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How to... internal threading/grooving

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scattermaster

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#1
Hey guys,
I'm taking my 1st crack at making internal threads. This time It's about a 2" ID roughly in aluminum. I'm making a 16 TPI thread.
I will need to make a groove to give the threading tool a place to stop.
Is there a boring bar with tooling that will make those?
I don't need to go very far in (about 2.5") but in the future I think I'll want to go deeper.
??
 

Tony Wells

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#2
Good for you!

If you are asking about inserted tooling, yes groove bars are made for that and should be used to cut an angular thread exit, usually a 45°.

On the other hand, a HSS holder type bar can be used with the appropriately ground groove tool.

You may find groove bars priced seemingly high.
 

Dave Paine

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#3
As Tony stated, special grooving bars can be expensive.

The HSS boring bars with right angle bend mentioned by Tony are readily available, just need to grind the end to width of the groove.

Another option is a double ended bar which can use inexpensive 1/8in square HSS cutters. An example from Grizzly, but this style is available at many locations.

I have one of these. The only issue I have is that the cutter tends to slip. Small set screw is not able to apply a lot of pressure, so light cuts needed.

Double ended boring bar
 

Charles Spencer

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#6
I use a high speed steel tool bit in a boring bar to cut a groove for a blind internal thread. You can make one yourself.

boring bar.jpg
 

P. Waller

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#7
Set up P.H. Horn internal groove tool this afternoon for parts that will run tomorrow.
Retaining ring grooves in a .985" bore 1 1/2" inside, this bar will go 3 1/4" deep.
internal groove tool.jpg
 

epanzella

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#10
If there's no particular dimension required for a relief groove I just use the threading tool. I plunge it in and hand feed it back and forth about .125" to form the groove. It's quick and uses the same depth setting as the thread.
 

rock_breaker

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#11
Nice job Scattermaster, you just passed an important milestone. Follow Kd4gij's instructions for use.
Have a good day
Ray
 

scattermaster

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#12
If there's no particular dimension required for a relief groove I just use the threading tool. I plunge it in and hand feed it back and forth about .125" to form the groove. It's quick and uses the same depth setting as the thread.
hmmm, that'ed be too easy!
I never even considered doing that. I would have thought it would break the insert.
Now I gotta go back and try it out.
 

magicniner

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#13
hmmm, that'ed be too easy!
I never even considered doing that. I would have thought it would break the insert.
Now I gotta go back and try it out.
It works fine, plunge the groove first to full thread depth, then cut the thread in your chosen way.
I use Iscar's recommended cutting speeds and depths for my Cham-Groove kit.
 
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