keyway.

[nickk]

I am converting an old turbine to generate electricity and need to cut a 1 inch wide keyway in a 4 inch diameter vertical shaft. It has to be done in situ.

I was thinking of making a fixture that clamps concentrically to the shaft and mounting my magnetic drill on an old lathe compound slide to give traverse along the shaft length.
There is lots of surrounding ironwork enabling me to clamp to to gain more ridgity.

Has anyone here tackled this problem and are able to recommend a better method to carry this out.

 

[garethp]

Sounds like it should work, take it nice and easy, remember the drill bearings wont be designed to take any side thrust from cutting and rough it out udersize before taking several finishing cuts. And take some photos

 

[Pete.]

That's the way I would do it!

 

[garethp]

when I say udersize I actually mean undersize udersize is a for a totally different forum

 

[madkayaker]

you will have probily thorght about this but would loctight bearing fit be sufficent to save haveing to machine the shaft?

 

[FranV8]

How about using a taperlock instead? No machining needed...

 

[awemawson]

if you make it uddersize it'll be a cow to fit

 

[Paul.]

How about using a taperlock instead? No machining needed...

A taperlock bush still needs a keyslot in the shaft, but depending on what the op is intending to fit to the shaft a keyless bushing such as a Trantorque may be suitable.

 

[nickk]

How about using a taperlock instead? No machining needed...

i am using a taperlock,& i thought the large capacity couplings require a key,this shaft will be driving a 77 to 1 gearbox & replying to m c,i wouldn't have confidence in loctite.

 

[nickk]

if you make it uddersize it'll be a cow to fit

ha ha! where are u in sussex,i lived near sheffield park until 1987.

 

[FranV8]

Okay, what is the shaft speed and how much power are you expecting to generate? As an alternative, there are people out there who do on site machining if it looks tricky, but of course it costs and I know most of us post here because half the fun is DIY!

 

[awemawson]

ha ha! where are u in sussex,i lived near sheffield park until 1987.

Battle, TN33

 

[nickk]

Okay, what is the shaft speed and how much power are you expecting to generate? As an alternative, there are people out there who do on site machining if it looks tricky, but of course it costs and I know most of us post here because half the fun is DIY!

not sure of shaft speed until monday,we have a 25kw generator,arrived last week,the turbine was installed in 1905!

 

[nickk]

Battle, TN33

my late auntie lived there,we had a week long school trip there in the '70's.Also had a friend living @ Seddlescombe,his step dad used to do up old GPO vans.do they still have the vintage/junk sales in the station yard?

 

[brightspark]

not sure of shaft speed until monday,we have a 25kw generator,arrived last week,the turbine was installed in 1905!

that will take some poke to run will definately need a keyway loads of torque there get the calculator out

 

[awemawson]

my late auntie lived there,we had a week long school trip there in the '70's.Also had a friend living @ Seddlescombe,his step dad used to do up old GPO vans.do they still have the vintage/junk sales in the station yard?

When I say Battle it IS actually Sedlescombe (no one's ever heard of the village so I usually say Battle! No junk sales no longer in station carpark, but general sales room close by

 

[Rudi McAnichal]

Three possible approaches to this problem.

1. A flanged hub shrunk onto the 4 inch shaft would transmit quite a large torque. You could pre-drill the flange and, after fitting it to the shaft, bolt on whatever gear, sprocket, pulley or coupling is to be used. Anybody with a big lathe could make the hub (best to make a spare at the same time because it would be very difficult to remove the hub other than by slitting it with an angle grinder). Shrink fit calculations can be found in engineering textbooks.

2. Rough and ready method, sometimes used to repair loose hubs. Assemble the hub on the shaft with the ends flush. Drill a hole, parallel to the shaft axis, exactly where you would make the keyway for a square key, and drive in a roll pin (spring tension pin). I don’t remember seeing this method, or roll pin sizing calculations for it, in any text. I suppose you could use two or more roll pins (but unless they were exactly parallel it might be impossible draw the hub off in future).

3. Consider a keyless bushing. I have no experience of them (and don’t think they had been invented when I was last assembling drives), but have a look at http://www.fennerdrives.com/catalogs/keyless_bushings.pdf

By the way, how was the power transmitted originally from the old turbine, if the shaft has no keyway?

 

[mikegolding]

If you use the method above using holes half in the shaft and half in the hub, drill and ream the holes and fit hardened steel extractable dowels. They will transmit more power than roll pins and if the holes are not all parallel the dowels can be pulled out one at a time and then the hub pulled off.
Mike

 

[awemawson]

Millwrights in days gone by would cut shaft keyways with a cold chisel. If you were to start with a hole drilled as per the last two posts, then cutting the semicircular trough into a rectangular one would not be too much effort I would have thought. You could then knock in a tapered key with an extraction heel. It is amazing what you CAN do with a newly ground good sharp cold chisel.

 

[pitmole]

Hi, I have a machine that I made for cutting windows in steel gas pipelines, it has a hydraulic motor turning a tct blade, depth control, would cut a key a meter long if you wanted it to and will strap to a 4" shaft no problem.
Where in powys are you? might be up for a visit!