internal integral keyway machining ??

the apron feed shaft on my colchester triumph 2000 has the typical 1/4" key slot, it passes through a hollow pinion shaft within the apron just like most other machines, this pinion shaft has a bore of circa 20mm and has a key running down its bore about 60mm. What I cant understand is the fact that this male key seems to have been machined as an integral part of the pinion shaft bore.

i.e. this is not a key slot with a key, but the key itself seems to be one piece with the bore, is this possible, and how could this have been machined.

On my old elliott lathe it was possible to replace the key when it wore, but in the case of the colchester it looks like the complete pinion shaft needs to be changed. I dread the thought of the cost of this.

Seems an odd way to design it but a male key inside a bore could be cut with a shaper and an indexing device.

I've not done it myself but I'm pretty sure it's possible - the real question is why would you want to do it like that, as it's a lot more work than a normal slot and key arrangement?

IanT

In production work this would probably be done with a broach. A broach is a long tapered device with a series of cutting edges, starting out small and increasing in size until the last is the size and shape of the hole you want. The broach is simply pushed or pulled through the job in a suitable machine. You can thus make a hole any shape you want. You start out by drilling a hole big enough for the small end of the broach. I have some square broaches lying around although I don't have machine to use them in.

John

.

Welcome to the world of Colchester spare parts, or rather the prices.

East peasy on a shaper or a slotting machine but a pain for anyone else.

Was probably done on a dedicated vertical slotter

Is there enough room to machine away the built-in key and then cut a new keyway in the pinion shaft, securing a new key with pins or screws onto the pinion shaft?

Martin.

Never in a bunch of Sundays, far too slow.

It would have been broached in one pass on a horizontal broaching machine in one pass, probably doing 4 or so at a time with a cycle time of around 5 minutes max for all 4.

Chances are on the Colchester the pinion is also hardened, so either get a new keyway cut by spark erosion, fit a key and drill thru with a carbide drill to either plug weld it or pin it.

Secondly get it annealed, broach a new keyway in and repeat as above but make sure it's fully soft or that's a £50 broach up the spout.

Thirdly, grip your ankles, bend down, take a deep breath and buy a new one.

Personally I'd go for option 2

.

My guess is that it was moulded from powdered metal, and sintered

... Seems counter-intuitive; but have a look at this low-cost component.

MichaelG.

Edited By Michael Gilligan on 26/04/2015 14:20:16

Edited By GT390 on 26/04/2015 14:44:43

Edited By GT390 on 26/04/2015 15:01:28

If you have to make enough of something then internal broaching is the way to go. Even Myford had broaching machines so more chance of Colchester having them as well.

[ EDIT ]  Is it 1/4" on the key ? Reason I ask is on a 25mm shaft 8mm key is standard but to make life easier they could have gone down a size to 6mm.

Personally because the key doesn't run the whole 60mm odd in length and doesn't need to if I had to do this as a repair I'd sleeve the oil seal track up at the non keyed end. On the keyed end I'd mill thru from the outside to get rid of the key making a closed slot. Turn the whole of the plain diameter up to the gear down by 1mm and weld the whole lot up in a spiral weld so it grabbed the key as well. Then turn and polish the final diameter.

From the look of the gear it's had the usual square head lurgy of an apron full of rusty water instead of oil. They are that renown for this I'm surprised that Colchester hasn't got a patent on rusty water.

If it's a standard gear you could buy a gear from say HPC at Chesterfield bore it and make a new shaft and press it into the gear. That is a second alternative

Edited By John Stevenson on 26/04/2015 16:15:19

Edited By GT390 on 26/04/2015 16:44:47

Is the whole width of the gear used? Perhaps part of it could become a ring. Does the key have to be where it is along the length? Perhaps it coud be moved down to a part of the shaft that again could be a thicker ring. Does the key need to be let in to the gear all the way along? Some are not recessed but have just one of more pins that secure them, either loosely, or perhaps glued or welded into place. (this would be my preferred method).

Most of the gear is used and the shaft is fully enclosed in a housing, so I cannot fit a ring.

I may have a go at making it from scratch, maybe brazing a key into a slot cut through the shaft before turning to final size

John, do you know the spec of the gears in the triumph 2000 apron, pitch looks to be 12DP but I am unsure of the pressure angle

thanks

Rob

If it were my job to do, I'd certainly consider remaking the shaft and riveting the key into position.

Martin.

For me, the clue that broaching was used is the view up the inside. The two diameters are not quite the same (or concentric), but the main clue is the axial striations in the bit where the key is, but not the nearer diameter. This is quite characteristic of a broached surface. The slightly smaller diameter at the far end was to allow the broach an easier time in the nearer part, as this end does not contact the broach at all.

I think.

Tim

I did find shaft adapters for electric motor drive shafts that had the same type of key, an internal half key at 12 o`clock and external half at 9 o`clock, could not find one the correct size though. The section of the shaft that has the key is much softer material than the half that has the gear, this is evident even by seeing the groove that the rubber lip seal has gouged into the surface of both ends, one much deeper than the other.

I have thrown in the towel and ordered a new pinion shaft and a set of halfnuts for the machine, a painfully expensive experience I must add.......

I think Blowlamp has the answer. I'd be inclined to do the same thing for the repair. Removing all that metal just for a small key section seem to be a hell of a lot of work.

John

Here's a gear outof my junk collection.

Ian S C