# How Do I Crown This Wheel?



## Wiebster (Oct 5, 2016)

Hi, I'm pretty inexperienced at machining and don't know what my next step is to crown this wheel.  The wheel is 5" diameter and 3 1/2" wide.  1/4" of it is held in the chuck.  I want the finished wheel to be 2 1/4" wide, crowned, and a LH 1/2-13 threaded hole right where the live center is located.  On the chuck side of the wheel I would like to dish or recess the wheel to make it lighter.   Can anyone tell me what order my next steps are to be to keep the the wheel concentric and the taper or crown centered?  Thanks for your advice and sharing your knowledge.


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## rwm (Oct 5, 2016)

This is not the "correct" way but it worked for me. I cut a rough crown in 4 passes. On the ends I set the compound at 1.5 deg and cut a taper each way. Then I set the compound at .75 deg and cut the next pass towards the middle. After that I ran the lathe and took off the high spots with an angle grinder (hand held) to make a gentle curve.  This worked well for my belt grinder. Dishing the wheel is not imperative for most applications but if you need to I would do half from each side. The threaded hole can probably be done last.
R


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## Wiebster (Oct 5, 2016)

Thanks for your reply.  I have made a jig to crown an idler wheel but I too plan on using the compound to crown this one much like you stated.  I just don't know where to hold this piece to do that.  The wheel is not its final width and I don't know what order to take to get it to its desired shape.  Do I taper it before I part it to its final size?  If so the left side would have to be plunged into the full diameter of the wheel.  If I part it to the final width how do I hold it and taper both sides with the chuck in the way?


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## jpfabricator (Oct 5, 2016)

Cut your recess, and thread your center hole. Then make an arbor to fit the threaded hole and turn between centers. Plan for the excess width to be parted off of the recessed side so you don't have as much metal to part. Do the crowning last.
That's how I would do it, so everything is concentric to the centerline. 

You may even wait till last to thread your hole if you are threading with a tap.

As long as The cuts are kept minimal The wheel can be superglue to a snug fitting arbor. The glue bond can be broken with The application of some heat.

The crowning with the compound as stated above is how I would do it also.

Sent from somwhere in east Texas by Jake!


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## rwm (Oct 5, 2016)

Jake makes some good points. The wheel would definitely be concentric to the shaft that way. I wanted to avoid making an arbor. Keep in mind the wheel can be gripped in the chuck even after cutting the crown since it is so shallow. So you could flip the workpiece to cut the crown on the other end. 
And sometimes I skin my cats from the tail first. 
R


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## Wiebster (Oct 5, 2016)

Those are great ideas.  I am using a LH tap for the threads.  What size would you suggest for the arbor?  The drill size for 1/2-13? Or something smaller?  Parting after recessing is something I did not think of and is a great idea.  How do I protect my new crown from the jaws while I tap the hole?  Thanks for your suggestions!


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## Wiebster (Oct 5, 2016)

rwm, you have already figured out what I'm making...a drive wheel for a belt grinder. Do you think it is not necessary to lighten the wheel with a recess?  Any pros or cons to either way?


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## jpfabricator (Oct 5, 2016)

The added rotational mass may help an underpowered motor 

Sent from somwhere in east Texas by Jake!


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## 12bolts (Oct 6, 2016)

Wiebster said:


> How do I protect my new crown from the jaws while I tap the hole?


After you have recessed your wheel you will have a boss in the centre that you may be able to reach with your jaws flipped around. Otherwise you can grip the inside lip of the outer wheel by opening your jaws to grip. Expanding the chuck jaws as opposed to clamping them closed on the workpiece

Cheers Phil


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## stupoty (Oct 6, 2016)

I made a smaller sized tension roller the other day, i cut the angles using the compound set around 1 or 2 degrees and filed and sanded to final shape, i did flip it to finnish the outside , i stood it on a sacrificial piece of aluminium on a face plate and used some all thread as a draw bar through the spindle to hold it down.  Indicating it was a bit of a pain as i had to use a rubber mallet method to get it into position, once their it worked fine.

Useing a recess sounds easyer 

Stuart


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## Wreck™Wreck (Oct 7, 2016)

You have failed to indicate the radius of the "crown" or if a manual machine or under NC control.

Depending on your proclivity for self abuse a reasonable radius may be made (with flat surfaces) from the compound. I can produce the angles and moves for you in a CAD drawing  with a spreadsheet, this will likely not make you happy.


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## 12bolts (Oct 7, 2016)

Seeing as its a drive wheel for a belt grinder being made by a "relatively inexperienced" operator I doubt very much if it is going to be an auto machine.
And seeing as how most suggestions have been for a couple of passes with the compound at differing angles before blending the cuts with a file or grinder I doubt that CAD spreadsheet would be of much use

Cheers Phil


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## Wreck™Wreck (Oct 7, 2016)

I understand, yet the often stated quest for .0005 accuracy would preclude filing and off hand grinding would it not?


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## george wilson (Oct 7, 2016)

I also just make an angled pass on either side of the crown-to-be. I frequently use a freehand HSS wood lathe tool for finishing off the crown. One with a square face on it. I just clamp a length of square bar stock on the Aloris tool holder,and use that for a rest.  I do have a good eye,and this is needed for freehanding a crown. They always work fine when I'm finished.


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## Reeltor (Oct 7, 2016)

Maybe taking a clue from how to do this on a wood lathe would help.  Mark each 1/4 or 1/2" on your part.  Using a parting tool, plunge in at each mark the required depth then machine the waste away.  File smooth then finish with some emery paper.

(George was posting while I was typing )


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## John Hasler (Oct 7, 2016)

Wreck™Wreck said:


> ...the often stated quest for .0005 accuracy...


I've not actually seen that stated here very often.    In any case I've found that crowned pulleys work fine with just a 2 degree slope on the outer thirds and a flat in the middle.  To make it pretty knock the corners off with a file and then sand.

Or, to do it the farmer way, put two wraps of duct tape around the middle third.


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## Wiebster (Oct 7, 2016)

Thanks everyone for your ideas.

Wreck, my machine is an old Enco with no CNC and I don't think I'm capable of those tolerances but I don't think they are required.  I believe the Machinist's Handbook states 1/8" per foot so for my wheel would need about .020 taper.  

I'd rather not freehand this if I can avoid it.  I don't mind putting the finishing touches on freehand.  For the 3" idler, I made a jig with a 20" radius that bolted to the cross slide and I just swept it back and forth taking small cuts creating a nice radius.  It worked very well but I didn't think it was very solid so didn't want to do it again on this more expensive piece of aluminum.  If I pushed down too hard it would be off the center of the work piece and cut less than it should have.  After multiple finish passes the wheel turned out to be within a couple of thousands in symmetry.  I wanted to try the compound this time maybe using 1 or 1 1/2 degree as described above.  Although I'm not sure of how to properly set that up either.

My real pressing question should have been about the order of the cuts and how to hold the piece keeping it concentric.  I just wasn't sure what the proper order was so I didn't screw up the next step.  I have decided to use the arbor idea and super glue it on while working on it (thanks jpfabricator for that idea). 

I appreciate all your input and will post a pic when it's done...its my last wheel to do.  Maybe this drive wheel doesn't even need to be crowned at all?


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## Wiebster (Oct 7, 2016)

JH,  I think a small flat is even better than a radius, but don't know that for a fact.


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## george wilson (Oct 7, 2016)

Anything will work,as long as it is lower at the edges. But,when I think about what the shape of the crown might do to belt wear,stretching in places and causing distortion to belts,I have to think that a smooth rounded crown is the best. Think about it: All of the old time machine makers used a smooth,rounded crown form. They did not use pieced together crown surfaces,though pieced ones would have been easier and cheaper to produce.

Those guys had loads more experience than we will ever have with flat belts. I'm going with their lead.


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## rwm (Oct 7, 2016)

I found the hand file to be too slow and inefficient on the large wheel so I went to the angle grinder with the lathe running and it worked great. Only one wheel in the system needs to be crowned. My drive wheel is crowned.
My drive wheel has a boss on the inside without a recess. I cut the crown opposite the boss first and then flipped it around to grip the boss. My chuck has a runout of less than .0002 so flipping was not a big deal. As Wreck implied this is not close tolerance work anyway.
R


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## Wiebster (Oct 7, 2016)

rwm, so are you implying I not even crown this drive wheel because my tracking wheel is crowned?  Because I'd be all for that if you think the belt would track.  

George, when you say a "smooth rounded crown", do you mean one large radius as I did on my tracking wheel or a flat in the middle then slowly reduced at the edges?


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## george wilson (Oct 7, 2016)

I mean a continuously smooth  radius over the entire width of the wheel. A flat center would be a 3 part crown.

Crown your drive wheel too,as well as your tracking wheel. This is how my Wilton Square Wheel grinder is made.

By the way,in spite of the couple thousand dollar price,I had to remove the large drive wheel,and true it up,too. hat did not make me happy. Eventually,I found out that,like EVERYTHING ELSE Wilton sells,the belt grinder is made in Taiwan!!! Then,they STILL charge an arm and a leg for their stuff. I think they are riding the name for all it's worth. That is my opinion.


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## John Hasler (Oct 7, 2016)

Wiebster said:


> rwm, so are you implying I not even crown this drive wheel because my tracking wheel is crowned?  Because I'd be all for that if you think the belt would track.
> 
> George, when you say a "smooth rounded crown", do you mean one large radius as I did on my tracking wheel or a flat in the middle then slowly reduced at the edges?


In my limited experience they *usually* track ok with only one wheel crowned.


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## george wilson (Oct 7, 2016)

I'd have to go look,but I know the large drive wheel on my Wilton is crowned since I had to true it up and re crown it. The tracking wheel may not be crowned,but it is too late since you have already crowned it. I don't think it'l matter.


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## rwm (Oct 7, 2016)

Actually I mis-spoke! Only the tracking wheel on my grinder is crowned. The large drive wheel is flat. I got that advice from Mark Frazier in his thread. Now that I think about it I initially crowned the drive wheel and later machined it off. I was concerned the double crowns would distort the belts.  It tracked fine both ways. You can always go back and crown the drive wheel later but I don't think you will need to.



R


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