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machining pulleys for vee belts

how to machine vee pulleys

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XD 35104/04/2013 06:23:10
845 forum posts
37 photos

H i all ,

I need to make some pulleys for some lathe and T&C projects and did the usual search on this site but got a big fat 0.

The pulleys are for sub horse power belts that are 10mm width across the outer dia and are about 8mm deep - the pulleys will be made from alluminium.

One thing i have never done is make a vee pulley as i usually use belts with a round cross section cut and glued together to form a belt .

I was thinking that if i first use a parting tool to cut down to the root dia + some clearance  (say 2-3mm)for the bottom so the belt rides on the vee sides then set up a small tool steel bit in the tool post and use the compound slide to machine the angle on each side of this groove .

I can set the compound slide angle accurately enough and was thinking that if i lock the saddle and use the the cross slide to feed in each cut until i get to the required width and note its total travel using the cross slide dial or lock the cross slide and use the saddle with a dial indicator set up to show its total travel so i can gauge the amount of metal removed from each side of the vee and hopefully they will be identical.

Any ideas ,links ,thoughts and hypothesis are welcome !


Edited By SLOTDRILLER on 04/04/2013 06:25:46

Andyf04/04/2013 08:43:54
392 forum posts

I’ve only made a couple, so others will doubtless know better, but I did it much as you describe, starting with a parting tool to make a groove. When it comes to angling the sides, I’m not sure how you would use the cross-slide when putting the angles on either side of the initial groove. I locked the cross slide and moved (then locked in place) the saddle between each cut. It helps if you have a handwheel and dial on your leadscrew to make fine adjustments, though if you have (say) an 8tpi leadscrew and put a 60T changewheel on it, each gear tooth will represent about 2 thou saddle movement. You suggest a dial indicator, but unless for some reason you want to be very accurate, that doesn't really seem necessary.

My pulleys-to-be were mounted on a mandrel, and once the angle on one side was done I reversed them on the mandrel to do the other, so the top slide angle didn’t have to be changed, and just shaved away the second side until the belt fitted in nicely with its top flush with the circumference of the pulley.


Chris Gunn04/04/2013 09:58:47
248 forum posts
16 photos

We used to make a simple form tool to finish vee pulleys, just a piece of gauge plate, grind it to match an existing pulley groove, relieve the cutting edges, and harden. take the big volume of metal out with your parting tool, plus a little at each side, then use the form tool to finish, no messing about, and all grooves will be the same, which is important.

Chris Gunn

RobC04/04/2013 10:09:29
49 forum posts
3 photos

This chap shows some interesting techniques over three videos.


Stub Mandrel04/04/2013 11:06:34
4305 forum posts
292 photos

Hi Ian,

I think I used a V-tool to make some for my lathe - I plunged it in, and then took further cuts each side, then traversed to leaf a flat bottom to the groove.

These were relatively shallow V-slot in aluminium that I actually run 1/4" belting in.

I made the first two using the milling machine with the blank in a mandrel and asideways tool ina vertical slide on the mill table - this was after swarf in the elctronics had silenced my lathe and I converted it to a siongle phase motor.

Once I had a pair, I was able to make temporary two and three step pulleys that I still haven't upgraded!


Edited By Stub Mandrel on 04/04/2013 11:08:55

Ian S C04/04/2013 11:29:10
6779 forum posts
224 photos

You sound as though you'v got it figured, jus remember to have the belt only running on the V, and not on the bottom of the groove. For setting angles (such as for the V pully) I have a set of angles made of sheet metal. Just place the angle plate betwen the compound slide and the chuck face, tighen up, cut, then turn the angle around and turn the slide to suit. Find the angle of the V belt, and cut a bit of sheet metal with tin snips, that should be not too bad, you could use a protractor the same way, its just that the stuff I'm doing (getting payed for) is OK that way, and its quick, and repeatable. Ian S C

Ian P04/04/2013 12:00:14
1891 forum posts
80 photos

The problem with form tools is that they cut on several edges at the same time which on a light machines leads to chatter and other problems.

I have cut many pulleys and large chamfers using a tool with the angled cutting edge much shorter than the finished surface. In fact I usually do it without the topslide having to be set at an angle.

The technique is so 'stroke' the cutter manually using the saddle and cross slide so that it follows the surface that it is cutting. I find that the majority of material and the best finish is achieved when the cutter is traversed in the outward direction. As long as the cutter edge is at the correct angle the final result will be more than good enough for a belt groove.


Trevor Wright04/04/2013 12:45:19
139 forum posts
36 photos

Ian, used the exact method use describe for the same size belt. I set the angle for the cross-slide by turning the belt inside out and placing the angled section along the cross-slide body and eyeing up the belt for square.

Did not consider a form tool as the chatter would wake the neighbours........


Gordon W04/04/2013 13:57:47
1961 forum posts

Just from memory, havn't got time to check, I seem to remember that the angle of the pulley V is different to the belt angle , and also varies with pulley diameter . maybe only applies to industrial practice and no need to bother at our sizes and power.

JohnF04/04/2013 18:05:04
624 forum posts
53 photos

Hi Ian, I don't know what type/make of lathe you have but unless it is a very lightweight and small machine I would defiantly make a form tool from HSS, make the tool to the correct flank angle on both sides but narrower than the finished groove width.

This way you can cut on alternate sides if the going gets tough but in ally you should have no problem, you can cut out the bulk as you and others suggest with a parting tool but try it without --you may be surprised at your machines capability ! Run slower than normal for allly with plenty of coolant, oil or paraffin.

Info on dimensions here



Good luck John

Ian P04/04/2013 18:57:22
1891 forum posts
80 photos


Lathewise I have a Boxford so personally I don't have problems. my comment was just a general one. If I had to make a quantity of pulleys I might make a form tool though.

By coincidence, yesterday I put a 15mm wide 45 degree chamfer on an 200mm diameter chunk of aluminium using the same 'stroking' technique. After turning the OD and face I rotated the toolpost so the (tipped) cutter edge was at 45 degrees, a few moments work produced a smooth chatter free chamfer.

In the above example the edge of the TC tip was about 7mm wide and if fed directly into the job it would start to chatter at some point. By keeping the tip moving so that it is cutting on a gradually increasing radius the cut proceeds really smoothly.

Yes, the same chamfer could have been done with a small radius tip with the topslide set at an angle, or it could be done with a form tool. For speed my way is more efficient.

Bubble04/04/2013 21:07:30
75 forum posts
6 photos

Hi Ian (Slotdriller)

All you need is one of these:


Google "grooving vee pulleys Duplex" to find an old ME article

Makes lots of swarf though!


XD 35105/04/2013 05:38:42
845 forum posts
37 photos

Hi all,

Thanks for the replies and ideas .

My machine isn't (unfortunately ) the most rigid unit and parting off is usually an adventure using the front tool posts even with a Glanze type tool .

The problem is how the compound slide / toolpost unit mounts to the topslide as i can see it flexing as i f eed in and it has a safety clutch on low gear that seems to want to add to my grief !

I made a rear mount and it gets me by but plans are afoot to remedy this issue - keeps getting put on the back burner until i get time !

Thanks to Rob C , John F and Jim Cahill for the links they have been a most useful source of info and i never knew there were so many videos on machining

I have down loaded the info on vee pulleys in the links from John F and filed them away for future reference as i did do a search on vee pulley / belt dimensions and seemed to get little of use from it as it seemed that most of the sites were trying to sell belts or pulleys - Might try a different search engine !

From what i can gather here i think a form tool would be faster and give more consistent results pulley to pulley provided the lathe can handle it .

I think for my machine (until i fix the toolpost anyway) i will stick with the method in the you tube video and as i have a few pulleys to make it would seem wise to make a stepped mandrel to fit the various bore sizes of these pulleys and machine them in one lot .

Once again thank you to all who took the time to answer this thread as you have made the procedure of this machining operation much clearer .

I 'm off to trawl you tube for more videos on machining /model engineering - cold beer in hand of course !


Dusty05/04/2013 09:11:59
446 forum posts
8 photos


A couple of points which might help if you go down the form tool road.

1. Reduce the overhang of the topslide

2. Make a leg for the tool, by this I mean a piece of 3mm plate the width of the tool, at the front end a length of say 3/8 sq welded or brazed to this at right angles so that the bottom contacts the cross slide when the tool is at centre height with the tool sat on the 3mm plate.

3. lock everything solid or as far as possible.

4. For finishing you can pull the mandrel round by hand. You can only take a scrape doing this but it will provide a chatter free finish within limits.

Hope this helps.

Ian S C05/04/2013 10:43:30
6779 forum posts
224 photos

Cut the center of the groove to depth with a parting tool, or you could use a tool with a V point, then use a left, and right hand tool down each side, there is less strain on the lathe than using a form tool, this should alleviate the chatter problem. Ian S C

Stub Mandrel05/04/2013 10:43:55
4305 forum posts
292 photos

The Duplex article is interesting, but much as I respect 'Duplex', I can't see any significant advantage in using a cranked tool instead of an ordinary parting tool (just rotating the toolpost to a different angle) unless you are turning a very small pulley in a large chuck.


Bubble05/04/2013 11:07:54
75 forum posts
6 photos

Hi Neil

I can only quote Duplex:

"The forged tool has its cutting

portion shaped like a parting tool,

but the angular set enables the tool

to be mounted in a way that avoids

fouling the chuck jaws or shoulders

on the work when machining the

grooves in either a plain or a threestep


If you try it you will see how much easier it is, with lots of side clearance for the tool.

Especially on an ML7 where the topslide cannot be fully rotated.

I have never experienced judder with this tool in spite of the overhang.


Jeff Dayman05/04/2013 12:49:56
1187 forum posts
31 photos

Just a thought from outside the box - V belt pulleys can be made in two pieces to avoid chatter, special tools etc. Make two disks with the angled belt faces, and bolt, weld, or rivet the disks together. The disks are simple facing ops in any lathe. A registration diameter on one disk and a close fitted hole on the other disk will ensure there is no relative movement when loaded.

I can't take credit for the idea- stamped sheetmetal pulleys for appliances and implements have been done this way for many years.


Michael Gilligan05/04/2013 13:10:52
11040 forum posts
475 photos


An excellent point

and ... taking it a little further; it's easy to adjust the effective diameter of the pulley.


Ian S C05/04/2013 14:09:39
6779 forum posts
224 photos

I'v even got a little press tool to make 1" V pullies for Meccano, just as JD discribed for pressed metal pullies. Ian S C

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