5C collet thread tap?

[Laverda]

Looking for a tap to fix the threads on a 5C collet closer. The 5C thread is 1.238" x 20. Searching for this thread size turns up nothing. Why did they pick such an odd size???

 

[iwananew10K]

1.250"x20 is the thread. The collet OD is smaller to provide some relief.

 

[Laverda]

1-1/4" x 20 sounds like it will be loose. Further research says to use a 1-15/64" x 20 tap which is also not available. Just need to fix the threads in the collet tube. Wish I had a 1-1/4" x 20 to try. Mcmaster has them for $97. Ouch!

 

[L Vanice]

Looking for a tap to fix the threads on a 5C collet closer. The 5C thread is 1.238" x 20. Searching for this thread size turns up nothing. Why did they pick such an odd size???

Pretty much the old design collets have special threads, so the 5C from around 1900-1910 is no exception.

I have two rather new-looking 1.238-20 taps, so they do exist.

I bought a round 5C collet block meant to be held in a 3-jaw chuck or something a few years ago from the maker, who sold them on eBay. He made the nut with a 1.25-20 standard thread and collets are very loose in the nut. Hardinge and other decent makers made their drawbars with close-fitting internal threads. I always single-pointed mine before I got the taps, a lucky find on eBay. I have never seen any catalog listing that tap, but there are places that make special taps.

Here is an old Hardinge catalog listing for collets and their thread sizes. The 5C collet was then known as a Cataract No. 5 draw back chuck and the original thread spec was 1.245-20. Somewhere in time between my 1950 and 1980 catalogs, the thread spec changed to 1.238-20.

Larry

 

[Laverda]

OK, so looks like I will be making a 1.238" x 20 tap. Just what I need, another project!

 

[DDoug]

OK, so looks like I will be making a 1.238" x 20 tap. Just what I need, another project!

Could you not just buy some chasers for a collapsing tap ?

IIRC I've got one that goes down to 1"

I would check with quality chaser in Detroit.

 

[JRIowa]

Why can't you chuck up the drawbar and single point? Am I the only one that does that anymore?
JR

 

[Booze Daily]

I usually use an ID threading bar or 20TPI threadmill and scrape it around the threads like a thread file.
Just keep scraping it around til you knock all the dings down and it screws together

 

[jim rozen]

Pretty much the old design collets have special threads, so the 5C from around 1900-1910 is no exception.

I have two rather new-looking 1.238-20 taps, so they do exist.

I bought a round 5C collet block meant to be held in a 3-jaw chuck or something a few years ago from the maker, who sold them on eBay. He made the nut with a 1.25-20 standard thread and collets are very loose in the nut. Hardinge and other decent makers made their drawbars with close-fitting internal threads. I always single-pointed mine before I got the taps, a lucky find on eBay. I have never seen any catalog listing that tap, but there are places that make special taps.

Here is an old Hardinge catalog listing for collets and their thread sizes. The 5C collet was then known as a Cataract No. 5 draw back chuck and the original thread spec was 1.245-20. Somewhere in time between my 1950 and 1980 catalogs, the thread spec changed to 1.238-20.

Larry

There are times when putting one vintage collet into another vintage drawbar, can lead to lock up on hardinge stuff.

Now I don't know what the OP wants to do, but if the problem is that the threads or the end of the drawbar got badly smooshed,
a tap really is the way to go. However...

If the collets are just snug and don't go on well, one can take an old scrap collet, coat the threads wtih silicon carbide lapping
paste, and have at it.

Another approach I would do is to take the most oversize thread, scrap collet I had, and grind cutting flutes into that to
fab up a sort of rough tap. The collets are reasonably heat treated and this will probably get you 95 percent of the way there.

 

[sandiapaul]

Jim, using the collet as a tap, that's a good idea!

 

[dsergison]

Why can't you chuck up the drawbar and single point? Am I the only one that does that anymore?
JR

+1

we already know you have a lathe. If your afraid to do it under power and mess things up then do it by turning the chuck by hand. put the cross slide perpendicular so you can use it to line up on the threads.

you could even use one flute of a 1/4 - 20 tap as a cutting tool.

 

[Dumpster_diving]

One other suggestion.

If the prospect of accurately picking-up the existing thread and single-point chasing seems too fiddly, you could always single-point an entirely new drawbar. Sometimes easier to thread from scratch rather than trying to accurately pick-up an existing thread inside a 1-2" hole.

 

[L Vanice]

I got out my 5C taps and will list the makers here to aid anyone wanting to buy one. Both makers advertise that they make specials.

1. "WIDELL INDUSTRIES INC. MADE IN USA 1.238-20 HSS H4 6FL DBLD PLUG TAP 591356" http://www.widell.com/tap_popularspecial.html

2. "WESTERN 1.238-20 NC [SIC, should say NS] HSS GH4 5 'C' COLLET" Bottom grind Special Taps, Dies and Gages Acme Tapping, Metric, J-Series, HeliCoil

Larry

 

[dsergison]

One other suggestion.

If the prospect of accurately picking-up the existing thread and single-point chasing seems too fiddly, you could always single-point an entirely new drawbar. Sometimes easier to thread from scratch rather than trying to accurately pick-up an existing thread inside a 1-2" hole.

doing it under power as a first time try on your one and only draw tube yes....

so turn the chuck BY HAND and back out of the cut each time you reverse to the start. use the compound to advance the tool to line up with the thread. no need for setting it at the flank angle, that just complicates things here.

 

[nitromarsjipan]

A possible alternative for future reference. This Schaublin collet manual lists a supplier of taps for W20 and W25 threads (on page 52 (marked as page 21.2)):

http://schaublin.ch/app/webroot/pdf/cat/5.pdf

A W25 collet thread tap has item number SV25 at dcswiss.com . They might have one for 5C ("W31.75" as they might call it).

 

[Laverda]

The end of the collet tube got squashed. I made an internal mandrel and gently tapping got it round again. The threads are not good but definitely fixable. Making a new tube is possible but would be a lot of work and there are extra things going on at the lever end of the tube. Could also cut off the bad part and weld on a new piece. You would think as there are probably millions of 5C collets in the world that the tap would be a common item. Thanks for all the good advice so far. I will check with the custom tap makers mentioned above. If really expensive, and as I should only need it one time may be better to make one. I have a scrap piece of 52100 laying close by that would probably work once cut and hardened. I need this fixed yesterday as I am tired of having to use the 4 jaw chuck.

 

[edwin dirnbeck]

I used to make and sell repair parts for 5 c collets tubes.s See my you tube video,ed631941 "5 c collet drawtube repair''I have done 40 or 50 of these. I know you are not suposed to sell things on this forum so I guess you could contact me from you tube . Edwin Dirnbeck

 

[mark costello]

Don't have to weld anything on after cutting the end off. Locking liquid is Your friend.