two fingers on the clutch lever. One change in the engine note, and those fingers averted a lockup. Gearbox seizures were a different matter. Normally no warning, and no possibility to
avert a rear wheel lock up. These events usually had poor outcomes, please check the accident of Mervyn Robinson in the North West 200 for an idea how such an event plays out.
So with an open mind on the machining approaches that can be taken, can I please urge great care ? Don't want to see you hurt in any way Fang !
Kev

[Music City Metalcraft]

Looking at the drill press and x-y table on hand, I would not do more than drilling holes in mild steel with it... the dogs and cogs are way too hard for that equipment. And achieving a correct angle and contact pattern on 6 mating surfaces on 2 round, centered parts, good luck.
I have looked into undercutting gears myself, but the required tooling and time makes the Cycle X offer ($289) looking pretty good.
Your hole saw idea might look good on paper, but it will shatter like nothing else, leaving you with a broken tool and a sub par surface quality, IF it cuts the gear at all, which I doubt. Have you ever cut a hole with a hole saw? Then you will know how much that tool moves around, even when it is angled perfectly square to the surface. Now cock that 1 degree, and watch what will happen... even on a super stiff mill.
I'm all for DIY, but this will not work.

[Music City Metalcraft]

This is how it's done on rectangular dogs:
Under-cutting dog gears.

[crazypj]

No quite the fixture I would have made but similar enough.
Setting up to do each dog will be real time consuming
That's a pretty expensive spin indexer

[754]

Looks like a Yuasa index..guessing 1500-2k worth.
.So those are cuttable with right grade of carbides, but not all gears are same hardness.
 And the flat surfaces are easy, its the rounded that are much trickier..

[Music City Metalcraft]

That's my point. The round ones are much more complicated to index in. Notice the rpm he's spinning the bit, wonder what kind of bit he's using. I t seems to have a 1-2 degree taper in it.

[754]

That is a very nice indexer, pretty sure its inclined afew degrees, then the gear is simply chucked..keep in mind a good index has very little runout.

[lostinthe202]

Yeah, they are spinning pretty fast, so carbide for sure.  That larger cutter looks like an Iscar indexible insert cutter.

And yes, very useful looking indexing head.  Couldn't say about quality, don't recognize the sticker on the chuck, other than being blue it doesn't look like Yuasa to me.  Black anodized handles aren't really their thing either I don't think.   

Looks like maybe that little guy is just to reduce the corner radius where the dog meets the body left over from the inserts.

I like the collar they made for holding the one gear, I like collars for stuff like this.  Kind of surprised they didn't didn't do something similar for the first gear as that didn't really look like rigid setup.

[lostinthe202]

Looking at that a bit more, seems like it's a dividing head, so it just rotates the chuck but doesn't do angles at all.  Despite the frame of the tool looking like it would rotate perpendicular to the chuck's axis, there really doesn't seem to be any provision for it.

So maybe they're getting the undercut angle by cutting along the length of that Iscar cutter.  Those have something pretty shallow in the way of clearance along the rotating axis, like 2-5 degrees.  So if you just kept moving in until you just kissed the top (seems like what they were doing eh?) then you could get your back-cut without having to setup any angles

[fang]

Just a quick little update, as I am still working on this project.

The short version is that all my tooling arrived, and its all wrong. 

The 15mm Carbide hole saw's ID was too small -- that was just a shot in the dark, and I am ok with this.  I already ordered a pair of 16mm ones.  Hopefully the tool's ID scales up with the OD.

The other tool, the 10mm end mill (flat bit) also arrived, but the guy sent me an 8mm round bit


So after three weeks of waiting for tools, I get to start over.

My shippers suggested that the parts will arrive sometime at the end of January.  So I guess I'll get to exercise a bit of patience.
Guns N' Roses - Patience (Studio Version)

[scottly]

People told me I was Nuts when I first mentioned I had back-cut my tranny by hand, with a dremel.

[fang]

You're nuts.

I mean you have nuts.

[scottly]

Just saying, I tried to figure out a way of precision machining the dogs with equipment similar to yours, and came to the conclusion I could do a better job by hand, eye, and dye.