How can I reduce the diameter of a 4" metal disc?

[frule]

My wife has a craft project going, where she has a few 4" metal discs (perfectly round steel discs, about .040 thick). I need to reduce the diameter slightly from 4" to 3.75". It needs to be fairly accurate. I don't have any metal working tools, but have a shop full of woodworking tools, bench & angle grinders, etc.

One thought I had (don't know if it will work), is to drill a hole in the center of a disk and insert a bolt tightened with a nut to the disc so I can chuck it in my cordless drill or drillpress. The spin it against an abrasive...or spin against my bench grinder.

Any easy way to do this?

Thanks!
Fred

[JGrout]

take it to a fabricator and have them punch them the correct size//////

that is by far the simplest, most accurate and will waste the least amount of time

[Alaric]

JGrout said:

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Go to a fabricator and have them punch three new ones that are the correct size//////

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Fixed, punching new ones that are the right size may be cheaper as it may require less set up time and labor. Ask the fabricator.

[daddo]

Do the hole, set it up in the drill press and while it is turning, use a hand grinder on it.

OR

Place it in the wood lathe and do the same.


Doing it from a hand drill won't work as it will bounce around too much.

[Dennis Puskar]

I have to agree with Jgrout much easier and safer this disc is only .040 thick.

[daddo]

What ever happened to do it yourself?

Why do we have tools?

This is quite safe, I've done it before with 18 gauge metal. Just use common sense and eye protection and go slow.

You learn nothing if you don't try.

[JGrout]

perfectly round steel discs about .040 thick)

I suppose he could go buy his own punch press

but what do I know

[frule]

Thanks, daddo. I want a diy way to do these. I'll try the drill press.

Another thought was to mount them on a "jig" that I can slowly move closer to my bench grinder.

[DogwoodTales]

Maybe use carpet tape to adhere a block of wood to them with a hole drilled at/near center to guide/spin it on a pin to a true circle - slowly feeding it on a set up on your D/P or grinder.

[bottd]

You said that you had a few. If you are talking just 5 or 6 or less I would do them all at the same time. Drill a hole in the center and then bolt them all together maybe sandwiching them between the largest fender washers you can find. Mount the assembly in your drill press on the lowest speed and see what happens. The hardest part in my mind is coming up with a way to keep the edge square as you grind or file.