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A Tailstock Crotch Center for the Lathe

by Russ Harman

I started this metalworking project last winter because I have always thought it would be handy to have a simple way to cross drill round stock in my shop.  I had planned initially to send this to Tyler for publication but Mr. James Instone beat me to the punch with his fixture for drilling holes in round stock.  After seeing his version I finished mine and successfully used it to put tee handles in my new chuck keys.

Mr. Instone’s fixture seemed to be popular and well received and since he invited others to send in their version of the same idea, I decided to share mine.

Tailstock Crotch Center with Drill Guides - Free Metalworking Project

Tailstock Crotch Center - Side - Free Metalworking Project -

I have always considered drilling holes in round stock to be a time consuming bore.  It seems to take a lot of time and effort to find the centerline just to drill a hole. The process is great when it works but irritating as hell when slightly off center, which is often the case when I try to hurry and “eyeball” it. Then every time I look at something I’ve cross drilled off center I am reminded of my laziness. Hence the necessity for my tailstock crotch center.

The whole project is constructed out of steel from the scrap bin, as is typical for these types of projects.  The cap screws came from the hardware store and the #2 Morse taper arbor was ordered from Shars for $6 plus freight. Which I consider cheap for what you get, especially considering how much work it would take to grind an accurate arbor myself.  In fact, I ordered two additional arbors just to have on hand for future projects. Amazon also sells them for $8 with free shipping.

Tailstock Crotch Center - Complete - Free Metalworking Project -

By using the #2 Morse with ½”-20 threads as a base unit I can easily adapt this fixture to my lathe head or tailstock, mill with R8 adaptor, or drill press.

By taking out the taper and putting in one of the large cap screws I can clamp it in a vice, lathe chuck or collet fixture.

Tailstock Crotch Center - Back - Free Metalworking Project

By replacing the arbor with a cap screw the fixture can be used in a vise, lathe chuck, or collet.

I used long small diameter cap screws for securing the clamping plate to accommodate larger diameter material.

I also made a storage box for my new tool.

Tailstock Crotch Center Storage Case - Free Metalworking Project

The right hand side of the box contains four drill bushings measuring 1/8”, 3/16”, ¼”, and 5/16”.  For other odd sizes I can simply use the clamping plate without a bushing and use a center drill to accurately locate my hole.  I tried to think and cover all the bases to make the fixture as universal as possible so it was not just another box taking up space in the drawer.

 Making the Tailstock Crotch Center

The first item of business was to cut a 1” disk off a 3 ½” diameter piece of round stock.  I then placed the disk in my three jaw chuck and faced it off.  Next the part was center drilled, drilled through, and chamfered in preparation for the tapping operation.  After tapping to ½”-20 the Morse taper adaptor was screwed in and all other lathe operations were done with it in place.  I took the chuck off and put a #3 to #2 adaptor in place so it would fit the taper in the headstock of my lathe.  I then faced the second side and rough turned the diameter.

To make the clamping plate a flat piece of 3/16” stock was screwed to the face of the part, center drilled and a .050” relief machined for the drill bushings.  The edges were then turned down to match the diameter of the body of the crotch center.  Next I removed the piece from the lathe and after removing the taper and clamping plate I secured the body of the crotch center in a tilting drill vice at 45 degrees to cut the v-groves.  Both the deep and shallow grooves were cut using a 5/8” end mill.  I like using larger mills whenever I can due to the extra rigidity they offer.  The drill bushings were then turned from oil hardening drill rod I which always keep on hand.

Making the Storage Box

The box bottom is a 2”x6” that was squared up on a jointer.  The cutouts were made and the holes drilled to accommodate the included pieces.  Cutouts for the Morse taper were made with 1/2” and ¼” ball end mills.  The box sides were made from 3/16” mahogany wrapped around the base.  The lid was then glued on and after it set up, I flushed up the edges with an orbital sander.  The lid was then cut off the box with a table saw.

Tailstock Crotch Center Storage Box - Free Metalworking Project

I like making boxes this way as there are no dimensions to match since the lid is identical in width and depth to the base.  Just remember to work as if you are inside the box so you leave clearance for the contents.  Mount hinges, apply stain and varnish, and presto! You’ve got custom fitted storage box.

Boxed items are safer, more organized, and just plain look COOL!  After all, everybody likes to look inside a box for the treasure to be found!

Now get out there and keep the SWARF flying!

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About Uncle Russ

Retired electrical contractor. Really always wanted to be a machinist so I am self teaching and having a great time.