broken gear

[hopeless]

Hi fellow metal termites.
I need to make a gear for my dremel drill press as the plastic one shattered due to age according to Dremel. Nope, can't buy just the gear need to buy the whole kit at $100+ even though it is easy to disassemble. Not an option as I'm on a pension and so I thought I have the machinery why not make one? Only drawback is I dont have a clue on gear cutting and no dividing head. The gear in question is 14mm (9/16th") thick, 38mm (1.5") overall diam and has 16 teeth and is of rack & pinion gearing.
As there is not a lot of pressure involved I am thinking aluminium or delrin as with delrin I may be able to use the scrollsaw. With aluminium I would need exta tools and the minister for war & peace said no. Any help would be appreciated.
Pete

 

[kcmillin]

This may depend on what you have for tooling. Single point gear cutting is relatively easy to do, but you will need some way of indexing the teeth, and you will have to make a holder to fit in your mill for a tooth ground HSS cutter.

If I am not mistaken the dremel drill press's pinion gear is missing teeth from the factory, this, I believe, is for assembly, as the pinion does not need to make a full revolution for the rack to go up and down.

I think you could do this gear with a scroll saw, like you stated, it does not have to be a perfect mesh.

Kel

 

[Dan Rowe]

Pete,
If you have onother gear with the same number of teeth it can be used as a simple indexer. The cutter can be ground to match a good section of the failed gear.

If you want to go the scroll saw method I can post a drawing with the specs. you provided for a template.

Dan

 

[Herbiev]

http://www.sdp-si.com/eStore/CoverPg/Gears.htm
I've found this mob sells the gears extra cheap 8)

 

[Dan Rowe]

Pete,
If you are going for a replacement gear the specs. you gave indicate a 12 DP gear. My guess is it is a 200 pressure angle but that can be checked with the rack the angle of the side of the tooth from the vertical is the pressure angle the usual suspects are 200 or 14.50.


Edit: by vertical that is if the rack is on the table with the teeth in the air. A square tooth rack has a pressure angle of zero.
Dan

 

[Norman]

Could you post a photo of the broken gear. If it is a simple plain gear I could maybe make it for you I'd need the remains of the gear so I can copy the size and the tooth profile.
Norman

 

[hopeless]

Kel your on the money It is missing 3 teeth I came up with sixteen by gluing it together with cryo glue (super glue to Aussies) and tracing the gear out to count the total. I've made a temp 1 out of hardwood while I toy with making a better one.
Thanks Dan I can now further my education and see if I come up with the same answer. I'll check the angle shortly as I'm making a new shaft to improve on the Dremel method of holding the gear in place. I like the idea of using a similargear which I now have abliet glued up.
Love your avatar Norman almost like my bike (1994 blue ultra classic ;D which still runs good.) and thanks for your offer of help. I'll keep it in mind if all goes pearshaped.
Also thanks for the link it has heaps of options for my other projects But I'll keep scheming to get a rotary table if at all possible as I see a couple 4" going cheap at JTS on ebay about $100ish posted to here
Cheers
Pete

 

[Norman]

The bike is a 1995 ultra classic 30th anniversary edition 1973 of 2000 first year for fuel injection, which has been changed to thundermax fuel injection with auto tune. I'll be riding this bike to Sturgis South Dakota to the Rally this Friday.
The offer still stands for the help.

 

[Dan Rowe]

Pete,
I used a gear program to arrive at the answer but it is simply a clever graphical interface with the formulas.

There are two methods you can use in this case to arrive at the diametrical pitch (DP). The pitch of a rack can be simply measured this is the circular pitch (CP). The formula is DP=3.14159/CP

The other formula that can be used with the information at hand is the relationship of the outside diameter (D) and number of teeth (N). The formula is DP=(N+2)/D.

Dan

Edit: fixed the formula, fat finger syndrome.

 

[hopeless]

Thanks again Norm for the offer. If all goes pear shape I will get back to you.
Over here HD didn't go fuel injected with the ultras untill 1999 ??? but hey still better than walking :big:

Dan thanks for the formula I now have a head start for making gears .

Many thanks to all offers I will post the results/pics when I'm done
Cheers
Pete