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Enco lathe can’t get it to cut 28 and 32 tpi

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hillriver171

Plastic
Joined
Feb 7, 2021
Hello
I was wondering if anyone would have any ideas on how I could get my lathe to single point thread 28 and 32 tpi. I’m going to thread the muzzle of my rifle for a brake , and just about every one out there is 28 and 32 tpi . The lathe is a late 80s 17x40 enco engine lathe.
The lathe cuts 1/n”
14,16,20,24,36,40
7, 8,11,12,18,20
3.5,4,5.5,6, 9,10
1.75,2,2.75,3,4.5,5
The gears are 91 / 96 with a 100 idler
 
Unless you’re set on a certain brake, I think the Little Bastard brakes are 5/8-24, even on the sub .30 cal models.
 
The gearing makes the 3mm lead screw sloppily approximate .125" pitch - meaning you are stuck with it (the gearing) for Imperial threads. ( I suppose it could also be a 6mm lead screw approximating .25" pitch)

The idler would be replaced by a compound (that is two additional gears) that did the thread you wanted



hillriver171 said:
Hello
I was wondering if anyone would have any ideas on how I could get my lathe to single point thread 28 and 32 tpi. I’m going to thread the muzzle of my rifle for a brake , and just about every one out there is 28 and 32 tpi . The lathe is a late 80s 17x40 enco engine lathe.
The lathe cuts 1/n”
14,16,20,24,36,40
7, 8,11,12,18,20
3.5,4,5.5,6, 9,10
1.75,2,2.75,3,4.5,5
The gears are 91 / 96 with a 100 idler
Click to expand...
 
I’m not set on any specific break at this time, I just see that most of them are 28 and 32 too.
I believe my lead screw is 4 tpi .
I’m doing a Ruger American youth model in 7mm08 . It has to be a 1/2 in thread due to the barrel diameter.
 
Before I got my lathe, I'm pretty sure the guy who threaded one of my barrels for a silencer used a die. The silencer or brake registers on the shoulder of the relief cut, so no need to get fanatical about the threads.
 
5/8 24 is kind of standard for 30 cal
That said not having 28 and 32 tip setting is just really weird

Might be better to ask the question of how to cut 28 and 32 tip on that lathe
In the general forum larger knowledge pool better chance to find some one who has actually dealt
With the problem
 
Might be better to ask the question of how to cut 28 and 32 tpi on that lathe in the general forum.

Might also ask MSC who owns Enco now.
 
hillriver171 said:
Hello
I was wondering if anyone would have any ideas on how I could get my lathe to single point thread 28 and 32 tpi. I’m going to thread the muzzle of my rifle for a brake , and just about every one out there is 28 and 32 tpi . The lathe is a late 80s 17x40 enco engine lathe.
The lathe cuts 1/n”
14,16,20,24,36,40
7, 8,11,12,18,20
3.5,4,5.5,6, 9,10
1.75,2,2.75,3,4.5,5
The gears are 91 / 96 with a 100 idler
Click to expand...

If the lathe already cuts 14 and 16 TPI, then you only need to introduce 1:2 ratio into the gear train somewhere. Then you'll have both 28 and 32 TPI. So the end result should make the lead-srew turn slower (1:2). Then set it to 14 for 28 or 16 for 32 TPI. Hope this helps.

Best Regards,
Bob
 
GGaskill said:
Might be better to ask the question of how to cut 28 and 32 tpi on that lathe in the general forum.

Might also ask MSC who owns Enco now.
Click to expand...

May not get an answer or get locked on the general forum for brand of lathe. Surprised that two common threads are not able to be cut on that lathe.
 
I was going to say, just make your own brake and thread it to whatever you want, but PM me for a quote, I can send you a un threaded brake and you can take it from there.
 
Some of the foreign lathes have a page in the manuals with pick off gear combinations to get one or two threads that aren't on the thread data plate.
I had a beautiful Takisawa TSL 800 that couldn't thread 13 TPI, and needing money I sold it without knowing about special gearing pages in manuals (I don't know if gears existed or any data on odd threads was in the manual). I still miss that lathe after all these years.
 
For now I’m gonna go with the die to get this project done, but I really want to get it geared up to to single point those other threads.
Thanks for all the reply’s , I know there gonna get me going in the right direction.
Matt
 
double check your lathe's gearing. My Enco was set up for metric threads from the factory. Imperial threads require different gearing set up. All required gears were included with the lathe. read the manual.
skid
 
hillriver171 said:
I’m doing a Ruger American youth model in 7mm08 . It has to be a 1/2 in thread due to the barrel diameter.
Click to expand...

That's not a lot of barrel for threading a 7mm. The minor diameter of a 1/2-28 thread is .457. With a .284 hole down the middle that leaves a wall thickness of only .086.

I know some gunsmiths will thread a .30 cal barrel 1/2-28, but I've never been comfortable with it.

--
Pat Jones
Firestone CO
 
hillriver171 said:
Hello
I was wondering if anyone would have any ideas on how I could get my lathe to single point thread 28 and 32 tpi. I’m going to thread the muzzle of my rifle for a brake , and just about every one out there is 28 and 32 tpi . The lathe is a late 80s 17x40 enco engine lathe.
The lathe cuts 1/n”
14,16,20,24,36,40
7, 8,11,12,18,20
3.5,4,5.5,6, 9,10
1.75,2,2.75,3,4.5,5
The gears are 91 / 96 with a 100 idler
Click to expand...

IIRC, the Taiwan lathe I have has an input section of the gearbox,and a geometric section of the gearbox to multiply the input by 2,4,8, etc. seems like yours must have something similar.

Input at 1.75, then doubles to 3.5,7,14
Input at 2, then doubles to 4,8,16
Input at 2.75, doubles to 5.5,11,no 22? Hmmm- this is weird.
Input at 3, doubles to 6,12,24,
Input at 4.5, doubles to 9,18,36
Input at 5, doubles to 10, 20, 40

Think about it systematically and see if there is a way to multiply
the 3.5 gearing by 3 steps. And the 4 gearing by three steps. It is entirely possible the lathe can do it, but the gearing selection plate is misleading.
BTW, I had to disassemble my 1340 and re-arrange the gears -the factory had assembled it incorrectly. Weird stuff happens.
 
I ran into this same problem on a small import and found the dies I needed on eBay for a few bucks. I’m looking for a lathe that I won’t have to remove gears for threading.
I believe the smaller calibers use the smaller 1/2 -28 threads and stuff 6mm and bigger use the larger 5/8 24. A die will get the job done and the gearing will drive you up the wall.
 
Any lathe with a lead screw will cut any thread desired! It may not be available on the quick change chart but it will cut any thread. The way to cut any thread desired including metric can be calculated. Simply look at a Machinist Handbook! All my lathes have inch lead screw but I cut metric threads. The threading dial may not work on some threads nor will it work when doing metric threads with inch lead screw and vise versa.So you will simply have to reverse the spindle without disengaging the half nut. In addition to machinist handbook I'm sure the method of calculating the gears needed are online.
 
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