precision keeper cutting....

[Possum]

Anyone have thoughts on how to cut keepers to length precisely? I've been cutting them on a bandsaw and grinding on a disc sander to length, but I don't like this method and too time consuming. Is there such a thing as a precision cut off saw?

[Bruce Johnson]

Anyone have thoughts on how to cut keepers to length precisely? I've been cutting them on a bandsaw and grinding on a disc sander to length, but I don't like this method and too time consuming. Is there such a thing as a precision cut off saw?

It's about the same as the discussion we had on cutting off slugs here:
http://music-electronics-forum.com/t17411/

The ideal machine is something like my little Barker mill, a small tabletop horizontal milling machine set up with a slotting saw blade. It'll cut off any kind of metal bars smoothly to length, within 0.001".

There are other ways too, using a small standard milling machine or mill/drill.

Remember, when cutting metal precisely, you want a slow speed and a sturdy frame, and a little bit of horsepower.

[Possum]

....

Well, cutting slugs is totally different, you're cutting something on a lathe, you can't do that with rectangular bar stock. I do have a small mill but its vertical.

[JGundry]

Have them done for you and buy them 1000 at a time. There is no tonal art involved in drilling and cutting a keeper bar. Give a shop a sample and the metal specs. and have them make it. It is a dead simple part to make for a machine shop. Same goes for slugs. Gibson had the slugs made on an automatic screw machine anyway. Your time should be worth enough to make jobbing it out the best route.

[Bruce Johnson]

Possum;

Round or rectangular doesn't make a lot of difference. My little Barker mill is what I used recently to make up a couple of batches of custom slugs for guys on this forum.

You can also certainly cut off rectangular bar stock in a lathe using either a four jaw chuck, a special collet, or a two jaw chuck with machined jaws.

If you've got a vertical mill, that'll work fine too. Set up a little fixture in the vise jaws with an end stop and support underneath the part, and trim the end of the keeper to length with an end mill.

There are lots of ways to do the job.

[David Schwab]

I've been cutting them on a bandsaw and grinding on a disc sander to length

I thought you had one of those little cut off saws?

I cut my blades on a large abrasive wheel cut off saw. I use a wooden stop block for different lengths. I push the piece to be cut up to the stop block. They all come put the exact length.

This saw leaves a burr that I have to get rid of, so I use a belt sander for that. The whole operation is quite quick.

[StarryNight]

what about a metal hand shear?

Amazon.com: TD Industrial 5" Sheet Metal Shear Steel Aluminum Copper Hand…

[David Schwab]

what about a metal hand shear?

Amazon.com: TD Industrial 5" Sheet Metal Shear Steel Aluminum Copper Hand…

That sure looks handy! (No pun intended)

[Possum]

....

I'll try the lathe but I would think the sharp corners hitting the cutoff blade would wreck the blade pretty quick.
We got some bolt cutters last nite, does a crappy job on keeper stock, I assume a hand shear would make a mess of the ends too.....

[StarryNight]

I'll try the lathe but I would think the sharp corners hitting the cutoff blade would wreck the blade pretty quick.
We got some bolt cutters last nite, does a crappy job on keeper stock, I assume a hand shear would make a mess of the ends too.....

don't rule it out that quickly. keeping the part perpendicular to the blade should produce a clean, straight cut. It would also be quiet and fast. no personal experience with one. maybe someone can chime in who has.

[Diablo]

Shearing adds cold work to the metal, and that will certainly impact magnetic properties.....maybe tone too.

[Possum]

...

For sure, but pretty much ALL vintage keepers were shear cut on the ends except maybe some earlier PAF keepers, and definitely ALL modern keepers are shear cut on all four sides, which is one reason they are so cheesy...

[David Schwab]

Shearing adds cold work to the metal, and that will certainly impact magnetic properties.

How so?

[David Schwab]

For sure, but pretty much ALL vintage keepers were shear cut on the ends except maybe some earlier PAF keepers, and definitely ALL modern keepers are shear cut on all four sides, which is one reason they are so cheesy...

Yeah, a lot of them look stamped.

But what does it matter? You don't see the thing.

[Diablo]

How so?

When you deform iron (or any metal), you add dislocations in the crystal lattice. This increases the hardness of the metal because the higher dislocation density blocks the movement of free dislocations. The internal strain also blocks the easy movement of magnetic domains. This raises the coreloss and decreases the permeability. Magnetically soft iron (that allows easy movement of magnetic domains) is also physically soft. Soft iron for magnetic circuits is typically used in the unstrained (or annealed-last) condition.