Threading Question.

[Arnak]

Hi Folks,

I am going to attempt to make a collet chuck for my spindle nose.

The question I have is that the thread required is quite deep and has a rounded root.

If I use a standard threading tool the root would be deeper than it should be and the bottom of the root would be a sharp angle, so is it better to shape the end of the cutting tool to be blunter to get a rounded root?

The spindle nose diameter is 2.250".

Thanks for any advice,

Arnak

 

[B-RAD]

I think I understand, and yes, if your good at making tools, that's what I would do.

 

[oops again]

Hi
I gring up HSS to 60' and dont bother too much about the tip radious. Look up one of the many charts and find the thread depth for the TPI that you are cutting, it is the same regardless of diameter. Leave the topslide on the X axis (no need to set it over) and use the cross slide for depth control. Feed both the cross slide and top slide in at a ratio of approx 3 to 1 that is 3 for the cross slide and 1 for the top slide. When you get to the nominated depth ajust the top slide only untill you get the desired fit. The main reason for setting the top slide over is to reduce the tool load and potental dig inns. This method gives the same result without moving the top slide that can be a pig to get back on the X axis again.

Dave

 

[ttrikalin]

[...] so is it better to shape the end of the cutting tool to be blunter to get a rounded root? [...]

you mean to have a radius, rather than ending in an acute angle (point). The tip of the tool forms the root of the female thread-- and this can be an acute angle without a problem.

It seems to me that it is the top of the female thread (minor diameter) that runs the risk of interfering with the root of the male (spindle) thread. If so, you can always adjust the minor diameter of the female thread to be a tad (== to-be-defined) bigger than the nominal, or you can do this afterwards with some emery cloth and trial and fit.

As bogs has shown in the past, it is much simpler of you make a copy of the male spindle thread for go/no-go testing of the female thread.

Apologies if I misunderstood.

my best

tom

 

[f350ca]

Arnak,
The root of your thread should be rounded, the radius is based on the tpi. The radius reduces stress risers. You'll find the cutter lasts longer with a slight radius on the tip when cutting large threads such as your spindle. Carbide is especially prone to loosing the tip on such deep cuts.
Greg

 

[Arnak]

Hi Folks,

Thanks for all the replies.

I'll go for rounding the tip of the threading tool slightly.

I am making a male thread first on a piece of scrap as a go no go gauge as suggested.

Arnak

 

[MachineTom]

Can I assume that you have a 2 1/4 x 8 spindle, and you want to make a backplate/body that would thread on. That is a very common thread for spindles, and is of the standard 60° profile, every one I owned did.

If the lathe has that size spindle it should be capible of cutting a thread that size. You need to grind a 5/16 or 3/8 bit, and very accurately cut that thread.

 

[Arnak]

Hi Tom,

Yes, that is correct it is 2 1/4" x 8 tpi.

Although I make mine to be a 55 degree thread.

I am actually making the 5c collet nose to fit straight onto the spindle.

Arnak

 

[123RWO]

I made my 5C collet adapter from a Morse taper #5 to #3 reducing sleeve( unhardened) many years ago and it has served very well. Still shows less than .0005" TIR on the collet taper.

RWO