Advice for WEDM a bore and keyway?

ManualEd · May 4, 2017

I'm trying to find an easier way to do the attached part.
Material is D2 tool steel, HT to about 62 RC. The small OD is 2 1/4, the larger one is 3".

The keyway is so long that a normal broach completely fills the gullets and I get tearing on the exit of the key.
The diameters get machined post HT.
Finish size of the bore is 1.440.
Keyway is .251-.252
I can rough machine the bore to any size to minimize WEDM time.
How much would it cost to skim the bore, and cut the keyway?

I've never seen a WEDM, so I haven't a clue about work holding.
It goes a bit wonky during HT, so would it be possible to keep it perpendicular to the larger diameters face?

Thanks for any advice,

Ed
Edit: Here's the photo.

JTB3 · May 4, 2017

This is a good wire EDM application job, kinda hard to answer how much it will cost without more info. What tolerance is being held on the bore? How perpendicular? What finish are you looking for ? What size radius can the key ways corners have? The bore is gonna need a decent amount of stock to " erode" then finish shave. how many parts also?

SeymourDumore · May 4, 2017

ManualEd said:
How much would it cost to skim the bore, and cut the keyway?

Ed

Ed, you do NOT ever want the EDM guys to skim the bore.
Like NEVER!!!.

They (us) may balk at the tolerances for a keyway vs. bore, but let them (us) have the part in hand, so they ( us) can take care of the fixturing to hold it for the feature.

What I am trying to say is that you finish EVERYTHING as it says on the print by whatever method you think will work, and then the EDM guy will figure
out how to cut it at the very end before it's shipped.

Sidenote: as I type this, one of my EDM-s is cutting similar keyways into 4" dia, 2" thick full-hard D2 knurling dies.
When I'm done, they get shipped directly to the end user.

IOW in this case the EDM shop should be responsible for the keyway ( and it's location ) only, while you're on the hook for everything else.

KilrB · May 4, 2017

SeymourDumore said:
Ed, you do NOT ever want the EDM guys to skim the bore.
Like NEVER!!!.

They (us) may balk at the tolerances for a keyway vs. bore, but let them (us) have the part in hand, so they ( us) can take care of the fixturing to hold it for the feature.

What I am trying to say is that you finish EVERYTHING as it says on the print by whatever method you think will work, and then the EDM guy will figure
out how to cut it at the very end before it's shipped.

Sidenote: as I type this, one of my EDM-s is cutting similar keyways into 4" dia, 2" thick full-hard D2 knurling dies.
When I'm done, they get shipped directly to the end user.

IOW in this case the EDM shop should be responsible for the keyway ( and it's location ) only, while you're on the hook for everything else.

Precisely!

We have several customers for whom we cut keyways.

Most times bores are finished, sometimes the customer finishes the bores after we cut the keyway.

Either way they supply a part with a good, centered, bore for us to locate from ... not just a drilled or rough bored hole.

In the rare event that a customer wants us to do the bore and keyway complete we specify a start hole only.

You are not doing the wire-edm guy, or yourself, the favor you think you are if you take the bore under-size so "all he has to do is skim it" ...

ManualEd · May 4, 2017

JTB3 said:
This is a good wire EDM application job, kinda hard to answer how much it will cost without more info. What tolerance is being held on the bore? How perpendicular? What finish are you looking for ? What size radius can the key ways corners have? The bore is gonna need a decent amount of stock to " erode" then finish shave. how many parts also?

Tolerance on the bore is 1.440 +.005/+.008. .010" rad in the keyway would be fine.
Finish and perpendicularity aren't critical. Its a clearance hole for 1 7/16 shafting.
How much is a "decent" amount of stock? Is WEDM kind of like a water jet, in that it needs the material on either side to keep the cut where you want it?

ManualEd · May 4, 2017

SeymourDumore said:
Ed, you do NOT ever want the EDM guys to skim the bore.
Like NEVER!!!.

They (us) may balk at the tolerances for a keyway vs. bore, but let them (us) have the part in hand, so they ( us) can take care of the fixturing to hold it for the feature.

What I am trying to say is that you finish EVERYTHING as it says on the print by whatever method you think will work, and then the EDM guy will figure
out how to cut it at the very end before it's shipped.

Sidenote: as I type this, one of my EDM-s is cutting similar keyways into 4" dia, 2" thick full-hard D2 knurling dies.
When I'm done, they get shipped directly to the end user.

IOW in this case the EDM shop should be responsible for the keyway ( and it's location ) only, while you're on the hook for everything else.

I had thought that it may be easier to do the bore and keyway in one shot.
It would be less critical to line everything up for the WEDM guy, as I put the roll on a mandrel to turn the diameters after.

KilrB said:
Precisely!

We have several customers for whom we cut keyways.

Most times bores are finished, sometimes the customer finishes the bores after we cut the keyway.

Either way they supply a part with a good, centered, bore for us to locate from ... not just a drilled or rough bored hole.

In the rare event that a customer wants us to do the bore and keyway complete we specify a start hole only.

You are not doing the wire-edm guy, or yourself, the favor you think you are if you take the bore under-size so "all he has to do is skim it" ...

I figured that might be the case. Trying to line stuff up to already made features can be a pain.

JTB3 · May 4, 2017

with that information I would think .010 per side stock would be enough . Probably use .012 wire and modified " erode" tech to hit those numbers. Uneven stock left on geometry can cause some issues but not as great as a water jet I believe. The bore would be the toughest geometry and the key is pretty straight forward.

6061Mike · May 4, 2017

JTB3 said:
with that information I would think .010 per side stock would be enough . Probably use .012 wire and modified " erode" tech to hit those numbers. Uneven stock left on geometry can cause some issues but not as great as a water jet I believe. The bore would be the toughest geometry and the key is pretty straight forward.

NOPE. Been a long time since I was in the Wire edm world, but the 'erode'(E4 on an older Charmilles) is time consuming. The only thing it saves is removing a slug for overnight burns, etc. Finish the bore to size, wire edm the key complete = NO "ROUGH MACHINING" required....

plastikdreams · May 4, 2017

JTB3 said:
with that information I would think .010 per side stock would be enough . Probably use .012 wire and modified " erode" tech to hit those numbers. Uneven stock left on geometry can cause some issues but not as great as a water jet I believe. The bore would be the toughest geometry and the key is pretty straight forward.

Due to the currents induced from flushing through a cylinder an erode would probably leave an irregular surface finish. It would be best as stated above to start with a pilot, preferably hole popped, and just do it in one profile, then switch to a lower (epack, I'm familiar with mits) to get a lower flush and basically spark out the finish.

ManualEd · May 5, 2017

Roughly how much would it cost to WEDM just the keyway, if you have some finished turned diameters on the outside to grab onto?

Waakzaamheid · May 10, 2017

We would quote that at no more than $150.

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Advice for WEDM a bore and keyway?

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ManualEd

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