timing belt gears

[firebird]

Hi

The wife went shopping this morning which gave me an hour or so in the workshop. I have decided to have a go at making a form cutter. I have started with a piece of 5/16 silver steel (drill rod) and machined it down on opposite sides to 2.69mm (.106"). Note I am using the square collet block. I'll let you know how it works.



Cheers

Rich

 

[HS93]

Spotted this , it may be off some help, he seems to get a nice finnish even with a small machine.


http://www.deansphotographica.com/machining/projects/gearcutting/gearcutting.html


Peter

 

[Majorstrain]

Hi Rich,
I don't want to take the fun and satisfaction away from you in making a form tool, but I would probably use a 3mm or 1/8" ball mill to cut the profile.

Then again I might of missed something in my speed reading of the thread. If I have then disregard the above comment.
Cheers,
Phil

 

[HS93]

again this may be of interest forgot the cnc part it just saves you winding the handels, but he used a ball end tool 2 passes and then a counter sink tool to form the tooth top so no tool making

[ame]http://www.youtube.com/user/hossmachine#p/u/57/a5hgHx7irqk[/ame]

http://www.cnczone.com/forums/761841-post232.html
hope it helps , I only want you to perfect it so I can try

Peter

 

[firebird]

Hi Peter

very interesting, thank you. Oh what I would give for CNC

Phil, a 1/8 or 3mm cutter will be too big. You haven't missed anything its me that's missed the target. I'm suffering from serious brain fade. :wall: :wall: :wall: A form cutter like the one I have shown being made won't work. It will still cut a square sided slot! I tried making a tapered D bit type cutter but that didn't work too well either. Trying to find technical info on belts and gears is harder than you might imagine but I have at last found some. I have a couple of belts which have the T5 tooth profile. They are still 5mm pitch but slightly different to the belts shown earlier. This is what the teeth look like.



this is the spec

Pitch (P) - 5.000mm.
Tooth Length (T) - 1.40mm.
Tooth Height (H) - 1.20mm.
Belt Height (W) - 2.20mm
Corner Radii ( r ) - 0.40mm.
Material:olyurethane Reinforcement::Fibreglass
Appearance::Translucent
Breaking Strength (N)::1190
Min Temperature (Deg C)::-18
Max Temperature (Deg C)::82
Tooth Angle (A) (Deg.)::40


Crucially the specs give the tooth form and the angle. I still like the slitting saw idea as several gears can be made at once in one length then parted off. I am currently working on a jig to grind the sides of a 2.5mm slitting saw to 40° to give the correct tooth form. I'll report back when more progress has been made

Cheers

Rich

 

[cfellows]

I made a 5mm pitch cutter out of a slitting saw to make some of these gears. I just bevelled each side of the cutter to the correct angle and the correct width at the tip for cutting the goove with the proper bottom width. I didn't try to put any side relief on the cutter. It worked fine in aluminum. I also made a cutter for a 3/8" pitch timing gear. The gear is about 5.5" in diameter and I've been using it on the spindle of my Logan 11.5" lathe for about 5 or 6 years now. Unfortunately, I don't remember how I made the cutter. Hmmm, wonder where that got off to???

Chuck

 

[tel]

You were on the right track with that form cutter - what you need to do is taper it, back off the two trailing edges, form two teeth on the end and away you go! use it same as an end mill. I've made several cutters loke the over the years (I think I originally got the idea from LBSC's Tich book) and they work remarkably well

 

[firebird]

Hi Chuck

That's encouraging to know someone else has done it with a slitting saw.

Tel
th_wwp th_wwp th_wwp th_wwp

Cheers

Rich

 

[Ken I]

Attatched short *.pdf "handbook" for Synchroflex belts.

Maybe of help.

Regards
Ken

View attachment synchroflex.pdf

 

[firebird]

Hi

Thanks Ken

Cheers

Rich

 

[Foozer]

Been reading this thread and something I suppose is so simple that it completely escapes me. The "P" dimension as shown on the flat belt drawing. Doesnt that change with pulley diameter?

I'm sitting here staring at a small toothed belt and pulley bending it around and the light will just not come on.

Robert

 

[Ken I]

Perhaps it would be less confusing if you visualise "P" at the pitch centre line at 1/2 "H"

(The neutral axis of the belt - otherwise you can envisage "P" being smaller on the inside of the PCD and larger on the outside of the PCD - don't sweat it.)

So for a 5mm pitch belt x 20 teeth you have a 100mm circumference PCD or (֦) 31.83 PCD plus "H" for the OD.

Sure the shape changes slightly with curvature but this is taken up in some slight clearance in the profile as well as the elasticity of the belt.

Regards,
Ken

 

[Foozer]

Perhaps it would be less confusing if you visualise "P" at the pitch centre line at 1/2 "H"

Regards,
Ken

The pencil and paper computer coming up, a few draw outs and I'll get it.

Thanks for the explain

Robert

 

[tel]

Tel
th_wwp th_wwp th_wwp th_wwp

Cheers

Rich

OK, first put a bit of silver steel in the lathe. Turn down a short section at the end to a diameter equal to the inner width of the gap, then turn a section to the wide (outer) width of the gap, then generate the taper. You should end up with something that looks like the secnd pic. Next time we'll take it to the mill, then back to the lathe.

 

[tel]

OK, now, as I said, over to the mill and slab down two sides to about the smaller diameter. You can see now that that little pip we machined has served two purposes - it has established the small diameter for the cone and it has acted as a depth gauge for milling the sides. But it is no longer of use - back to the lath and turn it away.

Now you should have something that looks like the last pic.

 

[tel]

All that's left to do is file some relief behind the cutting edges, harden it and try 'er out!

Works pretty good! I must stress, however, that I did not take a lot of care with this one - just a roughie to illustrate the process, the widths and angles were purely arbitrary sizes blah blah .....

 

[tel]

Well, it looks like that was a waste of time!

 

[ozzie46]

Not so Tel. I enjoyed it a lot.

I don't have any plans on making a tooth pulley yet but if I do you can bet this will be the reason I tried or did as I had no idea how to go about it before.

Ron

 

[Ken I]

Applause for going to the trouble.

Feel better now ?

I enjoy your threads also.

Ken

 

[Foozer]

Well, it looks like that was a waste of time!

Not at all, you just made it look so embarrassing simple.

Robert