Bruce Caulley

Rotary broaching question.

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Ahoy!

 

I am curious to know if a rotary broach needs full engagement to operate correctly. The application I am thinking of is squaring out one end of a slot. If the slot is 10mm x 20mm could I in theory use a 10x10 rotary broach to square off one of the ends?

 

Thanks

 

Bruce

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I think the problem with a rotary broach is that you really have no control of the angle that it starts. When we rotary broach, its usually on a lathe or a mill where we are broaching a square, hex, or terx head onto a part. The part (lathe) or tool (mill) just spins at the required RPM and when the part and tool touch they engage and start the broaching process.

 

Maybe you could feed the tool into the part at 0 RPM, get it lined up and pressing into the part, close the door and hit start and have the spindle turn on and start the broaching process.

 

Thanks

David

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David,

I was thinking of using an allignment bar for that. One of the supplier websites shows how to do that, can 't remember which one. I just wonder how stable the "wobble" will be if the tool isn't loaded up evenly. It might be a good idea to email a supplier direct and see what they say.

 

cheers

Bruce

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Is there any way to rotary broach first and then cut the slot into it?

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Lining up the broach manually, and by using the rotary broach brake only set the starting position of the broach. Only the guide post and dog set-up guide the broach all the way to the bottom of the hole. This method might be necessary because of the slot.

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David,

Doh! Sometimes the obvious is right in front of you, thanks for that!

 

Polygon,

The post and dog was the method I had in mind.

 

thanks

 

Bruce

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One challenge with rotary broaching this part will be the pilot hole. There needs to be enough room in the hole for the chips to accumulate. I'm not sure if that will ruin the slot. Additionally, most pilot holes for rotary broaching are slightly oversized to create individual chips when broaching. The dog should still work, but you will want to think about where the chips will go after you've machined the slot. Hope that helps.

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