QR50 - Retrieving Splines 2

As you will have seen from my previous posts, I successfully built up the kickstart shaft from it's previous mangled stump and cut the splines on it only to find that I had misunderstood the spline pattern Honda had specified - in my defence, the kick start lever shows maybe 24 of the 31 splines the shaft needs; I had estimated 32. You can see the difficulty in the picture below:

I had another Honda kickstart shaft knocking about from a PC50 which fitted the QR50 lever beautifully. When I found it, (after I had cut the new one, by the way), I discovered that it had 31 serrations, rather than the 32 I had assumed. After a lot of research, I found a drawing which matches the PC50 sample perfectly:

Building it up again was pretty straightforward.

What was much more of a problem was the fact that I had nothing to divide the shaft into 31 serrations - no 31 tooth gear, no 62 tooth gear and certainly no 93 tooth gear...

So, I'd have to make one. I took a chunk of aluminium I had knocking about and put it in the rotary table. Thirty-one divisions equates to 11.86° per division, which is not too difficult to resolve on the rotary table. I set up a small centre drill near the edge of this material, and drilled 31 holes around the edge, incrementing the rotary table by 11.86° each time:

That done, the next job is to move the three jaw chuck from the rotary table to the lathe spindle, trim the outside diameter and prepare the 12 mm centre bore.

Then the next job is to trim the outside diameter to start turning those holes into grooves. Really, the holes are only for angular positioning - they are not deep enough to provide the finished grooves and will be adjusted with a file later. The next time I do this however, I will run a drill through each hole while the work is still in the rotary table - that will save a lot of filing:

A little while later, we have the fledgling grooves exposed. The next job is to part off:

Of course it's not as easy as just parting off - I've extended the drilled holes using a hacksaw and needle files to form square-bottom slots the dividing pin will fit into neatly - we don't want it slipping out when we are trying to cut serrations.

I also dot-punched one of the slots so I could count them - I counted them several times to convince myself there was indeed 31. There was definitely 31, so I stamped the wheel to remind myself.

Next stop, prepare the shaft. This time, I managed to chip the carbide insert almost as soon as I laid it on the end of the shaft - carbide tips don't like intermittent loads, so I will use an HSS tool next time I try to machine an overlaid shaft.

This time, I am going to cut the splines in 0.125 mm (5 thou) passes to make sure the alignment is correct before going to full depth - full depth is about 0.9 mm. That saves straining hands and loading the machine, so the cuts should be more accurate. Here goes:

Part way through:

 Almost finished now, but have a look at the crests of some of the splines. A couple of things happen when cutting these splines and I'm learning how to avoid the problems they cause:

• the Honda splines run into a taper - they are blind, possibly because they are rolled in. The effect of this is that the tool comes to a dead stop which can potentially turn the toolpost, causing the tool to dig in or chip. Part way through this cut I turn an undercut for the tool to run into.
• If the tool chips, you have to remove it for a regrind, all well and good. The problem arises if you don't pay attention to the tool height. Now, when you are turning the tool height is fairly critical, less so if the work is relatively large but height is normally fixed by the adjuster on the toolpost. The thing is the QCTP typically does not repeat the tool height very accurately which is not normally a problem, but when you are cutting a serrated shaft the height of the tool has to be spot on to the height at which you took the last cut. If it isn't, the next cut won't land in the same place in the partially cut spline and will either cause it to be misshapen or could remove the spline altogether. So that's a lesson for next time.
• The reverse stroke of the tool has, I think, the potential to chip the tool. Shaping machines are fitted with a clapper box to allow the tool to disengage on the backstroke yet remain aligned on the forward stroke.
• The last thing is to do with the shape of the spline. I cut these splines with a tool ground to 60°, which makes 60° grooves between the splines. In a flat surface, 60° grooves would make 60° splines between them and the same would be true (to a lesser extent) on a shaft of very large radius. As the shaft diameter decreases, that same 60° produces a spline that increases beyond 60°. This is not too much of a problem, as long as you expect it - just grind the tool to suit.

Have a look at the spline at about 10 o'clock - there's a groove cut in the top of it:

So that's it. Finally, it fits; whether it will withstand a hefty boot is a tomorrow problem.

QR50 - Retrieving Splines

Well, as I had the lathe set up with the ER25 collet chuck and the fixed steady (for the crankshaft threads) I thought I would prepare the kick start quadrant for the spline repair.

Like a lot of bikes, this has suffered the usual calamity of allowing the kickstart to come loose, fret  and eventually turn on the splines. This one looks like there has been some weld repair, and it is full of holes...

I have a Honda Express transmission which I had thought would provide a replacement - unfortunately, it looks like Honda decided this design was inadequate as the Express quadrant is much bigger in this area.

We'll have to fix this one.

First of all I will have to put this in the lathe to clean up the mess

Then, I will have to build up the missing bits with the TIG set, followed by restoration of the splines. Options could be:

• milling, using an end mill in the lathe and indexing the part in the rotary table
• grinding, using a toolpost grinder
• shaping, using a suitable tool and indexing using the dividing attachment
• machining a plain journal and using a axial pin to provide the anti-rotation feature 

I could also make a new shaft to the correct size and make the splines in that, to avoid the building up operation - but then I would have to remove the old shaft and re-weld the new one.

Turning off the damage is pretty straightforward:

I need to look at the short taper behind the spline as well:

With it cleaned up, I can think about welding:

In this first picture, I have laid about 4-5 mm over the end of the shaft, with the machine set at 75 A. This is half a ball, and of course I need to build up a cylinder with a square end. This will probably need some more work:

Laying metal over the diameter:

Laying more material into the diameter, about the tapered section which will need recutting:

This is the kickstart lever. The major diameter of those splines is 13.5 mm and it looks like we have a 30° spline. Inside diameter is about 13.2 mm. It's quite difficult to count the splines, but it appears the full circle would have 30 splines.

Here, I've turned the weld down to a tad under 14 mm, to see where we are:

Here's the length, turned to 18 mm:

We need to build up more in various locations. I've decided to dispense with the peripheral groove, since I don't need it - I can decide where I want the clamp bolt clearance and cut a small slot in the appropriate location later:

Having built it up some more it is time to turn to the final size:

We use the usual dividing gadget to set the lathe up for dividing the 30 serrations:

Here's the tool set up for cutting the serrations:

Here's the first few, first stage of cutting. I'm using three passes at 0.075 mm per pass which in theory will give me 0.225 mm height to each serration, which equates to an ID of 13.05 mm. In practice, clearances and flex in the lathe will prove this is not sufficient:

All cut to the initial stage. Part way through this stage I tightened up the fixed steady which has had the effect of making the later serrations deeper than the initial ones - look at the last ones I cut at about 9 o'clock, against the first ones, about 11 o'clock.

Here's another view. You can see that the serrations are still truncated - the next stage needs to be deeper.

These are 0.05 mm deeper. You can see the form has taken shape by virtue of the small chamfer at the nose of the shaft:

And that is it - or it would be, if mating the two parts had not revealed that the Honda design has 31 serrations, not 30...

It should look like this:

Here we go again: