Barrel slots for blade sights

[rifle]

Anyone of the machinist types,or anyone, know the proceedure for centering the slot for a blade sight on a gun barrel like the 1860's and the Richard Masons and the Richards and the 1873 SAA?
I have ways to center and level the dovetail cuts for front sights but slots for blade sights are a little different. I figure the slot is made or can be made with a Woodruff key cutter. I figure there's a regular gunsmith machinist proceedure though.
I think this is where someone mentioned being a machinist so this is where I ask.
Is there a better place to ask?

[Lone Oak]

Well, here's what I do to locate TDC on an octagon to round barrel for trade guns etc. so the front sight can be soldered on. Maybe you can figure a way to adapt the procedure to your revolver barrels.

OK, I lay a file flat on my work bench. Then I lay the muzzle end of the barrel on the file at 90°, with the TOP flat of the breech end down on the bench, so then of course the top of the round muzzle is against the file. Then I adjust things so the file is as far from the muzzle as I want the front sight, and lightly work the muzzle back and forth on the file while holding the top flat down securely on the bench to keep things square. There will be a light file mark exactly at the top center of the round part of the barrel.

If you can find some way to hold the frame of the revolver square to your bench, this method should work for you, but if you have a milling machine or know someone with one, it should be a piece of cake.

L.O.

[rifle]

Lone Oak, I've got a milling machine and the octagon barrels aren't too difficult to get TDC but....the octagons aren't always exactly right so I've learned to eyeball to make sure. Sometimes the octagons get canted a few degrees when they are ground. The muzzleloaders with the dovetailed blade front sights are simple to bend the blade a degree or two ifin the sight looks canted a hair. You know how the slightest cant of the front sight is seen or noticed right off the bat.
It's the round barrels that can make trouble. I've always gotten the dovetailed front sights I've put on 1860 Army Colts straight up but....I may drink a cup of coffee and smoke a coupla cigarrettes "EyeBalling" the "pointer" I stick in the spindle to see the alignment. I use the whole gun(cap&baller revolver) in the vise at times and eyeball like I'm aiming the sights to see if I'm on TDC.
I want to find a machinist proceedure that is foolproof if there is one.......like putting scopes on modern rifle barrels or whatever.
I have a tool that's got to be on a top flat somewhere and it has like flags (plastic) sticking out to see and eyeball .....like for getting scopes crosshairs verticle and horizontal with the rifles lines. I don't trust it for cap&ballers and without a top flat to go by......
All I know is to get the barrel or the whole gun set in the mill machine vise with it's vertical straight up and let the end mill )or pointer I call them)make a small mark at the highest point. That all hinges on whether or not the gun or barrel is set in the mill straight up. I don't use levels like I've heard of. I don't trust the precision of a bubble. Maybe for building houses or something but not for gunsmithing. I've seen somesort of tools over the years but they aren't foolproof.  They all seem to benchmark offa something already TDC'erd. I'll just keep looking I guess. Maybe figure something better to do on my own.

[Pettifogger]

I'll tell you want I do, but I'm no expert.  On the round barrel 60's and other Colt type guns I put the barrel in the milling vice and use the flat sides of the barrel extension to get everything vertical.  Then I use an edge finder and bump one side of the barrel.  I raise the edge finder in the mill and move the table and then bump the other side and simply use the DRO to find dead center.  I make all my own front sights, so I use an end mill to make the slot in the barrel and then solder in the front sight blade.  Making the bottom of the cut and the bottom of the sight flat is easier for me than trying to cut a curved slot in the barrel and making a sight with a curved bottom.

[Fox Creek Kid]

Here's your answer:

http://www.brownells.com/.aspx/pid=13107/Product/TOP_DEAD_CENTER_PUNCH

[Mako]

Rifle,
If you are asking how to make the cut using a "keyway" style cut using a Woodruff cutter or "slotting saw" instead of an endmill like Pettifogger does then this is one procedure...

Leave the barrel mounted to the frame but clamp on the barrel for your cutting.  This allows you to use a small machinist's level placed on the frame to make sure you have the barrel straight up and down, or in this case perpendicular. Leave enough barrel sticking out in order not to crowd yourself, but keep it to a minimum for rigidity and to stop vibration during cutting.

You can get a Woodruff cutter in almost any width, common sizes are .125" and .09375". They usually have a tolerance of +.000 and -.001 on width.  Remember the slot will normally run .001 to .002" oversize than the cutter width in most home and small shop mills.  It takes a perfectly aligned head to cut it less than .001" oversize.  I used to use .100" cutters a lot in the days before good dovetailed front sights for the 1911.  We wanted a narrower width front sight (.125" was standard width target sights) for faster target acquisition.  We soldered these in place because the original Browning staked design had a habit of coming out with taller and bigger front sights.  A piece of .100" thick flat ground stock fit perfectly in these cuts for some silver solder or Hi-Force Solder Brownells sold.

Back to the sight...

• Mount your barrel turned 90° in your vice for a vertical mill, you will have it vertical if you happen to have a horizontal mill. Mount it so the top of the barrel is facing out, this will allow you to see your cut.
• If you don't have a vernier on your vertical axis or a DRO on your vertical axis you need to mount a travel dial indicator on the head that will touch off on a horizontal surface on your vise, table or some feature that is perpendicular to the axis of travel and can to touched as you measure both sides of the barrel.  Needless to say this surface must be parallel at all points you will touch.  Done correctly it should touch the same point for both measurements.



• Chuck up your Woodruff Cutter and bring it down to the end of the barrel, what you are going to do is touch off on the sides of the barrel, this will be the top and bottom of the barrel as it is now mounted, So I am going to say top and bottom  since we are measuring vertically.  Make sure you have clearance to do this.
• Bring just the portion of the cutter the actually has teeth down until it touches the top of the barrel.  This will be the bottom of the cutter to the top of the barrel.  I like to use either shim stock or a piece of paper to actually do this instead of actually touching the cutter to the barrel. Bring it down until the paper is trapped.  Raise it (by lowering the knee I'm going to talk about what the tool looks like it's doing to make it less confusing) and do it again, when you can't pull the paper it is there. Record your number that shows either on the vernier of the vertical axis, the DRO if you have one or on a dial indicator with at least 1" of travel (you can get by with less for barrel diameters under 1").  To make sure you have enough travel on a dial, compress it only about .05" for this top measurement.  If you don't have a knee on that mill it is hard to use the head quill to set your vertical height, not impossible, just harder.


• Now offset the table just enough to clear the cutter as you bring it down to measure the bottom side.  I would recommend going left or right (X-Axis) it makes it easier to see and keeps things lined up. Move the table back and raise the cutter until it touches the barrel.  I would use paper again.  Please watch two things.
  1.   As we move down you are compressing your dial indicator, don't overdo it, just clear that muzzle.
  2.   Also make sure when you make that lateral move it doesn't hit any features that with bind it or knock it out of alignment.  If you have to lift it a bit and place something for it to slide on a flat scale or piece of flat stock works well.
• There is a trick to getting a good measurement.  You need to take the backlash of your vertical lead screw  out of the equation.  This is what you do, after you pinch your paper back off until it just releases.  Record that number, not when it pinches it.  That way both of your measurements are taken when the knee is coming up (the table is being raised to meet the tool, you could do it the other way, but this is the tried and true method for loading your lead screw), hence your lead screw is loaded in the up direction each time.

Now comes the math.  I'm going to walk you through one barrel. 

• Assume you are using a .125" wide cutter, your barrel is Ø.635 in diameter and your paper is .003" thick.  You know the barrel diameter and could theoretically touch of on the top side and move your cutter down half of the distance plus half of the cutter width plus the thickness of the paper, this would be .383" but you want to make sure you are on center and you will use your two touch offs to verify this number.
• You touch down on top of the barrel and you dial reads .051" ( if you have a DRO, zero it, you can also reset the dial vernier ring on almost all vertical knee mills).
• You have moved to the bottom of the barrel and done as instructed above to get your backlash removed measurement and it reads .817" (your DRO, or reset vernier ring would read .766", since they started at zero).
• So subtract your initial .051" from .817" this gives you .766", this gets you back to just your movement and taking the dial reading out of the equation.  Note this is the same as if you had a DRO you could zero.  Some people take a bunch of time or have a dial they can rotate until it reads zero.  Either way it works.  Divide .766" in half and the answer is .383".  This is good because this is what you expected.  You may get a small deviation up to .003" (this is what tolerance is all about).  Remember .003" is the thickness of a sheet of paper, you have to decide for yourself what you will accept.
• Move the table horizontally to clear the end of the barrel and raise the table or quill watching your dial, to .383".  You can stop right there, if you over travel back off and raise it again.  Now lock your vertical axis with the gib lock while watching your dial.  If it moves try it again adjusting up and down accordingly trying to have it showing .383" when locked. Remember if you back the table down, overdo it a bit and raise it to the number you want this takes your backlash out.

Congratulations you are now dead on center.  If your barrel is perpendicular your cut will be centered on the barrel.  Now making the cut is a different story...

Regards,
Mako

[Fox Creek Kid]

Mako, far be it from me to say that is complicated but..................

[Mako]

Later I will expalin the simplified method of telling time using a common analog wrist watch...

[rifle]

Mako, thanks for taking the time to type that up. Seems like the way to go. Thing is....I don't have a knee on my mill(whatever that is) and I can't move my table up and down. Jusy the spindle or chuck or whatever it's called. You know the thing I put the R8 collets into. I have a lot of trouble with the backlash in the gears of this mill. I've tried locking the spindle and turning the wheel until I feel the gears are touching and the play is out going up and down. That gets too messy. Having a dial indicator zeroed tells me what the spindle does...drops down on it's own or doesn't move righjt away when screwed up.Pain in the arse especially when I want to control the depth of a dovetail cut to less than a .001 in. so I can put the bladed sight in the gun with the blade not rubbing bluing off going in put look like the blade touches the barrel put doesn't because there's a coupla .0001 ten thousands space that's hard to actually see.
Anyway....I can get a lot out of your explanation. I need a printer to save it on paper. Can you save that on your puter so when I get a printer I can print it?
What tolerance do you use for blade cuts? .003in. one way or the other? Maybe I should just use end mills and make flat bottomed cuts?
I should have spent more money on a mill and got a power feed someone told be has no backlash in the gears. Is that true?
I got the mill for the sole purpose of cutting dovetails in rifle barrels and drilling holes for screwing on ribs under barrels for half stock rifles like Hawkens. I've ended up doing a lot of different things with the mill and.....I cuss at it a lot.  
I never took any machinist classes or anything.
I had trouble with finding a way to center up on an existing hole to ream chambers in cap&baller cylinders. I went to a machinist web sight and found out about the Osborn method to center on a round piece. Back and forth half the diameter plus half the end mill diameter doing the x axis and the y axis over and over supposedly getting closer to exact center each time. Thing is I didn't think that would work inside a hole instead of on the outside of a round piece. I had Starrett make me a modified end finder with a half inch shank and the cone shaped end piece larger than normal at half inch so I can go inside a hole I hope is actually round and go x and y until I feel the edges of the pieces of the end finder and look some too until my finger nail feels no little edge between the pieces of the end finder so I'm centered up on a chamber. I get them pretty dang close like that. The end finder pieces are really precise in diameter compared to each other. How do center on an existing hole to ream a cylinder chamber?   I started using "pointers" I made to go into the hole. If it went in without hitting I figured it was centered. Of course Imhad to enter the hole shallow since the chambers on most the Italians guns are tapered and once inside a bit not round either. That's one reason the reamed chambered guns shoot better. Not solely the diameter compared to the grooves of the barrel but by making the hole round all the way down so the ball stays round and the same size in the chamber high or lower.
People accurrize their cap&baller guns and sometimes don't realize the chambers are undersized and also tapered and not round all the way down in. Obtuation isn't all it's cracked up to be. I don't believe balls obtuate a lot really. They are too light and move more than bump up. What say ye?
Anyway...someone mentioned Brownelles Hi-Force solder? I got some low temp Hi-Force solder and......I can't get that dang stuff to stick to anything. They say a coupla degrees off 400 degrees and it won't work well. Well....it don't work well fer me that dang evil stuff.
Having a good mill machine vise all parallel and vertical and all that to less than .0002 in. helps a lot for doing stuff and when I mount it to the mill I make it x and y to less than .0002 ifin I can find spots that are not microscopically bumpy. Usually because of the microscopic bumps I get within .0005 in.
Thanks again Mako and Lone Oak and Hat Creek and Pettifogger. Yous ta man's!

[rifle]

I'll reply to my own post.
I was thinking....I couldn't touch off on the top and bottom of the barrel with the slot I'm cutting facing me since my machine vise can't take the barrel any way but the slot facing up. I'd need a swivil vise or something.
I was thinking also to touch off on the top and bottom with the slot facing me so I could see it the woodruff key cutter would have to be a large diameter to hit the highest and lowest spots. You know...like I couldn't get in close enough because the shank of the cutter would hit the barrel and keep it from getting close enough. What diameter cutter would be used?
I guess I'd have to touch off on the top only. Then figure the distance to go down and be centered.
Anyway....I guess I'll figure what diameter cutter to use and get it centered the best way my tools would allow. probablt measure the barrel...touch the top and drop to center and cut.
I was wondering why the slots are curved at the bottom and I figure it's so there's more steel left since only the center is deepest.

[Flint]

Rifle, two items.  Machinists and gunsmiths regularly use bubble levels.  First, however, the machine itself must be levelled, by adjusting the feet on the bench or shimming at the floor.  Once the mill table is level, the bubble, such as in the Brownell's tool someone mentioned, or a machinist's level, can be trusted to give you a TDC or a level surface to cut. 

Second, if you see the replacement sights for many revolvers, the bottom is an arc, made to fit into a woodruff type slot.  This does two things, one you mentioned, leaves more steel near the bore, and two, gives you square ends, rather than the round ends an endmill will give you, where the blade sight either needs to have an overhang front and rear to hide the slot, or must have rond ends to match the slot.

[Matt Bastardson]

It seems like folks are attempting to over-engineer something here that is, in fact, relatively subjective.  You could do all of the calculating and math and figuring in the world, and use all manner of jigs and devices to get the sight mounted perfectly 'centered' mathematically, and still have the sight be 'off', because the rest of the firearm is not that precise (as someone previously mentioned).
The best method is to sight down the gun and mark the top of the barrel where the sight should be,  check it using the ruler/gauge, and using whatever method you desire, continue to trust your eye as to what is 'centered', and noting how that compares with the measured 'center', and adjust accordingly.

If the guns were perfect it'd be a different story.  They aren't.

Regardless, I always install the sights oversized, and file them down to 'perfect' to the eye for both windage and elevation after the fact

[Fox Creek Kid]

...The best method is to sight down the gun and mark the top of the barrel where the sight should be,  check it using the ruler/gauge, and using whatever method you desire, continue to trust your eye as to what is 'centered', and noting how that compares with the measured 'center', and adjust accordingly...

Good point.