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Old 01-11-2010, 08:14 PM   #1
NYECOGunsmith
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Default How To Install A Screw In Choke On A Shotgun

Geo was over here today, and as usual he had lots of questions about things gun related.
One of the questions he posed today was regarding the ins and outs of installing a screw in choke tube in a shotgun that currently has a fixed choke.
A fixed choke by the way is one that is machined right into the barrel at the time of manufacture, and is not removable. Well, not without permanently removing it that is.

Since Geo is about the 5th person to ask me about how one goes about installing a screw in choke in a fixed choke shotgun within the last week or so, I decided to detail it out for everyone and post it here on the forum.

This will take about 4 posts, as it is a somewhat lengthy explanation. Here's part one.

For starters, I don’t generally recommend a home gunsmith try to install a screw in choke in anything but a single barrel shotgun.
Installing them in a side by side double barrel or over and under can change the regulation of the barrels, and that’s something that only a experienced gunsmith is going to be able to rectify with any ease.

If all you want to do is remove a fixed choke that is anything other than a Cylinder Bore choke (I.E. a Improved Cylinder, Modified, Full or Extra Full choke) and be left with a Cylinder choke, that can be done two ways.

The first method you can employ is to can ream out the existing choke with a reamer, or alternately hone it out with a hone, although the reamer is a lot faster. If you go all the way with the reaming or honing, you end up with a Cylinder bore, that is, no choke what so ever.

Doing this carefully you can also change a Full choke to a Modified, or a Improved Cylinder, or a Skeet, or a Cylinder bore. You could also change a Modified to a Improved Cylinder, Skeet or Cylinder bore. This is known as “Opening up a choke”.

If the bore is chromed, you need to use the hone first until you get through the chrome, as it will most likely chip the reamer if you start with it, as the chrome is harder than the tool steel reamer.
This also applies to a chromed bore before you ream it and tap it for the screw in chokes. The chrome has to go first.

This leaves the exterior of the barrel untouched, and is the best (sometimes only) way to go about it if the barrel has a ventilated rib on top of it. Vent ribs are tough to cut and get to stay in place when you shorten the barrel. Not a task for a home shop or hobbyist in most cases.

The second way is to cut the barrel back about two (2) inches and move the front bead back.
This, of course, assumes that the barrel is sufficiently long enough to cut back by two (2) inches and still be of legal length.

Legal length by the way being at least eighteen (18) inches for a shotgun, unless you have filed the paperwork and gotten permission to create a Short Barreled Shotgun. But that’s another topic all together.

So we have a single barreled 12 gauge in our example, that does or doesn’t have a vent rib, but we want to keep the existing barrel length and have the ability to change chokes at will.

We need at this point to determine if the barrel is suitable for screw in choke installation.

First we check to see that the last fifteen (15) or so inches of the barrel are straight. If the barrel is even slightly bent, we can’t install the choke tubes with any degree of accuracy. Bent barrels can be straightened (usually) but again, that’s another topic.

To check the barrel for straightness we need to lay a eighteen (18) inch or so long straight edge against the barrel at four (4) positions.

At the 12 o’clock position (or as close to it as practicable if the gun has a vent rib) at the 3, 6 and 9 o’clock positions as well. Our gun has a straight barrel so we move on to determining if the barrel wall thickness is sufficient to allow for reaming and threading for the screw in chokes.

To do this you will need a good (Read: Accurate) dial or digital caliper, or a external micrometer with a range of at least one (1) inch.

Now we will measure the barrel’s Outside Diameter (O.D.) and record the measurement. For our example let’s say it measures 0.840 inches in diameter.

To be sufficient, the barrel wall thickness remaining after reaming and tapping must be at least fifteen-one hundredths (0.015) inches.
Some sources will say you can do it with as little ten-one hundredths (0.010) of an inch, using Tru Choke Thin Wall chokes.

While this is technically correct, it is not something I would suggest anyone but an experienced gunsmith try, as you risk the possibility of damaging the choke tube, or having a barrel blow out if the reaming and threading are not done perfectly.
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Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-11-2010, 08:16 PM   #2
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Begin Part 2 of 4
There are a number of factors to consider when deciding to install a screw in choke in a barrel with measured values of wall thicknesses that put the thinnest portion of the barrel wall at the 0.010” mark when the job is done.

These include judging the quality of the barrel steel, whether or not the bore is concentric with the outside diameter, the skill of the installer in measuring the wall thickness and his or her skill at the actual installation.

So for the purpose of this document I’ll just stick with saying you need at least the fifteen-one hundredths (0.015) inch wall thickness to do the job safely.

For further clarification, I would not try to ream and thread any 12 Gauge barrel that had a Inside Diameter of greater than 0.735 inches. The walls will end up too thin generally speaking.
If you are working on another gauge, the values are 0.780” for a 10 Gauge, 0.666” for a 16 Gauge, and 0.624” for a 20 Gauge.
There are values for minimum outside diameters of the barrel as well. They are 0.900” for a 10 Ga., 0.825” for the 12, 0.770” for the 16, and 0.700” for the 20.

Onward!

We’ve measured the O.D. of the barrel and found it to be 0.840”. Now using the inside measurement tips on our caliper, or a inside measuring micrometer (or if we have the money to spend, by using one of Dave Manson’s superb “Wall Thickness Gauges”, running right around $100 from Brownell’s) we are going to measure the Inside Diameter (I.D.) and record that value. For our example will say the I.D. is 0.700 inches.




Now we subtract the I.D. measurement from the O.D. measurement and divide the result by 2. This will give us the Average Barrel Wall Thickness. In our case, that would be 0.840-0.700= 0.140 inches, divided by 2 we then have 0.070” for our Average Barrel Wall Thickness.

But what if the barrel’s bore isn’t concentric with the O.D.? We may have a spot where it’s too thin.
So we use the calipers again to measure the actual wall thickness at the four points we mentioned earlier. We will record these and pick the one that is the smallest number which indicates that the barrel is thinnest at that point for use in the next calculation.

On our example gun those 4 measurements are : 0.068” at 12 o’clock, 0.069” at 3 o’clock, 0.071” at 6 o’clock and 0.072” at 9 o’clock.

Taking a look at these last four measurements, we can see several things of interest to us.

First, that the barrel wall is the thinnest at the 12 o’clock position.
We need to keep in mind that the front bead may intrude into the bore if we ream it out to accept the screw in chokes.

Second, that the bore is not concentric with the Outside Diameter.
Not that big a concern, but nice to know.

And third, that the barrel wall at its thinnest location is 0.002” thinner than the Average Barrel Wall Thickness we calculated earlier. We determined this by subtracting the measured thin point of 0.068” from the Average Barrel Wall Thickness of 0.070”. We need to make note of that difference.


The reamer for a 12 gauge for most screw in choke installations is 0.797 inches in diameter. If we subtract the reamer diameter from the measured barrel O.D. (0.840”-0.797” = 0.043” in our gun) and divide the result by 2 we find that we will have a Average Barrel Wall Thickness of 0.0215” AFTER reaming.
Now to allow for the non concentric barrel to bore relationship, we need to subtract the 0.002” difference between the Average Barrel Wall Thickness and the thinnest wall measurement from the Average Barrel Wall Thickness to get the final wall thickness at its thinnest.
Doing that we get 0.0215”-0.002”= 0.0195”, which is what the wall thickness will be at the thinnest spot after we are done with our choke installation.

If we adhere to the rule of always maintaining at least a 0.010” wall thickness, we will have plenty of metal left on this gun when we are done. So we can proceed with the actual work of installing the screw in choke system.

Now you need some tools to do the work with. Some you already have, but I will list them again just for drill. The others are specialty tools. These can be obtained from Brownell’s Gunsmithing supply, Midway USA, and from some gunsmith’s tool rental businesses that you can find online.

You will need the following tools:

1. A accurate Dial or Digital Caliper.
2. A good brace (used to turn auger type drill bits, Home Depot carries them, the Stanley brand is pretty good, runs around $25).
3. A strong bench vise to hold the barrel.
4. Padded vise jaws, wood or leather or soft lead.
5. A pilot bushing of the appropriate diameter for the bore you are working on.
6. The appropriate reamer for the gauge, in our case, the 0.797” reamer for a 12 gauge.
7. A quart of high sulphur content cutting oil, available at Home Depot in the plumbing department.
8. The appropriate choke tube thread tap for the gauge and brand of choke tubes being installed.
9. A 35 inch long flat blade screw driver.

If you use the non-lathe screw in choke tube installation kits from Tru Lock Tool company (makers of Tru Chokes) the kit will contain the correct Tap for the brand of gun, the 35 inch screw driver, pilots (a range of sizes for the gauge, in about 0.002” increments) and the reamer. These kits range from about $110 to $170 by the way.
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Just because you are paranoid doesn't mean someone ISN'T OUT TO GET YOU!
Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-11-2010, 08:17 PM   #3
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Begin Part 3 of 4

Now we can lock the barrel in our padded vise and get started. The barrel needs to be held tightly, but without marring or crushing it of course! And the vice should be rock solid as well. We don’t want anything to move while we are working on it.

I usually put the barrel in the vise horizontally, initially, until I get the reamer and pilot bushing installed. Then I switch it to the vertical position for the reaming part of the job.
And I tap it with it in the vertical position also.


Take the appropriate size pilot bushing from the kit, and after making sure it is very clean, slip it into the barrel from the breech (chamber) end. To pick the right size pilot, choose one that is about 0.002” smaller in diameter than the measured bore diameter. Since we measured ours at 0.0700”, we would want to use a 0.698” diameter pilot bushing.


We need to have the bushing be a tight fit, but it has to slide and turn within the barrel smoothly at the same time. Too much slop will ruin the job, too tight will make it tough to ream the old choke out and to tap the threads for the screw in choke tubes.


One end of the bushing has a screw driver slot cut into it, and this end should face towards the breech. Use the long screw driver to push the bushing towards the muzzle until it contacts the existing fixed choke constriction.

Make sure the reamer is also very clean, and gently insert it into the muzzle of the barrel.

Use the long screw driver to screw the pilot bushing onto the end of the reamer, but don’t crank down on the two, they just have to be hand tight. The majority of the reamer should be outside the barrel at this point.

A few important notes on using a reamer.
Never let them get dry (no cutting oil) while using them, never turn them any direction except clockwise (unless you are using a left hand reamer, but they are rare) and don’t bang the reamer on anything, especially anything hard, as you will dull or chip its cutting flutes.

Now take up the brace, and close its jaws around the reamer’s drive shank, but leave it a bit loose. In other words, don’t tighten the brace’s chuck jaws down tight, the slop will let the reamer “float” in the chuck and working in conjunction with the pilot bushing, it will find the center of the barrel easier. It will also reduce the stress that is placed on the reamer, pilot and barrel.

Put a good amount of the cutting oil on the reamer, all the way around it.
Push the reamer gently into the bore, and using a light to moderate amount of pressure, turn it clockwise to start cutting. Turn it about four (4) turns and withdraw it , but leave its end connected to the pilot and partially in the bore.
Clean the chips from the reamer and re oil the reamer thoroughly.
Remember to always turn the reamer clockwise only!
Continue the above process until the stop portion or “shoulder” on the reamer is between 0.060” and 0.075” away from the barrel’s muzzle.

Doing this is going to completely ream out the original fixed choke, and increase the diameter of the bore to the correct size to accept the thread tap.

Once you reach this point, remove the pilot bushing from the end of the reamer, take both out of the barrel, and thoroughly clean out the barrel. Clean the reamer too, and store it away carefully, you will be using it again shortly!

Now take up the thread tap, lubricate it thoroughly with the cutting oil , put plenty of the oil into the barrel as well, and start the tap into the barrel, being careful to start it straight! Look at the tap from several sides (at least 3) to be sure its straight, or have someone hold a couple of straight edges up to it for you, placed 90 degrees apart on the barrel.

Turn the tap no more than 2 revolutions and then turn it backward half a revolution. This helps clear the chips from the cutting flutes so that the tap won’t bind up.
Add some more cutting oil, go forward another 2 revolutions and repeat the above steps.

If the tap is hard to turn, change the turns to 1 turn clockwise followed by the half turn back, this will break up the chips faster.

Go forward in the above pattern until the tap meets resistance. This will occur when the tap’s leading end hits the necked down area of the bore.

When you get to this point, back the tap all the way out of the bore and clean both it and the bore very thoroughly. Make sure you get all the chips off the tap, and out of the bore.

Set the tap aside gently, you may be using it again shortly as well.
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Just because you are paranoid doesn't mean someone ISN'T OUT TO GET YOU!
Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-11-2010, 08:18 PM   #4
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Begin Part 4 of 4

Now carefully reinstall the pilot bushing and the reamer as you did the first time. Take extra care, go slow, you don’t want to damage the threads you just cut.

Turn the reamer (clockwise!) into bore until it stops cutting. It will turn freely when it reaches that point. This step is needed to “square up” the shoulder inside the bore that the choke tube comes up against when it is fully screwed into the barrel. This step makes that shoulder a 90 degree “step”.

Remove the reamer and pilot bushing, again being careful not to damage the freshly cut threads.
And again clean the barrel and threads very carefully, leaving behind no chips or slivers of steel.

Now take up a choke tube and try screwing it into the barrel.
It should go in smoothly, with nothing more than finger pressure on it to turn it. When it starts to bottom out, tighten it the last half turn or so with a choke tube wrench.

Now take a bright bore light and check the bore from both ends.
You should see a slight lip or step down from the bore going towards the muzzle, as it encounters the back edge of the choke tube.
In other words, the bore should “open up” when it gets to the choke tube.

Some times you may have to run the tap back into the barrel to clean up the threads after that final reaming. If you do, remember to use lots of oil, and be careful not to bottom the tap on freshly squared up 90 degree shoulder at the bottom of the cut.

Clean the threads for the last time, give them a light coating of anti seize compound (you can get a small tube at any auto parts store for around $2), put some anti seize on each of the choke tubes you have for the gun, and install one of them into the gun.

Clean the barrel from end to end to ensure no cutting oil or chips were left behind. Never clean the barrel without a choke tube installed, as you will damage the threads. And of course, never shoot the gun without a choke tube installed for the same reason.

That about covers the installation of screw in choke tubes on a single barrel shotgun, using the “no lathe” method.

If anyone has any interest in how its done on the lathe, with a reamer and tap, or solely with lathe bits, let me know and I will detail that out for you.

Any questions or comments, or anyone having other ways of doing this, tricks to make it easier, etc. please post them here for all of us, I always enjoy learning new techniques.
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Just because you are paranoid doesn't mean someone ISN'T OUT TO GET YOU!
Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-12-2010, 03:56 PM   #5
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That is a very good explanation.
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Old 01-12-2010, 11:21 PM   #6
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Thanks! I hope it answers some folk's questions, not only with regards to how the work is done, but why a gunsmith deserves what little pay he or she gets for doing such things.
The process is simple in and of itself, but it is also very easy to screw up the process and ruin the barrel. Slip up with the reamer, tilt the tap, tap a barrel that is too thin, lots of things that can go wrong here.
Knowing how to do it, and being able to do it are only two parts of the equation.
The third part is being able to fix your screw ups! AND still have the customer be happy with the work when you are done.
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Just because you are paranoid doesn't mean someone ISN'T OUT TO GET YOU!
Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-11-2012, 12:46 AM   #7
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Thanks for posting the screw in choke installation information. I Am trying to get a lathe up and running to thread barrels for chokes (with lathe bits) and to make my own chokes. If your offer to explain how to do this is still open, I would really appreciate your posting that information. Thanks, Tom
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Old 01-11-2012, 04:09 AM   #8
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Default Lathe Method For Installing Threaded Chokes In Shotgun Barrels

Hi Tom.

Well, if that's all the work you want to do (just installing shotgun choke tubes), going the way of the lathe-less install will be much cheaper, BUT a lathe is so darn handy to have around, and so much fun to run, you might want to get one anyway!

Doing a choke install on the lathe is a bit more fussy than doing it with the tools as I described above.

If you are working on a single barrel shotgun with no vent rib, and can get the breech end of the barrel into the spindle of the lathe, and put a spider on the outboard side , then threading the barrel is just simple single point internal threading.

Of course, all the conditions for being able to thread the barrel as I described earlier must still be met.

There must still be sufficient barrel wall thickness, you still have to remove the fixed choke, etc.

If the barrel won't go through the spindle of your lathe then you will have to use a steady rest to support the muzzle end of the barrel.

And of course that will only work on a single barrel with no vent rib. By the way, being able to put the barrel through the spindle using a chuck on the front side and a spider on the outboard side usually requires either a fairly short spindle , or really long single barrel.

It's either one of those, or you need a lathe with a large spindle bore, 3.25 inches or larger, with the breech inside the spindle, the chuck holding the barrel just beyond the chamber, and the steady rest supporting the barrel just back from the muzzle far enough that it's not inline with where you will be installing the choke threads.

The more common way to git'er done with any barrel, single, side by side double, or over/under, is to use a Palmgren type milling vise mounted to your cross feed in place of a tool holder.

You line the barrel up with the spindle's axis by using a Blake Coaxial Indicator mounted in the chuck , and with it’s indicator inside whichever barrel you are going to work on first.

Move the cross feed in or out, and the Palmgren Vice’s vertical axis up or down to get the bore dialed in perfectly.

Then you lock the cross feed and compound feed so they can’t move on you, and do the same for the Palmgren vice.

You will move the barrels along the X axis by using the carriage hand wheel, and in this way will move the boring bar in and out of the barrels.

Now install one of the following in the four jaw chuck and indicate it to run true with the lathe's axis. You do that by using a Dial Indicator on the smooth, straight shank of one of the following:
A fixed reamer of the appropriate size to remove the fixed choke, or a adjustable/expandable reamer, or a boring head.

I generally prefer to use the fixed reamer, as it will remove the choke and cut the shoulder in one operation, but when I was starting and money was tight, I just used the boring head. Saves some time this way, as you will also use it to thread the barrels. Also saves some on tooling cost.

BUT it requires a delicate touch to do it! It’s really, really easy to ruin a barrel when threading it for screw in choke tubes on the lathe.
Best to practice on some of the Gray Schedule 40 PVC you can buy at Home Depot for running electrical wire in, it’s cheaper than standard white plumbing PVC and a bit easier to see the cutting on. A 10 ft length of ¾ inch will run you under $2. When you think you have it down, move up to the heavy wall metal conduit for more practice, then to a piece of schedule 40 galvanized iron pipe, and finally an old scrap barrel (you can cut it back and practice a number of times with the scrap barrel) before you try a customer’s barrel or one of your own.

I used to have my apprentices do a dozen of the PVC practice runs, and at least a dozen on scrap barrels before I let them do a customer’s barrel alone.

It takes practice and patience to do it this way, which is why I generally recommend the non lathe process. Less to go wrong with that method.

OK, so if you've used the reamers, and the fixed choke is gone, now install and indicate in the boring head by using the Dial Indicator against the boring head’s straight shank.

If you are going to be using only the boring head for everything, then install it's straight chucking shaft in your 4 jaw chuck and indicate it to run perfectly true with the lathe's axis with a Dial Indicator placed against the straight shaft.

By the way, I am assuming here that you already know how to use a 4 jaw chuck along with a Dial Indicator to get things to run true to the lathe’s axis. If not, you will need to learn how. I’ve never seen a 3 jaw scrolling chuck that would run true enough for this kind of work. But a 4 jaw independent chuck can be dialed in to just about zero run out in less than 2 minutes. Ask Vegas50 and JFComfort, they learned how, and now prefer the 4 jaw for pretty much all work, as do I.

If you are going to use the markings on the boring head's offset dial to judge how deep your cutting ( I don't recommend this, but some folks will do it that way) you are going to have to know how much the dial's reference numbers relate to the actual amount of movement. This is because of lash or take-up in the threads inside the boring head.

So, to figure that out, put a piece of straight drill rod of the proper diameter (varies by boring head, the common sizes are 0.375” Ø, 0.500” Ø and 0.750” Ø) into the boring head's outboard hole, where you will be later installing a boring bar.

Indicate this rod to run true using a Dial Indicator, by adjusting the boring head's offset mechanism to move the boring head’s offset in or out as required.

Now move the boring head offset to the first mark on the dial on the boring head so as to advance the boring bar TOWARDS YOU, and with your dial indicator that you just used, measure how much the bar shifted towards you.

You need to know how accurate the dial is IF you are going to trust it in this operation.

You'll want to take notes on how much it actually moves for each number on that dial, as the amount may not (probably won't be!) the same for each advancement due to wear, inaccurate machining, etc.

I don’t like trusting the dial on the boring head, but some folks do, and do it that way. But it can lead to disaster I think as the boring head wears.

Better to be safe every time and just use the Dial Indicator.

Personally, I prefer to just install the boring bar that has been ground to a cutting end that will produce a square shoulder when it's cutting an internal bore and use the straight, smooth portion of it’s shank to dial in the boring head to zero run out. Just saves time this way is all.

When I do it that way I use a Dial Indicator against the smooth non tapered (straight) portion of the boring bar's shaft where it protrudes from the boring head. I pre-load the DI against this spot some small amount, say, 0.200 inches then get it running true.
Then I zero the DI's dial. This is my starting point.

Now I can bring the boring tool’s tip into the barrel, and by using the boring head’s offset mechanism, bring it gently into the barest of contact with the inside of the barrel.

At this point you want to zero the dial on the Dial Indicator again. This is the starting point for cutting metal.

Now I can move the boring head's offset mechanism to increase the depth of cut, which results in enlarging the bore.

I can read the depth of cut increase on the DI's dial, remembering that for every X amount I move the boring bar towards me , I am actually increasing the radius of the circle I am cutting by 2X.

So if I move it 0.001" towards me, and feed it into the barrel, I will increase the barrel's bore diameter by 0.002".

Now you can use this set up above to remove the fixed choke, and cut the shoulder for the choke tube to seat against.

To do so, leave the cross feed and compound feed locked and use the carriage feed to move the barrels over or off of the boring bar.

Use the boring head offset adjustment to move the boring bar in or out for a deeper cut or a more shallow cut, or no cut at all as you retract it out of the barrel to clean out the chips.

Set it up for the first pass with only a 0.001” depth of cut as measured by your Dial Indicator.

Set the lathe up for manual carriage feed, and install a Dial Indicator on the ways so that it bears against the carriage, or, if you have a DRO (Digital Read Out) zero the X axis reading.

One or the other, but you need one of them to let you know when you have gone the correct distance down the barrel with either your boring operation or the threading operation.

Move the carriage towards the headstock with the lath running at slow speed, and take your first pass.

Stop it and check to see that it cut perfectly evenly all the way around the inside of the barrel.

I like to coat the inside of the barrel with red Dykem layout dye so I can see this first pass and be sure it is cutting a complete and even circle. If not, you will need to re-zero the barrel to the lathe axis, otherwise you will be cutting a off center hole and will come through the side of the barrel.

Continue on with cuts no deeper than 0.002” per pass until you have removed the fixed choke, created the shoulder, and opened the bore to the required major diameter for the choke tubes you will be installing.

Once that's done, switch the boring bar to one with the tip ground to a 60° included angle for threading. Repeat the set up above, zeroing the bar to the lathe’s axis, gently inserting it in the barrel, bringing it into gently contact with the barrel’s inner surface, rezero the DI, etc. and you are reading to cut the threads.

You do this at the absolute slowest speed your lathe will run, hopefully under 50 RPM, using lots of cutting oil, and watching the depth of cut on EVERY PASS.

Once the threading is done , all the chips are cleaned out, and the choke tube screws in smoothly, don’t forget to add a slight bevel on the muzzle, not much, just the barest hint of one, almost invisible, to make it easier to start the choke tubes into the threads.

Put anti seize compound on the internal threads, and on the threads of all the choke tubes. Try each tube to be sure it seats easily and fully, either flush for flush tubes, or to the line on extended tubes.

That’s about it.
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Just because you are paranoid doesn't mean someone ISN'T OUT TO GET YOU!
Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-11-2012, 04:19 AM   #9
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PS Tom:

Making your own choke tubes is just a matter of being able to bore an internal taper in a piece of steel bar stock, turning the outside to the correct major diameter, and threading it to the correct TPI for the barrel.

That's the (relatively) easy part.

PLUS being able to get the taper perfect, and get a superb finish on both the inside and outside of the tube. They have to be mirror bright on the inside, and near that on the outside. That takes a lot of time spent polishing them without changing the taper you just spent so much time cutting/boring out.

And you need a mill to cut the installation notches in them. Although I guess you could do it by hand with a pillar needle file, but getting them space evenly would be tough to do.

If you want to do that just for the self satisfaction, that's fine.

If you are thinking of doing it as part of a business, forget it.

The amount of time it takes to turn out a choke tube on a manual lathe would put you in the red before you got the first tube done.

They are cranked out really fast on CNC equipment, and only cost anywhere from $12 to a maximum of $100 for the really exotic alloy ones that are precision CNC machined, like the Browning Diana grade Titanium choke tubes are.

No way a manual lathe machinist can compete, it will take you at least 3 hours per choke tube to do it and get it right, and that's after you have done a few hundred of them. First few will be 8-10 hours each.

You'd have to charge $100 per tube for simple Stainless Steel chokes that the customer can buy a more precisely machined one for under $20 at Wal Mart even when you get it down to the 3 hour mark.
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Just because you are paranoid doesn't mean someone ISN'T OUT TO GET YOU!
Just because a complaint was never filed doesn't mean a defective parachute was never made.
I've been to three world's fairs, two rodeos and a goat roping contest, but I've never seen the likes of the stuff that goes on around here before!
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Old 01-11-2012, 06:16 PM   #10
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Hi Steve, Thank you for posting that information. That is a lot to digest and I will have to do some studying. I already have a lathe with a 1 3/8 spindle bore, and am trying to learn how to use it properly. I want to make my own chokes so that I can try various configurations with an eye to very tight patterns at 30 yards. Thanks again...Tom
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