Boring and broaching a 4 belt pulley (sheave)

[914Wilhelm]

I have a steel 4 groove pulley that is 3.2" wide with a bore of 38 mm (1.496") with a 10 mm keyway. I have 14x40 lathe, bridgeport style mill, a 5 ton Dake style press, a 20 hydraulic press, and a # 20 Dumont broach set. I need to fit this pulley to the end of a 1.5" shaft for a rock crusher. Given the choice would you bore and rebroach a new key way in the pulley or turn down the end of the 20" long shaft and cut a keyway for it? Why? Do you think its possible to broach a pulley 3 1/4 wide with my broach set and presses?

[firbikrhd1]

You could bore the pulley and cut the keyway right in your lathe using a boring tool with a bit the right size for the keyway and the carriage as a makeshift "shaper". I did this on a 4 step aluminum pulley recently and it worked great.

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[bob ward]

I reckon I'd leave the pulley alone as long as the bore and keyway are good. Skim the shaft to suit the bore, put a keyway in the shaft. Done.

[digr]

If you broach the pulley I would suggest that you make a new broach collar that is long enough for the pulley. Like Bob said I would turn the shaft

[lakeside53]

Given the choice of pulling the shaft from a rock crusher or boring 4 thou from the pulley... lol... bore the pulley! Even if it's out of the machine, I'd still bore the pullley and leave the machine shaft "stock".

Broaching... depends on the broach size you need, but you might not need to - you can just make a stepped key to adapt the existing pulley keyway to the crusher shaft.

[wierdscience]

Lakeside has it,bore the pulley and make a step key,done in a half hour or less.

[914Wilhelm]

After much perseverating and a short vacation I just went ahead and did it. Put the shaft in the 4 jaw and centered it. Fortunately the lathe spindle can take 1.5". Skimmed it down to 38mm. Then put it on the mill and using a 3/8 keyway cutter did the first pass and then lowered the table an additional .0187" so the keyway would be 10mm wide. That way did not need to make a stepped key. Like lakeside said 1/2 hour. Just had to over think it for 2 hours though. Hardest thing turned out to be the metric-English conversions.

[bandsawguy]

[QUOTE=firbikrhd1;837204]You could bore the pulley and cut the keyway right in your lathe using a boring tool with a bit the right size for the keyway and the carriage as a makeshift "shaper". I did this on a 4 step aluminum pulley recently and it worked great.

I have to say after boring and cutting a key in my lathe in an alum pulley I am not to sure about doing a steel one. Of course the hole size on mine was almost the same as the boring bar I had so there wasn't much room.

[big job]

Aggree we did it that way back when. OK for steel just takes awhile. Life is
funny, you get a long stretch of never seeing keyways, then all of a sudden
its keyway week. So I bought a shaper, thats the end of that. Then the
perfect bride & groom A shaper and a Mill. They get along perfectly. sam

[firbikrhd1]

[QUOTE=bandsawguy;840639]

You could bore the pulley and cut the keyway right in your lathe using a boring tool with a bit the right size for the keyway and the carriage as a makeshift "shaper". I did this on a 4 step aluminum pulley recently and it worked great.

I have to say after boring and cutting a key in my lathe in an alum pulley I am not to sure about doing a steel one. Of course the hole size on mine was almost the same as the boring bar I had so there wasn't much room.

It works as well with steel as it does in aluminum. Cuts are made only .001" to .003" at a time, which seems like it would take forever but it really goes quite fast. Certainly the size of the boring bar has an effect. If it's so large you have to keep stopping to move the cutter out to continue the cut to depth it would be more difficult. By the same token, if the boring bar used were too slender flex would work against you. Reality is that you don't need a proper boring bar to do this kind of work. A ground piece of HSS will do the job or a mild steel bar of the right diameter with a hole drilled in it for a HSS bit properly ground and an set screw will do the job as well.

[Rosco-P]

Was this a paying job? Was a 10mm keyway broach available for purchase? Did you lock yourself in with a price and delivery time before finding out that the pulley required a metric key? If all the facts were available at quote time, I would have added the cost of the additional broach to the cost of the job.

[Arcane]

........... Then put it on the mill and using a 3/8 keyway cutter did the first pass and then lowered the table an additional .0187" so the keyway would be 10mm wide..........

That would result in the center line of the KW being off center by over .009". Did you notice any trouble getting the key in when you fitted the shaft and pulley together?