Wooden clock gears.

[HAKAMA]

Hello, I am going to try to do something that I have never done before and that is to make a wooden gear clock, I have the plans which calls for the gears to be made from 3/8 inch birch plywood which I cannot get where I live but I may be able to get 9mm plywood. Will that do. I am used to metalworking but not so good with wood. I do have the use of a Clarks bandsaw and lathe also a Delta scroll saw and would be most grateful for any advice on the cutting of the gears, I live on an island and sourcing material can be difficult, Thank you.

 

[paulrbarnard]

I would expect 9mm to be fine. Sounds like a great project!

The scroll saw should be great but it might be an excuse for a CNC laser cutter

 

[Terrytpot]

I don't know what sort of accuracy you're aiming for but maybe this can provide food for thought

 

[Yojevol]

I've just completed my 2nd clock (hopefully I'll post a video tomorrow). All the gears are made in 6mm ply. My first attempt used 6 and 12mm ply but if I were making it again I'd use 6mm. 9mm will be fine.
If you search for clock under my username you'll find what I have posted so far.
Brian

 

[J-G]

I agree with what's been said already about 9mm being OK. Converted to Imperial it is 0.354 whereas 3/8" is 0.375 or 9.525mm so just a little 'shy'. You may well have to adjust some other dimensions if there are more than 2 gears on one spindle but as long as you take that into account you shouldn't have a problem.

Cutting the teeth needs some care but the good thing is that you don't need to be too concerned about the fit being 'loose'. In fact some clearance can be a benefit since gears in a Clock always move in the same direction so 'backlash' isn't an issue.

Since you are used to metalworking you may be familiar with 'Involute' form gear teeth but I would strongly recommend that you avoid this form opting instead for 'Cyclodal' form or at least straight sides.

I use CorelDRAW! to create my gear drawings but if you have bought plans you may have full size templates.

You may find my W.I.P. in the [Projects] section interesting, though it is an on-going thread - mostly concerned with using a CNC approach to making a clock.

 

[amakah]

Hello, Thank you all for the replies. I apologise for the late reply but due to health problems I have not done much but am now back on the project. Has anybody had any luck with using a small router to cut the wooden gears. As I have said I cannot get balsa birch plywood I am going to use a good quality plywood and use a wood hardening solution to harden the gear teeth. Any views on this. Thank you all so much.

 

[Yojevol]

Nice to hear you're getting going again.
Have you seen my 2 threads on clock making; No.1 and No.2. I've just started No.3 which you can see in the latest post here.
I've been through the leaning curve on gear cutting and have discarded (and sold) the scroll saw method. I homed in on basic cutting with my bandsaw and then final finishing on a belt sander working to a CAD generated pattern pasted on to the workpiece. I've now moved on to a CNC machine as I am making a clock for a fare-paying customer. I found I was spending a lot of time fettling my handcut gears to get them to run faultlessly. The slightest hint of friction in the latter stages of the gear train will cause a stoppage, so I needed to up my game in terms of time and quality.
I don't think cutting gears with a hand router is feasible.
The gears in my first project were made from 6 & 12mm commercial B/BB grade birch ply. This is quite satisfactory but higher grade birch ply, intended for laser cutting, can be obtained in small sheets but it is expensive. With my own home made ply I am down to 5mm thickness.
Balsa birch ply? I've not heard of that being used for clock making. Nor have I heard of hardening. If you are going to harden the teeth don't do it until the clock is running satisfactorily, it may hinder any tooth profile adjustment.
Are you making a clock to a published design or have you designed your own?
Brian

 

[amakah]

Hallo, Thank you for your reply. I did not think that my post had went on the site. I posted another post saying that I find it difficult to follow a line with the scroll saw due in part to my lack of practise and I also think that a shorter blade would be better as I only want to cut 9mm plywood so why have a much longer flexible blade. My clock plans came from a book called Making wooden gear clocks from the editors of woodworking. I could not justify a CNC but I can see the attraction. Have you tried a coping saw I have one but have not tried it. It would be slow but maybe more accurate Logan.

 

[Yojevol]

Hallo, Thank you for your reply. I did not think that my post had went on the site. I posted another post saying that I find it difficult to follow a line with the scroll saw due in part to my lack of practise and I also think that a shorter blade would be better as I only want to cut 9mm plywood so why have a much longer flexible blade. My clock plans came from a book called Making wooden gear clocks from the editors of woodworking. I could not justify a CNC but I can see the attraction. Have you tried a coping saw I have one but have not tried it. It would be slow but maybe more accurate Logan.

I tried a scroll saw but soon gave up on it because it was obvious I didn't have the skill level and I didn't want to spend years acquiring it. I haven't tried a coping saw, Just the thought of cutting 150 gear teeth would put me off the whole exercise. What method does the book recommend?
Brian

 

[amakah]

Hello, Thank you for the reply. The book is all about wooden clock gear cutting using a scroll saw. I find the CNC machine interesting as I had a friend many years ago who built his own. Can you give me some info on your machine. Do you use a laser to cut the gears or can it be done with a router with a small bit. I built a water jet for cutting wood some years ago using sand/water mix and a high pressure washer but it was only a partial success. Logan

 

[Yojevol]

Hello, Thank you for the reply. The book is all about wooden clock gear cutting using a scroll saw. I find the CNC machine interesting as I had a friend many years ago who built his own. Can you give me some info on your machine. Do you use a laser to cut the gears or can it be done with a router with a small bit. I built a water jet for cutting wood some years ago using sand/water mix and a high pressure washer but it was only a partial success. Logan

You can see my m/c in the link I gave in the recent post. here it is again.
It's a 20 year old Denford which was marketed for educational use so it's good and robust, although I had to do some renovation work to get it accurate enough for gear cutting. My biggest hurdle was getting to grips with the software side of things even though I am pretty adept at CAD.
I used it today to cut 2 gears. Took me about 20mins including setting it up. I used a 2mm end mill to do the job.
@J-G also has the same model and you can follow his efforts at clock making in great detail here .
Brian

 

[J-G]

Well -- there's a surprise!

Can't understand why but this forum (General Woodworking) wasn't open in my browser (I have many permanently open) so I haven't seen quite a few conversations - I may take some time to catch up !!

Thanks for the reference Brian - It's put me back in the frame.

In fact I haven't been in my workshop doing 'Real' work for over 12 months, not through any physical constraint, just that I've been doing 'different' work on the theoretical side.

My clock(s) are still unfinished - a mix of frustration, a realization that my quest for accuracy is a hinderance, and that wood 'moves'.

 

[okeydokey]

About 40 years ago I made a simple wooden clock with a jigsaw and hand fret saw. Had a full size paper template that was stuck onto solid wood and cut around. Seem to remember buying dowel for the spindles it worked and has long gone. Not that this a recommendation ... just saying