Making an Aloris AXA Toolpost Tool Holder

by John

Finished tool holder - click image for larger view

I recently had a project where I needed to bore a deep and large diameter hole in some hard steel. The problem was that our boring bar holders were meant for 3/4" shank boring bars and 1.25" boring bars. Our 3/4" boring bar wasn't long enough or stiff enough, and the hole was too small to use our 1.25" boring bar. However, we had a nice 1" diameter boring bar that would definitely get the job done. The solution: make a 1" boring bar holder for the Aloris AXA toolpost on our lathe. Normally, you would want steel for something like this to reduce flex and wear. We didn't have any handy at the moment, so I used a chunk of 6061 Aluminum. I figured the aluminum would work fine since it won't be used very regularly (and boy was I right).

The first step is to cut the block to size, making sure all sides are parallel in the proccess. For this project, making everything perfectly parallel isn't the most important since it will be for a boring bar holder. However, if you wanted to use it for holding reamers, you would definitely want all faces perfectly parallel.
	In order to do make the stock parallel, you must make sure to debur all edges after you surface each face. Then machine the face that is exactly opposite to the one you just cut. Repeat for all 6 sides.
After the block is square, lay out where you want the boring bar to be held, making sure to leave room for the dovetail and plenty of material between the hole and the dovetail. You will also need enough room on the other size for the fasteners which will be used to apply clamping force.
	Here's a test fit w/ a 1" shanked tool after the hole was drilled.
Next step: Drill 3 holes for the fasteners. In this case, I decided to go with 1/4" bolts. Also, I knew that I'd have to apply a large clamping force to keep any of the tools from twisting, so I was hesitant to rely on taping the aluminum.
	My solution: just drill through holes and use through bolts with nuts on the other side to apply the clamping force. You will want to drill the holes slightly oversized, because when clamping force is applied, the ends will want to bow inward, misaligning the holes (remember, there will be a slot cut here).
If you want to use a height stop like the standard Aloris tool holders, you will need to machine a shoulder into the block. Most tool holders are only 1.5" tall, and this one is 2" tall, so to keep the same height adjustability, 1/4" shoulder was needed. When the shoulder is milled, drill and tap it for the thumbwheel. (3/8"-16 if my memory serves me).
	Next step is to use and end mill to make a u shaped profile where the dovetail will be.
Now machine the dovetail. The Aloris toopost uses a 60 degree dovetail, so make sure you buy the 60 degree cutter, not a 45. The width of the dovetail is extremely critical in making sure that the tool post clamps onto the tool holder with enough force, so make sure to get the dimensions correct. Use an existing tool holder to copy the exact dimensions.
	If you are also doing a 1" tool holder, it should look like this so far.
This is the last step, cut a slot in the end!
	Since this was aluminum, and I didn't want the tool holder getting damaged when it gets thrown around the shop, I decided to anodize it which will help a little with durability. If you want to read more about anodizing, click here.
So how did it work? On heavier cuts, the Aloris tool post could be seen flexing and the boring bar never slipped. Nor did the tool post deform/break. Some more finished pictures are below:

Back to Completed Projects...