A Method to the magnets

Remember that the spirit of box modding starts with the simple act of re-purposing.

The Hammond 1550P Enclosure is well-known in the box modder community for its small size and tight fit.  The “P” is typically the last Hammond enclosure that an amateur box modder would be advised to work with as it is certainly one of the most challenging in the Hammond family.  Being able to work comfortably with 1550P is a test of experience, not mechanical ability.  For all of its flaws and constraints, the variety of exotic configurations I have seen done to this enclosure is impressive.  Successfully making use of one requires some patience and hopefully some creativity.

And then there was the lid.

While the 1550P has obvious size differences compared to its bigger brothers (1590G & 1590B) – the most troubling difference is one that is unseen.  The lid fitment has a lot more  side-to-side play not “fastened” to the box.

The matching machine screws do a great job of centering the lid over the enclosure when torqued down – but most of us are going to be using magnets for quick access, so we’re going to need a better way to center the lid.

There is also the issue of the guide rails/posts along the inside of the lid.  These rails can interfere with battery sled contacts, buttons, and locking nuts.  This would not be an issue if we didn’t need to fill every bit of space inside that box, but guess what?  Sometimes we do.  Therefore, let’s assume that the rails must go as well.

Again, the magnets will not only need to attract the enclosure to the lid, but will also need to be “guided” in a way that centers the lid on the enclosure and prevents lateral play.  Nobody likes a box mod that can’t keep its shit together.

A Method to the Magnets

Take advantage of consistent hole depth.  The depth of the threaded holes on any 1550P enclosure will always be the same.

Take advantage of consistent hole width.  Again, the factory holes are consistently and predictably sized.  There are three different hole diameters – two in the lid and one in the enclosure.  To fit magnets with the least amount of eyeballing or guesswork possible, we need to use multiple magnets sizes in each hole.  Three of them.

Magnet A: 1/8″ x 5/8″ Cylinder (K&J Magnetics D2A)
Magnet B: 3/16” x 3/16” Cylinder (K&J Magnetics D33) OR stronger (D33-N52)
Magnet C: 1/4″ x 1/16” Discs (K&J Magnetics D41) OR stronger (D41-N52)

Tool X: 1/8″ High Speed Carbide Bit (Dremel #9901)
Tool Y: 3/16” to 1/2″ (Amazon #2, 6-Step Bit) [exact brand is unimportant]
Tool N: Rotary Tool & Drill (or Drill Press)


The 3-Point Method


I strongly recommend Drilling BEFORE painting.  Wear eye protection.

1. Using a 1/8″ Carbide Bit, Bore the 1/8″ diameter holes until magnet A can easily slide into the bottom of those holes without any interference from the threads.  The goal is to widen the hole by deburring its threading.  Do NOT deepen the hole.  The Dremel Attachment does the job perfectly with the right amount of speed and the right touch.

2. Drill the top of the same holes with the 3/16” step bit, this is where our 3/16” magnet B will go.  If you’re using the step bit that I specified, it will come in handy when we move onto the lid.  This hole needs to be deep enough for magnets A and B to touch.  You can overshoot the depth of the hole and the magnets will still be the correct height because they are resting on each other.

3. Now, from the outside of the lid, use the same step 3/16” bit and slightly bore out the inner hole by drilling from the outside.  This should only widen the inner diameter.

4. Finally, use the second “step” of our bit and begin drilling a 1/4″ hole from the outside of lid to fit the outer 1/4″ magnet C.  The 3/16” inner hole should help guide the step bit straight through.  Careful not to drill too deep here.  Over-drilling here will disrupt the inner hole we drilled earlier.  

Test fit all 3 magnets together.  Ensure that they fit in their respective holes with very little lateral play.  Notice (below) that even without the magnets epoxied, the lid wants to stay seated.

5. Once satisfied, epoxy enclosure magnets A first, followed by outer lid magnets C, then finally magnets B on the inside of the lid.  I typically epoxy magnets C and B at the same time.

The Result

Things to Consider

The 3-Point method only requires 2 corners (diagonally from each other) to be effective.  This is helpful for many of us who have to delete a corner post to make room for parts.

In some cases, it can be advantageous to substitute or omit magnets on 1 or more corners

1. Use a longer magnet A 1/8″ by 3/4″ (D2C) in one corner (which will now sit flush with the enclosure) to create an orientation lock for the lid (top vs. bottom).

2. Use a spherical magnet B 3/16” (S3) in one corner to allow easy lid removal by rotation from a single pivot point.

The combined magnetic force of 3 axial magnets in 4 corners of a box is extremely strong (especially if using N52 grade).

1. As a side effect, this will cause the reverse side of the lid to attract the reverse side of the enclosure.  I like this because it keeps the lid and body together when replacing batteries.

2. Another idea is to alternate magnet polarity from one corner to the next, which will force the lid to attract and repel as it is rotating.  I’m not a fan of this.

3. Consider adding vent holes to your box.  There IS a such a thing as a lid that is too hard to remove and it is not necessarily a good thing.

Until Whenever,