Dremel Holder

A month or two after getting my Mini, I started wondering if there was a way to attach my Dremel to the tool post so I could use it for grinding, polishing or maybe even cutting key-ways or splines. Somehow a ground finish really makes a job beautiful and precise, which works with my sensibilities.

Of course, Little Machine Shop had a couple of options. One is an actual tool post grinder that replaces the compound rest. It is quite large; for straight grinding I think it would be great. The other was a rotary tool mount for the Proxxon rotary tool. A cool idea but felt the rotary tool would take a lot of travel on the compound rest, minimizing the stock sizes you could work with. I also found a holder for Dremels' on the web...again I think it takes up a lot of travel.

My Dremel is a few years old now (a 400XPR), but again the body is pretty large compared to the mini. Luckily, I also have the flex shaft for it and it's a much smaller diameter and it doesn't use an odd-ball large thread, on the nose of it.

This is what I came up with in a few hours, on the fly. The mounting tool was easy to build and tucks in pretty well to the holder.

The Dremel hangs on a bungee from a hook on the ceiling so the flex shaft has a nice arc into the tool post, and the switch is easy to reach.

Here are a couple of pictures of the actual mounting tool. It's made it from 3/8" aluminum plate because I didn't have a piece of 3/8" steel plate in the bin. The tool post part is 3/8" square. It is about 3.25" long with the holder part about .88 square. To pretty it up some, the radii on the corners were done on the disc sander. The threaded hole is a 1/2-20 for mounting the flex shaft head.

The threaded hole is centered in the square end, so adjusting the holder to get it on center line of the chuck is necessary. This was done to leave plenty of material (AL) to support the shaft head equally around, during operations. After trying it, I found it's not really an issue. The real issue is a little flex in the plastic shaft head and its end bearing.

So far it's been used successfully with grinding stones, rubberized wheels, buffing wheels, sanding drums, and various cutting tools. Over all it works pretty good on brass and steel. However using the stones on aluminum is not good because the wheel can load up, overheat and explode...not a good thing! (Imagine exploding rocks at 8,000 rpm.) I've used it on mild steel and the stones and the sanding drums do work well.

I also took one of my broken carbide circuit board drills and made it into a scribe point by grinding with a stone at a 15° compound angle. That was slow going and worked but pretty much ate that stone. I always save these carbide tools and use them for various things using a grinder to get what I want...so this is a plus on the Mini.

Side milling with a burr was not as successful, primarily because of the burr/end mill I had, and the flexing of the spindle in the head...not the holder or the post. You have to make shallow passes and many of them to cut a key way or a flat. I have a couple of ball mills but haven't tried them yet. The other thing about side milling is indexing the chuck and locking it down. I've been thinking of a way to index it and found a few things on the web using an index plate on the gear end of the head stock, but none look appealing yet. When a simple, elegant idea comes up, I will post it.

Here are a couple of pictures of the two ways it mounts.

About speed for the Dremel and the lathe: mid-speed on the dial of the Dremel works best. I am guessing it's around 8-10k but haven't measured it with the laser tachometer. In the top picture just above, you can see the reflective tape on the chuck I use for this. These little, inexpensive tach's are great for checking all kinds of things around the shop. I don't check the lathe much anymore because I now have a pretty good feel for the running speed based on the dial on the lathe controller. With the Dremel grinder I spin the lathe about 400-600 rpm depending on the material. Also you need to consider the diameter of the stone or wheel and the diameter of the stock, considering it a Gear Ratio to get the actual speed or probably more correctly the SFM...not sure how critical this is in the long run. It may be better to just find it empirically by the results you are looking for, with the materials and diameters involved. Sometimes it's easy to forget this is a Home Machine shop and I am a learning novice. ;-)

Overall this is a pretty good add-on to the Mini's tool kit and simple to make. It still needs refinement and maybe a metal, flex head attachment with multiple bearings to support the load. I also think rotating the tool post 180° for milling puts the cross slide a little too far out on smaller stock sizes. Maybe a right angle holder would work better, especially if you could position the head in several places along the run of the holder. It would make set up a little more complex but ultimately position the head where it works best...just thinking out loud...

I'll keep using it for a while to see about coming up with a design for something a little more simple and elegant for this wonderful Mini! If you like the design give it a try...it's pretty simple, just not elegant yet. 8-)