# Timing Pulley size & Dimensions



## Charley Davidson (Nov 15, 2013)

I'm gonna make my pulleys tomorrow hopefully for my cnc plasma table. I need to know what size I should use like XL, L ,H?

I also need the dimensions for the tooth profile so I can grind a cutter for this job. Not sure if I'll do it with a fly cutter or a regular cutter yet.

I need to make several about 3" dia. no bigger though.


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## xalky (Nov 15, 2013)

I'm using L x 1/2" wide for the drive belts and the reduction belts on the one I built Charley. Are you doing a gear reduction? The econobelt link has fantastic prices on pulleys. You might not want to be bothered making them. I bought mine and bored them out and put keyways and setscrews on them.

Here's a couple of good sites for info: http://shop.polybelt.com/main.sc     Lots of info

http://catalog.bbman.com/db/domains/static/bbman/config.html  reduction calculator

http://www.econobelt.com/     best prices I've seen.


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## Charley Davidson (Nov 15, 2013)

I think I'm going 3 to 1      I guess 1" on the motor and 3" on the transfer shaft & drive, sound right?  Or can I go with 1" motor & transfer shaft?  On my Z one to one, My Y is a self contained linear tracking mechanism.

This is a drawing of how my drive system is setup


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## xalky (Nov 16, 2013)

I don't remember all the details Charley. If you want to read thru my build log over at the Longevity forum and cnczone here:http://[URL=http://s1124.photobucke...3abe3ea.jpg.html][ATTACH=full]163369[/ATTACH][/URL] and here http://www.cnczone.com/forums/plasm...numeric-control_plasma_table_build_xalky.html

Using the pulley teeth as your reduction ratio is easier to nail down your ratio, rather than going with a set diameter. Most of my stuff is documented In those 2 places. I went with a 4 to 1 belt reduction, because I wanted the ability to change direction quickly to cut thin stuff. My gantry weighs roughly 90lbs. The weight of your gantry is gonna determine how fast it can change direction. With the small pulley your going to have to  make an idler so as to wrap as much belt around it as possible to avoid belt slippage. You can see those details in my build logs.

Marcel


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## Charley Davidson (Nov 16, 2013)

So unless you or anybody else sees a good reason that this won't work this is the way I'm going, I may change the sprocket size but I think everything else looks good.


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## xalky (Nov 17, 2013)

Sounds like you got it figured out. 

Without table specifics, I can't make any recommendations.

Marcel


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## Charley Davidson (Nov 17, 2013)

xalky said:


> Sounds like you got it figured out.
> 
> Without table specifics, I can't make any recommendations.
> 
> Marcel



Like what?


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## xalky (Nov 17, 2013)

Pictures, gantry weight, what kind of motors, rack or something else, etc. Didn't you have a build thread somewhere?

Sent from my SPH-L710 using Tapatalk


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## xalky (Nov 17, 2013)

Ok... I remembered where i saw your build log and went to take a look at it. http://forum.longevity-inc.com/showthread.php?3556-Charley-s-CNC-Plasma-Table-Build/page5 Your gantry seems to be pretty light, which is good, except for that Z axis. It looks like you're gonna have 2 drive motors on the gantry, thats good! Your steppers are the same size as mine 640oz/in, thats good! I would go for a 4 to 1 ratio belt reduction. For the most part your table is gonna be very similar to mine. Take a look at how I set up the belts. If you need specific pulley diameters, I can get you those. I had a lot of help from Tom over at CandCNC, he made the reccomendations and it worked out really well. It looks like your gonna use a belt drive for the gantry travel, so you can pretty much copy what I did and I guarantee your table is gonna be badass. The only thing I would change on mine is the Z screw is a bit too fast at 1tpi on the screw. If i were to do it again, and I might change it eventually, The Z should be around 5-6 TPI to allow for more reaction time of the THC. Mines a bit too fast and it overshoots the mark a little. I managed to dial it in acceptably with The THC delay.


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## Charley Davidson (Nov 17, 2013)

xalky said:


> Pictures, gantry weight, what kind of motors, rack or something else, etc. Didn't you have a build thread somewhere?
> 
> Sent from my SPH-L710 using Tapatalk



http://www.hobby-machinist.com/showthread.php/5528-Build-thread-for-my-CNC-Plasma-Table

I'm using a fixed chain that the sprocket runs on to move the gantry, I would like a rack & pinion system but its not in the budget right now, gantry weight less than 100 pounds I'm sure


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## xalky (Nov 17, 2013)

Check out my post above your last post. Chain drive should work fine, any idea what the backlash will be, if any? One of the reasons why I went with the timing belt drive was to virtually eliminate the backlash, and it's very quiet. For the belt reduction I used a 10 tooth and a 40 tooth pulley. The 40 tooth is linked on the same shaft to another 10 tooth for my final drive pulley. Your sprocket is going to affect the final drive ratio, so take that into consideration when doing your calculations.

Here's where I got my stuff for timing pulleys. Best prices I've found anywhere. http://shop.polybelt.com/40L050-Aluminum-Pulley-40-tooth-MPB-OD4744-inch-P40L050-6FA.htm I couldn't find the link earlier.


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## Charley Davidson (Nov 17, 2013)

These guys that you gave me a link to have the best prices http://www.econobelt.com/


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## xalky (Nov 17, 2013)

Yeah, you're right. Hardly worth making them at those prices, unless you have lots of time and no money. )


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## Charley Davidson (Nov 17, 2013)

xalky said:


> Yeah, you're right. Hardly worth making them at those prices, unless you have lots of time and no money. )



 I fit that description


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## GK1918 (Nov 17, 2013)

perhaps check out Graingers  some where they have a chart.  and I got mine with those dimis. from napa..  Ya 50 bucks.


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## DAN_IN_MN (Nov 17, 2013)

Charley Davidson said:


> These guys that you gave me a link to have the best prices http://www.econobelt.com/




Yes, thankyou for the link!  I too am looking for the best price on timing pulleys and belts for a small belt/disk sander I picked up a while ago.  I still need to learn of their shipping costs.  I see they charge $3.95 for handling.   

My table saw may need a belt too.


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## DAN_IN_MN (Nov 17, 2013)

Found this vid on the tube.  Thought it might help out in this thread.

[video=youtube;kCiujbcrQzc]http://www.youtube.com/watch?v=kCiujbcrQzc[/video]


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