How do i go about turning a crown on a idler wheel.

[NeoTech]

For a belt grinder.. It needs a 2degree crown it states in my description.. i have no frickin idea how to make it though and smooth. have no radii turner attachment either.  :|

[Rob.Wilson]

How wide 20mm or 100mm ?

What sort of lathe do you have ?


Me i would just make a rad attachment  to do the job   then its always there if you need it for future projects 


Rob

[NeoTech]

Its a 60mm wide wheel of 100mm in diameter.

And uhm i have Optimum 320x920 ( http://www.roughedge.se/blogg/wp-content/uploads/2011/12/k%C3%A4llare4.jpg )

I got this far

[Rob.Wilson]

Ok , much better with more info Andreas 

 is  your lathe top slide free to rotate 360 Deg ?


Rob

[NeoTech]

its a hinge pin on the topslide, a big bolt more or less. on that ive mounted the multifix holder. But the topslide it self can be set to a degree, by loosing 2 bolts.. i dont think it will freely rotate a full turn if i remember correctly the topslide have the 2 bolts sitting in two circular slots.

[Rob.Wilson]

What i have done in the past , is mount job on mandrel between centres , so there is plenty of room to work,  remove tool post , mount tool further  back and with  the top slide nuts just slack enough for it  to move freely,  then working it from side to side ,feeding in with the cross slide , but the job must be small enough to clear  the top slide .





Rob

[BillTodd]

May not be suitable for your lathe but might provide some inspiration:

[Rob.Wilson]

Now thats a clever use of a TTA Bill , my Myford one could be adapted very easily  to that setup .

I will remember that one .


Rob

[NeoTech]

nice, gonna do a dry run for both of those setups by turning som blanks in hardwood or something. =)

thanks! =)

[Rob.Wilson]

Don't forget to show how you got on 

Rob

[Jasonb]

When I do it on flywheels and pullies I roughly divide the pully face by 5. The middle 1/5th does not get touched, the 1/5th either side of that get a 1deg taper and the outer 1/5ths get a 2 degree taper put on with the topslide. Then just blend wth file, hand scraper or flapwheel.




J

[andyf]

If there was an easy way of rotating the pulley while cutting it, you could mount it transversely on a mandrel on the cross-slide and use a boring head in the spindle (or a cutter mounted off-centre on the faceplate) to create the crown.

But the easiest way might be to cut tapers from each side, starting with (say) a pair of 0.5^o ones, leaving a flat strip down the middle a few mms wide, and then two more at 1^o, then 1.5^o and finally 2^o. Then take a file to it to turn the series of tapers into a smooth crown.

Andy

[NeoTech]

Jasonb, Andyf

This is what i thought myself at first aswell, but it seemed it would be "edges" but i guess they can be easily sanded down?
But seems its the valid way of doing it, cause i have not material to produce a radii tool, or can do that nify thing with my compound (explored that option yesterday).

[andyf]

OK, here's another way. File a bit of scrap sheet to the profile you want and mount it horizontally on the bench behind the lathe as a template. Have a length of rod sticking out from the back of the cross slide so it contacts the template. The rod should be in line with the tip of your turning tool.

Set the pulley in the chuck, such that the tool is touching it half-way along and the rod is in contact with the middle of the template. Then, cutting away from the chuck and using the cross-slide handle to keep the rod in contact with the template, form one half of the crown. Reverse the pulley in the chuck and do the other half, and if necessary use a file to get rid of any tiny ridge left due to slight lack of concentricity between each operation.

Come to think of it, you only really need half of the curve on your template, but it would probably be easier to judge the shape while filing it up if it was full-length.

Andy

[75Plus]

I don't understand why this project is such a problem. Had the question been "How do I replicate a Morse or Jacobs taper" half the members on this board would have explained how to do so by off setting the top slide the proper amount and, using the top slide feed, produce the required angle.

Call it a "Crown" and it's a new game. Why, the principles are the same. There is nothing that says the crown must, or should be, a radius. Identical tapers on each side of the wheel center is all that is required. If desired, the tapers can be blended into the center with a bit of emery cloth.

[NeoTech]

I actually found turning a Morse taper easier than turning this.. More or less cause the morse taper is of a smaller diameter and a longer stock. But yes, your right. Turning bevel and blend em with emery works.. i was looking for a easier way to do it i guess.

[NeoTech]

I went about and tried to crown the wheel in question. i messed it up in 2 places

1) the crown is slightly more angled on one side.

2) when puttin bearings in the idler, i missed on the hole with the thickness of 2x 80g paper pieces.. and this heavy idler will vibrate so slightly.. i will fix this with a collet of paper and some cylindrical locking fluid.