Author Topic: left-handed Alex Henry/Stanton/Bob Roller lock. Part 5. The fly  (Read 953 times)

Offline Rolf

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Making a fly that works is by far the part of this project I’ve struggled most with. This was due to my lack of my understanding how the sear, tumbler, and fly function together. I’d like to thank ALR members for answering my questions in the gun building forum. I think I understand how the fly functions.
Short discussion on fly function
The fly’s function is to keep the sear nose out of the half cock notch on the tumbler when the lock is fired with a set trigger. If you are not going to use a set trigger, skip the fly.

The tip of the fly is a triangle with corners A, B and C.

In the next pictures I’ve removed the bridle so you can see how the fly moves in relation to the sear and tumbler.

When the lock is set, the fly is in the forward position, side AB functions as a ramp that keeps the sear out of the half cock notch when fired.

When cocking the lock, the tip of the sear must engage with side BC to move the fly to the rear position, and side BC of the fly must be parallel or below with the bottom of the half cock notch to clear it.

If the sear only engages B, tip of the fly, it will hang up on the fly and not move to the rear.   If this happens, increase the curvature of the tumbler in front of the fly cutout (red area). This increases the angel of attack of the sear nose, so it applies pressure to the side BC and not the tip B.

When cocking to full cock, the tip of the sear must press down on side AB of the fly to move it to the front position to clear the full cock notch. To do this, B (the tip of the fly) must be below the bottom of the half cock notch. If not, the sear will hang up on B (the tip of the fly).

Locating and drilling the hole for the fly tit(axel) on the tumbler.
The center of the tit hole is located on a radius that starts at the center of the small tumbler axel and intersects the midpoint between the half cock and full cock notches. The tit hole is located as close to the small tumbler axel as possible.

The easiest way to do this, is to make a brass gage. I used 3mm thick brass rectangle from sheet stock.
Strike a line and drill two holes centered on the line. 4mm hole for the tumbler axel and 2mm for the fly tit.

Mill away the brass down to the line, keep the holes intact.

Paint the tumbler with dykem, mark the mid-point between the tumbler notches.

Superglue the gage to the tumbler and align with the mid-point. Drill out the tit hole 4,5mm deep (the tumbler is 5mm thick).

Milling the fly cut-out
The fly cut-out is a wedge 1,9 mm forward the half cock notch and 1,9mm reward the full cock notch and tangents the tit hole.

Mark off these points on the tumbler, put a drill bit in the tit hole, draw the tangents.

Mill out to a depth of 1,8mm with a 2mm end mill. Go slow and careful. These mills break easy.

Clean up the bottom with files and stones.

Making the fly
The fly was made from 1075 spring steel. First step is to cut a square blank 5mm x 6mm x 60mm.
Mill out the tits 3mmx3mmx3mm.

I rounded tits with a hollow mill I made to 2mm in diameter. Notice the tits are place all the way at the edge of the blank. The flies are wedge shaped and done this way there only one side that has to be cut.

Cut out the edge and round the point so it fits in the tumbler cut-out.

Make two brass caps to clamp the fly in place on the tumbler.

Clamp the fly in the rear position in the cut-out and trace a line that fallows the bottom of the half-cock notch.

File down to this line. The tip of the fly must be somewhere along the line C-B*.

The next step is to file off wedges along D-C until B*is a hair above the top of the half-cock notch. Then file the rear facet of the fly.

The rest is just decorative filing, hardening and heat bluing. Sometimes even when the fly looks correct, it sometimes fails to clear the half-cock notch when cocking the lock. This is usually easy fixed by cycling the through fired- half cock -full cock with the harden fly mounted in the tumbler. The fly removes high spot on the sear that caused the sticking.

Here is a couple of pictures of the project so far.

The next step will be the main spring and the stirrup. Any suggestions on how to locate where the hole for the main spring should be?

Best regards

Links to the other parts:
left-handed Alex Henry/Staton/Bob Roller lock. Part 1. Lock plate and Hammer

left-handed Alex Henry/Staton/Bob Roller lock.Part2. Four post bridle and screws

left-handed Alex Henry/Staton/Bob Roller lock. Part3 The tumbler.

left-handed Alex Henry/Stanton/Bob Roller lock. Part4. The sear and searspring.

« Last Edit: June 29, 2023, 10:31:58 PM by Rolf »

Online Curtis

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Re: left-handed Alex Henry/Stanton/Bob Roller lock. Part 5. The fly
« Reply #1 on: July 01, 2023, 08:03:29 AM »
Looks like you are getting it figured out, Rolf!  And the finished product has to be the prettiest fly I have ever seen!  ;)  You have a lot of work represented in those six locks.  Can't wait to see the rifles!

Curtis Allinson
Sometimes, late at night when I am alone in the inner sanctum of my workshop and no one else can see, I sand things using only my fingers for backing

Offline Bob Roller

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Re: left-handed Alex Henry/Stanton/Bob Roller lock. Part 5. The fly
« Reply #2 on: July 01, 2023, 07:10:08 PM »
Earlier I tried to respond to this lock making thread and the message would not go.Three loud burps to the electronic world! >:( >:( >:( >:(
Rolf is doing an outstanding job and I am very glad to see this work being done and 6 at a time by ONE man is really amazing
to thing that has kept me out of the shop is the medication I took medication for BPH and it caused more problems than the BPH and the reaction it caused for me is lower spinal stenosis..Thanks to this stuff I can not stand at a bench for any length of time as I once did.*I hope I can walk around at the CLA show in Lexington.It,s an easy cruise of only 125 miles on I-64 for us.
That is a good job on the fly and one identifier on these locks is that rifle locks had a fly and shotguns did not even if all else is identical.
I have made ONE out of about 40 without the fly and paid more attention to the full cock than usual so it would be a "crisp"break on the release.I have a small "4 pin"that was started 4 years ago and then I quit working on it. If possible I'd like to finish it and so far this year NO shop work has been done.Keep up the good work,Rolf and please send any and all pictures that will keep us looking.
Bob Roller
*I take no meds at all and after taking this one I am having lower back spasms I have not experienced at any time in my 87 years of life.
Maybe NOT having the table top covered with medicine bottles is why I have lived this long.Long life is good unless it becomes a burden to
others as well as yourself.
Bob Roller
« Last Edit: July 01, 2023, 11:38:20 PM by Bob Roller »

Offline Bob Roller

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Re: left-handed Alex Henry/Stanton/Bob Roller lock. Part 5. The fly
« Reply #3 on: July 02, 2023, 12:03:46 AM »
I just NOW noticed your question on where to install the mainspring.After it is forged,shape the upper limb and file the pin.Make sure all tool marks are polished away.The link must be in the tumbler arm and the lock on fill cock Good luck and let us know how it works and this IS and held by the sear and sear spring.Place the claw of the spring on the hook and THEN with a small scribe locate the hole and a wee bit of Dykem helps here also.I made mine as close to .086 as possible and used a #44 drill.After all this lower the tumbler with the link all the way down below the lock plate and then use a curved and tapered wedge to open the spring and Keep it at least to a low orange color and be sure the lower limb has a curve to place it a bout 9mm and both limbs must be tapered from the bend back.
below the link.Heat the spring to bright orange and quench it and let it cool in the oil.Remove it with a magnet,wash it of with whatever you have that works then  polish it and then temper.Taylor Sapergia posted a picture of the internals of one of my locks this week so look it up and magnify it if possible. Found it from 28 June in the "Polishing an L&R lock article.
Bob Roller
« Last Edit: July 02, 2023, 01:30:57 AM by Bob Roller »

Offline Bob Roller

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Re: left-handed Alex Henry/Stanton/Bob Roller lock. Part 5. The fly
« Reply #4 on: July 02, 2023, 03:50:08 PM »
Trying to give instruction on making a mainspring is like a mail order hair cut.Not easy.The term "fly" is an identifier,The correct term is an
intercepting cam but that is not acceptable. I have seen in German magazines the words "Fliege und Kette"meaning fly and link."Kette" is
 usually a chain.I used to get DWJ and Visier .  DWJ-Deutsche Waffen Journal.
Bob Roller

Offline flatsguide

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Re: left-handed Alex Henry/Stanton/Bob Roller lock. Part 5. The fly
« Reply #5 on: July 04, 2023, 04:58:52 PM »
Great craftsmanship and photography. Thank you for taking the time to explain and document this. For something like the fly that appears so simple is really an amazing gadget. Thanks for making it appear to be simple.
Cheers Richard