Internal Threading Bar

[Sandia]

Need some advice here you guys.
I have a part I need to thread internal to 1X14TPI. The part is just a little over 1.5"long. I do not have any internal threading bars and would like to use an indexable bar with a lay down insert. I don't want to sale the farm to buy one, so what do you guys use and what would you suggest.

I have read a little about them and little stumped on inserts. Some are advertised as full thread and some as partial thread. What would I want to use ?

Even thought about just making a bar and grinding a 3/16 tool. I guess a square tool in a round hole with a solid set screw would hold the tool in place.

Educate me here guys?

Thanks, Bob

 

[BGHansen]

I have one of the Shars internal threading boring bars pictured below. Runs around $38 + shipping, includes 1 insert - model # 404-2290. Style is 16 IR A60 or 16 IR AG60. Hit eBay for more inserts instead of Shars, you can get them for under $3. There's a picture below of it threading a piece of stainless.

By the way, make sure if you buy one of these bars you get the right sized inserts. 3/8" inserts are 16 series, 1/4" inserts are 11 series. The lettering after 16 or 11 should be IR for internal RH threads (E for external, L for left-hand threads). An AG60 insert is good for threads from 8-48 tpi, A60 is 16-48 and G60 is 8-14 tpi. They also sell them with UN suffixes; number in front is for that specific tpi. For example, 16 IR 14 UN is a 3/8 internal RH thread 14 tpi. 11 IR AG60 is 1/4" internal RH 8-48 tpi insert.

Bruce

 

[T Bredehoft]

Home made internal threading bar.... You can use a broken tap or center drill, (round shank/round hole) with a set screw to hold it. Don't have to use a square shank tool.

 

[Bob Korves]

You could make an internal bar from an ordinary HSS tool blank, would need to be a longer blank and would take considerable grinding to fit in your hole. I bought a bunch of tool bits used, already ground, for cheap. It is easy to dress them as needed. Your idea of using a boring bar type tool with a square tool in a round hole will work, or a round tool in a square hole, or even a square tool in a square hole, as intended. The round tool can be made from an old broken drill bit. A standard boring bar with square cross holes makes a dandy and cheap internal threading tool by grinding a 60 degree V shaped bit for it. I have lots of tools like those and have not even looked for an internal insertable threading tool holder. I have a nice insertable boring bar set like these:
http://www.toolingsolutions.com/catalog/everede_2012_catalog.pdf
I have the set 200-C on page 52.
They also sell inserts for these tools, with various end shapes or as blanks, carbide and HSS, and grinding fixtures for sharpening them. Starts on about page 60. Triangular bits in triangular holes...
Bought the whole set, including a mount for a lantern tool post (pages 56/57), and about 50 assorted extra bits, including ones ground for threading, adapter sleeves, and a tool bit grinding fixture, used for $30. Have not used them to cut a thread yet. For shallower holes the tools made from HSS tool blanks are quick and easy to set up and git-er-done.

Edit: Insertable internal threading tools and the inserts that fit them are quite expensive, especially considering the small amount they are used by a H-M.

 

[Wreck™Wreck]

Vardex makes excellent tools for this, however I prefer Kennametal Topnotch tools due to their versatility, many inserts are available for internal threading and grooving, 1 tool will make many internal features with the correct insert. Laydown threading tools use up a lot of bore diameter by design.

 

[kd4gij]

I have the 1/2" for id and od threading
http://www.mesatool.com/products/threading-tools/

 

[Sandia]

Thanks for the quick come guys, gives me alot of ideas. Might try making one for the time being. The indexable tools are expensive no more than I would use them and nothing on Ebay. The Shars tools Bruce recommended are cheap enough, might give one of them a try.

Thanks much fellows

 

[John Hasler]

Even thought about just making a bar and grinding a 3/16 tool. I guess a square tool in a round hole with a solid set screw would hold the tool in place.

That works for me.

 

[Tony Wells]

I also like the TopNotch style. They are very rigid and reliable. I use some laydown.....well, I guess I have some of every kind, but for my money, carbide rules. It last forever in a home shop. Maybe not the best idea for learning to thread, but once you are comfortable, make the switch, you'll be glad you did.

I have a shop made bar that holds a vee bottom flat top double ended insert(dogbone style) that works great. Can get inserts for nearly any thread. Acme, Stub Acme, API, UN, UNR, UNJ, you name it. I'll put up a pic tomorrow. Need a mill to make it, but it's very simple and straightforward.

 

[dave_r_1]

I got a boring bar that has a slot for a short piece of HSS, I think it's about 1/8" square, maybe a touch more, with a set screw, each end of the bar has a slot that holds the HSS at a different angle, you break off a piece of a bar of HSS, grind the end how you want it, then put the HSS in the bar, and off you go to find your Uncle Bob. It was cheap too, under $10 at busybeetools. there are some larger versions of these as well. worked fine for making some 15mm left-hand-thread nuts.

http://www.busybeetools.com/products/boring-bar-d-e-1-2-sq.html