Lapping swaging dies

kombayotch

kombayotch

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What's your technique for doing it in long blind hole?

The polishing bits that come with the Dremel work really good (spinning the die in the opposite direction). But they don't reach very far and are often too big. Been meaning to create some of my own rods that are longer to extend the range of them.

I've tried dowels, balsa wood, leather, lead, bullets and brass/copper rod with lapping compound/JB/Flitz/sandpaper. These work ok, but take a long time. I know, lapping takes long...
 
You need a long rod and a drill press. For something like a swaging die, all pressure needs to be equal on all surfaces all the way around and for the entire length.

Just take a look at how lapping tools are used for stoning cylinders on engines and hydraulic/pneumatic cylinders. They are purposely are designed with spring mounted arms or hundreds of abrasive beads at the end of flexible spring metal rods. Even their shafts have spring joints that work in a similar fashion to the CVE joint on your vehicle.

Similar lapping tools are available in very small sizes, less than 5mm I believe. Hand lapping is OK, if it is done with proper equipment. It isn't OK using non flexible shafts in a hand drill or Dremel. It's almost impossible to get a concentric hole.
 
For what you're doing, lead would be your best choice.

When you say a blind hole.........do you mean completely blind or do you have a knock-out hole in the end?
 
I in case you haven't already tried, use the die body as a mold, pour some lead into it to make lap slugs the size of the cavity, use those to lap the die.
Sadly, there is no fast way around it :(
 
You need an expadable lapping "bullet" made of steel to the profile
of the bullet you'll want to make, use diamond lapping compound, and
measure often or else.
everything else mentioned will only polish, and risk an out of round
hole.
it really is an art, especially with carbide.
 
marshman said:
You need an expadable lapping "bullet" made of steel to the profile
of the bullet you'll want to make, use diamond lapping compound, and
measure often or else.
everything else mentioned will only polish, and risk an out of round
hole.
it really is an art, especially with carbide.
Click to expand...


It'll just be tool steel. The reamers are made by hand, so I guess the lap would need to be at least the same or larger.
 
I picked up some diamond grit pastes off ebay a while back with intents to use it with copper laps for swage die uses.

Life interferes, though. The grit worked well on a cast iron flat lap for putting a really nice edge on a watchmakers lathe graver, other than that have not used the stuff as I had planned.

Lee Valley Tools is stocking a couple different grades of diamond paste now, if you don't want to buy from overseas.

Cheers
Trev
 
There's a Lee Valley near work. I have some lapping compound I bough at Crappy Tire, but the fine is still pretty coarse (280 grit).
 
kombayotch said:
There's a Lee Valley near work. I have some lapping compound I bough at Crappy Tire, but the fine is still pretty coarse (280 grit).
Click to expand...

Yeah, try the diamond then. They sell it for the guys that want to put stupid-scary sharp edges on their funky alloy plane irons.

Maybe take a look at the richontools site, and put a cheap order together to see if you are happy with their stuff. They sell diamond powder, as well as polishing pastes, and a huge array of polishing bobs and the like that otherwise would kill a fellas budget if he was buying the stuff here in Canada. Worth a look anyways. A bud pointed me at them. I have read good reviews, but have not dealt with them yet. <shrug> Can't spend money everywhere, eh?
At a buck and a half a tube, rather than $13, it looks worth a try.

Cheers
Trev
 
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