High Speed Cut Off Saw attachment for your Milling Machine

[rbertalotto]

I've been using a Dremel MotorTool attached to the quill on my milling machine for some precision cutting of CZ-527 Magazines ( www.rvbprecision.com ). Although the Dremel is acceptable, it is very under powered and take too long to make the cuts I need. A more powerful motor is needed.

I went by Horrible Freight and picked up a Rotary Saw. Price was $24.95 and they gave me 20% off and a free pair of work gloves! I'm not sure how they can offer such price points and still make a profit.

This is the saw I purchased:

I had to cut the top handle off so it would fit on the adapter I welded up to mount it to the spindle on my milling machine.

When I got it home, I installed the 1/8" collet and my cut-off wheel arbor to see how true it might spin. Once again, you get what you pay for! It was terrible. The arbor is about 1" long and the run-out at the end was nearly an 1/8"!. Totally unacceptable.

Try as I might, I couldn't get it to run true. I mounted the Rotary Saw in my milling machine vise and put an indicator into the bore of the collet chuck. It ran very true. About .001 TIR. This was good news. Upon inspection of the collet nut, I could see the hole was drilled off center by about 1/32". This was the cause of the run-out. I attempted to true up this collet nut, but even the threads were off center. The only true area was the inside of the main shaft.

So, on my lathe I made a new mandrel that would register on the inside of the shaft. I made it a very tight fit and turned the end to fit into the bevel of the shaft.

I then took the collet retaining nut and turned the inside face to simply hold the new mandrel in place. It wouldn't be indexing anything, just holding the mandrel into the main shaft.

Once mounted up I still had unacceptable run-out. So I turned the center section of the new mandrel so it wouldn't touch the sides of the main shaft. I'm not sure why, but this worked great! Once installed TIR was .002.....plenty good enough!

All set and ready to do some precision cutting!

Here is a video of the tool running. As you can see, I'm using a Dremel MotoTool speed controller which works very well with this motor.

http://public.fotki.com/Rbertalotto/machine_tool/milling-machine-spi/p1020533.html

 

[Eddie Harren]

Ever heard of a slitting saw?

 

[Samdweezel05]

That's alot of work. What happens when the cutting wheel diameter changes over the course of the cut? I guess if the depth of cut isn't your goal then your all set. I would also have to worry about the "flex" of those cut off wheels.

 

[rbertalotto]

Slitting saws will not touch the hardened steel that a rifle magazine is made from. I've been modifying a particular magazine and trigger guard for the Cz527 for years. I've done over 170 of them. They are very hard but thankfully thin material. The dremel has worked well, but just to slow. This new motor cuts like butter.

As long as the wheel runs true, there is no flex to worry about.

 

[jonbearman]

Ever seen a slitting saw explode trying to cut heattreated metal.They work lousy on cold rolled.Great for slotting screw heads on home made screws though. Bob is a great crafty guy.Lets learn from him.Give him credit where credit is due.

 

[Eddie Harren]

Jon, His credit has been extended to an unlimited status. Mea Culpa!

 

[Clark]

I too was disappointed when high speed steel and Cobalt would not cut Beretta magazines to put a 92S magazine release slot in a 92FS magazine.

I had to use carbide.

I am big fan of Roy's posts. He is just like me, but a couple years ahead.