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Rotary broaching 316 SS Tooling Issues.

Jameshb

Plastic
Joined
Mar 25, 2019
Hi I'm having issues with forming this 10mm Hexagon hole. I had my cham drill go on me just fresh out the vend oops! This had ran around 150 parts before the insert went on the cham drill. The machining method follows with Spot drill, carbide 10mm cham drill. Bored to 10.25 mm diameter with a 6mm indexable boring bar TCMT 0.4 Insert rad, then rotary broached goes in and forms the shape. Then we go in with a second carbide insert drill to get rid of the horrible burr or petals as we call it in our machine shop then back down with the boring bar to remove the entry marks when the broaching tool is first leading into the hole.

We have switched to a 10mm HSS drill to remove the burr the broach pushes over in hope this should last longer and hopefully not wipe any tools out. After this incident I set up the tool load monitors on my roughing tools and drills.

I've thought about using and slot drill to help get rid of this material at the bottom of the hole, has anyone else got any suggestions or tips I'm new to broaching and new to the machining world and learned a lot of things on my journey so far and always looking to improve. The machine I'm running is a doosan TT1800SY and the tools are running with through coolant except the broach.
Rotary broach insert gone.jpgRotary broach 1.jpgCham Drill Rotary b.jpg
 

cnctoolcat

Diamond
Joined
Sep 18, 2006
Location
Abingdon, VA
Best to machine an ID groove at the bottom of the hole, this way your broaching chips have a place to go, and will usually break free.
Always provide a generous starting chamfer for the broach. And machine the hole as large as possible within tolerance.
Also the very end of your broaching tool should be indicated as close to centerline in X/Y as possible.
Good luck with it, 10mm is a pretty-good-sized hex to broach in 316!

ToolCat
 

wmpy

Hot Rolled
Joined
Dec 16, 2011
In your second picture, the chips at the bottom seem really packed in there. Can you drill your pilot hole deeper?

See here for some pre-broach hole recommendations.

Also, using a HSS drill instead of a carbide drill to clean out the chips at the bottom is a good idea. That's too abusive an application for carbide.
 

guythatbrews

Hot Rolled
Joined
Dec 14, 2017
Location
MO, USA
Since your cleanup drill is 10mm it might be stiff enough not to push off center in that nasty stuff at the bottom of the hole. But we use a 4 flute endmill with a small corner radius, maybe .020. Won't push off and lasts quite a while.

As mentioned, 10mm is pretty good sized in 316. Personally that big I shape the corners in. The parts have a relief groove at the bottom but it's not wide enough to allow petals to fall free so gotta shape.

Never have had reliable results with chamdrill in 316. We use solid carbide. Trashing a chamdrii is not cheap, and as you know can wreck subsequent stuff.
 

guythatbrews

Hot Rolled
Joined
Dec 14, 2017
Location
MO, USA
BTW make the pilot hole as big as you possibly can. Broach as shallow as your tolerance allows. Less material to push put of the way.
 

Jameshb

Plastic
Joined
Mar 25, 2019
Thank you for the replies everyone, the HSS has held up for over 1000 parts and hasn’t wiped any more tools with the Tool load monitor on the Cham drill.

Forgot password so sorry for late replies but will have to try the slot drill trick next time 😃
 
Joined
Nov 10, 2015
Location
Florida, USA
Hi I'm having issues with forming this 10mm Hexagon hole. I had my cham drill go on me just fresh out the vend oops! This had ran around 150 parts before the insert went on the cham drill. The machining method follows with Spot drill, carbide 10mm cham drill. Bored to 10.25 mm diameter with a 6mm indexable boring bar TCMT 0.4 Insert rad, then rotary broached goes in and forms the shape. Then we go in with a second carbide insert drill to get rid of the horrible burr or petals as we call it in our machine shop then back down with the boring bar to remove the entry marks when the broaching tool is first leading into the hole.

We have switched to a 10mm HSS drill to remove the burr the broach pushes over in hope this should last longer and hopefully not wipe any tools out. After this incident I set up the tool load monitors on my roughing tools and drills.

I've thought about using and slot drill to help get rid of this material at the bottom of the hole, has anyone else got any suggestions or tips I'm new to broaching and new to the machining world and learned a lot of things on my journey so far and always looking to improve. The machine I'm running is a doosan TT1800SY and the tools are running with through coolant except the broach.
View attachment 380351View attachment 380352View attachment 380353
Here is a our guide to part preparation:
If you need any assistance I would be more than happy to help. Just give us a call.
 








 
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