Author Topic: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring  (Read 2813 times)

Offline Rolf

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Frizzenspring

The frizzen springs were made from an old truck leaf spring, 12mm thick
(about 1/2inch). First step is to hack saw out a rough blank about 13cm x 2,2 cm.  The blank is annealed by heating in a heat-treating oven at 800 Celsius for 30 minutes and buried in a bucket of pearlite overnight. Since the blank is oversized, loss of material from scaling does not matter.


This blank is then milled to a rectangle 120mm x 19mm x 8mm and the leaf rough milled out 3,2mm thick and 90mm long.
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Mark out the width of the leaf and the placement of the spring peg. Drill, saw out and mill to correct dimensions.


I then made a hollow mill for the peg from 10mm round stock silver steel. I center drilled a 2,5mm through a 30mm piece round stock, filed the teeth then drilled a 4mm hole from the rear, almost all the way through. Heat bright orange with an acetylene/oxy torch and quench in cold water.


If you don’t relieve the inside of the mill, there is a tendency for the peg will stick and twist off, no matter how much cutting oil is used. I did this mistake on my first attempt to make a hollow mill.


To center the peg blank, use a 2,5mm drill in a drill chuck mounted in the mill. Replace the chuck with the hollow mill in a 10mm collet. Mill out the peg using plenty of cutting oil.


Next make the jig for locating the frizzen screw hole.  Take a strip of brass the same width as the final blank end(8mm). Mark a center line. Drill a 2,5mm hole for the peg, drill a hole the correct distance for the frizzen screw. Glue to the blank. Drill the hole for the frizzen screw(3mm). Notice the frizzen end is kept way to long. This is so it can be held steady in the vice for milling and drilling.


Make a template for the frizzen final. It’s basically a 3M screw with a 6mm head and a 6mm round «nut». Mount it in the frizzen spring screw hole.


Mill away as much as possible of excess metal.


Use a pillar file to file the screw cylinder round. Make a simple jig to hold the spring blank at an angel for milling the taper.


File out the tail of the final.  Heat the bend location with the smallest oxy/acetylene torch and bend. Heat bright orange, quench in clean cold water. I tried using oil, but that gave a mushy spring with this steel. The spring was then annealed in an oven at 370 Celsius for 30minutes. The spring works great.


Picture of the unbent spring on a rough blank, shows the amount of steel removed.                                   Finished spring mounted on the lock.




Main spring
The main spring was made from 3mm (1/8 inch) thick 1095 spring stock from Brownell. Won’t be buying that stuff again. The stock was rock hard, especially the edges which must have been work harden. The lengths were 16 inch long.  Way to long for annealing with an acetyl/oxy torch.  To cut it with a hacksaw, you grind through 1/6 inch of the edge with a Dremel before you could saw it.


I followed the booklet «Simplified v-springs» by Kit Ravenshear in making the spring. Cut off a suitable length of steel, marked off the placement of the peg and eye hole with a brass pattern. 


Next I heated and twisted the eye tab, heated to annealing temp and buried it in pearlite to cool overnight. Next day, I drilled, sawed and milled out the peg. The peg was milled rounded with the same hollow mill used on the frizzen spring.


Glue the brass pattern to the blank, drill out the screw hole. File out the eye and the outer profile of the blank.
 

I used the same jig to mill and taper the main spring and frizzen spring. First i mounted it horisontal in the vice to reduce the thickness of the hook end to 2mm, then mounted slanted to mill out the taperd portion of the lower leg.


The same jig Is great to hold the spring for draw filing and polishing.


The springs where bend using an oxy/acetylene torch, following Ravenshear’s booklet. I’m not to happy with his methods. Two main problems.
1.   Twisting the tab for the screw eye creates a “threaded” neck between the eye and the short leg. See the nick on the left side of the underside of neck in the picture to the right. There is a similar nick on the right side of the topside of the neck. This weakness made the neck break when I reduced the thickness of the eye to 1/16 inch, no matter how careful annealing. The only solution was to leave it 1/8inch thick.

 
2.   Lack of repeatability when bending without jigs and fixtures. Even though the spring blanks were identical, and the bends marked out the same the placement of the main bend and the start of the hook varied +-3/32 inch. This could interfere with the placement of the front lock nail and cause the hook to jam or fall of the tumbler.

Think I would prefer to use thicker spring stock and mill/ file out the eye and the hook.  If you look at the pictures of the finished locks, you’ll see the main bend is U shaped not a sharp V shape. I tried a sharp V on the first spring. Did not work. The sharp V placed the long leg to high up on the plate.  When trying to set the lock on full cock, the spring jammed on the mainspring screw. Not enough room to move. The U bend lowers the leg on the plate and gives it ample room to move.


Both locks work fine. Whats left to do is final clean up an polishing before case hardening. Don’t know when I’ll have time for this. No more vacation time and I have to make crucbles and do test runs before try it on the locks. Never pack harden before.

The next and last chapter will be Pack hardening the locks. Here are links to the parts done sofar:

Part one, the lockplate.
http://americanlongrifles.org/forum/index.php?topic=49769.0

Part two, the cock.
http://americanlongrifles.org/forum/index.php?topic=49838.0

Part three, the pan.
http://americanlongrifles.org/forum/index.php?topic=50191.0

Part four, the frizzen.
http://americanlongrifles.org/forum/index.php?topic=51056.msg506885#msg506885

Part five, the tumbler, bridel and sear.
http://americanlongrifles.org/forum/index.php?topic=52824.msg527631#msg527631

Best regards
Rolf

 

« Last Edit: August 28, 2019, 10:57:13 PM by Rolf »

Offline runastav

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Hi Rolf!
You make very Nice Locks(Delux ;))
Runar

Offline smart dog

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Hi Rolf,
Very nice work and tutorial.  I make a fair number of springs. I simply file the pegs round rather than use a mill.  On frizzen springs, I make them like you did the mainspring. The tab bent perpendicular to the leaves is then used as the base upon which I weld metal for the screw boss and finial.  Your mainsprings look very strong but I suspect the lower leaf is bent upward forming a a belly in the middle when the lock is brought to full cock.  I prefer the lower leaf to be straight when cocked.  That distributes the force along the whole leaf.





The solution is to pinch the main bend in the spring as I did on the spring shown above and then arc the lower leaf downward slightly over its whole length.  That along with tapering the thickness of the lower leaf produces a very strong but "whippy" feeling spring.  On your lock you mentioned the tight bend resulted in the lower leaf hitting the mainspring screw.  The solution would be to drill the peg hole in the lock plate a little lower so the upper leaf of the mainspring is angled downward more.

dave
« Last Edit: August 28, 2019, 02:39:11 PM by smart dog »
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Online Bob Roller

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Fine looking lock and I am wondering about all the drilling and sawing along the edge of
the mainspring when you have a milling machine that will eliminate all that work.Back
in the days when I was really serious about lock making I would mill them 6 or 8 at a
time. Now I might make 2 or 3 locks and a few triggers a month and call it done.
Keep up the good work but you can save a lot of work with that milling machine minus
all the drilling and sawing.

Bob Roller

Offline Jim Kibler

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That or just a decent hacksaw will work well.  You can also get a small hand held portable bandsaw and put a stand on it.  These cut surprisingly well and are pretty affordable.

Offline Rolf

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Thank you for Your kind comments and suggestions.
Dave :
- I tried making a frizzenspring by Welding up the tab, but my skills are not good enough. To many small gaps/pores in the weld. Easier for me to use solid Stock.
- The hole for the main spring peg is placed where the orignal Locks have it, which is why I chose to keep it there. Don't know why they did not Place it further Down. I have not seen an orginal mainspring, but the only reason I think of is that the either they had a U-bend or used springstock over 2/8" thick.
- I've Attached Pictures of the Locks at full Cock and the springs out of the Locks. The lower leaf is slightly arced Downward. Should it be arced more?

Bob:
I use mostly 10mm endmills from Dormer. They cost about 45$ a piece. Tried cheaper chinese stuff With disapointing results. Drilling and sawing saves wear and tear on the endmill and saves Money. As it is, I use up about 2 endmills  pr Lock. I've bought a cooling spray system for the mill to try to make them last longer, but stopped using it because it made a mess of the shop. Do you know where I can find cheaper, good quality endmills?

Jim:
Like the idea of the hand held bandsaw. So far, havn't found any in Norway. Will keep looking.








Best regards
Rolf

Offline Justin Urbantas

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Well done Rolf. I am curious, how much time do you think it took to make that spring?

Offline Rolf

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Well done Rolf. I am curious, how much time do you think it took to make that spring?
Once I figured out the Dimensions and how to do it, and made the jigs and patterns, the main spring takes about 10 hours. The frizzen spring takes about 21-24 hours. A bit hard to estimate since I was working on several springs at the same time. In a fit of hubris, I started on four more 1772 Locks. Had steel left over and it seem to be a Waste to make only two Locks, after making all the Tools and patterns.

I do have to admit, I'm running out of elbow grease and having secound thoughts.

Best regards
Rolf



Offline msellers

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Rolf,
Those are very fine looking locks. Also, thank you very much for showing your process of builing these, as with all of your builds.

As far as a handheld bandsaw goes, if you are able find one of the deep cut models, as the standard will be frustrating especially with some of the cuts you are making. The Milwaukee deep cut gets you 5 or 5.5" of availability. Is a very nice machine. There are also many aftermarket accessories to go with it. I will end up with one and the bansaw table accessory at some point. Makes for a small space exceedingly useful piece of equipment.
Mike

Offline jerrywh

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This makes me glad I live in the USA. 
Nobody is always correct, Not even me.

Offline Gunnermike

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Re: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring
« Reply #10 on: September 13, 2019, 09:10:29 PM »
Excellent work as usual Rolf!. I admire your tenacity in making all those parts by hand and with liberal application of "elbow grease".  This is what I use now to save on excessive use of elbow grease:



Believe me that crappy chinese saw (the chinese saw blades are worthless by the way) has made things easier for work like you are doing.  I used that bandsaw a lot last year when I was making a wheellock & recently when making mule ear lock (not nearly as nice as your beautiful Kongsberg locks though).  You are a real craftsman.  Mike

Offline Justin Urbantas

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Re: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring
« Reply #11 on: September 13, 2019, 09:23:13 PM »
Is it not much easier to forge the spring close to final dimension,  then file and harden/ temper?

Offline Rolf

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Re: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring
« Reply #12 on: September 13, 2019, 11:07:07 PM »
Is it not much easier to forge the spring close to final dimension,  then file and harden/ temper?

Maybe if You are very skilled at forging. I've forge knife blades out of Chains saws, cable and damscus. I allways had to forge the blank at least  3/32 to1/8 of inch oversized in all directions to be able to straigthen /taper it,  get red of forge scale and hammer marks, do get the size an shape I want. I don't think forging would save me much work. Take a look at Mike Miller's dvd on forging a flintlock. He forges the spring blanks, but 80% of the work he does on the springs is filing.

Best regards
Rolf

Offline Justin Urbantas

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Re: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring
« Reply #13 on: September 14, 2019, 12:36:22 AM »
A guillotine tool like these may be a big time saver for you. Allows you to isolate material and make fairly accurate shoulders.




Offline Rolf

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Re: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring
« Reply #14 on: September 15, 2019, 11:56:58 AM »
A guillotine tool like these may be a big time saver for you. Allows you to isolate material and make fairly accurate shoulders.

I have a simulare tool, its great for starting the shoulders for tangs on knife blades. Not so good when it comes to removing hammer marks. I can't get enough force With a hammer, when used With a wide/large die/Block. I still have to make the blades at least 1/16 -3/32 inch oversize. There is a knifemaker in Norway that uses something simulare to forge blades to almost finished shape and Dimensions, but he uses spesially made Dies and squeses the tool in a 20 ton hydrolic press.

Chris Laubach says he uses forged springs on his CNC jeager Lock. Maybe he could explain us how he does it?

Best regards
Rolf

Offline Jim Kibler

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Re: Copying a Kongsberg 1772 pistol lock. Part 6. Frizzen spring and main spring
« Reply #15 on: September 16, 2019, 06:02:05 PM »
Thank you for Your kind comments and suggestions.
Dave :
- I tried making a frizzenspring by Welding up the tab, but my skills are not good enough. To many small gaps/pores in the weld. Easier for me to use solid Stock.
- The hole for the main spring peg is placed where the orignal Locks have it, which is why I chose to keep it there. Don't know why they did not Place it further Down. I have not seen an orginal mainspring, but the only reason I think of is that the either they had a U-bend or used springstock over 2/8" thick.
- I've Attached Pictures of the Locks at full Cock and the springs out of the Locks. The lower leaf is slightly arced Downward. Should it be arced more?

Bob:
I use mostly 10mm endmills from Dormer. They cost about 45$ a piece. Tried cheaper chinese stuff With disapointing results. Drilling and sawing saves wear and tear on the endmill and saves Money. As it is, I use up about 2 endmills  pr Lock. I've bought a cooling spray system for the mill to try to make them last longer, but stopped using it because it made a mess of the shop. Do you know where I can find cheaper, good quality endmills?

Jim:
Like the idea of the hand held bandsaw. So far, havn't found any in Norway. Will keep looking.








Best regards
Rolf

A 6mm or 1/4" endmill is a good choice for this sort of work.  Carbide with a slight corner radius (.020" or less) is my preference.  In the states here, I can buy these for around $13 for a decent brand.  I use a lot of product from Lakeshore Carbide.