[Memran]

Hello!

I've been trying out a new way (new for me) to cut timing pulleys.

I was unable to find a form for any pulley, so I had a go at creating one. This was done on my manual lathe, and then milled the "teeth" on my 4th axis:



I then hardened it, by heating to a nice cheery cherry red, and quenching in fresh oil:



It came out ok, but not perfect. Anyway, I tried cutting with it and had good results, but they quality of cuts declined very fast. After about 9 teeth, the blank was getting hot, and the cut was not clean at all!



Here is a video of some cuts.
Turn volume down a bit!
[ame="http://www.youtube.com/watch?v=dr_HE1LS8K4"]http://www.youtube.com/watch?v=dr_HE1LS8K4[/ame]

The machine is a Sieg X1 (150W), with home-made 4th axis from a 7x10 lathe head.

My settings:

• 9 tooth cutter, 25mm radius
• 1000rpm
• 100mm/min feed
• 0.6mm doc
• Mist coolant

So can anyone help me achieve better cuts without having to babysit the machine?
I realise this is probably not too easy, given that the tool is home-made, but please try!

Thanks!

[hoss2006]

What kind of steel was it in the first place, different steels require different heat treat procedures.
Did it actually harden? Check it with a file.
Did you regrind the cutting edges to make them sharp?
The low rigidity of the mill would do better with a few passes instead of one at full depth.
Hoss

[Connor]

Sounds like it didn't get hardened correctly. I think your suppose to heat till it a magnet can no longer stick to it.. the quench as faster as possible in WATER. (To Harden it) Heat again till it's glowing straw yellow, quench again in water. (To Anneal is slightly so it won't shatter)

[Memran]

I am not 100% sure of what kind of steel it is, as it was bought on ebay, a long time ago. I believe it is "bright mild steel" which should have some carbon in it, but a small amount.

I did the file test, and it is definitely harder. The file sort of slides across, compared to original where it cuts deeply.
After my attempt at hardening, I did resharpen it.

Do you think that there is enough relief behind the cutting edge?

The cuts I was taking, were 2 passes of 0.6mm. I guess I need to try much lighter still, say 4x 0.3mm.
Should I also be climb milling?

Thanks again!

[keebler303]

If you aren't stuck on the trapezoidal belt design, there are easier ways.

http://www.cnczone.com/forums/mechan...g_pullies.html

This could be done from aluminum just as well. I've seen one fellow who drilled holes for the teeth and was therefore able to make the flanges integral to the pulley.

Matt

[Memran]

Thanks
I've used that method before to make the pulleys for my 4th axis, but I had a lot of difficulty with thick pulleys. I was breaking end mills if I tried to go much wider than 10mm.
The belts are trapezoidal, but if this is too tricky, I don't mind switching to HTD.
It would be nice to get this working though, for my own satisfaction more than necessity!

[bozidar22]

I have had good results using single point tools made from HHS lathe blanks.

Here's some videos on grinding the cutters.


[ame=http://www.youtube.com/watch?v=BtWedz55IOM&feature=channel&list=UL]grinding profile cutters part 1 - YouTube[/ame]



[ame=http://www.youtube.com/watch?v=5QGQwA7DSBY&feature=channel&list=UL]profile cutters part 2 - YouTube[/ame]



Hope this helps

[hoss2006]

I am not 100% sure of what kind of steel it is, as it was bought on ebay, a long time ago. I believe it is "bright mild steel" which should have some carbon in it, but a small amount.

I did the file test, and it is definitely harder. The file sort of slides across, compared to original where it cuts deeply.
After my attempt at hardening, I did resharpen it.

Do you think that there is enough relief behind the cutting edge?

The cuts I was taking, were 2 passes of 0.6mm. I guess I need to try much lighter still, say 4x 0.3mm.
Should I also be climb milling?

Thanks again!

Zooming in on your pic shows it needs more relief, right up to the cutting edge so it won't rub.
Stay cutting conventional, 3 passes may do it.
File hard is plenty hard enough for ally.
Hoss

[Memran]

Thanks bozidar22, that is a very neat way to do it!
And thanks Hoss too I'll make the reliefs better tomorrow. Have to stop for today because the neighbours have a baby trying to sleep.

[keebler303]

Thanks bozidar22, that is a very neat way to do it!
And thanks Hoss too I'll make the reliefs better tomorrow. Have to stop for today because the neighbours have a baby trying to sleep.

The sensitivity of the neighbor's ears can be reduced with gifts of CNC'd trinkets.

[MrWild]

Bright mild steel is not the right choice. It is VERY important to use the correct steel. A2, O1... After heat treat, the cutter must be drawn back also. Drawing back is where you polish the cutter back out to shiny and then slowly heat it to a light straw color and IMMEDIATELY quench in water. Too dark starts to anneal is, and not enough leaves it brittle and prone to fracture.

Relief is best roughed in before heat treat as metal removal is easier (although not as easy as mild steel). Once heat treated and drawn back, finish the relief so that there is about .005-.010 land. Less is better and a good hand/eye will have it almost to the edge. The reason I give .005-.010 versus saying close to the edge, is that it take practice to do it right, and you're learning new skills. To help see the cutting tooth land, use some Dikem to highlight the teeth.

Another tip is you don't need a ton of teeth. You can do it with two, or three, and it allows you to remove all the rest of the material that makes grinding back the relief so hard when the cutter is loaded up with teeth which get in the way of the grinding wheel.

[CNC-Joe]

Are there any programs available that will generate G-code to cut the timing belt gear profile using a plain end mill and a rotary 4th axis ?

[H500]

Something to note is that the XL(trapezoidal) tooth belt has only a fraction of the load capacity as a similar width HTD (round) profile. The latter is also much easier to make. Use a 1/8" round nose milling bit to cut a .08" groove on a proper diameter disc.

[Bubba]

mrcodewiz made a program available some time back and can be followed in this thread:

http://www.cnczone.com/forums/bencht...ne_timing.html

You might PM him to see if it is still available. The thread also has some additional ideas.

[H500]

I have had good results using single point tools made from HHS lathe blanks.

That's an interesting way to make cutter shapes. I thought the grinding wheel wear would be a problem, but apparently not.

Have you tried it for making gears?

[cyclestart]

I was unable to find a form for any pulley, so I had a go at creating one

It would be great these were available as some of the tooth profiles are complex and (apparently) deliberately obscure regarding exact profile details. If cutters are available I've searched in the wrong places. China doesn't know we want them ? lol

Gearotic has a tool wizard for a few profiles. Just something I've spotted, not something I've tried.

[hoss2006]

Are there any programs available that will generate G-code to cut the timing belt gear profile using a plain end mill and a rotary 4th axis ?

I wrote my own programs early on till Bob came out with this program which made it easy.
It has many new advanced features now.
Make your own Timing Pulley
Hoss

[CNC-Joe]

Thank You - Art/Bubba, MrCodeWiz/Kevin, Art Fennerty - for the great programs!

I love this forum !

[hoss2006]

Your welcome.

[bozidar22]

I guess any shape can be made this way. As long as it has an "open curve" (not sure how to describe it) and the grinding wheel is compensated for.

Some tooth profiles are patented and are hard to find or they change with pulley size.