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Making A Stepped V Belt Pulley


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#1 29 Chev OFFLINE  

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Posted June 10, 2020 - 10:36 AM

I have a Craftsman 6" metal lathe that my dad purchased new in the early 1960's and a few years ago the set screw hole that secures the pulley to the key on the motor pulley stripped out.  As a temporary fix I drilled and tapped a new set screw hole but it does not secure the shaft key properly.  The pulley (as well as the original gears) is made out of a product called Zamak and while it was a great metal to introduce a low cost lathe to a growing hobby the material is not user friendly as far as welding it.  The way the pulley was produced was what I would call economical without any excess material and as a result there is not much of a way to sleeve the pulley and attach it to a new hub.  Due to the age of the pulley it is also becoming worn in the smaller v groove since this is where the belt runs a lot of the time.   

 

I have decided to try and make a new pulley out of steel which will make it a little heavier but also much more durable.  Thought I would do a post on it as others may encounter a damaged, worn or missing stepped pulley in other applications and think that creating a new one may be virtually impossible.  Normally I would check at the local hardware store and see if they had any ready made pulleys in stock which I did but did not find any that could be easily adapted since most V belt pulleys are made for 1/2" wide belts and the lathe uses 3/8" wide belts. While owning or having access to a metal lathe is a definite necessity to making a new pulley on initial inspection of the original pulley one might think that it would be necessary to have a chunk of round stock approximately 3.25" OD by 1-1/2" wide and while that would work I am going to form the pulley out of 2 pieces of steel I had laying around left over from other projects. The other benefit of making the pulley in piecemeal form will be to cut down on the time to machine the smaller diameter of the pulley step. Got the two pulley diameters cut out of a piece of 1/2" x 6" flat steel approximately 3-1/2" wide and a short piece of 1" round stock will be used to create a hub to mount the flat steel pieces to.  Used the chop saw to cut the piece of 1/2" flat steel into the three smaller chunks. The circle diameters were marked out on the two pieces of 1/2" flat steel and the centre marked with a centre punched.  Once the O.D. of the circle was marked I used a hack saw to cut the four corners off and then used the sander with a flap wheel to round the outer edges to change the shape from rectangular to reasonably round. This will save time when the two pieces are mounted to the centre hub and trued up before they are turned to the correct size and width. Used the drill press and drilled a 3/4" hole in the two flat pieces of steel. 

Attached Thumbnails

  • 1 Original Pulley.jpg
  • 2 Original Pulley.jpg
  • 3 Small V Worn.jpg
  • 4 Set Screw Threads Damaged.jpg
  • 5 Set Screw Threads Damaged.jpg
  • 6 One Inch Cold Rolled Stock.jpg
  • 7 One Inch Cold Rolled Stock.jpg
  • 8 Pieces Cut From Piece Of Six By Half Inch Flat Steel.jpg
  • 9 Piece Of Half Inch Flat Steel.jpg
  • 10 Rough Cut Larger Pulley.jpg
  • 11 Used Old Pulley To Mark Approximate Outside Diameter.jpg
  • 12 Piece To Make Smaller Diameter Pulley.jpg
  • 13 Approximate Pulley Sizes.jpg
  • 14 Pulley Beside Tape Measure.jpg
  • 15 Pulley Beside Tape Measure.jpg
  • 16 Pieces Roughed Out And Corners Rounded WIth Sander And Flap Wheel.jpg

Edited by 29 Chev, June 10, 2020 - 12:40 PM.

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#2 29 Chev OFFLINE  

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Posted June 10, 2020 - 12:20 PM

For those wondering what "Zamac" is here is a link to Wikipedia that describes its makeup - also commonly referred to as pot metal.

 

https://en.wikipedia.org/wiki/Zamak


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#3 sharkman OFFLINE  

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Posted June 10, 2020 - 12:31 PM

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#4 LilysDad OFFLINE  

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Posted June 10, 2020 - 01:05 PM

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#5 29 Chev OFFLINE  

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Posted June 11, 2020 - 09:52 AM

Got a bit more done late yesterday.  Faced the large and smaller pieces of flat steel on one side and also bored them so they would be a snug press fit on a .875" shaft.  I turned a step on the hub shaft so that it would be .875" where the two pieces of flat steel will be pressed onto it.  This produced a slightly smaller than 1" O.D. shoulder once I cleaned up the outer surface.  Pressed the hub into the larger piece of steel with the faced part up against the shoulder and tack welded it in place.  Then I welded the face to the shoulder and at the same time built up the shoulder with weld to create a final shoulder O.D. of 1.25" - this will give me lots of material for the set screw threads where it will be located above the keyway that I hope to eventually broach in the hub.  Once things had cooled down I turned the weld down to clean it up and find any low spots and then built the low spots up with more weld.  After I got it built up and the weld cooled once more I turned the shoulder down to 1.25", turned the piece around and mounted the 1.25" shoulder in the 4 jaw chuck and turned the outside diameter round and very close to the finished O.D. of the larger step pulley. I also began facing the piece so that it will be the correct width to form the larger step of the pulley. 

Attached Thumbnails

  • 1 Larger Piece Faced And Bored To Be Press Fit On Hub Shaft.jpg
  • 2 Smaller Piece Faced And Bored To Be Press Fit On Hub Shaft.jpg
  • 3 Hub Turned To Create .875 Inch Step On Shaft.jpg
  • 4 Hub Started Into Larger Piece.jpg
  • 5 Hub Pressed In And Tacked To Larger Piece.jpg
  • 6 Hub Welded To Larger Piece And Built Up With Weld.jpg
  • 7 Partially Machined And Welded Up Low Spots.jpg
  • 8 Weld Turned Down To 1.25 Inch And Chucked In Lathe.jpg
  • 9 Truing Up Outside To Make Round.jpg
  • 10 Facing Side Of  Larger Piece To Create Correct Thickness To Form Larger Step.jpg

Edited by 29 Chev, June 11, 2020 - 09:54 AM.

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#6 29 Chev OFFLINE  

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Posted June 12, 2020 - 02:50 PM

Got the large piece faced and created two recessed areas that will serve as weld channels.  The recess in at the shaft got welded back in creating a bond between the large piece of plate and the shaft.  Once the weld cooled I used the die grinder to clean up most of the excess weld and then finished cleaning up the weld with the lathe leaving a slight radius.  This creates a large step that will be used to create the large pulley V groove.  Used the die grinder to create a slight taper on the faced side of the small plate (faster than setting up the 4 jaw chuck to hold it and then changing the chuck back to hold the shaft again) and then pressed it onto the shaft to start to create the smaller pulley step.  The smaller step will be turned down close to size and then welded to the face of the large step where the outer recess is. 

Attached Thumbnails

  • 1 Recesses Cut For Welding.jpg
  • 2 Large Step Welded To Hub.jpg
  • 3 Recess Roughed Out To Clear Weld.jpg
  • 4 Weld Cleaned Up With Lathe.jpg
  • 5 Smaller Piece Pressed On To Hub.jpg

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#7 29 Chev OFFLINE  

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Posted June 14, 2020 - 02:36 PM

Tack welded the smaller piece to the hub just in case it decided it wanted to move while being turned.  Also took a few pictures of the dial gauge I use to set the pulley back up in the four jaw chuck so that it runs reasonably true - can usually get it within .001" - .003" difference between the four jaws as you can see in the pictures.  

Turned the smaller step round and then close to the correct outer diameter - machined a nice recess at the inner edge of the smaller step to match the one I had formed in the larger step.  This will be filled back in with weld to help secure the two steps together.

Attached Thumbnails

  • 1 Piece Tack Welded.jpg
  • 2 Setting Piece Back Up In Chuck Using Dial Gauge #4 Jaw.jpg
  • 3 Setting Piece Back Up In Chuck Using Dial Gauge #3 Jaw.jpg
  • 4 Setting Piece Back Up In Chuck Using Dial Gauge #2 Jaw.jpg
  • 5 Setting Piece Back Up In Chuck Using Dial Gauge #1 Jaw.jpg
  • 6 Smaller Step Turned Close To Size.jpg
  • 6 Smaller Step Turned Round.jpg
  • 7 Recess For Welding Small Step To Large Step.jpg
  • 8 Recess For Welding Small Step To Large Step.jpg

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#8 29 Chev OFFLINE  

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Posted June 17, 2020 - 07:09 AM

Welded the outside of the small step to the face of the large step and once that had cooled I ground off the two tack welds at the end to the hub.  Wire brushed the weld and then used the die grinder to clean up the majority of the weld - this saves time and dulling of the bit tip as it tries to cut into the uneven weld on a small lathe.  Chucked the pulley blank back in place and finished cleaning up the weld and also faced the smaller step to the correct thickness and machined a recess so the hub and the small step can be welded together at the outer edge.

Attached Thumbnails

  • 1 Recess Filled In With Weld And Tack Welds Removed.jpg
  • 2 Weld Wire Brushed.jpg
  • 3 Weld Ground Down And Pulley Rechucked In Lathe.jpg
  • 4 Inner Weld Cleaned Up And Small Step Faced And Grooved.jpg
  • 5 Hub Cut Off With Hack Saw.jpg
  • 6 Recess Machined For Welding Small Step To Hub.jpg

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#9 29 Chev OFFLINE  

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Posted June 17, 2020 - 12:59 PM

Got the recess welded in to bond the hub to the inner part of the smaller step.  Used the sander to remove most of the excess weld once things had cooled back down.  Now I have the rough step pulley blank formed and hopefully I can chuck it back in the 4 jaw chuck one last time and cut the two V grooves, face the weld and bore the hub.  I hope to do these three steps without removing the piece from the chuck which should make the two V grooves and the hub bore all true with each other. 

Attached Thumbnails

  • 1 Recess Welded.jpg
  • 2 Weld Levelled With Sander.jpg
  • 3 Step Blank Formed.jpg

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#10 29 Chev OFFLINE  

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Posted June 19, 2020 - 07:06 AM

Got the weld faced off and then started to machine the V groove for the larger pulley.  Started in the centre of the large step with the regular bit I was using but after taking a few cuts I changed to a narrower bit I had created a few years ago to get into the tight areas of a pulley groove.  Ideally a parting off tool bit would probably be the best choice but since I don't have one I made do with the bit I had.  When I took measurements of the originally pulley I had measured the face angles and found them to be approximately 40° total so that is what I went with for the new pulley.  Over the years after checking on various websites the belt angle of a pulley seems to depend on the diameter of the pulley, the width of the V belt used and what the manufacturer of the pulley decided would work as there does not appear to be a standard chart for pulley V angles.  Using the narrow bit it required cutting the V in a bit until I couldn't go any deeper and then facing the two sides with the compound slide set at 20°( left and right of 0°) to widen the V out so I could then take the V groove deeper. Took a bit of time but I finally got to where the belt was sitting in the V groove of the new pulley about the same amount as it did on the old pulley and the sizes checked out very close to what I had measured.  Took light cuts so that the tool bit didn't hog in as that would probably jamb the pulley and make it shift in the chuck jaws which wouldn't be good.  One groove down and one to go (I hope). 

 

If you notice in figure 11 there is a large pulley mounted on the motor shaft - this pulley is only there so the set screw in it holds the shaft key in place.  Hopefully with the new pulley the second pulley will no longer be required. 

Attached Thumbnails

  • 1 Weld Faced.jpg
  • 2 Centre Of Large Pulley Marked For V.jpg
  • 3 Switched To Narrower Bit To Begin Machining V Deeper.jpg
  • 4 V Cut As Deep As I Can WIth Bit.jpg
  • 5 Compund Slide Set To 20 Degrees.jpg
  • 6 Starting To Widen Groove Out On Right Side.jpg
  • 7 Widening Left Side Of Groove.jpg
  • 8 V Starting To Take Shape.jpg
  • 9 Centre Cut Deeper.jpg
  • 10 Checking To See How Belt Sits In Groove.jpg
  • 11 Belt Sits Lower In Original Pulley.jpg
  • 12 V Widened To Lower Amount Of Belt Sitting Above Pulley.jpg
  • 13 V Widened To Lower Amount Of Belt Sitting Above Pulley.jpg
  • 14 V In Large Step Machined.jpg

Edited by 29 Chev, June 19, 2020 - 07:11 AM.

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#11 secondtry OFFLINE  

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Posted June 19, 2020 - 08:32 AM

     Please give closeups of your tool setup for cutting the angle on the inside of the small pulley. I am sure I would have to chew on that one for a while. It would be easy on my Unimat lathe Excepting that the size envelope wouldn't allow. I don't know how I would get it done.

   Don


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#12 29 Chev OFFLINE  

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Posted June 20, 2020 - 11:04 AM

Got the V groove machined in the smaller step but I encountered a slight hiccup in the process.  One of the secrets of using a smaller lathe is to take light cuts - especially when cutting into metal such as is required to create a V belt groove. Things started off good but I got a little greedy while cutting to the bottom of the groove and the bit hogged in leaving a curl of metal as you can see in picture #2.  This caused the bit to jamb and resulted in the pulley shifting in the chuck jaws resulting in the pulley wobbling.  Had to remove the pulley, used a file to remove most of the metal curl and then spent about 15 minutes setting the pulley back up to make sure it was running true both on the outside and on the side face - got it to within .001" on the outside and .0015" on the face so I carried on.  Resharpened the bit and took very light cuts and eventually got the V machined to the correct width and depth.  With the narrow bit I use (which was made by grinding away the one side) I was just able to get it to cut the V but required positioning it multiple times, removing a bit of material and then turning the tool post a little bit to get in at the inner part without cutting into the side V's. For those wondering about the tool bit and tool post I have attached pictures - the tool bit was ground using a flap wheel on an angle grinder to remove the material.  This was done slowly so I didn't generate too much heat all at once.  The tool post is one I made many years ago before the newer style quick change ones such as the AXA that are popular now.  The tool bit holder was originally made to hold 3/8" square bits but I now I find 5/16" bits are handier so that is why there are shims under the bit you see mounted so it is at the correct height for cutting.  Perhaps if the pictures don't clarify things for member secondtry he would post pictures of his lathe setup - I still think a narrow parting off tool would work as good or better than my home made bit to machine the inner faces at the proper angle. 

Attached Thumbnails

  • 1 Starting To Machine Groove In Small Step.jpg
  • 2 Things Were Going Good Until Bit Hogged In And Jammed.jpg
  • 3 Pulley Moved In Jaws.jpg
  • 4 Remounted In Chuck And Taking Very Light Cuts.jpg
  • 5 Narrow Tool Bit Just Fits In.jpg
  • 6 Tool Post And Bit Turned To Take Inner Face Angle Cut.jpg
  • 7 Turned To Face Outer Angle.jpg
  • 8 Turned To Face Outer Angle.jpg
  • 9 Smaller V Machined.jpg
  • 10 Smaller V Machined.jpg
  • 11 Bit I Use To Machine Groove.jpg
  • 12 Bit I Use To Machine Groove.jpg
  • 13 Bit I Use To Machine Groove.jpg
  • 14 Bit I Use To Machine Groove.jpg
  • 15 Bit I Use To Machine Groove.jpg
  • 16 Bottom Of Home Made Tool Post.jpg
  • 17 Tool Post Side View Upside Down.jpg
  • 18 Tool Post Mounted On Compound Slide.jpg
  • 19 Bit Set In Tool Post.jpg
  • 20 Bit Extends From Tool Post.jpg

Edited by 29 Chev, June 20, 2020 - 11:08 AM.

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#13 29 Chev OFFLINE  

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Posted June 21, 2020 - 02:21 PM

Started drilling the centre of the pulley with a 1/8" drill bit - once the hole was started I used a 1/4" bit to drill all the way through the pulley.  Then increased the hole size to 1/2" in increments so that my boring bar would fit into the hole.  Bored the pulley centre out to .625" and then did a couple of passes in and out without changing the slide setting to clean out the hole so that my 5/8" test shaft would fit in ok.  Once that was done I polished the pulley a bit with some oil and sandpaper to smooth up the finish and the two grooves a bit and then I removed the pulley from the chuck and tried it on the motor shaft - it is a nice slide on fit.

Attached Thumbnails

  • 1 Drill Bit Started.jpg
  • 2 Hole Drilled All Way Through.jpg
  • 4 Enlarging Hole.jpg
  • 5 Hole Enlarged To Half Inch.jpg
  • 6 Boring Hole Out To Five Eights.jpg
  • 7 Verifying Hole Will Allow Five Eights Shaft Into It.jpg
  • 8 Polished Some Of The Pulley Surfaces.jpg
  • 9 Pulley Removed From Chuck.jpg
  • 9 Pulley Removed From Chuck.jpg
  • 10 Boring Tool I Used.jpg

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#14 29 Chev OFFLINE  

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Posted June 22, 2020 - 02:04 PM

Got the keyway cut in the .625" (5/8") pulley bore - needed a 3/16" wide keyway for the pulley to work and be driven by the motor shaft.  Several years ago I purchased a 3/16" keyway broach to form a splined collar to repair a PTO coupler on my Bolens tractor and I have a 9/16" collet that works well to create those splines.  I do not have a 5/8" diameter collet that would normally be used with the broach to create the keyway but I figured with a little help the 9/16" collet would work fine since I was only doing one pulley.  I calculated the difference in the bores between a 9/16" and 5/8" diameter which worked out to approximately .062".  Taking .062" and dividing it by 2 worked out to .031" - this would be the amount I would have needed to shim the 9/16" collet to have it centred in the .625" diameter bore.  Since I had some .010" brass shimstock I cut and shaped two strips so they would fit in the hole between the collet and the pulley bore - this allowed the collet to be about .011" closer to the one edge of the pulley bore which I figured would still give me a pretty square keyway compared to the pulley centreline - just that the keyway would end up being shallow and not deep enough for the key and the pulley to fit on the shaft.  Did the first pass with just the broach using my new 10 ton mini press and then did a second pass using the correct shim that came with the collet and broach when I bought them.  For those unfamiliar with broaching a keyway the broach is pushed into the bore of the pulley with the back edge of the broach against the collet - the teeth on the broach are tapered so that as the broach passes through it shaves metal away with the teeth to form the keyway.  Shaving the metal material requires lubrication and puts a bit of stress on the broach and as a result it is designed so that the initial pass only removes some of the material to create a shallow keyway and then a shim is placed between the broach and collet to remove more material on a second pass to create the proper depth of the keyway.  After the second pass I had a distance from the keyway to the opposite side of the bore of approximately .670" and a 5/8" pulley should have approximately .710" between those two points according to another 5/8" bore pulley I had on on hand - as I had assumed my keyway was slightly shallow of where I wanted it to be by about .041".  Used a sheet metal shim and a .005" brass shim that I had made to work with the collet when I was making the splined hub for my Bolens (since I needed to cut the splines a little deeper than what the 9/16" collet would do using the stock shim) and after two more passes I was within .003" to where I wanted the keyway to be so I tried it on the motor shaft with the key and it slid on fine so I was happy with the result.  Getting closer to having a working pulley - just have to create two set screw holes and remove a bit of excess material on the hub to keep the pulley as light as I can.  

Attached Thumbnails

  • 1 Piece Cut And Shaped From .010 Brass Shimstock.jpg
  • 2 Two Pieces Of Shaped Shim Stock.jpg
  • 3 3-16 Inch Broach And 9-16 Inch Collet.jpg
  • 4 9-16 Collet.jpg
  • 5 3-16 Broach.jpg
  • 6 Shim For Broach Second Pass.jpg
  • 7 Math Of Bore Difference Between 9-16 and 5-8.jpg
  • 8 Two Brass Shims In Bore.jpg
  • 9 Placing Collet In Bore.jpg
  • 10 Collet In Bore.jpg
  • 11 Bottom View.jpg
  • 12 First Pass Of Broach Using Press.jpg
  • 13 Shavings From Broach.jpg
  • 14 Keyway Starting To Form.jpg
  • 15 Depth Of Keyway From Oppositie SIde After Second Pass.jpg
  • 16 Sheet Metal Shim Added Under Normal Shim.jpg
  • 17 Brass Shim Sandwiched Between To Metal Shims To Get Close To Correct Depth.jpg
  • 18 Keyway Cut.jpg
  • 19 Keyway Cut.jpg
  • 20 Keyway Viewed From Other Side.jpg

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#15 secondtry OFFLINE  

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Posted June 22, 2020 - 03:40 PM

    Nice. I have never used tools that nice to make a key way. Only don it once with a hack saw,series of files and hours of work. 

   Looking at the setup for cutting the v in the smaller pulley I am sure my lathe would chatter so bad with that much reach out on the tool that it would drive me nuts Your lathe must be much tighter than mine.

   Don


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