Looking for Gun Smith to cut Metric

29 September 2011, 04:08

Looking for a Gun Smith to cut metric threads on a minnie Mauser barrel located in Eastern Iowa or Western Illinois. My lathe goes from 16 to 18 threads, need 16.75 or 17 TPI.

Thanks in advance.

29 September 2011, 05:04

WoodHunter

What is the lathe? A lot of them come with a metric transpose gear (127 teeth) A bit of technique required when cutting metric, but once you have cut a couple it is easy.

Open the gear train cover on the left, look for a gear snugged up to another, but not engaged to any other gears. Count the teeth. If 127, you have a transpose gear. The feed/thread index on the front of the lathe, or the instruction manual, should show how to put the transpose gear into the train for metric. If you have the gear but no instructions, pipe up and I will post the method.

29 September 2011, 06:23

olcrip

KOOL Woodhunter. I'll check it out in the morning. It's an old belt driven engine lathe with a bunch of gears stacked all over it's storage area. Thanks a bunch.

29 September 2011, 06:34

ssdave

Reason that the transpose gear works, and the conversion to figure out the pitch is that 254 mm = 1 inch. 127 is half of 254. You can use the ratio to calculate the mm pitch the 127 tooth converts the inch pitch to.

dave

29 September 2011, 06:48

olcrip

Thanks SSDave. When I find that 127 gear I will return to the forum and get more clarification so I can figure out what to do, Thank you much.

29 September 2011, 06:51

WoodHunter

quote:
Originally posted by ssdave:
Reason that the transpose gear works, and the conversion to figure out the pitch is that 254 mm = 1 inch. 127 is half of 254. You can use the ratio to calculate the mm pitch the 127 tooth converts the inch pitch to.

dave

Roger dodger. We old fart machinists learned this back when Noah was looking for nails and found nothing but locust wood trunnels.

My first lathe (1937 South Bend) had a bucket full of change gears and , horrors, no quick change. So I became proficient at obtaining greasy fingers when changing feeds and thread pitches.

29 September 2011, 06:51

jeffeosso

www.mcmaster.com

opinions vary band of bubbas and STC hunting Club

Information on Ammoguide about
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What is an AR round? Case Drawings 416-458-470AR and 500AR.
476AR,
http://www.weaponsmith.com

29 September 2011, 06:56

WoodHunter

quote:
Originally posted by olcrip:
KOOL Woodhunter. I'll check it out in the morning. It's an old belt driven engine lathe with a bunch of gears stacked all over it's storage area. Thanks a bunch.

You might not have one, back in early days of lathes no one cut metric and the transpose gear was a special order, it was not automatically included with a lathe. But, you can buy them from Boston Gear, its nothing but a 127 tooth spur gear. Maybe on ebay.

My old South Bend manual has a good treatis on metric threads and gearing, I will hunt up the book and maybe post some of the data and illustrations.

29 September 2011, 06:57

olcrip

I just came back from the shop. I don't have a transpose gear. The biggest gear is a 120 tooth. Can such a gear be purchased for it?

29 September 2011, 06:59

WoodHunter

quote:
Originally posted by olcrip:
Thanks SSDave. When I find that 127 gear I will return to the forum and get more clarification so I can figure out what to do, Thank you much.

AR has a pile of machinists and experienced lathe hands in the membership, keep asking questions, someone will pipe in and help you out.

29 September 2011, 07:03

WoodHunter

quote:
Originally posted by WoodHunter:
quote:
Originally posted by WoodHunter:
quote:
Originally posted by WoodHunter:
quote:
Originally posted by olcrip:
I just came back from the shop. I don't have a transpose gear. The biggest gear is a 120 tooth. Can such a gear be purchased for it?

Yep, read the above posts. Might even be able to buy one from Grizzly. Need to know the diametrial pitch of the gears, the Boston Gear site should explain this.

The 120 will be used in the gear train when cutting metric, so it is nice that you have one.

29 September 2011, 18:30

LesBrooks

What lathe do you have to work on? This was the problem that I had trying to find someone to cut the metric thread with the project of Stockmaker Show and Tell thread at the top. I posted a picture of the old Atlas lathe that was found in a barn. I was able to cut the metric thread with this old Atlas. It isn't how good a lathe that you have, but how you are able to make the lathe do the job. I have the picture of the chart on the inside of the end cover which shows the combination of gears.
I had sold all my own machines when I decided to make the 204 Ruger.
The 7X12 lathe that Grizzly sells will cut these threads. I have used it when I had my own shop and needed to cut metric threads. The spindle bore is only about 3/4 inch dia. and will work on a barrel up to sporter weight. I posted the chart, but it wasn't clear enough to read. I will PM you the chart of the gears for the old Atlas lathe if you would need this info.

29 September 2011, 19:08

Jim Kobe

I have fit a number of barrels to metric threaded actions. Email me if you are interested in sending it to Minnesota.

Jkob60@msn.com

Jim

29 September 2011, 21:52

olcrip

Jim, what part of Minnesota are you in? I will be taking a trip to Winona on the 14th of OCT. with my car club. I could leave a day early if you are in the vacinity to meet up with you.

29 September 2011, 21:56

Jim Kobe

PM Sent

29 September 2011, 22:23

brad may

Ain't no such thing as a 16.75 or 17 tpi metric thread.
You can make anything fit, doesn't mean it's right.

29 September 2011, 23:07

olcrip

Thanks Brad, I needed that. 1.5 MM transposes to 16.75 threads per inch. 17 threads comes within .00023 of 16.75 or 1.5 MM. Actually the size is 22 mm (Mini Mauser dia.) X 1.5 mm which converts closely to .866" X 16 3/4 T.P.I.. Hope this clears it up more for you. We all learn something new. This is a great forum.

29 September 2011, 23:19

FOOBAR

As metric threads have a different designation and need to be converted, Brad, maybe Olcrip did the best he could at the time.

Oldcrip...there are several online metric to english, english to metric conversion tables...http://www.newmantools.com/tech/pitchconversions.htm...might get ou there or just go to Newman Tools and surf to the conversion tables.

What your are describing could be a 16.93 tpi or 1.50 metric pitch. You need to calculate the pitch for metric the same way as for English...1 divided by the number of threads per inc...in this examle 1/16.93 tpi = 0.05906 pitch in inches times 25.4mm/inch - 1.513mm - pitch in mm.

In any event you still need the correct toothed gear...maybe You and Jim can get together on a solution.

1.50 mm is a standard metric pitch as is 1.00, 1.25" etc.

Luck

30 September 2011, 00:13

brad may

What I was trying to get at was that if the threads are short you can make it work. The longer the threads are the sloppier they will have to be to fit. Before you pull all your hair out, I would try to find someone with a lathe that can cut metric.
Metric threads are designated by pitch. Only thing I like about metric.
If I knew anything about gunsmithing you could ship it to me, and wouldn't even charge you.
Didn't mean to come off as an asshole.

30 September 2011, 00:44

olcrip

Brad, I'm sorry but I didn't mean to imply a name. I'm at the hair pulling stage now. I'm looking for the gearing to transpose so I can cut it on my lathe in my shop. I do appreciate your input.
Olcrip

30 September 2011, 00:57

brad may

Do you have enough meat in the receiver to kill the threads you have now? 1.5mm pitch is kind of fine. Could you kill the metric threads and rethread the receiver with standard American pitch threads?
I know they do this with Winchester receivers.
Just a thought. More than one way to skin a cat.
I'm not the one though to tell you there is enough meat in the receiver to be safe. Need to ask a gunsmith that.

30 September 2011, 01:14

olcrip

I don't beleive there is enough material to convert to Standard threads. If I ever should sell this mini Mauser there would be a liability involved by remanufacturing it to other specs. I'm going to find my gears for my lathe eventually but in the mean time I just might drop a visit with Jim Kobe in Minnesota when my car club comes close to the area. Thanks for the idea, a last resort, MAYBE.

30 September 2011, 02:51

D Humbarger

Cutting metric threads is not rocket science. Once you find the right gear combo you just NEVER disengauge. You just take a cut, back out (real quickly) reverse, feed in & take another cut, reverse again & keep repeating the process. It makes some folks a bit uneasy because you have to back out & reverse fast so you done run into the barrel shoulder. Once you get the hang of it it is not hard. You just have to pay close attention to what you are doing & be quick

30 September 2011, 03:11

kcstott

quote:
Originally posted by D Humbarger:
Cutting metric threads is not rocket science. Once you find the right gear combo you just NEVER disengauge. You just take a cut, back out (real quickly) reverse, feed in & take another cut, reverse again & keep repeating the process. It makes some folks a bit uneasy because you have to back out & reverse fast so you done run into the barrel shoulder. Once you get the hang of it it is not hard. You just have to pay close attention to what you are doing & be quick

There is a way to run the lathe in reverse with the tool holder on the back side of the part this allows you to start at the shoulder and cut to the breach.
We did it this way for years and years on part that needed thread right up on a shoulder.

Gunsmithing has nothing to do with single point thread cutting. Machining does!!

30 September 2011, 03:35

olcrip

Gentlemen, I have cut threads in my past. I used to be a Tool Maker years ago before I went into carpentry work. It's not the ability to cut threads but the equiptment to do the job with. I cut American threads all the time on my machine but not metric. My dilema now is that I have two new Remington barrels that are shank cut for the mini Mauser but can't be threaded because of metric thread.

30 September 2011, 05:35

D Humbarger

quote:
Gunsmithing has nothing to do with single point thread cutting. Machining does!!

30 September 2011, 10:08

kcstott

Olcrip.
I'm not coming down on you. Nor did I mean to insult you in anyway. My comment was purely general in nature addressed to "whom it may concern".

Now if it were my rifle and my machine I would not even sweat the metric threads and just cut them at 17 tpi and be done.

We've been down this road before and some don't feel comfortable doing it. I'll say it again. How worn is the lead screw on the machine being used? That in itself adds variance to the thread pitch. so why worry about two thou over an inch when the barrel tenon is not even 3/4 of an inch.
The other statement I made on cutting metric threads using an american lathe was how many guy are using 60 degree cutters when they should be using a 55 degree?? Not to mention how square you get the tool to the part. Yada yada yada

30 September 2011, 11:23

olcrip

Kcstott, my lathe chart jumps from 16 TPI to 18 TPI. For about 5/8 of an inch of shank lenght it wouldn't make a hoot of difference but I don't have 17 TPI on my old engine lathe, I think it was left on the old ship it came off of. Thanks for the thought. If I could find the 100/127 transposing gear and a 48 T I would have it made even without shade.