Bore This Pulley On Lathe Or Mill? Rule Of Thumb?

[Banjo5]

Silver-

Thanks for your suggestion. My only hesitation with the heating/cooling method is I don't want to get the bore hogged way out, and then use a tight squeeze on the bushing, because I'm afraid of cracking the cast iron- it would be pretty thin by the time I get .125" past the old keyway. I'm just about to the bottom of the keyway now(photo), and that bore is .890". I think I will be 1.0" when I get to the bottom of the keyway, and I'm thinking that's all I want to go. You can see in the photo that the woodruff key chewed out a pretty big section beyond the original keyway - it must have been loose for a long time. I think I'll put the new keyway in a different place.

The piece of tubing in photos 681 & 682 is already .750" bore, and 1" OD, although I'm sure I have other stuff on the bone pile to make a new one of different size.

The overall diameter of the boss that the bore is located in is 1.890", if I remember correctly. So subtract the 1.000" and divide by two, and I only have about 1/4" per side until I'm into the spoke area. I'm not sure how strong Cast iron is, but someone mentioned about it being weak in tension, as when being shrink-fit around a bushing. I like shrink-fit, and I like brazing , and I like the pegging of the bushing in with set screws too - one of those three.

Banjo5

 

[f350ca]

Your right Banjo, cast iron is very weak in tension, if you go for a shrink fit I't go no more than 0.0005 interference. That would be all thats necessary when shrinking it on. If you have a heavier wall tube, you'd be better to bore the 3/4 dia after the sleeve is in place.
Looking good.

Greg

 

[Banjo5]

Hi all:
Continuing on my journey with sleeving this pulley. . . . I'm learning a lot!

I've been off my hobby shop work for awhile - I was in Toronto a few days, and the frigid weather here takes some of the fun out of my unheated shop(well- a Kerosun ain't much help).

I got it bored to size - I just stopped boring after I bored out the old keyway, and then turned the sleeve for a light interference fit - at least that was the plan.

As it turns out I turned the sleeve just a skoshe undersize for an interference fit. It is a push fit - it is snug, but can be removed. I turned a 1.5" dia flange on one end of the sleeve for added strength since the keyway will cut most of the way through the sleeve in the bore. I plan to Loctite the sleeve in, then drill and tap for a headless setscrew between the sleeve and cast iron part. Additionally, as you can see in the photos, I lucked out and was able to drill & tap the sleeve 3/8-16 to accept the original jack screw, which threads through the cast iron, and continues through the sleeve. I think that alone will hold the sleeve in place - the loctite and setscrew should just be insurance.

In the next days, I plant to Loctite it, finish bore to size, and cut the keyway, re-assemble to tractor.

Thanks for all the suggestions. Will keep you posted.

Banjo5

P.S. - I got to use my new-to-me Vee-Block that I got for $8 at Cabin Fever Expo two weeks ago, at Lebanon, PA - very nice show. The block is ground all over, and in very nice shape- the drawback - there was no clamp with it. I don't see any name on it, but will start to look for a clamp for a 2" wide block.

 

[GK1918]

In my opinion lock tite maybe so-so. This is a common repair here. Take the extra time and drill between the bushing and
pulley and slam a spring pin in, then grind any excess off the pin, then cut the keyway. That aint going anywhere and is
replacable in the future.

 

[Banjo5]

Hi all:
Well, it's been nearly a year since my last post on boring out this pulley. I finished the project last Summer and got it installed on the tractor in time for the owner to drive it in our local tractor parade last Fall. I wanted to post a couple of images of the finished project, and thank everyone for their advice. I ended up loctiting the bushing in, and the jack screw threads right through it to a dimple in the shaft - looks pretty solid.

Thanks all!

Now thinking about adding CNC capability to my Jet mill, but it's a well-worn machine, so I don't know.