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View Full Version : Pullys and their design



GeorgeD
01-08-2010, 06:44 PM
How are these pullys made? can't find a vid on youtube of them being made?

http://www.bearingboys.co.uk/10-3M-09_Metric_Pilot_Bore_Timing_Pulley-21167-p

Smiler
01-08-2010, 06:56 PM
How are these pullys made? can't find a vid on youtube of them being made?

http://www.bearingboys.co.uk/10-3M-09_Metric_Pilot_Bore_Timing_Pulley-21167-p

I imagine just like any pulley. Machine the blank to shape then an indexer to machine the flutes at the required pitch (Machining centre would I imagine do all these operations in a single run) then two sidewalls pressed on to keep the belt tracked.

But I could be wrong :-)

Jeff.

GeorgeD
01-08-2010, 07:18 PM
Hi Smiler

I think they're made as one unit? as I've seen em in Aluminium,hence me asking how they're made.

I know how the spur geas are cut,but for the life of me just can't see how these are made.

:smile:

Ross77
01-08-2010, 07:25 PM
I think they're made as one unit? as I've seen em in Aluminium,hence me asking how they're made.

The ones I have are still made as separate pieces, theres no physical way it could be made in one piece. If you had semi circular belt tooth then maybe with a ball end mill but the edges would have to be over cut

routercnc
01-08-2010, 07:34 PM
Hi Ross,

There is a way :wink:. At work we have a very expensive machine called a spark eroder. You make a male electrode from a graphite type of material using a cnc miller or std miller. In this case the shape of the tooth on the belt. This is then attached to the eroder, and lowered into the blank gear, and spark eroded to create the negative shape. You can cut square holes this way, or any shape you want.

I had a special hex bolt made this way once. Not really a production volume method though since it takes a while.

Smiler
01-08-2010, 07:58 PM
Hi Smiler

I think they're made as one unit? as I've seen em in Aluminium,hence me asking how they're made.

I know how the spur geas are cut,but for the life of me just can't see how these are made.

:smile:

The one you showed is almost identical to the one I bought from BB last week, it is definately a three piece unit, main pulley body and two sidewalls which are pressed on and I think peened in place.
As ross says, it would be difficult (not impossible, as you could cast it as one piece) to make any other way unless you had either the ends of your belt teeth rounded or overcut the tooth at both ends.


Jeff.

GeorgeD
01-08-2010, 08:00 PM
Think I've sussed how its made?

They mill the blank with an over depth pitch and then turn its sides on the lathe and at the same time turn the pitch teeth so that at the requied depth the sides are evident and the pitch teeth are narrower?

GeorgeD
01-08-2010, 08:44 PM
C'mon someone correct me if I'm wrong? :whistling::wink:

Because I have one here in ally and its deffo a one piece unit.


Mill the blank,turn the sides and lower the pitch teeth. :dance:

routercnc
01-08-2010, 09:18 PM
Hi George,

I can't quite picture what you mean. Do you have a sketch you could scan in, or give it another go at the description. Do you have a picture of the Ali one you have there?

Thanks

John S
01-08-2010, 09:30 PM
Commercially they are hobbed and the sides are pressed on. Takes about 20 seconds to do the one you have linked to.

GeorgeD
01-08-2010, 09:30 PM
Here's a pic of what mine looks like,its the one in the top row middle of the five.http://www.econobelt.com/e-store/Pulleys.jpg

Look at the bottom row,this is how it will start out in the milling process,now if we put this on a lathe(with shaft to hold before parting) we can then turn the sides and at the same time reducing the teeth pitch to the desired depth and then we end up with something on the top row pullys.

If I had a lathe it would be simpler to show rather than explain.

John S
01-08-2010, 09:37 PM
The one in the top middle row has side plates pressed on. Also it's not the same as the one you linked to originally.
the one you linked to is a M3 HTD series, the one in the top middle is a trapezoid form like a XL or L series.
Two different animals.

GeorgeD
01-08-2010, 10:01 PM
I know its not the same as the one I linked to at the begining,RCNC asked did I have a pic of mine and found one on the net rather than photograph mine. :rolleyes:

John S
01-08-2010, 10:21 PM
Whatever.
The answer still applies they are hobbed from bar stock irrespective of the tooth form.

http://www.youtube.com/watch?v=EXvBeQMKIEI

Look about 1:28 into the video, shows the hobbing of a batch followed by the fitting of the side plate.

This video gives a better explanation of the system.

http://www.youtube.com/watch?v=ZhICrb0Tbn4

It is a gear but all that differs is the cutter shape.

.

Scott
03-08-2010, 09:53 AM
try here http://www.youtube.com/watch?v=Mm5MzBUmL2Q

GeorgeD
03-08-2010, 10:06 AM
Thats exactly how I said it might be done in an earlier post,though why he did not do two sides I don't know?



Cheers Scott. :wink:

John S
03-08-2010, 10:17 AM
Because he's going to have radii at both ends of the cut and if the belt tracks across into them it will wear the belt.

this is why they are hobbed thru and then sides are pressed on, so there is always parallel tooth form under the belt.

.