Reaming metal cover holes

[Zhangliqun]

So I got a request for a Mini-90 with a metal cover. Center hole minihumbucker covers exist, but the only ones I can find have the true mini-size holes. What's the best way to ream them out wider for full-size P90 polepiece holes to keep the hole edges clean?

[StarryNight]

Perhaps look into some jewellers tools. Diamond coated or carbide burrs might do it. You might find a tapered or ball shaped one that is the exact width you want at its widest point. Not chipping the plating is the challenge.

[galaxiex]

Would a step bit work?
They are meant for cutting clean holes in thin materials.



There are many different kinds....

https://www.google.com/search?q=step...w=1920&bih=937

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[nevetslab]

Years ago, I invested in Taper Pin Reamers. They start at size 7/0, which ranges from 0.0497" dia to 0.0666" dia, have square end to fit a tap wrench. I've provided a link to the list shown at McMaster-Carr which covers sizes 7/0 thru 14, which starts at 1.25" dia to 1.542" dia. I mostly use sizes up to #8, which ranges from 0.3971" dia to 0.505" dia. I bought them on ebay over a number of months, as the cost new is astronomical. Great tools to have, in addition to a full number & letter drill set, along with fractional size drills. As the size of the reamer grows, you need increasing sizes of tap wrenches to drive them. They also work well in a variable speed drill, though I generally use them with a tap wrench.

https://www.mcmaster.com/taper-pin-reamers/

[David King]

A tapered reamer for sheetmetal is a very inexpensive item that used to be sold at every Radio Shack. https://www.amazon.com/Military-Port...qid=1596405041

[Mick Bailey]

The downside of a tapered reamer is it can cut polygonal holes in sheet metal. It all depends on the number of flutes and the material being cut. With thin metal you can get a hole with as many sides as there are flutes.

[Helmholtz]

So I got a request for a Mini-90 with a metal cover. Center hole minihumbucker covers exist, but the only ones I can find have the true mini-size holes. What's the best way to ream them out wider for full-size P90 polepiece holes to keep the hole edges clean?

Do you really need to sink the screw heads into the cover?

[nevetslab]

The downside of a tapered reamer is it can cut polygonal holes in sheet metal. It all depends on the number of flutes and the material being cut. With thin metal you can get a hole with as many sides as there are flutes.

If we're talking 10mil thin material, then that is a potential risk. You'd have similar issues using a twist drill. When I've had to open up holes in thin material, using a Taper Pin reamer of suitable size, I've had to add an additional piece of sacrificial material having the same starting hole dia, clamp it into position so the two pieces are acted upon by the reamer to prevent that shape distortion. I've had excellent results with the Taper Pin reamers over the years.

An alternative, which was mentioned above, is using a tapered Carbide burr. Typical shaft dia on those I have are 1/8" dia, which chuck into my Foredom hand piece quite find. I do have larger 'cone-shaped' burrs on that same shaft dia, though now you're cutting a more noticeable cone-shape into the material unless it's real thin material.

[David King]

You can use a single flute tapered reamer to keep the holes round. These are used in violin repair but only to cut wood so don't expect some one to lend you theirs for this job.

[Bloomfield]

A straight-flute drill would be worth a try. The single flute will help keep the hole round, and the lack of helix will stop it from grabbing. https://www.mscdirect.com/browse/tn/...navid=12106212

[Magnut]

Chucking reamer, preferably one with a pointed tip. Works great. I did it for years. You may to step the sizes up to what you want. One or two steps should get you there.

[Possum]

Step drill would be your best bet I think. Make a block of wood that sits solidly inside the cover first, so you have support otherwise you'll tear up the cover.

[RedHouse]

Use a punch.