Grinding internal grooving tool

[Spokerider]

Guys,
I am soon to attempt internal threading for the first time.
I have a HSS 60 degree internal threading tool, but I'm not sure what type of tool is required for cutting the major diameter relief, where the threads will end, inside the tube?

What profile do you grind on a HSS blank, for this purpose?

Since I'm using a ML7, threading in reverse is not an option..... until I devise a method of securing the chuck on the spindle threads, from loosening.

So yeah, I do need that major diameter relief groove, while I am learning internal threading on my lathe.

Thanks for your thoughts.

 

[woodchucker]

Guys,
I am soon to attempt internal threading for the first time.
I have a HSS 60 degree internal threading tool, but I'm not sure what type of tool is required for cutting the major diameter relief, where the threads will end, inside the tube?

What profile do you grind on a HSS blank, for this purpose?

Since I'm using a ML7, threading in reverse is not an option..... until I devise a method of securing the chuck on the spindle threads, from loosening.

So yeah, I do need that major diameter relief groove, while I am learning internal threading on my lathe.

Thanks for your thoughts.

so I recently added a screw to my new to me Bison chuck on an SB9 (1.5 8tpi ). I used a 10-32 and drilled into the spindle so it locks it on. It won't handle heavy cuts, but it is capable of reverse threading if you do light cuts.
Previously my old chuck had a brass set screw, and it worked pretty good, but it did let go on one important reverse thread. So the screw will hopefully never wind up cut by too aggressive a cut.

At any rate, I also have done a bunch of internal in the forward direction.. I use a boring bar with a 90 degree hole in the bar. either round (smaller bars) or square tool (larger bars). only a very small amount of tool sticks out of the holder.. I have also used the angled hole for when I have to reach in and thread a blind hole. I'll get some pics later.

 

[extropic]

Not enough information.
What size is the thread?
Do you have a boring bar you intend to use to hold a HSS tool bit?
Or, do you want to grind a HSS blank from scratch? What size blank?
Alternatively, the link is to an eBay listing for some carbide grooving tools. The listing includes numerous images of the grind.

MGR Lathe Internal Micro Boring Bar CNC CarbideTurning Tool Holder Cutter Groove | eBay

Specification: Type: Turning Tool Material:Tungsten Carbide Model: MGR Applicable Material:Suitable for processing stainless steel, alloy steel, modulation steel,aluminum,iron,cast iron, titanium alloy, magnesium alloy, etc. Package Including: 1pc Small Bore Boring Tools.

www.ebay.com

 

[WobblyHand]

Some people grind a tool for this. Others may simply use the same tool for threading to make the groove. I've done both, but it's simple to use the threading tool to make a groove with 60 degree sides. Just go easy when you are widening the groove.

My threaded spindle has retainers to prevent loosening, but the retainers have never saved the day, since the chuck has never loosened. I use them as a safety but I think they are overrated. If you take small cuts, which you'd ordinarily do for threading, I'd bet the chuck wouldn't loosen. When I change chucks I have to use wrenches, because it locks up very well. Your lock up could be different, so whatever you are comfortable with, go with that. Reverse threading does remove a whole lot of the pucker factor for internal threading. Did a M8x1 internal thread on an adapter I made - reverse threaded it because I simply couldn't see the end point. I'd probably do more normal internal threading if my minimum RPM were 50, rather than 100, but 100 RPM is as slow as I can get.

 

[benmychree]

The question was what tool to use for recessing for the end of the thread; it would likely look like the threading tool on several ways, but generally blunt on the end instead of pointed to 60 degrees. The thread tool itself can be used to make the relief by simply plunging it in the required amount (or a bit deeper) and feeding it endways until the relief is long enough, the thread tool's angles will make little difference in the completed job.

 

[woodchucker]

sorry about the pic, had to find some of them and hand holding the one with the fishtail and camera I'm a little off, it does square up.
So to thread almost to the end of the blind hole... I use that one. Otherwise I just use the squared off 90 degree ones.

 

[woodchucker]

I also have this type , and a few others that are just ground away blanks.

 

[mattthemuppet2]

What Ben and Wobbly said, use the threading tool to cut the relief but make sure the cutting part of the threading tool is at least a little bit deeper than the thread depth you want to cut. That will allow you to cut the relief a little deeper than the root of the thread if you want too.

Or you can grind a little grooving tool, which can come in handy if you ever need to cut an 0-ring or snap ring groove. Just make sure you have relief looking down at the top of the tool AND the at the cutting edge from the perspective of the material.

 

[Spokerider]

Thank you all for your input. It helps.

I didn't know that using the threading tool itself, is an option for use as a grooving relief tool. Now I do.

Since I have plenty of hss blanks, I will likely grind one to a grooving tool profile, and leave the spendy Warner internal threading tool for threading..... just in case sumpthin goes sideways.

I do have a spindle hand-crank for the ml7.
Is this hand crank something that could be employed for cutting internal threads, in "reverse" direction? That way, should the chuck decide to unscrew itself during the threading, a chuck-launching event would be easily diverted.

 

[woodchucker]

Thank you all for your input. It helps.

I didn't know that using the threading tool itself, is an option for use as a grooving relief tool. Now I do.

Since I have plenty of hss blanks, I will likely grind one to a grooving tool profile, and leave the spendy Warner internal threading tool for threading..... just in case sumpthin goes sideways.

I do have a spindle hand-crank for the ml7.
Is this hand crank something that could be employed for cutting internal threads, in "reverse" direction? That way, should the chuck decide to unscrew itself during the threading, a chuck-launching event would be easily diverted.

yes, just take light cuts