Looking for some help

Mike8623 said:
Mark, i made a couple of blanks today. I'll send them to you along with the female part. You can just cut threads on them or if you think they are too primitive you can make a couple. You will not hurt my feelings.

I would like .645x30 tpi.
Click to expand...
Wouldn't it be better to thread the blank(s) before fluting, so you don't have to thread with an interrupted cut?
 
What did you use to cut the flute profile? It's hard to tell from the pics what you've done. Cut em now, or cut em later, you'll need to deburr and after HT you'll need to grind to sharpen anyway, so I don't think it makes a difference. My inclination is to thread first, but it really doesn't matter.
 
Did you offset the CL of the ball mill from the CL of the tap, or did you just cut a semicircular channel right down the middle? Taps are usually ground with form-dressed wheels to create an acute cutting angle on the cutting side of the flute, and a flatter relief on the other. With the right size ball and an offset tool path, you could do it with a ball mill. I just wanted to see how you approached it.
 
I just turned it on my lathe then centered it on my mill and cut them from the top with a ball mill. I'm barely an ameteur.
 
Remember, to have a tap you need at least some taper, somewhere around 2-5 degrees of taper. Mark can easily set up and make a taper for you, and will have to if the threading is at that exact taper, which it should be.

You can hand stone your cutting edges after heat treat to make a very usable tap... (The will have a slight negative rake, but that sould be all right for a shop made tap)
 
So let me ask

On a tap at .645 +- dia. and at 30 tpi...what degree of taper would you put in it?
 
Here is a bit of useful information for taps.
 

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  • Taps - Number of flutes and relief angles.pdf
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@Mike8623

The graphic that John put up tells the tale.

One other problem with homemade taps is that factory made taps are not cylindrical. You can see, in figure 3, that the outside of the tap, behind the cutting edges, has reducing radius (clearance) from the cutting edge. That clearance is to reduce friction so the tap doesn't drag/gall the workpiece.

Simple homemade taps can be used for many things, but to cut quality threads in your adapters, I recommend buying a quality tap or working out the change gears required to single point them on your lathe.

Alternatively, you might sketch up the part(s) you want and ask for someone to make them for you.
 
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