Angle Grinder Spindle Adapter

Created: January 3, 2014
Last Revised: October 19, 2023

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About the Spindle Adapter

I have several small angle grinders. Some have 5/8-11 spindle threads and some have 10 X 1.25 mm threads (about 3/8" diameter). In addition to handling the 10mm disks and wheels they are designed for, the flanges and lock nuts that come with the small-spindle grinders are designed to center disks and wheels that have 5/8 inch holes, so that's no problem.

But, there are times when I want to use 5/8-11 threaded flap disks or wire wheels on the small-spindle angle grinders and that simply won't work.

So I decided to make my own removable spindle adapters.
Angle Grinder with Spindle Adapter installed

After I made several of my own design of adapter, I found that commercial adapters are available for between about $4.00 to $10.00 US.
The adapters that I have seen for sale look like a short 5/8-11 bolt with a 10 X 1.25mm tapped hole through the center.
I'm sure that will work fine, but since there is a head on the "bolt", the wheel will be held a little farther away from the body of the grinder.
Commercial Angle Grinder Spindle Adapter
See Ebay or just google "angle grinder spindle adapter".
If you want to go that route, read no farther.

Anyway, my adapter is simply a .400" long internally and externally threaded tube that screws over the existing spindle. It has a slot in the outward end that accepts a homemade slotted "screwdriver" for removal.
Spindle Adapter showing threads

Making the spindle adapter:

I made my mine from a 5" long 5/8-11 bolt. As you know, a bolt this size generally has only about 1 1/2" of threads.
Bolt Used to make spindle adapter

Here's the process I used to make the adapter:

I chucked the bolt in the lathe with the threads facing outward. The unthreaded part of the bolt was long enough that the jaws of my chuck didn't touch the threads at all so I knew I'd have the piece well centered.
-Face the end of the bolt
-Center drill and drill a 0.339" (R) diameter hole into the bolt. This bolt only has threads for the first inch and a half or so.
So I drilled as deep as the threads went plus a half inch. I don't think my tap had enough threads to tap the whole 1 1/2", so I had to retap as I cut individual adapters off the stock.
-Chamfer the hole
-Thread the hole (10MM X 1.25 tap; this thread is NOT the more standard 10MM X 1.5 size)
-Part off at .400 inch.
-Saw a slot about 1/8" deep in one end with a hack saw
-Widen slot to about .070" with a jewelers file
-Clean up threads in saw cut area
-Chamfer external threads

After making one adapter, I still had threads left on the bolt that was still in the lathe, so I made two more of these adapters before I ran out of threads on the bolt.

Screwdriver or "key" for removal of adapter:

Spindle adapter with wrench
I simply marked out a 2" long 3/4" wide "key" on 16 ga. steel and cut it out, filing the notch in the "blade" to final shape.
I drilled a 1/4" hole in the handle end so I could hang it on the hooks where I keep my extra flanges and lock nuts.
Looking back, I could have made the handle in the shape of a skate key.

Summing it up:

The nice thing about this style of adapter is that it doesn't change the geometry of the spindle at all. You do have to remove the guard in most cases, to use the threaded wheels however.

Note about Spindle Threads

Just a couple of days ago I needed a cup wheel for an angle grinder. I went to the Fleet Farm store in the area and found that they had them in both 10MM X 1.25 and 10MM X 1.50. I couldn't remember which thread I needed so I guessed and bought the 10MM X 1.5 cup wheel AND IT FIT the grinder that I wanted to put it on!!!
This means that I have some grinders of each thread; and, when I made those adapters, I picked a grinder with the other thread to design around. So, now I need to check all my grinders (just 3 other ones) to see how many of each I have.
And then, of course make at least two of the 10MM X 1.5 size.

The moral of my story:
First find out for SURE which thread you have on your grinder's spindle.
Then, either make one yourself, or google "angle grinder spindle adapter" to find one for sale.