Internal thread

R

rzw0wr

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I need to turn an internal thread.

It is a 1/2" thread. The tpi are not standard so I can not use a tap.

I made a boring bar for threading but it keeps flexing. The hole is 1" deep.

I can not find a boring bar small enough to fit into the hole.

Any ideas on how to thread this hole.
 
They do make insert bars that would fit into that bore . If it was a blind bore , I'de be threading out .
 
It is not a blind hole. Who make a bar that will fit the minor dia. of a 1/2" thread?
 
What material are you threading? You can make a threading tool out of HSS pretty easily. I have had good luck using broken drills as long as I am not working with anything really hard. You can get as fancy as you want or need to make it work.

Turn it, grind it, whatever it takes to get there.
 
rzw0wr said:
It is not a blind hole. Who make a bar that will fit the minor dia. of a 1/2" thread?
Click to expand...

Much depends on the depth of the hole so you need to give us that. For a 1/2" deep hole, I would personally use a3/8" diameter inserted carbide tool with a carbide shank that will let me go 3.75" deep. Micro 100 also makes solid carbide threading tools that will work really well. You can also turn down a piece of tool steel with a 60 degree profile on the end and grind half of the tip off to make your own tool. You can harden and temper it easily in your home shop.
 
Here’s one I made in a pinch from an old tap. Obviously the plus-side is that the 60 degree point profile is already done for you, you just need to make the rest of the teeth disappear and give a bit of clearance. Lots of ways to do it, pick your poison.

-frank

27198290-FF27-43C5-A756-D410D4CF8E90.jpeg
 
I have a boat load of them from Manchester , TopNotch etc . I just located them down the basement looking for something else .

rzw0wr said:
t is not a blind hole. Who make a bar that will fit the minor dia. of a 1/2" thread?
Click to expand...

That's a big one ! ;)
 
My Carmex 3/8" internal bar that uses 11IR inserts will thread a 1/2 hole. 1/2" hole is the smallest I thread with it. But the clearance is tight so have to be careful when backing it out. I use my DRO to keep track of it so luckily I've never had a mishap with it. There are better options though for more comfort. As MIke suggested, Micro100 is a good choice. They make quality tools & I like them.

(Yeah I know my bar is mounted upside down, don't mind that, that's just how I use internal threading bars :big grin: )
20191024_233015.jpg
 
darkzero said:
(Yeah I know my bar is mounted upside down, don't mind that, that's just how I use internal threading bars :big grin: )
Click to expand...

Back in my cnc days , I always ran the slants upside down . The machines were limited to the distance over spindle center . The machines didn't mind at all . Just a M3 code vs. an M4 code ! :big grin:
 
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