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  #1  
Old 03-12-2009, 09:53 PM
DJCarbine

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Making gun parts, cold rolled steel



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The charging knob on my old savage 187 is just so small. Its less than an inch, in a very non-egronomic way. Its just a round nub that is a pain (actually can physically hurt) to hold open to clear a jam, rack a fresh round in, etc.


Since the existing handle/knob is just a perfectly round rod inserted into the action, with a grove cut in it for the firing pin and misc parts, I decided to see if I could make my own.
I went to home depot and got a rod of cold rolled steel. I used my dremel and cut it down to size, so that it sticks out about 1.5 inches from the action when inserted. I also cut the groves needed and it works flawlessly with the action.

Aside from being a round rod sticking out of the bolt, it works great. It gives you positive gription (I made that word up) and lets you hold the bolt open and rack in a fresh round when you reload with ease. The blowback is not affected, and works great as well.

I'm going to file the handle flat and curve it so that its more like a ruger 10/22 cocking knob.



::EDIT

I made the part.
I quenched it twice to harden it up.




The back of the bolt is flattened, and the front has a round indentation that your index finger grabs nicely.
The part is SLIGHTLY less heavy than the original part. I still need to round off some edges and do some finishing polish.


My question is, is cold rolled steel strong enough to be safe?

Last edited by DJCarbine; 03-13-2009 at 06:03 PM. Reason: Made the part
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  #2  
Old 03-12-2009, 10:02 PM
ShootNut
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With gun parts strong isnt a problem, hardness is the problem! If the parts arent hardened enough they can and will wear very fast. Another thing you need to watch is cycling issues, adding extra weight to the bolt of a semi auto can cause problems with extraction, ejection and jamming, so just keep an eye on it espcialy with lower velocity ammo.
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Old 03-12-2009, 10:23 PM
riflesmithy

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DJ,

Your cold rolled steel bolt knob will probably work for a short, read unknown, length of time. Cold rolled stock is generally soft and will wear quickly due to friction, stress, shear and peening.

There are better materials available to fabricate from. O-1 oil hardening stock is easily machined or worked but needs to be heat treated for proper results. LaSalle Fatigue Proof or LaSalle Shock Proof steel can be had already heat treated yet is still workable. The LaSalle steels are my preferred materials when fabricating small parts that will be subjected to repeated stress and/or shock load.

I would try to keep the weight of the replacement part the same as the original to avoid timing issues during cycling.

smithy
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Old 03-12-2009, 10:40 PM
DJCarbine

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I will look into the steel types you listed. The rifle timing is of a double sear, blowing back and staying back untill you release the trigger. I makes a CLACK CLACK sound, and cycles very slowly. It is a bit more forgiving I think to minor changes in weight.

I will go through a few hundered rounds and note any abnormal wear in the metal just for fun though.
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Old 03-12-2009, 11:23 PM
Jack404

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DJCarbine

in general yes

but as the experts here have already stated its the hardness that counts

Cold rolled is generally 1020,1030 or 1040 grade steel or Mild carbon steels in a non hardened form

to harden it get a small gas torch

put the item on a brick once you have it working as you desire ( working correctly is the main thing)

heat it until lightly red not glowing red

useing pliers or similar you can either drop it into some case hardening powder and coat it well then keep it hot for 15 minutes ( hard to guess though for a newbie ) and then quench in water

casenite or similar i have bought in the past, follow the instruction on the hardener as they vary a lot

or drop it into a mix of sump oil and graphite powder ( even better and simpler)

1/4 pint of oil ( older and more used the better actually)
and maybe 5 teaspoons of graphite powder is the mix ratio i use

( a full pint need 20 spoons, level, mixed well so its a sludge but you dont need that much to quench something like a hammer or handle)

this is called quench carbon hardening and the easiest to do for the home person

this will lift the RC ( Rockwell hardness guage) from the mid 40"s where the steel is when you got it to the low 50's or higher

more than enough for your needs

hope this helps

jack

Last edited by Jack404; 03-12-2009 at 11:27 PM.
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Old 03-12-2009, 11:33 PM
DJCarbine

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it helps a lot, I always thought about heating and then quenching, just wasn't sure of proper procedure. I may try that after a range trip to "break" the part in. If its soft now, it will work out all the rough edges and maybe work smoother before hardening.
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Old 03-12-2009, 11:45 PM
Jack404

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DJCarbine

thats the idea

while its in its natural form its easier to work it so get it working as you want it before treating it

old diesal engine oil is best

because diesal dont burn as clean and this gunk gets into the engine oil the old oil requires less graphite

taking the item to cherry red without knowing the exact composition of the steel may make it too hard and brittle so go a dull reddish to be safe

a few RC points wont matter (51 or 57 its all good, 65 however you need a chrome moly alloy to be safe and not brittle )

what your actually doing is adding a layer of carbon into the steel a few molecules thick ( its a surface hardener only)


carbon is the base of diamonds

graphite is a fine almost pure form of carbon

but the diesal oils waste it a series of carbons and they are great for surface treating steel ( just dont breathe the fumes when you dunk the hot metal in ok?? along with the complex carbons thers other , real nasty stuff with it too)

hope this explains it better

cheers DJCarbine

good luck

jack

Last edited by Jack404; 03-12-2009 at 11:51 PM.
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Old 03-13-2009, 12:10 AM
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Quote:
Originally Posted by DJCarbine View Post
It gives you positive gription (I made that word up)
No you didn't,back in the late 80's I was told to remove a few leafs from the rear spring packs on my 72 f250 highboy to help it "ticklate for better gription " when climbing the ledges.I don't know how old that word is but I would bet it came from some jeepers a long time before I heard it.

As far as the cocking knob,does it hit on or rub anything?If it does not come in contact with any other parts then cold rolled is fine as well as alumnium or brass,proper wieght for proper function is the key.If it does come in contact with other parts then you want the cocking piece to be softer then those it touches but not to soft!

Like when you got proper tikulation on the ledges and are getting unreal gription,if something breaks you want it to be the cheapest most easiest to replace part possable and not damage anything else but it should not break to soon!Think of it as a mechanical fuse.
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Old 03-13-2009, 09:49 AM
DJCarbine

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Originally Posted by mejeepnut View Post
No you didn't,back in the late 80's I was told to remove a few leafs from the rear spring packs on my 72 f250 highboy to help it "ticklate for better gription " when climbing the ledges.I don't know how old that word is but I would bet it came from some jeepers a long time before I heard it.

As far as the cocking knob,does it hit on or rub anything?If it does not come in contact with any other parts then cold rolled is fine as well as alumnium or brass,proper wieght for proper function is the key.If it does come in contact with other parts then you want the cocking piece to be softer then those it touches but not to soft!

Like when you got proper tikulation on the ledges and are getting unreal gription,if something breaks you want it to be the cheapest most easiest to replace part possable and not damage anything else but it should not break to soon!Think of it as a mechanical fuse.
It doesn't contact anything at all, it only serves as a handle. I may do a heat/quench cycle in used oil still though. Gription and proper angulation/easification were the only reasons for the new bolt handle
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Old 03-13-2009, 06:04 PM
DJCarbine

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I ended up making the bolt handle, I posted pictures in the first post. It needs to be finished up, but I'm happy with it so far
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Old 03-13-2009, 08:06 PM
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If I were in your position, I would have made the part out of 1018. 1018 is what we call CRS at the shop, but who knows what you got supplied. Anyhow since the part doesn't touch anything I would have left it soft because you're not going to have any wear issues, the rifling in your barrel will be shot out long before you could wear away the steel of the handle with your hand. You won't hurt anything by hardening your part, but I don't see any gains by doing it either.

In general, when you heat treat and temper a piece of metal, the harder you get it more brittle it will be. If you drop or hit a piece of soft 1018, within reason, it is going to bend rather than break. If you do the same thing, to say a piece of hardened O1, it is going to break or shatter rather than bend. Admittedly when you case harden some metals, like 1018, you get the best of both worlds, a hard exterior, that is only a few thousandths deep, that will resist wear with a soft interior that will (depending on the steel) bend before it breaks.

If you're curious take the old part, and with a fine file try to cut into the part by taking the edge of the file on a 45 and use a sawing motion. My guess is the file will cut easily into the part, showing you that it was soft.

Last edited by Shaky; 03-13-2009 at 08:32 PM.
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Old 03-13-2009, 08:39 PM
DJCarbine

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The file cuts easily into the old part. I'm pretty sure the new part will hold up fine. Function-wise its great
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Old 03-13-2009, 10:40 PM
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I had thought of using one of these to make a new charging handle for mine. Your handle looks good.
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