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GT
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Inscribing lines on a sight
Aug 22nd, 2018 at 9:37pm
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I've been asked a couple of times by individuals here about the sights I make and some of the processes I use, the following has worked well for me.
For the lines I tried all kinds of rotary methods, in the CNC going about 5000 RPM a diamond works fairly well but it's a PITA.  What I've been using the last few years is a piece of HSS silver brazed onto a 3/8 or 1/2 CR round stock and ground to a point like a threading tool, grind a negative rake on the top of the tool for strength and the tip'll last a little longer.  I put this in a collet in the mill, lock the spindle and just broach with the quill.  As for depth, .008 to .010" is usually plenty if it's flat and finish is left to a file with a piece of 400 Grit wrapped around it.  I usually stroke the "0, .25", .50" and .75" marks to about .080" long and the marks in between around .040 - .050" long.
Is your mill is a Bridgeport J-head? or do you have a variable speed?  The j-head locks solid if the side lever goes forward but don't lift the top out for back gear.  For the variable speed turn it to the slowest rpm before shutting it off.   
Now when you are scribing the lines, you may know this already but the lines on the staff are .050" apart but on the traveling block, they are .040" spacing in order for the graduations to work...
I've attached a couple of pictures hoping to clarify the process.
  

"To invent, you need a good imagination and a pile of junk"  T. A. Edison
"If you don't know what leever A does, then leever B... you Dumb@$$"  G.C. Tryon
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craigd
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Re: Inscribing lines on a sight
Reply #1 - Aug 23rd, 2018 at 7:06am
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Thanks GT for the explanation along with the pictures.
  
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rodneys
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Re: Inscribing lines on a sight
Reply #2 - Aug 23rd, 2018 at 9:43am
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Good clear explanation, Greg
  
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Kevin B.
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Re: Inscribing lines on a sight
Reply #3 - Aug 26th, 2018 at 6:38am
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Thank you for this post. Clear, complete and valuable information.

Kevin B.
  
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boats
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Re: Inscribing lines on a sight
Reply #4 - Jan 20th, 2019 at 10:53am
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Great post thanks

  Boats
  
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Jason B
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Re: Inscribing lines on a sight
Reply #5 - Jan 21st, 2019 at 7:22am
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I used this infornation for a tang sight on Saturday and it worked very well. It made a lot cleaner lines than trying to use a rotary type tool.
  
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ireload2
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Re: Inscribing lines on a sight
Reply #6 - May 4th, 2019 at 3:13am
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Today some manufacturers do this operation with a CNC laser resulting in inferior results.
When a light laser marking is used the line may not be dark enough to be read easily. A heavier laser mark leaves a rough fuzzy furrow that is not so easy to see and is often ugly when viewed up close.
  
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GT
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Re: Inscribing lines on a sight
Reply #7 - May 4th, 2019 at 12:19pm
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The method I use and described here works quite well and is fairly simple but I have found a few flaws that I'd like to point out.  In the first picture I'm attaching, the tool I made for marking the lines in the sight block was from a used carbide insert, silver brazed to a bar and the tip was ground to a fine point. If you look closely, the lines were cut from left to right.  As I proceeded the marking process one can see the tip is breaking down rapidly - it was a short distance, few marks, but it was A2 tool steel- carbide cuts the harder material but it doesn't like being "dragged" back through the cut - the tip breaks off.  Resharpening isn't a problem, but with old eyes, picking up location and resuming is a real challenge.  The staff in this picture was from mild steel and the markings were cut using a piece of HSS silver brazed to a steel shank and then sharpened, it held up fine and produced decent markings.
The second picture if you look close was a staff from Damascus that I had to regrind the tool several times and my markings aren't what one really likes to see.  The Damascus took it's toll on the number stamps too so for these markings I used a diamond scribe, not real appealing either but functional for my rifle.
In most of my sight markings, I use HSS material and have had good results.  I have tried my pantograph engraver, the etch-o-matic, and a rotary engraver in the mill for marking the lines.  I've seen the results of the laser engraved markings and they don't inspire me to go this route.
The last two pictures are marked with a cobbled up tool using HSS tool bit scraps.
Greg
  

"To invent, you need a good imagination and a pile of junk"  T. A. Edison
"If you don't know what leever A does, then leever B... you Dumb@$$"  G.C. Tryon
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