Author Topic: Make your own 60 degree lathe insert holder --  (Read 2573 times)

Offline goodfellow

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Make your own 60 degree lathe insert holder --
« on: June 19, 2010, 10:45:30 AM »
This one takes a bit of time but it's worth it. Brazed ceramic inserts are too expensive, while honing HSS takes too long when doing roughing and general machinig work. Here's a way for you to buy cheap TNMA inserts from e-bay and never have to worry about cutting tool costs again.

I'll try to show how to make a 60 degree straight roughing cutter, and in a follow-on thread also make an offset RH cutter

I started with the following items:

1) 3ft.  1/2" square steel bar from Tractor Supply -- $6.00

2) TNMA-333 inserts bought bulk on ebay -- got 100 of them for less that 25 cents each

3) Some 5mm hardware for mockup

First i cut some 4" blanks from the steel bar and machined the ends square

Next take an insert and use a carbide scribe to marke the outline of the pocket

These TNMA inserts don't have a rake to them (that's good). The second letter "N" indicates "no rake" and that means that these inserts will have a total of six useable cutting edges. However, for accurate cutting, a rake (or offset) is needed; hence I'll have to machine a rake angle into the holder. This isn't "rocket science", any rake angle from 4-8 degreees should be ok!

I opted for a 5 degree rake since it's easiest to read on an angle finder.

Here it's positioned in the viise

Mill the depth to the approximate thickness of the insert --

Use a loose insert to check fit --

Once it's machined to size, run the bit thought a wire wheel on the bench grinder to deburr it, and it should look like this --

Mark the insert for a screw hole with a center punch (use the insert itself as a template), and clamp the holder in the drill press vise at a 5 degree offset (so it will sit square) to drill a hole.

Do a little hand fitting with a file to make sure the insert fits tight.

Now mark the sides of the holder with the carbide scribe and mill both sides to 30 degrees

Here is the finished product --

Please note that I used this cheap nut and bolt for mock-up only. I will get a proper grade 8 capscrew this week. I used a nut to secure this insert because I have found that even if I tap these holders, eventually they will come loose and the threads will strip. With this method, I can just replace the capscrew and nut when they get worn from stress. 

Here is our new holder compared to a brazed bit -- ours is stronger, lasts longer, costs pennies and will last forever.

Next thread -- a RH bit holder.  Enjoy!!!!!!

Offline cegreen

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Re: Make your own 60 degree lathe insert holder --
« Reply #1 on: July 13, 2010, 01:05:12 PM »
When did you buy those Kennametal inserts?  That price seems unbelievably low. 

At the moment, the cheapest I could find them on eBay is 10/$22.00, or $2.20 each, and that seems like a pretty good deal.

I'll bet the seller's helper in the shipping dept. mistakenly thought that 10/$25.00 meant 10 boxes of inserts, not 10 inserts.  If so, you got quite a deal!


The Garage Gazette

Re: Make your own 60 degree lathe insert holder --
« Reply #1 on: July 13, 2010, 01:05:12 PM »