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Wooden 3-Number Combination Lock

 

My next lock is the combination lock.

 Here is what the lock looks like in the book.......................

 

 

 I decided to make the main body of the lock from walnut.  It is 1-3/4" thick and 4.5 x 4.5".  I decide to convert a split log of walnut into a rectangular piece of lumber similar to shown above in previous lock projects. The piece I selected turned out to have some splits and worm holes inside.....but I decided to use it anyway.  The split log yielded a 1-3/4" thick piece with enough wood to make the bases for 3 locks.  Since most of the time making locks in in the set-ups, I'm going to be bold and brave and make 3 locks at once.

One challenge I found drilling the deep hole for the shackle was that my Forstner bit would only go to the depth required if I just barely grasped the bit in my drill press chuck.  Book author must have a longer length Forstner bit..at least the 3/4" diameter size.

When I made the shackle, I used 10" piece of stock. I sawed off the extra at the end of the round section, then chucked in the lathe.  Very carefully, I turned the notch to depth checking with calipers. Have to be very careful on this operation, or lathe tool hits chuck or round end of shackle!  Then I cut the shackle to finished length on the long portion.

When I was making the 3 curved shackles, as I was routing the last one with a 3/8" round-over carbide bit on the router, the bit caught and blew up the shackle ....   Fortunately, I had my safety glasses on and only the oak shackle was injured .....   I will have to make a replacement shackle.  Out of a total of 7 shackles I have made, I lost 1 of 7 or 86% success rate.  Given how fragile the cross-grain section is at the top of the shackle, you should expect some failures.  After all , the Space Shuttle is only about 98% success rate (2 losses in about 100 flights!).  On the failed shackle, I did route it in 2 steps, 1/4" bit first, then 3/8" second....so it wasn't like I was hogging out too much wood by trying to do it in 1 pass.

 

 

 

When I made a replacement shackle out of oak, I routed first with 1/4" bit, then switched to 3/8" round-over bit. I went to straight section and found best feed direction, then used this on round weak section.

How to mark the dial marks and numbers.  I decided to photocopy the pattern from the book, cut out the circle for the inner knob, then also cut out carbon paper with a hole for inner knob. I marked the dial using a pencil and the paper pattern with carbon paper under it. Then I used electric iron to burn in the marks and numbers.

Drilled 3/16" hole in dial blank to use face plate with center screw on lathe to turn it.  Better to use rounded end tool vs small or large gouge, because gouges tend to catch on end grain.  Boy, it has been 20 years since I have used my lathe face plate! Did kick lathe up to high speed to 220 grit sand oak dials.  Low speed sanding was ok on maple dial, did not need high speed.

Had trouble with 1 of 3 locks getting combination to work. Turned out #3 drive dog was too long, and was turning #2 tumbler without the #3 dog driving it!  Ground down with Dremel and sanding drum, fixed it ok.

Lock does not seem to be designed to 100% return 1/2" dowel back to its locked position when you lock it back up and spin the dial. Sometimes you have to shake the lock sideways to get the 1/2" dowel to return to its locked position. Could use a design improvement here, but I'm not sure how to change design to assure 1/2" dowel always returns.  Go to 0 position on dial and shake sideways to fix it.

When I went to assemble the lock, I found the 1/2" hole for the dowel had been drilled too deep...it kept the 1/2" dowel piece from moving smoothly when you unlock the lock. I recently bought a plug cutter set, so I filled the hole with a 1/2" plug cut from pine......and glued it into hole.

 

 Below is base with plug glued in...

 

 

 

 

 I very carefully turned the groove in the shackle at low speed on my lathe....be careful on this one with swinging shackle end!

 

 

 

This lock requires 2 thin wood washers between the tumblers...here they are marked and ready to be cut out:

 

 

 

 This lock requires you to have a lathe to turn the dial using a faceplate:

 

 

 

 

 

I am not good at freehand drawing or lettering, so I photocopied the dial numbers from the book, marked them on the dial using black carbon paper, then burned them in using electric burner...

 

 

 

Here is 1 completed clock, except for applying the polyurethane coats:

 

 

 

I made a flat bottom on these locks....versus the rounded bottom in the book plan...so lock would set up and display itself on a table or shelf.

I made a temporary drying rack to hold the parts from 3 locks why they dry:

 

 

 

 And now for the finished locks:

 

 

The walnut body and white maple dial looks the best:

 

 

 

  

 

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