Cutting taper keyway in fly wheel

[bob shutt]

Does anyone know of a source for tooling to cut a taper keyway in the fly wheels for the Little Brother hit n miss? It calls for .094 wide with a 1/8 per ft taper? The hole is .312 dia

 

[Charles Lamont]

Does anyone know of a source for tooling to cut a taper keyway in the fly wheels for the Little Brother hit n miss? It calls for .094 wide with a 1/8 per ft taper? The hole is .312 dia

You don't need to buy anything special. You can use the lathe as a slotting machine. Put a tool like a parting blade on its side in the toolpost and wind the saddle back and forth, putting very small cuts on with the cross-slide. I have lever that clamps to the bed for the saddle movement.
The three pics (put there recently for someone else with a similar query) at the bottom of this page show the idea: http://www.charleslamont.me.uk/Seagull/timing_gears.html

For a taper you would need a taper turning attachment, or would need to use the top-slide rather than the saddle, in which case it would be better you could take the feed-screw out and rig up a similar lever for the reciprocating motion.

If you want to do slotting more regularly, a dedicated slotting attachment can be made. There is a kit available from Hemingway Kits.

 

[kvom]

Assuming you mean a 8-1 taper rather than 1/8" per foot, then the angle is 7.1 degrees. If you can hold the wheel on your mill inclined 7 degrees you can mill the slot with a 3/16 endmill and then square the end of the slot with a file.

 

[idahoan]

The other option which is what I used on my engine would be to use a standard 3/32" A sized broach and make a special bushing that has the proper angle machined into it. The broaches should be available from most the tool suppliers.

Dave

 

[Jasonb]

As Dave says make a bush with the bottom of the slot tapered and use a standard broach. Shars sell reasonably prioced ones.

J

PS it is 1/8" per foot or 1:96

 

[abby]

If the hole is 0.312" dia , presumably this is the small end of the tapered hole ? how thick is the flywheel ? I assume around 1/2" ?
At a taper of 1/8" to the foot it is virtually parallel so just use a parallel keyway , if the taper is 1:8 which sounds more correct the big end of the hole will be about 0.344".
A 0.094" parallel key will still give more than sufficient contact , the taper provides most of the the locking force not the key.
Just my view ! why complicate the issue with special tooling and jigs when a simple solution will work.

 

[Jasonb]

Its not a tapered round hole its a tapered slot for the matching taper on the keyway to locate onto.

The taper is used to stop the flywheel moving along the shaft, if it were a plain key this would take the load but there would be nothing to stop the flywheel moving sideways.

If you put a tapered ket into a flat keyway there is a risk of it cocking the flywheel off to one side as the wedging force will only be applied to one edge of the hub

 

[MachineTom]

Cutting a tapered slot is a lot easier than a a tapered slot with a tapered bore. So buy a "A" size 3/32 broach, Make a bushing 5/16 and mill the slot with a taper of 1:100, Depending on your equipment a 3/32 keyway cutter, an indexer set at the taper angle, likely the easiest.

I'd make the bushing first then make a key to fit the final taper.

look on ebay those broaches are small so not so expensive.

 

[abby]

Ah , I see , I thought it was a tapered shaft and matching hole like a ships propellor fits to it's shaft.

 

[bazmak]

What you have shown is a standard drive key.I cant remember the proper name
The keyway is not tapered and the key has to be filed slightley untill
you achieve a drive fit.The key is tapped home with hammer and removed using the shoulder
with a taper of 1/100 if the key is 2" long the taper is 20 thou.I recall fitting this type of key
was an apprentice exercise.The keys were blued and filed to a good fit.They were/are used on
Large engineering ie ships propellors etc,cant see there use on model engineering
Will somebody please confirm the name of this type of key

 

[Jasonb]

I know them as GIB headed keys but you can also get plain tapered without the gib head

 

[idahoan]

What Jason Said, (Gib Head Key)

All the ones I have seen and worked with on the full sized stationary engines; the key way in the flywheel has the same taper as the key.
This is common practice, at least in the US.

Dave

 

[kvom]

Gib Head Keys:

http://www.mcmaster.com/#machine-keys/=phpq6v

 

[Charles Lamont]

It is a gib-head key, and the keyway in the hub is supposed to be tapered, but that does not mean that in full size it would not be blued up and filed to fit.

 

[bazmak]

If your using a gib head key in model engineering its purely for aesthetics
the small size dictates the taper will only be a couple of thou.Run a file over the keyway
in the shaft and file/fit the key.The small taper is only to lock the key in place

 

[MachineTom]

I believe they are called cotters as a general name, then tapered, Flat etc. MHB of 1952 still referres to them as cotters.

 

[Jasonb]

If your using a gib head key in model engineering its purely for aesthetics
the small size dictates the taper will only be a couple of thou.Run a file over the keyway
in the shaft and file/fit the key.The small taper is only to lock the key in place

Quite likely to be more than a couple of thou', the current engine I'm doing has a flywheel hub that is 1.5" wide so that would need 0.015" of taper as it works out at ).010" per inch.

 

[bob shutt]

Looks like I started quite a discussion. I was able to get a broach. I plan on making a bushing with a taper slot. The engine is the Little brother. Here is the progress so far. The shaft is not the crank shaft yet. That is in the lathe now.

 

[gus]

What you have shown is a standard drive key.I cant remember the proper name
The keyway is not tapered and the key has to be filed slightley untill
you achieve a drive fit.The key is tapped home with hammer and removed using the shoulder
with a taper of 1/100 if the key is 2" long the taper is 20 thou.I recall fitting this type of key
was an apprentice exercise.The keys were blued and filed to a good fit.They were/are used on
Large engineering ie ships propellors etc,cant see there use on model engineering
Will somebody please confirm the name of this type of key

Hi Bazmak,

Let me make a wild guess----------Gib-head key.

This is a very old design. Saw my uncles cutting them on a overhead pulley driven Shaper.