Threading parameters

RBC

RBC

Deceased
With all the new talk about live threading and Eloh's nifty gadget, I thought it would be helpful to share some information on how to determine proper threading parameters.

There's tons of information out there if you just google it, but here's a link to a simple way to come up with successful thread parameters.

http://rick.sparber.org/ftt.pdf

This takes something that seems pretty complicated math wise, and simplifies it.

Threading is very satisfying when you get it down right. It also makes for a strong clean way of attaching collars and butt caps and such.

Enjoy!
 
Mc2

Mc2

AzB Silver Member
Silver Member
Very nice find. Do you have any information like this for the female side?

Jim
 
GatzkeCues

GatzkeCues

It used to be a hobby
Silver Member
This is great, I thoroughly enjoyed this.
I picked up a machinist tool box with quite a bit of these tools in it recently.
Now I know what some of them will be useful for.
Extra thanks again.
 
conetip

conetip

AzB Silver Member
Silver Member
A great find and post Royce.
In the article they mention about the cutter jumping and the stock moving.
The main causes for that is a tool geometry that requires too much pressure to create the cutting shear action. This is similar to a dull tool. But a positive hollow ground tool can greatly reduce this. To create the positive top rake, you need a way to carefully grind a groove just inside the edge of the tool.The down side is the tool is not easily reground.So your home made tool will look like the geometry in comercial carbide threading inserts, which are available in ground and sharp , similar to inserts for cutting Ali.
To measure threads, a thread wire set is a cheap and fairly consistent way to get the correct thread pitch diameter, which is what you are really after in Engineered threads.
In cue making threads they tend to either fit to the thread root/ minor diameter or they work on the thread major diameter, and any combination of the above.
It comes down to the ability to measure what you are making if quality is important to you.
One last way of making a threader is to make only a 1/2 tool. Only the leading side of the tool is made to the 1/2 thread angle so it will be 30 deg for a 60 deg thread form. On the very front is a radius and a very small amount of the thread form , just for the length of the depth of cut. The compound slide is turned to the 30 deg and the trailing edge is a generated edge only , with only the leading edge is cut from the from of the tool.
Neil
 
RBC

RBC

Deceased
Mc2 said:
Very nice find. Do you have any information like this for the female side?

Jim
Click to expand...

Thanks Jim!

Actually, I'm pretty sure you can use the same information, just to the opposite side of the thread.

In other words, the Inside diameter would be the Nominal Diameter, and all cuts would just be made in the opposite direction. Basically, the difference between the Nominal diameter and the actual Major/Minor diameters would give you your clearance.

I just know that I've gone to the machinists handbook too many times to look this stuff up, and this seems to make it simple. I have usually ended up just cutting them until they look right and a nut will spin on. Certainly most of the threads I do are for collars and butt caps so they are basically a one time use clamp. They don't have to be perfect because they just hold the parts together for the glue to cure. But, even if they are one time use, I still want to make the correctly. I used this method to thread the ends of the lead screws on 4 new turning centers I'm building and it worked perfectly. The fit was just like it was supposed to be and I have no fears of issues down the road because of improperly fitted threads.

Hollow ground threading cutter sounds pretty cool Neil. I know I used to advance my tool in at zero angle and cut on both sides of the cutter. I would get ugly threads that way. When I read about advancing the tool at a 29.5 degree angle it all made sense. Of course, that changes the amount I have to turn the dial to get the desired thread depth, but nowadays I just let the control do the math for me.


Thanks

Royce
 
conetip

conetip

AzB Silver Member
Silver Member
In steel for live tooling, to get less chatter on the threads, you can take a 4 flute thread forming tool and alter each one, so each is making only a part of the form to make a whole thread. This is not new of course, the timber molding industry has been doing this sort of segmented form work for decades.
 
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