Hardinge vs. Rivett 4NS Collet Threads

[n2zon]

With a machine I got came a ratcheting lockable positioning fixture that takes 4NS collets. It offers a lot of the capabilities of a dividing head at 1/4 the size and weight. It has German language markings, so I presume it was made there. It came with one Hardinge collet marked 4NS.

A while back, a member here was selling a partial set of Rivett 4NS collets. It seemed like a great way to extend my collection of "one" to something useful, so had my son pick them up because he lives not too far away. I visited my son a couple of weeks ago and brought the collets home.

They don't fit in the knurled knob type closer. They start, go in about about a turn and a half, and no more.

I measured the ODs of a Rivett and the Hardinge and they're different by .009". After dropping my 3 wires about sixteen times I measured what I think is the pitch diameters. This is frustrating enough that I ordered a (cheap) thread mic to verify the measurements. Off to the web I go, to find that Rivett apparently created the 4NS collet and that the thread ought to be 13/16-20 UNEF.

The Rivett's OD and PD seem to match that spec. The Hardinge thread is smaller, but it's the one that fits. Will the real 4NS please stand up?

OD: Rivett - .807", Hardinge - .798"
PD: Rivett - .776", Hardinge - .765"

The ID of the closer is about .749".

So obviously, it seems, I need to make a new closer. This shouldn't be that big a deal even though it will be my first try at internal single-point threading unless I buy the tap.

But can anybody shed any light on this? Are there *two* 4NS specs? Is there a metric one or an older DIN spec? If so, it would be what seems to be a nonstandard thread close to M20.5x1.25-ish, which isn't listed in Machinery's Handbook and for which I can't find any specs (though I could calculate them from the formula, I guess).

 

[L Vanice]

I have never seen a Rivett Lathe and Grinder Co. or earlier Rivett publication with their collet dimensions. Hardinge lists their 4NS collets as having a .812-20 thread and a .826 body. I have a brand new Hardinge 4NS collet that has a .825 body and a .7985 thread OD. Hardinge collets are supposed to match the dimensions of the other brand they copied.

Rivett was a very old company. In the beginning, Rivett and other precision bench lathe makers would call their lathes by a simple single digit number to signify the relative size of the collet. Each lathe maker had their own unique collet spec, so there was no commonality. Rivett had collet sizes 1, 3, 4 and 5. At some point, they increased the maximum capacity of the 4 and 5 collets, so then they had to call them Rivett No. 4 old style and 4 new style, or 4 O.S. and 4 N.S. etc. In the same period (early 20th century), Hardinge made Cataract bench lathes in sizes 3, 4, 5, 6, and 7. The collets were known as Cataract No. 5, etc. Hardinge made collets for all brands of lathe from around 1900 or so, but there was no marking system on the collets other than the Hardinge or Dale name and the hole size. In the early 1930's, Hardinge reorganized and moved to Elmira, NY and emphasized the collet business. That was when they began the system of naming collet types and putting the type on each collet. The Cataract No. 5 collet was marked 5C to fit the small space on the face of the collet. And Rivett No. 4 new style became 4NS in the Hardinge catalogs.

I do know that different collet makes have variations in dimensions for 5C collet threads. Even Hardinge changed the published thread diameter a little bit on their 5C collets some years ago. I suppose that Rivett could have changed theirs at some point. Around 1990, I made a new drawbar for one of my Hardinge lathes. I did not then have the "official" 1.238-20 tap, so I single-pointed it using a new Hardinge collet as a gage. I made it a fine running fit that felt just right. Some time later, I had one of my rare occasions to use a metric 5C collet. My metric set is mostly some NOS South Bend 5 collets. I found that my South Bend collets would not fit my new drawbar. But the several Hardinge-made 5C draw bars I have are loose enough to work with any of the many brands of 5C collets I have. I never got out the thread mike to see the actual dimensions on the various brands of 5C collets I have.

Larry

 

[Ron Hofer]

I have never seen a Rivett Lathe and Grinder Co. or earlier Rivett publication with their collet dimensions. Hardinge lists their 4NS collets as having a .812-20 thread and a .826 body. I have a brand new Hardinge 4NS collet that has a .825 body and a .7985 thread OD. Hardinge collets are supposed to match the dimensions of the other brand they copied.

Rivett was a very old company. In the beginning, Rivett and other precision bench lathe makers would call their lathes by a simple single digit number to signify the relative size of the collet. Each lathe maker had their own unique collet spec, so there was no commonality. Rivett had collet sizes 1, 3, 4 and 5. At some point, they increased the maximum capacity of the 4 and 5 collets, so then they had to call them Rivett No. 4 old style and 4 new style, or 4 O.S. and 4 N.S. etc. In the same period (early 20th century), Hardinge made Cataract bench lathes in sizes 3, 4, 5, 6, and 7. The collets were known as Cataract No. 5, etc. Hardinge made collets for all brands of lathe from around 1900 or so, but there was no marking system on the collets other than the Hardinge or Dale name and the hole size. In the early 1930's, Hardinge reorganized and moved to Elmira, NY and emphasized the collet business. That was when they began the system of naming collet types and putting the type on each collet. The Cataract No. 5 collet was marked 5C to fit the small space on the face of the collet. And Rivett No. 4 new style became 4NS in the Hardinge catalogs.

I do know that different collet makes have variations in dimensions for 5C collet threads. Even Hardinge changed the published thread diameter a little bit on their 5C collets some years ago. I suppose that Rivett could have changed theirs at some point. Around 1990, I made a new drawbar for one of my Hardinge lathes. I did not then have the "official" 1.238-20 tap, so I single-pointed it using a new Hardinge collet as a gage. I made it a fine running fit that felt just right. Some time later, I had one of my rare occasions to use a metric 5C collet. My metric set is mostly some NOS South Bend 5 collets. I found that my South Bend collets would not fit my new drawbar. But the several Hardinge-made 5C draw bars I have are loose enough to work with any of the many brands of 5C collets I have. I never got out the thread mike to see the actual dimensions on the various brands of 5C collets I have.

Larry

Even tho I don't have any of the machines mentioned, I just wanted to shout out Larry's expertise in this and so many other matters. We lesser mortals are in your debt.

 

[JST]

Just as a point of comparison, I have a number of 4NS collets (that do not fit my 5C Rivett). Most or all are Hardinge.

I pulled out 2 of them to check, both Hardinge.

#1 shows body 0.8250, Thread OD of 0.8089, PD 0.772 with a thread mic (checked against a 7/16-20 gauge)

#2 shows body 0.8247, thread OD of 0.8052, PD 0.771.

These collets are not new, although they look decent, so they might be a little off from wear.

 

[n2zon]

Wow. Thanks so much to both Larry and JST.

From my former profession, this seems appropriate here:

"The wonderful thing about standards is that there are so many of them to choose from." - Andrew S. Tanenbaum.

Thanks for making me less confused! Now I know I also need to be aware of variations in 5C collets, too. Even though with at least four different brands I have never encountered a thread incompatibility for 5C, that day might come.

 

[n2zon]

Larry, BTW, I did find this in my search but forgot it was from Rivett (because it didn't have the thread specs I was looking for):

http://www.neme-s.org/Shaper Books/...lets B100-B [PDF]/4_Rivett_Collets_B100-B.pdf

 

[JST]

.....

I do know that different collet makes have variations in dimensions for 5C collet threads. Even Hardinge changed the published thread diameter a little bit on their 5C collets some years ago. I suppose that Rivett could have changed theirs at some point. Around 1990, I made a new drawbar for one of my Hardinge lathes. I did not then have the "official" 1.238-20 tap, so I single-pointed it using a new Hardinge collet as a gage. I made it a fine running fit that felt just right. Some time later, I had one of my rare occasions to use a metric 5C collet. My metric set is mostly some NOS South Bend 5 collets. I found that my South Bend collets would not fit my new drawbar. But the several Hardinge-made 5C draw bars I have are loose enough to work with any of the many brands of 5C collets I have. I never got out the thread mike to see the actual dimensions on the various brands of 5C collets I have.

Larry

I have seen the exact same thing with 3C collets. Made a drawtube, and there is a difference between Hardinge and Southbend versions, which as I understand it are intended to be the same.. I have a vertical head that takes 3C, and it accepts some but not others.

Finally, I have a B&S 9 collet adapter for a dividing head that takes 3C, and IT takes all of them without a problem.

 

[Doozer]

It might be nice to buy (or make) an ER32 size straight shank
adapter and machine the shank to the size/shape of a 4NS collet.
That way you can adapt your fixture to more common ER series collets.
Just a thought. You might have to start with a Morse or R-8 shank
as most of the straight shank adapters are hollow and threaded for
a stop screw to keep the tool from going too deep.

-Doozer

 

[n2zon]

It might be nice to buy (or make) an ER32 size straight shank
adapter and machine the shank to the size/shape of a 4NS collet.
That way you can adapt your fixture to more common ER series collets.
Just a thought. You might have to start with a Morse or R-8 shank
as most of the straight shank adapters are hollow and threaded for
a stop screw to keep the tool from going too deep.

-Doozer

Interesting thought. ER collets look nicer overall from a functional perspective as well. I'm not sure there's room to put an adapter in the spindle, or whether I'd need to make an entire spindle to accommodate ER32. I'll take a look at that, out of curiousity, but making the spindle is too much effort since I do own a dividing head and tailstock. This smaller (indexed, rotating, lockable) fixture looks like it will be good for small parts and/or light cuts in the mill.

Anyway, I did manage to pick up the internal thread and enlarge it to a good running fit with the Rivett collets. Then I found those darn thorough Germans had honed a bushing inside the spindle to a gnat's butt larger than the Hardinge collet body. You guessed it. The Rivetts are bigger and still wouldn't fit! I chucked the spindle in the lathe and honed out enough for the Rivetts to be a good sliding fit. I didn't measure, but I doubt I took out more than a couple tenths. So next time I have something suitable for this small fixture I won't have to lug the dividing head over to the mill.

Now, if someone will just sell me the missing 4NS collet in my set, life will be even better!

 

[L Vanice]

...Now, if someone will just sell me the missing 4NS collet in my set, life will be even better!

What size do you want? I have a 1/4 inch round.

Larry

 

[n2zon]

What size do you want? I have a 1/4 inch round.

Larry

3/8" round. The only one missing in my set.