Recutting Keyways - How is it aligned in the mill?

[David2011]

We have some shafts that have wallowed keyways. They were originally 9/32" so I have to recut them to 5/16". I know how to recut a keyway so that's not the question. The new key stock is oversized so I'll cut .008" off of each side of the slot.

The shaft will be held in a 5C collet and collet block. The question is: Once the shaft is centered in the mill, what is the best way to clock the shaft so that the bottom of the existing slot is perpendicular to the sides of the end mill?

 

[Batmanacw]

Once you find center use a pointer to visually clock the the center of the mangled slot. You could use a gage pin the width of the original key.

 

[David2011]

One of these days I'll buy some gage pins. In the mean time some 5/16 round stock will have to be close enough. That's one method that crossed my mind; just wasn't sure it was a valid idea. I guess if the shaft is centered and a 9/32" pin will go to the bottom of the slot, it must be in the correct position. One side of the slot is square and the other side leans a degree or three but the bottoms don't seem to be beaten out.

This is more Battleship Texas stuff; gears to either operate something on the 5" guns. Probably elevation of the barrel. Little shafts and gears lead to bigger shafts and gears.

 

[David2011]

The guy that asked me to do this job just sent a text saying that these gears are part of the assembly that engages a big rack to set the elevation of the sight yoke. It's a massive piece that spans the barrel trunnions.



Shots of the gears and shafts. It's not uncommon to see the key broken off in the keyway as below. The key was originally part of the gear casting. We cut new keyways in the gears after machining away any remaining key when necessary. The new keys will have to be filed to fit since they always order oversized key stock for these old guns. The guns date to 1912. They're original to the ship and have USS Texas engraved into the barrels.




The distorted key is easy to see, below.

 

[RaisedByWolves]

Are these gears timed?

If not you can send moly not worry whet 12oclock is as you will be cutting them deeper to accommodate the new larger key.

If they are timed and you need to be exact you will need to indicate them or make a jig that engages two teeth with a pointer to assure they both match.

 

[David2011]

Are these gears timed?

If not you can send moly not worry whet 12oclock is as you will be cutting them deeper to accommodate the new larger key.

If they are timed and you need to be exact you will need to indicate them or make a jig that engages two teeth with a pointer to assure they both match.

They are not timed. They just attach to a hand wheel to move the sight up and down.

Unsure what the second line means.

Since the amount of metal to be removed is very small (~.008") per side and .016" off of the bottom it seems like getting the original keyway square with the (edit) end mill (end edit) is pretty important.

 

[RaisedByWolves]

They are not timed. They just attach to a hand wheel to move the sight up and down.

Unsure what the second line means.

Since the amount of metal to be removed is very small (~.008") per side and .016" off of the bottom it seems like getting the original keyway square with the is pretty important.

Spell check murdered my sentence.

If not you can (Something) not worry where 12oclock is as you will be cutting them deeper to accommodate the new larger key.

Im not even sure what I meant, but I cleaned it up a bit.


.008 per side is a mile to me. Put one in the vise and find center with an edge finder, then use an indicator to find the center of a good portion of the keyway and recut. Just eyeball it as good as possible, and you may have to rotate the shaft a bit to get it perfect, but its doable and you should be able to get it within .002 easy enough.

 

[682bear]

They are not timed. They just attach to a hand wheel to move the sight up and down.

Unsure what the second line means.

Since the amount of metal to be removed is very small (~.008") per side and .016" off of the bottom it seems like getting the original keyway square with the is pretty important.

I think what he was saying is if the gears aren't timed, then just turn them over and make new slots in a fresh location.

-Bear

 

[David2011]

I think what he was saying is if the gears aren't timed, then just turn them over and make new slots in a fresh location.

-Bear

While that makes sense for an easy repair, it's not appealing for restoration work. Indicating the slot and recutting it will be unnoticeable while having an extra slot would be very obvious. I'll just center the shaft under the spindle, make sure a pin enters the bottom of the keyway and call it good.

 

[David2011]

The Battleship Texas Foundation guys ordered a broach set to cut new keyways in the gears where the cast-in keys had broken. I cut all but the last few thousandths of the keys away on the mill, finishing up on the lathe with a boring bar. I had never used a keyway broach before but it went very well. Now I can adjust the depth of the new keyways in the shafts as necessary.