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

Banjo5

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Happy New Year, all.

A first project for my new-to-me tools - ATLAS 10 & Jet 6x26-

I have a little lathe experience, but no mill time, so I'm wondering about the use of the mill vs lathe.

I have this pulley off a Jacobsen lawn tractor that is egged out and needs re-bored and sleeved back to 3/4". I'm guessing I will have to remove 1/16 to 3/32" to clean it up. I'm looking for advice about doing this whole project, so feel free to chime in. I intend to bore it and make a steel sleeve to be pressed & loctited in. the sleeve will probably be split full length to accommodate the woodruff key, but there is also a large jack screw that holds the pulley on. The hole for that would be drilled through the sleeve and threaded after installing. There is a large dimple on the shaft where the jack screw tightens in to hold the pulley on. The transmission shaft this pulley fits on is in pretty good shape, but not perfect.

I believe the pulley is cast iron because of the chipped area in photo 642. First off, how can I tell for sure it is cast iron, and the type - Malleable, Gray, Ductile, Steel? I'm wondering about this because if it was steel, I could weld a sleeve in, but cast iron will have to be pressed in w/ loctite, and the keyway split all the way may be a problem.

As far as getting the boring done -should I clamp it in a 4 jaw, or clamp it on my mill table? It seems easier to me to center up in a 4-jaw because the outer edge of the pulley is machined, and I think I could center it fairly easily with a dial gauge. What is the rule of thumb for this decision? If I use the mill, (I don't have DRO) it seems easier to make a centering mistake for the bore location, but would be fairly easy to clamp down. I have some experience on the lathe, so that would feel more comfortable to me.

What about tooling? I have ground bits and boring bars for both the mill & lathe. Will cast iron wreck my cutter? I have a boring bar for the mill with a carbide cutter. Would that be best?

Appreciate any advice.

Banjo5

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Happy New Year, all.

A first project for my new-to-me tools - ATLAS 10 & Jet 6x26-

I have a little lathe experience, but no mill time, so I'm wondering about the use of the mill vs lathe.

I have this pulley off a Jacobsen lawn tractor that is egged out and needs re-bored and sleeved back to 3/4". I'm guessing I will have to remove 1/16 to 3/32" to clean it up. I'm looking for advice about doing this whole project, so feel free to chime in. I intend to bore it and make a steel sleeve to be pressed & loctited in. the sleeve will probably be split full length to accommodate the woodruff key, but there is also a large jack screw that holds the pulley on. The hole for that would be drilled through the sleeve and threaded after installing. There is a large dimple on the shaft where the jack screw tightens in to hold the pulley on. The transmission shaft this pulley fits on is in pretty good shape, but not perfect.

I believe the pulley is cast iron because of the chipped area in photo 642. First off, how can I tell for sure it is cast iron, and the type - Malleable, Gray, Ductile, Steel? I'm wondering about this because if it was steel, I could weld a sleeve in, but cast iron will have to be pressed in w/ loctite, and the keyway split all the way may be a problem.

As far as getting the boring done -should I clamp it in a 4 jaw, or clamp it on my mill table? It seems easier to me to center up in a 4-jaw because the outer edge of the pulley is machined, and I think I could center it fairly easily with a dial gauge. What is the rule of thumb for this decision? If I use the mill, (I don't have DRO) it seems easier to make a centering mistake for the bore location, but would be fairly easy to clamp down. I have some experience on the lathe, so that would feel more comfortable to me.

What about tooling? I have ground bits and boring bars for both the mill & lathe. Will cast iron wreck my cutter? I have a boring bar for the mill with a carbide cutter. Would that be best?

Appreciate any advice.

Banjo5

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I am no machinist but I picked up a 3 groove pulley for my wood lathe and when I go home I realized the garage sale find had a egg shaped hole in the center, it was what seemed like cast iron with the shaving as powder, I turned it larger and made a .500 id sleeve to press into the cast iron and the I reamed out the hole to .500 after the press in fit. also lock tited the sleeve. BUT mine used a set screw not a key so I did not have to worry about that part. Been working great so far. I did this in my metal lathe and bored with a small carbide insert boring bar.2015-10-11 16.04.58.jpg 2015-10-11 16.02.22.jpg
 
Here's your rule of thumb.

If its round, put it in a lathe
. Mills are for non-round pieces.

Its' far easier on a lathe, On a mill, securing a piece square with the spindle and centered, is considerably more work.
 
I'd bore it out on the lathe beyond the existing key, then sleeve it. A thin wall sleeve as your suggesting will be hard to work with and probably hammer out quickly if the shaft is worn. The pulley is probably cast iron, so I'd chamfer the sleeve and pulley and braze it in. The carbide boring bar you have should work fine even on the intermittent cut. If the pulley only turns one direction the keyway doesn't have to be perfect so you could rough it out with a hacksaw and file after you bore the welded assembly back to 3/4.
Greg
 
Bore it in the lathe, for a good solid sleeve (as Greg has suggested). To secure the sleeve there are a number of options, which one to pick depends on what you are comfortable and the resources available to you. Brazing is good. Loctite is pretty good.

One method I have used is to make you sleeve to an interferance fit of about 0.0006"/" of hole. Then heat shrink it into place (heat the pully). Then drill and tap some set screws into the split between the sleeve and the pully (see example below - it is the drive pinion that engages the rack for my lathe carriage travel. The shaft was really worn, the gear was good, but it was a one piece assembly. The second picture is the new shaft ready for the gear wheel, and the old shaft with the gear about to be trimmed off).

For the new shaft bore, the key is a bit of a problem. If you can borrow a broach - that is very slick. You can buy a single broach, they are not very expensive and the job is very quick (you'd need to make your own broaching sleeve). My avitar is of a gear set, and I needed a keyway in every gear (I borrowed a broach, the sleeves are shown at the top left). You could also drill out the majority of the material in the key way (before you bore the hole in the sleeve, drill a hole where the key is going to go). Then complete the sleeve ID/OD and file out the remainder of the keyway.

Let us know what you finally do.

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I think the rule of thumb for many of us would be to use whatever machine will get the job done with the least amount of fuss given the tooling we have on hand. I would use the lathe personally.

Does this pulley mount on the drive shaft? If it will get hot from the engine, probably not wise to rely on Loctite.

I would bore it out bigger than the keyway as well, and make the sleeve ~0.001" over sized. If you make the sleeve too tight, it could crack the pulley. Use something softer than the shaft for the sleeve, 1018 is probably a good choice.
Looking at the pic, I think I would make the sleeve about half again as thick as the depth of the keyway. This should give a good balance for strength of the pulley vs sturdiness of the sleeve. I would also pin it after it is pressed in like Chipper5783 recommended over brazing. If you do braze, the sleeve should be undersized enough to allow the braze to flow between the parts.
Either way, you should do the final boring of the sleeve after it is installed.

Cutting a new keyway is a pretty simple procedure on the lathe. There are some videos kicking around of it being done. If you are lucky, you have a parting blade the right thickness to make the keyway. Otherwise you can grind a piece of HSS or drill rod (harden it) fairly easy. Just make sure the tool has very little rake, it will flex a bunch and too much rake will cause it to dig in. I do prefer the lathe for this operation because I can use a square tool blank, and I can angle the tool going into the bore. Angling the tool simplifies grinding a great deal because you don't have to grind a long thin tool to reach the end of the bore. When you are done, the tool can be easily reground into something else later on.
If you are not familiar with the technique, and can't find a video let us know. I have some suitable scrap and a tool I made for keyways and I can post some pics for you.
 
Thanks for the ideas everyone.

T Bredehoft- The rule of thumb is noted.

F350ca - This is a transmission shaft so will probably see 175 deg F to 200 deg max. Isn't Loctite good to 300-350 deg F or so? Will 200 deg degrade it? The keyway is damaged on both sides of slot by woodruff key by the power/hold back action of the transmission, so I'm thinking a tight keyway is called for.

Joshua43214 & Chipper5783 - I like the idea of pinning a press fit sleeve in because though I have an acetylene torch and have brazed before, I usually have trouble getting the metal 'wetted," and a good job. I'll have to read up on brazing - it's been awhile.
The keyway- I don't mind buying the 3/16" broach and sleeve to get started on collecting a set, but I'm intrigued by the "push through" method using a cutting tool and tailstock(?) (or carriage?). I have read about this method before, and it would be a good technique if you didn't have just what you needed today. I have a box of blank tools, and some are pre-ground, so I could probably come up with, or grind a tool to the profile needed. I'm not sure what you mean by angling the tool so it doesn't have to be long and thin though. Do you mean angle it in a boring bar? I also have an assortment of cut off blades to look through. Could you please post a photo of what the ground HSS tool cutting edge looks like?

Regards,
Banjo5
 
here are some pics. You will have to excuse my 4way tool post. I sent my QCTP back for service.

The first pic shows what I meant by angling the tool. You can see how only about 1/2" of it is ground to the width of the key, but it can easily broach through this ring that is about 1" thick. I estimated the length of the ground part by simply holding the tool into the hole at an angle and eyeballing the amount of tool I would need to broach to the bottom of the keyway.
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Here are some pics of the broach and the tool. I did not take the time to get the tool exactly on center height, so the broach is a bit off center. It looks to be angled, but it is not - it is off center. I made 0.005" deep cuts at each pass. I did not finish the broach either, just made a few cuts for demonstration. I used this cutter to make the keyway to adapt my power feed to my mill.
I ground the cutter width by comparing it to the key as I was grinding. No need to break out the scribes and ink, just grind it to the size of the key. I intentionally ground it on one side of the tool so I can regrind it later into a grooving tool that will work up to a shoulder. The top of the tool is rounded over to clear the inside of the hole.
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Note the angle of the cutting tip in the first and last images. I ground the tip at a steeper angle than needed, set it up in the lathe, then tool the tool back to the grinder to get a more blunt face. By eye, it has about 2* of positive rake.

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Thanks joshua43214.

I think I can make the bit & cut the keyway from what you've shown. My pea-brain was thinking that the keyway would be cut at the 6 O'Clock position, so the tool would have to be angled down from the tool holder. I get what you mean now that I see the obvious side position(DUH). I found a bit already ground that is the size of the keyway - 3/16". Kind of small for angled clamping with the hold down screws on my AXA, but I'm going to try and see if I can clamp it. If not, I will grind one like yours from 1/4".

I have a question about the chuck-up of the pulley. Is it safe as shown in these photos? This is my first use of this particular 4 jaw that came with the lathe, and as you can see, the threads are only about 1/2 engaged. I counted the available threads on the jaw - 13. I am engaging 6 of them, though there is a scribed mark on each jaw at about the 1/2 way point, and I'm way out past that. Are these warning lines, or just reference lines? I'm thinking reference. The setup feels solid to me, (but I don't know much), and I am able to tighten the jaws to what I would normally call "tight". Not looking for anyone to make the decision for me, just let me know if I'm breaking one of the "thou shalt nots" of lathe set ups that everyone knows but me. Other than that, I'm going ahead - I don't guess there will be THAT much torque on the setup because of such a small bore, anyway.

Banjo5P1040660.JPG P1040661.JPG P1040662.JPG P1040663.JPG
 
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