Threading tool helix angle

[Martin22250]

I'm new to the hobby, and grind my own hss tools for my lathe work. I grind my threading tool with no helix angle, maybe that's the wrong term? Just a 60 degree angle, I've read and seen you tube videos of helix angle grinds on the tools. I haven’t did less than 16 tpi yet on my lathe and my threading seems to work fine, just curious how many hobbyists are grinding helix angles on their tools.

 

[Karl_T]

Do you mean bottom rake angle?

I put ten degrees on the left, zero on the right. For left hand threads, do just the opposite.

 

[Martin22250]

I guess that's what I'm talking about, I thought it was called helix angle, that's why I'm asking cause doing a fine thread compared to a course thread would change the grind angle. I haven't put any angle on my tool and it seems to work fine just curious if I should be doing it

 

[Karl_T]

Ya, I'm not sure of the term either. Might be called a relief angle.

At any rate, the thread is at an angle on the part, I'd call that the helix angle, and the tool should not rub on it. Ten degree would be way more than ever needed.

 

[4GSR]

I haven't ground a threading tool in many years with the inserted tooling I use now days. About 7 to 10 degrees is about right, generally did this on both sides. That way if I had to cut a left hand lead thread, I didn't have to grind another cutter. The only time you have to worry about heliex angle having an effect on threading is cutting multi-start threads and very coarse threads on smaller diameters. Such as 3/4" 5 Acme or similar. Ken

 

[tertiaryjim]

Martin It's helix angle plus relief angle for the leading edge of the tool.
Relief depends on the material and is usually 4 to 6 deg. Can be less for hard materials or more for soft materials
if you want to check the charts.
Helix angle "increases" as the number of threads per unit, metric or inch, "decreases".
I use a total clearance that will allow me to thread 40 to 12 TPI on most pre-made tools but when it comes to
special projects or very coarse threads like acme I make a tool by the formulas for that one.
Over time you'll build a lot of threading and special tools so they will be on the shelf when you need em.
I find it easyer to do the math and then grind a number of tools with the same setup so there's sharp ones in the
box ready to go.

 

[mikey]

[QUOTE="Martin22250, post: 484403, member: 44966"... just curious how many hobbyists are grinding helix angles on their tools.[/QUOTE]

I don't grind a helix angle on my threading tools and haven't had a problem.

 

[Tozguy]

I grind enough relief on the side of the tool to account for the helix angle plus some. It is good to be aware of the helix angle of the thread being cut in case it becomes a factor.

 

[epanzella]

I cut enough relief on both sides to thread either way. I have not yet needed to thread anything less than 13TPI. So there's that.

 

[Wreck™Wreck]

The helix angle changes with diameter, roughly a right angle triangle.
The adjacent side is the circumference, the opposite side is the lead, the adjacent/hypotenuse angle is the helix angle.