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View Full Version : Making a gib - step two



rohamm
12-24-2009, 08:26 PM
I slid the table off my 'new' Millrite MVN and found the x-axis gib busted up into three pieces.

I swang by the local foundry today - Nashua has the only one left in the state of NH - and picked up a rectangular bar that's plenty big enough, so step one has been achieved.

Step two is making a tool to cut the beveled edge. A DNMG insert nestles into the table's dovetail perfectly, so that's my weapon of choice.

I made a dovetail cutter using a triangular insert and have made a few Axa toolholders that fit better than CDCO's, so I figured I'd make a chamfering tool for this project.


My question concerns the carbide grade. I have a package of new Kyocera cr600 inserts I picked up for ten bucks. At 25 cents per edge, I'm not concerned about going through them too quickly, but I wonder how satisfactory the cut will be on gray cast iron.

The new owners of the Millrite brand - DC Morrison Co. - have gibs in stock for two hundred bucks, but you don't get bragging rights for just reaching into your wallet. Hence my cockamamie idea for making my own. When that doesn't work, I can always buy one.

In the meantime, what is the considered wisdom of the group?

Dick Hamm
Nashua NH

Black_Moons
12-24-2009, 08:44 PM
Iv heard cast iron cuts pertty well reguardless what you use to cut it with due to its high graphite content acting as lubracant (Much like the lead added to make free machining steel)

I mean im sure you can find tools that won't cut it well, but those are likey the same tools that say 'Great for aluminum/plastic and other materials as soft as butter'

Give it a go and see how the finish is, you likey have many cuts to make before your finishing pass that you can expairment with to get the right surface finish.

rohamm
12-25-2009, 09:29 AM
It occurred to me during the night that I should be less concerned with the insert's carbide grade than its negative rake.

I know Gadgetbuilder built lathe toolholders employing negative rake inserts for a home shop lathe. He chose inserts with a chipbreaker that simulated a positive rake. I wonder if that approach would work for a chamfering milling cutter.

Black_Moons
12-25-2009, 09:44 AM
Negative rake cuts. I know its weird idea but it does. likes to run really fast though.