cutting treads and timing

[tcbnick]

Just a ? only because I like to know how things work not that I really need to know. If your cutting threads on a barrel, for lets say a reciever and its an octagon barrel , the threads have to stop and be tight at the same time that the barrel flat is at the perfect top and level for the sights to work. Or another, say a muzzel brake with side vents, it has to stop at the right spot or you'll get dirt in your face. But how is this done, back in my Drag racing days we would use thin washers under spark plugs to index them but that was a trail and error method, and not what I woul guess that a gunsmith would do, or some in depth math formulla. Not that I will go out and through my barrel in the lathe but I would just like to know.
Thanks Nick

[williamwaco]

Nick.

That is why a good gunsmith is worth his asking price.


.

[Reload3006]

I am a machinist tool n die maker I can think of several ways it can be done. the easiest would be to use a DRO and face off the chamber end to fit the action. then you could shim it (same as facing off the chamber end) or if you have an NC mill you can calculate it out and start your lead in the correct place. But The honest answer is Face it till its right. (at least how I do it)
edited to say shoulder on chamber end. LOL necessary or not I do face to keep the same length so If I take off .020 from the shoulder I take .020 off the end too. Probably not necessary but I do it anyway.

[tcbnick]

I get it, No we measure once and cut twice till it fits. LOL
But really, a man that knows his trade is worth his weight in gold.Thanks Reloader Now I know
Thaks Nick

[Mooseman]

When setting Back a Barrel , you can measure what the distance of one complete turn of the barrel thread is (gap)and machine off Close to that amount. Using the index mark on the barrel compared to the index mark on the action you test thread the action back on , and it should seat shy of full indexing to allow for torquing the barrel to line the marks up. Usually about 3/16 inch to 1/4 inch shy of the marks lining up will torque properly.
The amount removed from the barrel shoulder is is the same amount to be removed from the barrel face before it is torqued into place.
It is then ready to rechamber to spec.

Rich

[felix]

Me, a BR guy, does not understand the words "torqued into place". It seems to me the builders of these guns use constant torque from the very first thread. In other words, the resistance must be absolutely consistent as the barrel is turned and then stopped at the zero headspace/datum spec. ... felix

[rbertalotto]

You thread the shank of the barrel and install on the action.

You see where the "flats" land. If the tenon threads are 16 to the inch, each full revolution of the barrel is 1/16 of an inch closer to the receiver. If with the barrel up snug to the receiver and it needs to turn another 90 degrees to index properly, you would face off from the barrel shank "1/4 of 1/16"" which is .0156". Most will face off .014 and leave .001 for a bit of a "crush" factor.

Same thing would be done on a muzzle brake. Once you know the "threads per inch" , and how much of a revolution the brake needs to turn to index properly you can simply do the math and face off the brake that amount.

Shim washers are actually used on military rifles (M-16, AR15, etc) to index the flash hiders and muzzle brakes. On a military rifle looks are not important. This would NEVER be done on a quality hunting or target rifle.

[MBTcustom]

Thats why you buy a barrel blank that is longer than what you need. Like rbertalotto said, degrees of rotation are a function of how far the barrel is able to screw into the action. The experience comes in because the smith has to stop cutting when the action is able to touch the shoulder, but has not lined up yet. He takes the barrel out of the lathe and installs it in the barrel vice and uses the wrench to set a certain torque. An experienced smith is able to call his shot and that sucker will be perfectly flush when the torque is right. Its just a matter of knowing how much crush you get for a given thread.

[Hang Fire]

Hope not hijacking thread and although not the same, thought this might prove helpful.

Correctly fitting a muzzleloader breech plug presents a similar problem, but it is two fold. One wants the plug to seal on the internal bore shoulder and the tang bolster to mate up with the top flat, with both doing so simultaneously, did I mention this is hand filing work.



Few years back I wrote up a short article at http://www.americanlongrifles.com/index.htm as to how I breech a muzzleloader which explains the procedure.

http://www.americanlongrifles.com/Workshop_Fitting_Breechplug.htm

[John Taylor]

Timing can sometimes be a fun project. New octagon barrels are not to bad when you have eight different spots to time to but put sight dovetails on first and then you have one spot to time to. Most of the barrels I do get threaded and chambered before octagon or dovetails so there is no problem. Thread pitch makes it impossible to say hand tight and then so many degrees for toque. With 16 threads per inch you can probably get about 20 degrees from hand tight to tight with a barrel vice, a coarser thread would be less. When doing a barrel thread I leave the barrel in the lathe and test the action for fit taking a wild guess at where it will tighten up. This is where experience comes in, you only get it by doing lots of barrels. If a barrel comes up a bit shy from lining up you can get it to go further by loosing it and tightening it several times. It's a good idea to lube the threads so there is less chance of galling the threads, be very careful with stainless barrels and actions as they gall easy.
As Hang fire said, fitting a breach plug can be harder. I use lay out die for checking fit. Most muzzle loading barrels are softer than high power barrels so the threads can be moved more with torque to "seat" the plug in place.

[JIMinPHX]

When making machine parts, I've timed threads in two different ways. On CNC machines, You can program the thread start position. A CNC lathe has a zero index point on the spindle & if you mark the chuck, you can reference from that mark. When thread milling on a CNC mill, most modern controllers will let you program your lead start wherever you want it.

When working on machines that are not under NC control, I usually make a thread indexing fixture that consists of a tapped hole or threaded stud with a flange that has pin holes or a clamp plate so I can rotate it to where the thread needs to start.

On a gun barrel, I would probably just cut the thread blindly, then face the shoulder back until I got the alignment that I wanted.

[MBTcustom]

Now that we know what a pain this issue is, think about all the british enfield rifles that have interchangeable barrels and bolt faces. Those Brits made them all timed so that an armorer could unscrew a cordite eroded barrel, and screw another one right on in its place and upon applying 120 ft lb. of torque, the front sight would land strait up and in line. Head spacing was accomplished by using different sized bolt-faces, each one threaded in time to the bolts so that when the bolt is closed the face was screwed all the way in.
I got with an old friend of mine, (Ive only known him about 3 months but he's 85 years young) and we took the bolt faces off of three different enfields and they all interchanged!
As a machinist that blows my mind. That also conclusively proves that there is a way to time threads other than the cut and check style that we are all familiar with.

[John Taylor]

Now that we know what a pain this issue is, think about all the british enfield rifles that have interchangeable barrels and bolt faces. Those Brits made them all timed so that an armorer could unscrew a cordite eroded barrel, and screw another one right on in its place and upon applying 120 ft lb. of torque, the front sight would land strait up and in line. Head spacing was accomplished by using different sized bolt-faces, each one threaded in time to the bolts so that when the bolt is closed the face was screwed all the way in.
I got with an old friend of mine, (Ive only known him about 3 months but he's 85 years young) and we took the bolt faces off of three different enfields and they all interchanged!
As a machinist that blows my mind. That also conclusively proves that there is a way to time threads other than the cut and check style that we are all familiar with.

Some of the bigger companies like Winchester used thread cutting mills for the actions. I made up a gauge for checking model 70 barrels when cutting the threads and marking with a witness mark and they will line up with the frames. Then there are companies like Stevens that just used a tap for the frames, can't inter change barrels. Most of the military rifles I have seen are very close when it comes to timing.

[rbertalotto]

Some day whem I'm out Washington way, I'd like to stop in and visit with John Taylor.......seems like the most practical gunsmith I read on these forums...........I bet a folk could learn a bunch from him...........

[John Taylor]

Some day whem I'm out Washington way, I'd like to stop in and visit with John Taylor.......seems like the most practical gunsmith I read on these forums...........I bet a folk could learn a bunch from him...........

I could use an apprentice, I can't keep this work up forever. Problem is I can't afford insurance on someone coming into the shop. Had a guy working in the shop a while back and got the lawyer scare. Anyone looking to buy a gun shop? My mortgage company says I have to work till I'm 90, I'll do my best.

[Hang Fire]

I could use an apprentice, I can't keep this work up forever. Problem is I can't afford insurance on someone coming into the shop. Had a guy working in the shop a while back and got the lawyer scare. Anyone looking to buy a gun shop? My mortgage company says I have to work till I'm 90, I'll do my best.

Know what you mean about the lawyer scare. Back in the late 90s wife and I started a cottage industry thingy making products. it was slow going for a bit, then when word of mouth spread, it took off on steroids. With the wife almost overwhelmed with assembling, shipping and handling, it reached the point where I was on the phone and Internet much more of the time than in the shop producing things. We thought about hiring a couple of workers, but when looked into the labor rules, regs, and the legality of it, spooked up off that idea real fast. Medical problems finally resulted in our shutting it down.

The bloody government makes it hard enough to start a mom and pop business, but when it came to expanding and the hiring of workers, the daunting challenge of it became a nightmare.

[rbertalotto]

Know what you mean about the lawyer scare. Back in the late 90s wife and I started a cottage industry thingy making products. it was slow going for a bit, then when word of mouth spread, it took off on steroids. With the wife almost overwhelmed with assembling, shipping and handling, it reached the point where I was on the phone and Internet much more of the time than in the shop producing things. We thought about hiring a couple of workers, but when looked into the labor rules, regs, and the legality of it, spooked up off that idea real fast. Medical problems finally resulted in our shutting it down.

The bloody government makes it hard enough to start a mom and pop business, but when it came to expanding and the hiring of workers, the daunting challenge of it became a nightmare.

And this , ladies and gentlemen, is what is horribly wrong with America and why it will never be what is was in its glorious past! "Death by a thousand cuts!"

[HollowPoint]

"And this , ladies and gentlemen, is what is horribly wrong with America and why it will never be what is was in its glorious past! "Death by a thousand cuts!""

Which in turn is why folks hire illegal aliens, cheat on their taxes and and generally hate the IRS with a passion.

HollowPoint

[nanuk]

there has to be a way around it.

[Mooseman]

There is...Its called a "Sub-Contractor".
The apprentice gets a business licence under his own name or makes up a company name.
He then works in the shop running his own business and is responsible for his own taxes and insurance.He learns and does jobs and is paid by the Shop Owner a straight job hour wage that is usually about 1/3 of the Shop rate . The shop owner has no taxes or SS to worry about paying or bookkeeping. The Apprentice has to handle that at tax time as "Self Employed".
The Apprentice can then deduct his tool costs and all business expenses legally.
He is not only learning the trade, but also learning Business Management and bookkeeping. He invoices his jobs to the shop owner. Its All Legal.

[rbertalotto]

I've owned five businesses in my lifetime........The IRS was never an issue. You pay your taxes as a cost of doing business.....no issues there.

It was the State, Local and Federal rules, regulations, laws, changes, fees, and worrying that you dropped the ball somewhere.

All chicken-s--t stuff. But little Barney Fifes running around with their clip boards justifying their phony baloney jobs...........I actually had one inspector tell me that the only reason he was inspecting me was so he could secure a larger budget the next year. It was a woodworking shop with a candy machine and he was a food inspector!!!!!!!!!!!!!!!

Don't get me started!

I'd open my sixth business tomorrow if I didn't have to jump through so many hoops. I could hire a couple dozen folks within a month. But I just don't have the stomach for it any longer.

When young folks ask me about starting a new business, I can't lie to them. I tell them to get a phony baloney civil service job with a good state or federal pension. Suck off the teets of all the private sector folks. Go out on a phoney disability...........Hire a lawyer and sue them if they turn you down! That splinter in your finger is a career ending ordeal!

I have a bumper sticker.........." I'm working my *** off so 40% of working age Americans don't have to!"

Whatever....................:cry:
So sad...............

[rbertalotto]

There is...Its called a "Sub-Contractor".


Its All Legal.

Can you send me the name of your lawyer and accountant...........and you might want to have them call Mircosoft. Could have saved them about a half a billion!

Be real careful about hiring subcontractors........

[John Taylor]

There is...Its called a "Sub-Contractor".
The apprentice gets a business licence under his own name or makes up a company name.
He then works in the shop running his own business and is responsible for his own taxes and insurance.He learns and does jobs and is paid by the Shop Owner a straight job hour wage that is usually about 1/3 of the Shop rate . The shop owner has no taxes or SS to worry about paying or bookkeeping. The Apprentice has to handle that at tax time as "Self Employed".
The Apprentice can then deduct his tool costs and all business expenses legally.
He is not only learning the trade, but also learning Business Management and bookkeeping. He invoices his jobs to the shop owner. Its All Legal.

The problem comes when he gets injured running one of my machines in my shop, even if he signs a waver, his family can take everything I have if he gets his self killed.