Difficulty While Making A Pulley

[prasad]

Guys,

I was making a pulley out of aluminum stock. The pulley needs a round groove 5mm wide and 2.5mm deep with diameter at the bottom of the groove at 17 mm. I ground the round profile on a HSS tool bit. Cutting was not easy. I was getting very loud growling sound and heavy vibration. I tried many changes such as varying tool bit height, increase front clearance angle & side clearance angle, back rake and of course feed rate. Nothing resolved the problem. Finally I had to plunge the tool at extreme slow rate at all settings. I also used WD40. I am attaching photos of the tool tip I made.

Where did I go wrong?
What is the better/right way to do it?

Thanks
Prasad
Wynnewood PA

 

[Micke S]

If you are attempting to turn the complete groove in one step I think it will cause this type of problem.

 

[Flammable_Solid]

I think you are doing this on your 9x20 lathe, correct? That is a big cut do do in a single pass.

Rough it out and only cut one side of the belt radius at a time.

 

[RJSakowski]

As Micke S stated, generally, trying to cut with a broad surface causes chatter. Try making a narrow tool to rough out most of the material and finish with your form tool. You can either calculate the tool path or make a template to get you close. If you go the calculation route, set your compound up parallel to the ways and use the compound and cross feed for your z and x position.

 

[Bill C.]

You didn't say how you are holding the workpiece. IF I was making it I would face both ends then drill and bore out the ID. I would use the tailstock with a ball bearing center to hold the piece steady. Like the others said rough out the groove(s) then finish the bottom with a form shaped bit. If the finish cuts are not blending in use a smooth flat file to remove any lines.

Good luck, please post a finished photo

 

[kd4gij]

Take somthing like a parting tool and rough it out in steps and then go in with the form tool..

 

[prasad]

Thanks everyone. Yes, I am using my 9x20 Grizzly lathe. The work piece is held in a 6" 4-jaw chuck. Work piece is a 1.25" aluminum rod and it is initially turned down to 22mm OD and then I cut the pulley groove. I have 1" aluminum rod on order at McMaster.com which may arrive in a day or two. I will grind another tool bit to a narrower size and cut one side at a time. I do not want to use parting tool suggested by Martin. I always had same or similar problems with it. I will post picture once I have it finished.

Thanks
Prasad

 

[kd4gij]

A threading tool would work great for roughing it out.

 

[prasad]

Guys,

I finally made the pulleys to an acceptable level of finish. Pictures are attached. I used all the suggestions given by all. Main change I made was to thin the groove profile tool down to 3 mm wide from the previous 5 mm width. I want to thank everyone of you for your advice.

Thanks again
Prasad
Wynnewood PA

 

[turnitupper]

Could you use a 5mm bullnosed end mill and something like this?
John.