I'm missing some teeth.

[90LX_Notch]

This is what happens when you don't take care of your teeth!


This is the spindle pulley for my Atlas/Craftsman 618 MKII. The gear is part of the pulley casting and drives the bull gear when the lathe is used in backgear. The part is no longer available and even if it was, I am sure it would cost more then the $250.00 that I bought the lathe for. There's not enough meat to bore the pulley out and key a new gear to it. It doesn't make sense to reproduce the whole thing. I will probably just rig up a counter pulley system to replicate the back gear rpms.

 

[smfr]

Did you try eBay? I see quite a few Atlas 618 parts there, but didn't see anything that looked exactly like yours.

 

[miner49r]

is it Zamak?
Alan

 

[steamer]

What Miner said! and could your bore and face the recess and put in a aluminum insert with meat enough to do what your want?

Dave

 

[steamer]

Could you make up a .03" wall tube with the gear on the end, bore the entire center of the pulley .06" over and loctite the new piece in?

Could make it out of pretty much anything, but would probably use bronze....if it were me.

Dave

 

[steamer]

If you need something bored out Notch....I'm only a couple of states away.....USPS is your friend....

Dave

 

[90LX_Notch]

SMFR- Not to many MKII parts come up. However, there is a complete headstock listed now on eBay.

Alan- Yes it's appears to be the dreaded Zamak. I pushed it too hard because I was in a rush with a part for my Jeep that I needed to drive yesterday afternoon.

Dave- There's not enough there to bore it out. That was my original plan but, it's an investment casting and they made sure to use the least amount of material possible. The hub would be very thin if it was bored out. (It also has two sleeve bearings in it.) Thanks for the offer to bore it. I really appreciate it.


I have two other lathes (MKI and a 7x12 mini lathe) so I'm not dead in the water and this one will still operate fine as long as I don't use the back gear. That's why, I will eventually come up with a intermediate counter shaft between the motor and spindle pulley to drop the rpms.

-Bob

 

[rake60]

We had a similar but much larger part to repair at work several years ago.

The engineers decided we would make a gear with a larger hub on the end that would be threaded
into the original part. Since the pressure direction of the gear would be clockwise both the new gear
hub and original part would be threaded with a left hand lead.

My job was to set the original part up, machine the gear off and bore and thread it for the repair gear.
When I was within an inch of the size for the thread, I noticed a thin black line appearing on the face.
This thing had been repaired like this before.
However, the original repair was with a right right hand thread and I'm running a counterclockwise rotating
vertical boring mill.

The it got thin enough for that thread to break loose, the original threaded repair insert spun up smashing
my tooling and created one of those, "time to change your pants" moments.

In the end that type of repair did work.

Rick

 

[Blogwitch]

I know it was a while back, but I used to have an old Atlas 10F, and managed to get a second hand Timken head complete and shipped across from the US all for about 200 bucks.

I am sure that a good second hand bull gear will be available somewhere, and if not, Clausing keep spares for most of these older machines, and I found them very reasonable, even to the UK.

Any of the Mazak parts on the Atlas are almost impossible to do repairs on, they are just too thinly cast. In fact on mine, I had copies cast out of bronze.

John

 

[Maryak]

If you can't beg, borrow or steal a new one.

I don't know how thick the base is but looking at your picture I would cut off the gear, bore down and out to the base of the 3 ribs, the make a new gear on a boss and weld the boss to the base inside the ribs,with the whole thing mounted on an arbor for alignment whilst welding.

Just my 2 bobs worth.

Best Regards
Bob

 

[steamer]

Hey Notch,

I would only bore it to the OD of the bronze bushing inside of it, and then sleeve it with a sleeve with the bushing ID that has a gear cut on the end of it. All one piece. If it lasted umpteen years with Zamak parts, it'll last longer with a bronze one.....

But if your convinced there's not enough metal....I'll believe ya....hope you find another one....but I'll leave the offer hanging for ya ;D....Just leave it in the back pocket.....

Dave

 

[miner49r]

I like Daves idea. It's not a shear load and pinned to the pulley ought to be plenty strong.
The bull gear on my 618 pins to the pulley set which happens to be worn. This gives me an idea to bore the four holes and press in some bronze bushings. If I ever get a hair up my ___ over it.

 

[steamer]

Oh I think I'd just loctite it in.

Dave

 

[90LX_Notch]

Everyone- Thanks for all of the ideas.

Alan- On the MKI (original Atlas 618) the pin is used when you are in direct drive. You disengage the pin when you engage the bullgear for backgear operation. The MKII (Square head Atlas 618) has a dogged collar at the end of the spindle that engages this pulley for direct drive. When the MKII is put into backgear, the collar is disengaged from this pulley and the bullgear is engaged by an eccentric like the MKI.

Dave- Would a bronze gear cause premature wear on the Zamak bullgear? Will the Locktite hold? Backgear steps down 7.6:1 from direct drive.

Thanks,
Bob

 

[Omnimill]

We call it Mazak over here although some folks call it "monkey metal"

Vic.

 

[steamer]

Hi Notch

As far as strength is concerned, the proper loctite product will produce a joint stronger than the surounding part!....

I've put the center rotor of a 6 horsepower High precision spindle drive , which is a stainless steel tube surrounded with magnets held in place with epoxy and an aluminum ring on the center motor shaft with nothing the proper loctite product, once it's on there....its on there.

As far as wear is concerned, unless you run your lathe coated in abrasive I don't think Bronze will not cause premature wear on Zamak die casting. If your anything like me, you probably over oil the gears when you use them.

But I WILL say that if the ZAMAK is starting to crack with age, it will break regardless of what kind of material it's engaged with.....

For this application, I would get some SAE 660 bronze tube. The gear appears to be 24 tooth, What's the OD of the gear? From that I can tell you what DP it is and if I have a cutter for it, and if I have any stock on my shelf.....

It'll need a faceplate "bucket" fixture composed of a plate with a counterbore with some toe clamps mounted on the faceplate.

If the bushing is deep enough and stout enough, I might just replace it with one that has a gear on the end...and not take any metal out of the pulley at all......

Take some more good photo's of the area's you think are too thin so I can see.....and we'll talk

If it's something you want to tackle,,,,,,I can help you do that too......it's all entirely up to you....

But I would put all the information together in one place ( required TOOLS, STOCK, ECT) and then make the decision.....


Dave

 

[90LX_Notch]

Dave- Thank you very much I'll start compiling pictures and information. A one piece bushing/gear loctited in the pulley would probably be the best bet.


Bob

 

[n4zou]

This is what happens when you don't take care of your teeth!


This is the spindle pulley for my Atlas/Craftsman 618 MKII. The gear is part of the pulley casting and drives the bull gear when the lathe is used in backgear. The part is no longer available and even if it was, I am sure it would cost more then the $250.00 that I bought the lathe for. There's not enough meat to bore the pulley out and key a new gear to it. It doesn't make sense to reproduce the whole thing. I will probably just rig up a counter pulley system to replicate the back gear rpms.

Don't rig up a counter pulley system to replicate the back gear system. Do it at the motor spindle. this would be the simplest way to do it and have it work properly. The only reason they geared the back gear system was the pressures involved when gearing down the spindle at the spindle. The only reason for back gearing the spindle that was was the speed of changing over from direct drive to back gear drive and most people would not purchase a lathe without back gears that all lathes of that era had. Once you change over to the motor reduction system shown in the link below you'll find switching between normal and reduction a pain in the ass, which was the reason for back gear drive system in the first place. The question is how many threading jobs do you do at home on the lathe? Like most of us at home the answer is not very often. When I do set up for threading on a project I usually wait until I have all the parts that need to be threaded completed except for the actual cutting of the threads on all parts that need them. This saves set up time on the lathe and in your case switching over to a big pulley would only need to be done once and removing it after all threading is completed.

This link shows how to gear down a drill press spindle which is also the system you would add to your lathe to replace the back gear system. http://www.vintageprojects.com/machine-shop/LoSpeedPress.pdf

 

[90LX_Notch]

n4zou- I'd rig it more like the original MKI 618 I have. The more thought I've given it, I would probably make a backgear arrangement on the counter shaft if I decide to go that route.

That drillpress design is a bit absurd.

 

[steamer]

Cool! I look forward to seeing them!

Dave