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Atlas 618 come back to life

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WCraig

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#1
Hi:

Then:

Atlas618_front
by Craig T, on Flickr

Now:

IMG_2799
by Craig T, on Flickr

The motor isn't mounted properly but I couldn't resist chucking up a poor little piece of brass...

My first chips (ever):

IMG_2797
by Craig T, on Flickr

Pretty stoked to actually cut spinning metal. It seems that the homemade indexing tool post is pretty close to on-center with 3/8" tooling.

I plan to switch from the 1/4 HP motor that is on it now to a 1/2 HP that is still at the motor shop. Hopefully soon.

Craig
 

wa5cab

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#2
Be a little careful with the machine with the 1/2 HP motor. Atlas recommended a max of 1/3 HP. With the 1/2, you could break something if you aren't careful.

Lathe looks good.
 

WCraig

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#3
Be a little careful with the machine with the 1/2 HP motor. Atlas recommended a max of 1/3 HP. With the 1/2, you could break something if you aren't careful.

Lathe looks good.
Thanks, I kinda like the 2-tone gray colours.

My copy of Manual of Lathe Operations says: "1/3 or 1/2 HP, depending on the type of work being handled.”

I was practising facing with a 2" disc of aluminum last night. The lathe bogged down a couple of times even though I was taking as light a cut as I could and feeding pretty slowly. According to my speed chart, I was turning the work at 835 rpm so the motor effectively had about a 2:1 mechanical advantage. OTOH, the motor is just clamped to the table and the belt tension and alignment are far from ideal.

BTW, the current 1/4 HP motor I'm using is very old. AFAICT, it will only run in one direction. There are just two connections in the motor and reversing the leads does not change the direction of rotation. Running in the opposite direction would allow me to tuck the motor under the countershaft and free up a bit of table space. The 1/2 HP motor--if the motor shop can get it to work--is reversible.

Craig
 

Bi11Hudson

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#4
Just a thought here;

A half horse motor is a little heavy. Leaving the belt tension a little loose may pay off when something jams. The motor weight pulling against the belt should suffice. I set one up with a 1/2 HP motor aft of the machine, like your's. The motor base was hinged at the front so the motor weight would tension the first stage belt. The user was happy with it, but had a little experience with a machine that size.

What caught my attention was the tool holder. You would do well to place a bit of sheet metal above the tool for the screws to clamp on. It will prevent the screws from "marking" a softer tool shank. This actually applies to any user of the 4 way tool holder, a common holder for Asian lathes.
 

wa5cab

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#5
My copy of Manual of Lathe Operations says: "1/3 or 1/2 HP, depending on the type of work being handled.”

Craig
Bear in mind that all MOLO's printed from 1937 through 1953 actually were written for the Atlas 10". With threading supplements for the Craftsman 12" and at least once, for the 618. The majority of the content is pretty much good for any machine. But some of the specifics like the motor size are really for the 10" and early 12".
 

wa5cab

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#6
If you use the motor weight as the belt tensioner, you should still either lock the mounting bracket in place or tighten the belt tension bolt until it is touching the bracket. Else you may sometime be doing an interrupted cut at a speed and through say a bolt circle that is just wrong and get the motor to bouncing.
 

WCraig

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#7
If you use the motor weight as the belt tensioner, you should still either lock the mounting bracket in place or tighten the belt tension bolt until it is touching the bracket. Else you may sometime be doing an interrupted cut at a speed and through say a bolt circle that is just wrong and get the motor to bouncing.
I'm pretty sure I can position the motor so that when I use the countershaft tensioning handle, it will tension the motor belt, as well. After all, the motor has a 2-step pulley matching the countershaft. It is designed to allow switching between high and low range speeds.

A hurdle has cropped up, though. The motor pulley has a 1/2" bore (no keyway) but the 1/2 HP motor has a 5/8 shaft. I have a handful of reamers but, of course, none of the 0.625" variety. A quick search shows chucking reamers in that size are $50 to $70 in Canada...except from one from Amazon for $15 with a single 1-star review ("not concentric"). Any suggestions for a reasonable source in the Greater Toronto Area?

Craig
 

wa5cab

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#8
Craig,

The reason for the various specified belt lengths on the various Atlas lathe models and each countershaft type on each model and the specified countershaft mounting bolt hole locations on those countershafts not physically attached to the bed, left leg and/or headstock is so that the belt tensioner mechanism will tighten both belts at the same time. The motor location relative to the countershaft position is normally set by using the specified motor mounting bracket, which in most cases is pivoted off of the countershaft bracket. If your motor is bolted directly to the bench, you are on your own, so to speak.

On the pulley bore diameter question, most 1/4 and 1/3 HP and some 1/2 HP made in the 1930's and 40's had 1/2" diameter shafts. This began to change in the 1950's with the 56 frame size becoming the defacto standard. So you have an early pulley.

What you can do if you have a 4-jaw chuck (and if you don't, you need one) is to use the 1/4" dia. HSS boring bar that used to be standard in the boring bar kit and after carefulley indicating in the existing hole, bore it to 5/8". And I strongly recommend that you then take the pulley to your friendly local machine shop and have the proper keyway broached. Either that or buy a good broach set and do it yourself' But decent quality broach sets ain't cheap! Otherwise, sooner or later the set screw will get loose and you will ruin the motor shaft.
 

WCraig

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... What you can do if you have a 4-jaw chuck (and if you don't, you need one) is to use the 1/4" dia. HSS boring bar that used to be standard in the boring bar kit and after carefulley indicating in the existing hole, bore it to 5/8". And I strongly recommend that you then take the pulley to your friendly local machine shop and have the proper keyway broached. Either that or buy a good broach set and do it yourself' But decent quality broach sets ain't cheap! Otherwise, sooner or later the set screw will get loose and you will ruin the motor shaft.
There is a bit of a Catch-22 there! I can't run the lathe without the motor pulley on the motor!!

I do think I can do the work accurately on my drill press. If I chuck a straight piece of 1/2", and the pulley on it, I can then accurately fasten down the pulley in alignment to the chuck. Then slide the 1/2" out and mount a 39/64" drill. After drilling, swap the drill for a 5/8" reamer and I should have a new bore concentric with the old one.

Rather than trying to find a machine shop, I wondered if I could get some 'half-height' key stock--that would effectively give me a flat where the keyway is that I could tighten the set screw onto. AFAICT, the existing pulley does not have a key. There is a flat on the motor shaft.

Craig
PS I do want to find a 4-jaw chuck.
 

wa5cab

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#10
If you are careful and don't try to go from 1/2" to 39/64" in one operation, that should work.

If the 5/8" motor shaft has a flat instead of a keyway, then just tighten the set screw onto the flat or onto a piece of flat steel no more than 1/32" thick. Even if the set screw should loosen slightly, the shaft still can't spin in the pulley, scarring the shaft as it could if there was no flat., Just check the set screw periodically. The set screw in the motor pulley on my 3996 does work loose over time. I put a split collar on the end of the shaft up against the pulley and that seemed to help.
 
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