Inside threading tool
- Thread starter Casull
- Start date
Are you talking about threading in a lathe?
I use different size boring bars and grind a high speed bit for the job. Nothing I inside thread requires carbide tooling.
You can also buy bars from various tool suppliers that accept inserts....... fairly pricey....
I use different size boring bars and grind a high speed bit for the job. Nothing I inside thread requires carbide tooling.
You can also buy bars from various tool suppliers that accept inserts....... fairly pricey....
Casull,
Ebay usually has a good selection of boring/threading bars. Find the largest diameter you can use to help avoid chatter while cutting. If you want a carbide insert type bar, find a "top notch" type (this is the insert type, not the brand). These bars are very versatile because there are many types of boring, grooving, and threading inserts available. Try KBC tools. They are a pretty reasonably priced supplier that you can mail order from. Just google "KBC Tools".
If you feel like grinding your own HSS toolbits, find some kind of basic machinists handbook or textbook at your local public library or online. Most of them will have all the info you need, along with good diagrams.
Cheers,
Michael in Edmonton
Ebay usually has a good selection of boring/threading bars. Find the largest diameter you can use to help avoid chatter while cutting. If you want a carbide insert type bar, find a "top notch" type (this is the insert type, not the brand). These bars are very versatile because there are many types of boring, grooving, and threading inserts available. Try KBC tools. They are a pretty reasonably priced supplier that you can mail order from. Just google "KBC Tools".
If you feel like grinding your own HSS toolbits, find some kind of basic machinists handbook or textbook at your local public library or online. Most of them will have all the info you need, along with good diagrams.
Cheers,
Michael in Edmonton
Do you grind your own HSS tool bits? If not - it's time to start! For smaller internal threads I use a square HSS toolbit I ground and I just put in a tool holder (see pg 8 in the pdf of the link below). For the bigger stuff I use a boring bar with a 60 degree tool bit held in the end. I use the same bit as I use for external threads (do you have one?) You can easily make your own bar if you've seen one before and it's really handy to have one that allows you to change the toolbits. That way you can use the best bit for boring and a different one for threading.
I did a quick google to try and find some pics and came across this link:
http://www.metalartspress.com/60 degree threads.pdf
Edited to add: If you look in the KBC tool cat.( http://www.kbctools.com/can/main.cfm ) on pg 72 you'll see some boring bars. You can't see in the pics, but there is usually a set screw holding the square toolbit in place. It's either tapped in the end or on the side. Also if you file or mill a flat on the boring bar it will sit more secure in the tool holder.
Good luck.
I did a quick google to try and find some pics and came across this link:
http://www.metalartspress.com/60 degree threads.pdf
Edited to add: If you look in the KBC tool cat.( http://www.kbctools.com/can/main.cfm ) on pg 72 you'll see some boring bars. You can't see in the pics, but there is usually a set screw holding the square toolbit in place. It's either tapped in the end or on the side. Also if you file or mill a flat on the boring bar it will sit more secure in the tool holder.
Good luck.
Last edited:
You are using a 9" south bend , correct? Don't use carbide's in it, it doesn't have the power or rigidity to use carbides. Use razor sharp H.S.S. bits. Do you have a copy of south bends booklet "hoe to run a lathe"? There is some good basic tool grinding info in there.
MIKE's advice is good. You can sometime's buy pre-ground bits sets for Myford lathes on e-bay, sometimes they are mis-advertized as carbide bits.
You can also buy pre-ground H.S.S. bits here http://www.arwarnerco.com/index.html
The best thing is to buy a book and a tool grinder and start learning.
MIKE's advice is good. You can sometime's buy pre-ground bits sets for Myford lathes on e-bay, sometimes they are mis-advertized as carbide bits.
You can also buy pre-ground H.S.S. bits here http://www.arwarnerco.com/index.html
The best thing is to buy a book and a tool grinder and start learning.
That's right, I have a 9" SB with I think a 1HP motor. I do have the book and a few others. I was just fishing for "tips" on inside threading and tool making. I have not inside threaded anything yet. I have been learning a bit about tool bit grinding mostly by reading and experimenting. I'm getting better, I ground some 55º thread cutting bits out of necessity when I couldn't find any to cut threads on a Mauser barrel. They are coming out pretty well now too though not fast.
When you are grinding these inside thread cutting bits from square HSS tool bits, do you grind the entire length back for clearance? I think I am missing something here.
Rob
When you are grinding these inside thread cutting bits from square HSS tool bits, do you grind the entire length back for clearance? I think I am missing something here.
Rob
If it is a small thread and not too deep, I start with a new piece of 1/4" tool stock and grind the middle section back to form a shaft about 1/2 the thickness of the tool stock. I leave a bump at the end which I then grind into a 60 degree point. Remember that when cutting an inside thread you are probably going to be cutting on the back edge of the 60 degree point. I also put a felt pen mark on the tool so I can tell when I am at the end of the thread.
For larger threads (and larger holes) I make up a boring bar out of square stock and use 1/8" tool stock to form the cutter.
cheers mooncoon
For larger threads (and larger holes) I make up a boring bar out of square stock and use 1/8" tool stock to form the cutter.
cheers mooncoon
Here is a tip I got from the "Machinist Bedside Reader" and it greatly changed the quality of my threading. You may already know this. After you grind a thread cutting bit or turning bit I assume too, you hone it with a stone like you would a knife blade to a very smooth sharp edge. So the bit looks polished and great and cut very smoothly, and gives great even and accurate threads.
Rob
Rob
It would be best if you get a few double-ended boring bars from Busy-Bee.
From ½” to ¾” these things are really cheap, from $9 to $18.
And then get some ¼” high speed tool bits to fit these bars.
Now grind them to the required angels, and don’t forget a good positive side rake of at least 5° (or more). And at least 10° side relief on both sides.
Then it is just a matter of practicing you threading skills.
From ½” to ¾” these things are really cheap, from $9 to $18.
And then get some ¼” high speed tool bits to fit these bars.
Now grind them to the required angels, and don’t forget a good positive side rake of at least 5° (or more). And at least 10° side relief on both sides.
Then it is just a matter of practicing you threading skills.
