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x39
07-22-2008, 06:19 PM
I've been asked to make an extractor that utilizes a left hand "Harvey Grip Thread". Anybody got a source for a die to cut this thread? It tapers from 1/16" to 1/4" over a length of 1/2", 24 tpi. Thanks.

Astronowanabe
07-23-2008, 02:54 AM
I've been asked to make an extractor that utilizes a left hand "Harvey Grip Thread". Anybody got a source for a die to cut this thread? It tapers from 1/16" to 1/4" over a length of 1/2", 24 tpi. Thanks.


I have never done this, I'm just getting the hang of cutting normal threads but ... wouldn't that be an ideal job for a lathe?

From the description I would try
offset the tailstock
make the taper
set the pitch to 24 tpi
cut the thread towards the tailstock

seems a die would have a hard time cutting a tapered thread for the same reason it makes a good extractor, if it engages all at once you would have to cut it with a die all at once. a lathe cut would let you cut along one point as you go.

mark61
07-23-2008, 05:26 PM
Pipe threading dies cut tapered threads with no problem. Problems comes from running the die too far on to the pipe and then the threads will not mate tightly to the taped -female-side.
Does your lathe have a taper attachment? If not as stated go with the tailstock offset.

mark61

x39
07-23-2008, 06:36 PM
The only lathe I currently have under power does not have a taper attachment. Setting the tailstock over isn't much of an option, as the small end of the thread is only 1/16" in diameter, which doesn't leave much room for a center hole. I've got an old South Bend with a taper attachment, I guess I probably better get the old bird wired up and running.

johnnyd
07-23-2008, 06:53 PM
I have ordered buttress taps & dies from Widell Industries in the past & have had good service. Although I have never seen a tapered one, I don't dought that Widell can make one.
Check out their web site...it's awesome !

No affiliation.....but a very satisfied customer.

"Make Swarf & Prosper"

John

x39
07-23-2008, 10:11 PM
Thank you John, I will check them out.

oldtiffie
07-24-2008, 08:47 AM
I hope no one is kidding or being kidded here.

I'd hate to think that there is a "Troll" in the back-ground somewhere.

According to my "Machinery's HandBook" 27 Edition, page 1891:

"Harvey Grip Thread":
The characteristic feature of this thread is that one side inclines 44 degrees from a line at right angles to the axis, whereas the other side has an inclination of only 1 degree. This form of thread is sometimes used where there is considerable resistance or pressure in an axial direction and when it is desirable to to reduce the radial or bursting pressure on the nut as much as is possible.

See BUTTRESS THREADS.

Buttress form threads are at page 1849.

I am trying to imagine a buttress form thread which meets the OP's requirements:


I've been asked to make an extractor that utilizes a left hand "Harvey Grip Thread". Anybody got a source for a die to cut this thread? It tapers from 1/16" to 1/4" over a length of 1/2", 24 tpi. Thanks.

ckelloug
07-24-2008, 10:25 AM
Googling for this thread, the only references I could find were in old railroad handbooks describing the maintenance of way.

The Harvey Grip thread bolt was used on the bars that hold pieces of track together. It said that the bolt was tapered and had a serrated head such that when the serrated nut was tightened the serrations would lock together and that the tapered threads would be squeezed preloading the bolt so it didn't unscrew. Essentially, when the nut was tightened to the proper amount you would get an interference fit as the thread of the nut was squeezed into the thread of the bolt.

I'm a little hazy on why anyone would want to make anything that was expected to move more than once using a Harvey Grip Thread although I freely admit I may not understand what's trying to be done.

oldtiffie
07-24-2008, 11:18 AM
Thanks Cameron.

I got more of less the same results as there is not much about.

My main concerns are the details of the OP's thread:


I've been asked to make an extractor that utilizes a left hand "Harvey Grip Thread". Anybody got a source for a die to cut this thread? It tapers from 1/16" to 1/4" over a length of 1/2", 24 tpi. Thanks.

He asked for a die to cut what will be an all but impossible thread.

That is to say:
it is a left hand(ed) buttress thread;

it tapers from 1/16" to 1/4" over a length of 1/2" which is ((1/4 - 1/16)/(1/2)) = (3/16" per 1/2") = 3/8" per 1" which requires a compound angle setting of 3/16" per 1"
which is arctan 0.1875 = 10.62 arc degree;

it is 26 tpi (ie the lead = 1/24 = 0.0417").

the depth of thread = 0.6 x pitch = 0.6 x 0.0417 = 0.025"

Now there can be no support at the "small end" as the "root diameter" will be 1/16" - (2x 0.025) = 0.0625 - 0.050 = 0.0125" (about 1/80") so you can forget about a centre drill or support from a tail-stock centre!!!

If the lathe is turning "forward" the thread cutting will progress (right) toward the smaller end.

Further, there is no way that anything that can be cut with a die or a lathe tool, let alone that small will "extract" anything in its "as machined" state and not in its "hardened and tempered" state (if it could be done) either.

Anyone fancy the job of grinding the lathe tool if the dies can't be bought and the extractor has to be made?

The OP has been conspicuous by his lack of information thus far and in my opinion unless he "shows" shortly and gives a satisfactory explanation:
- he is "Troll";
- he has sucked lot of people in who jumped in too quickly without seeing what the real situation is;
- he has played some like a fish, in which case he has excellent trawling as well as trolling skills; and
- if his intention was to make some look "silly" he has succeeded admirably!!.

coldformer
07-24-2008, 12:58 PM
Thanks Cameron.

I got more of less the same results as there is not much about.

My main concerns are the details of the OP's thread:


He asked for a die to cut what will be an all but impossible thread.

That is to say:
it is a left hand(ed) buttress thread;

it tapers from 1/16" to 1/4" over a length of 1/2" which is ((1/4 - 1/16)/(1/2)) = (3/16" per 1/2") = 3/8" per 1" which requires a compound angle setting of 3/16" per 1"
which is arctan 0.1875 = 10.62 arc degree;

it is 26 tpi (ie the lead = 1/24 = 0.0417").

the depth of thread = 0.6 x pitch = 0.6 x 0.0417 = 0.025"

Now there can be no support at the "small end" as the "root diameter" will be 1/16" - (2x 0.025) = 0.0625 - 0.050 = 0.0125" (about 1/80") so you can forget about a centre drill or support from a tail-stock centre!!!

If the lathe is turning "forward" the thread cutting will progress (right) toward the smaller end.

Further, there is no way that anything that can be cut with a die or a lathe tool, let alone that small will "extract" anything in its "as machined" state and not in its "hardened and tempered" state (if it could be done) either.

Anyone fancy the job of grinding the lathe tool if the dies can't be bought and the extractor has to be made?

The OP has been conspicuous by his lack of information thus far and in my opinion unless he "shows" shortly and gives a satisfactory explanation:
- he is "Troll";
- he has sucked lot of people in who jumped in too quickly without seeing what the real situation is;
- he has played some like a fish, in which case he has excellent trawling as well as trolling skills; and
- if his intention was to make some look "silly" he has succeeded admirably!!.
824 posts thats some pretty good trolling.
or maybee he is just a HOME SHOP MACHINIST looking for help because he does"nt know everything

x39
07-24-2008, 06:07 PM
maybee he is just a HOME SHOP MACHINIST looking for help because he does"nt know everything
Yep, that's about the extent of it. Here's the deal. A friend of mine asked me to make this tool. He is somewhat of an exotic carbueretor guru. He sent me a print entitled "Bendix Fuel Division, Detroit, Michigan, Priming Plug Extractor", print no.C161-15, dated 10/24/72. The tool basically consists of a piece of 1/4" dia. steel round stock, bent into an "L". the long leg is 6 1/4' long, and has said "Harvey" thread on the end. The short leg is 1 1/2" long. The specs call for cyanide hardening the entire tool, I was just going to use a piece of W-2, harden it and draw the body of the tool to a spring temper and leave the business end a bit harder .My guess is that the tool is used to remove a brass plug from a carb body. I've cut a lot of threads, but this one is new to me.

x39
07-24-2008, 10:11 PM
Having thought about it a bit more, I'm beginning to wonder whether this thread may have been rolled rather than cut on the original part.