hello all
i have a lathe and a manual milling machine (i had a cnc one but i disassembled it to build a better one)
i have already build a dividing head (no completly fiinshed)

now i want to cut pulleys!
my question is

1. can normal gear cutters cut timing pulleys as well ?
as i can put it on a shaft , insert it on the lathe chuck and put the pulley stock on the divider head and place it on the tool holder of the lathe

2. any link that sell the a carbide cutter that works with flycutter ?

i am open to suggestions

thanks all

I made some years ago. I ground a form cutter to do it and did them in a bridgeport on an arbor and put the cutter on an arbor.

max, Timing belt sprockets are commercially produced either by the gear hobbing or shaping process. Some are castings. To DIY your fly cutter method is probably the most appropriate. However, you must be very accurate as to tooth form. If not, you might have severe belt wear and/or noise. The belts have different shaped teeth between manufacturers and individual designs of each manufacturer, mostly propietary designs. Also, like gears, the form changes slightly with the number of teeth of a given pitch on the sprocket. You will probably end up with a library of cutters. Guard them with your life. lol !!!!

hello Richard
thanks a lot for your reply
but is it possible that i can cut pulleys with a gear hobbing cutter ?
which cutter will be the most suitable for it ?
any links will be appricated

thanks a lot

max, The cutter in question must have the form of the belt tooth profile whether it is a fly cutter, hob, shaper or single index milling cutter. This form can sometimes be found on the belt manufacturers engineering portion of their websites.

note: try www.cptbelts.com/pdf/manuals
You should be able to find something at "synchronous belts" or "Panther" under drives_design. I,m sure others will provide similar.
add: www.martinsprocket.com careful, old imperial pitches

Years ago in the racing days we wanted a 60% overdrive for the blower but none was available so I found an industrial pulley combination at the local tool supply house and they allowed me to make a Cero metal mold off them Since I bought belts from them. I used this to make the flycutter tools like you would use a radius gage. When I was done I marked the pulleys promenently with the 40% od sizes so our competitors wouldn't know the difference. It worked for me.

There is usually ample tooth space on commercially made timing pulleys, that I don't think that that is critical. Smooth corners with nice little radii would be good, of course, to prevent chewing the belts up.

The really critical dimension of a timing pulley is its OD. Actually, its OD is most commonly referenced as the pitch diameter, because that is where the belt's true pitch circle is created. The belts are manufactured with very exact and accurate tooth spacing. If this pitch diameter of the pulley is not exactly correct, then the belt is going to tend to 'crowd the teeth' on the pulley, and cause wear. There is a fair amount of frictional grip of the belt on the OD of the pulley, and the belt does not readily fall back into the gaps created for the belt teeth. So, "hack out" the tooth space however, but make sure the OD of the pulley is an exact multiple of the belt pitch.

eg.: 3/8 belt pitch, 10 tooth, OD of pulley is (10 * .375) / 3.1415927

I've machined a few timing pulleys both with form cutters and with slitting saws. I typically would gang a pair of slitting saws far enough apart to straddle two teeth on the blank, as this creates a bit of a natural angle on each side of the tooth face. That leaves the work of filing or sanding a bit of a fillet radius on the top corner of the tooth before the pulley is put into service.

The pitch diameter (pd) is actually larger than the outside diameter (od) of the sprocket. The pd is usually the diameter at which the belt cord runs. Its like the pd of a gear where the pd is at the mesh point of the gears which is a smaller than the od. For example, a Goodyear Blackhawk 8mm pitch 30 tooth sprocket dim's. pd = 3.008", od = 2.955"

can u make something like this? all it is, is a 2" (or whatever size u need) dia. piece of aluminum, a hub turned, with a groove to align the belt. holes are drilled in the side to make the timing teeth. all u would need is a lathe to turn it to the size u need and a mill/rotary table to drill the holes.

skmetal7, That would work IF you can find a belt that has a round tooth contour and you put the round holes on the correct pitch diameter and pitch that matched the tooth spacing of the belt. However, all the readily available belts that I'm aware of are of propietary shaped teeth and they are not round. They are compound blended angles with blended radii designed to mimic the involute gear teeth. Unless the application of your pulley is slow speed and limited use, the pulley (sprocket) would eat the belt alive. Snoop around a bit, there may be a belt available that fits your idea.
BTW, I live near you, Hartland, WI

excellent idea
but i agree with richard about belt shape.

This pulley teeth were cut with a "hand grinded tool.. So If I can do it, you can do it to...

Don't forget shaping or broaching. A slotter attachment & rotary table/indexer would allow you to use a hand ground tool to produce a sprocket. Any slotter or shaper could be utilyzed. Without an indexing device, you could make a fixture to locate the sprocket center and undersized holes from skmetal7's idea to position radialy. The shaping/broaching could then be used to finish the contour. Just an idea.

Seems counter productive to make your own timing pulleys. Lots of research went into designing the GT type belt/tooth shape to increase accuracy. I'd rather spend the couple bucks and buy the pulleys, even if my budget can only afford plastic.

Of course this only applies to small ones.

Hi Guys

This seems to be semi relevant to this post so here goes

http://www.cnczone.com/forums/showthread.php?t=24688&page=2

Posts 16 and 18

Two ways you can go.

1. Grind your own cutter based on 'ideal' profile and ......
2. Mill the ideal profile by splitting the pulley in half and ......

For the 36 tooth pulley I posted the minimum radius is R1.25 so you can use a 2.5mm dia cutter. The profile is as per Gates design, straight off their website.

Cheers

can u make something like this? all it is, is a 2" (or whatever size u need) dia. piece of aluminum, a hub turned, with a groove to align the belt. holes are drilled in the side to make the timing teeth. all u would need is a lathe to turn it to the size u need and a mill/rotary table to drill the holes.

Iv'e cut this type of profile before on our Fellows gear shaper but it was so long ago I had to think a while. I seems to most closely approximate this profile.

33444

skmetal7, That would work IF you can find a belt that has a round tooth contour and you put the round holes on the correct pitch diameter and pitch that matched the tooth spacing of the belt. However, all the readily available belts that I'm aware of are of propietary shaped teeth and they are not round. They are compound blended angles with blended radii designed to mimic the involute gear teeth. Unless the application of your pulley is slow speed and limited use, the pulley (sprocket) would eat the belt alive. Snoop around a bit, there may be a belt available that fits your idea.
BTW, I live near you, Hartland, WI

Richard alot of automotive "timing" belts are starting to use round tooth contour, I cannot garauntee that is perfect radi, but when I was still working at a local(to you to also) ford dealer now owned by a one time govenor canidate, they were just starting to come out on the newer vehicles. I was told by a completly unreilable but none less inteligent source that they provided better preformance at higher rpm of modern engines with some gripping sacrafice. Thats not that big of a deal as they tension them in many ways sometimes more then once.

max-imum_2000 if its not a round tooth then I would be shaping, seems like the most logical approach short of horz. miller with the right contour cutter esp if more then one is needed. Either way if its a stock belt I would just order the thing someone must have the right sizes.

Chris (in grafton,WI)go badgers!

Personally, I would buy/modify an existing sprocket. However, max-imum2000 is located in Egypt and stated he wants to make his own sprockets for his own reasons. I am just making suggestions and giving cautions to help do that. Obviously I am not the only or last word on the methods etc. As to the round teeth, the new belts are far superior to belt construction and materials of only a few years ago. I do not believe the new construction is available in the old style belts. Could be wrong though.

I'm flat out amazed that a milling cutter for this is not readily available and easy to find???

Buy and modify...not always possible, certainly not fast enough for quick prototyping.