Tapping Threads in Aluminum Spindle

Today I will show how I tapped threads in a Aluminum Lawnmower spindle.

My Riding lawnmower spindle broke and I bought a replacement one, but it comes not threaded. So I will try and show the process of tapping out the threads.

Note: my holes are already drilled, but if they aren't, you will need to drill the holes according to your tap size, be sure and check the chart for your tap size.

I have also included a video, showing how to tapped threads in a Aluminium spindle for a lawnmower.

You will need:

A Tap and Die set

Clamp or Vise

Dial Caliper or other measuring device

Cutting Oil (Optional)

First you need to know the size of the bolt diameter, I measured it with a pair of Dial Calipers. It measured .305 thousandths of a inch. I then checked the chart and found that it was close to 5/16".

Then we need to find the pitch of the threads or TPI ( Threads per Inch). Using the gauge that comes with my Tap & Die set, I found hat it was 18. You use the gauge to find the one that matches the threads. So now I know that we need a 5/16" Tap with a pitch of 18.

I then clamp the new spindle into my Vise as shown.

Using the Handle that comes with my Tap & Die set, I inserted the tap and tighten it. Now gently start the tap in the hole, holding the tap as straight as possible. Slowly turn the tap clockwise for about a half turn then turn counter clockwise. Repeat this process until you are done.

Note: Don't try to go to fast or try to cut to much at one time. Work slow and steady.

Check out the video that I uploaded for more detail on the process

Now that you are done, your bolt should thread into the hole easy, if it doesn't, take your tap back thru the hole. Just repeat process for all holes. Thanks for checking out my Instructable.

Then I install the bearings from the old spindle and put it back on the lawnmower, it worked fine.