# Building A New Change Gear Quadrant For My 12x36 W Qcgb



## master53yoda (Mar 14, 2015)

Well i finally decided to bite the bullet and make a new quadrant for the change gears on my QCGB so that I can do metric threads.   my patch job had worked ok untill i tried to cut the 8 TPI on the 1.5 spindle thread on my ER40 collet chuck that I'm working on.   it dropped out the gear on the last cut about half way through and destroyed the thread.    

I'm going to make it out of some 1/2"  flat plate,  i've cut it out with the torch and once i get it cleaned up Ill post some pics on the mill when i start that part of it.   I have been watching EBAY for 9 months and haven't ever seen one come up, they normally are tied to the QCGB when they get put on EBay.

Art B.


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## Smudgemo (Mar 15, 2015)

I'd like to see photos of both projects, even if they are only in-process.  The collet chuck is on my short list of projects if I ever finish refurbishing the neglected wood windows on my house.  
-Ryan


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## roadie33 (Mar 16, 2015)

Art, sent you a PM about Quadrant.


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## master53yoda (Mar 16, 2015)

here is the roughed out quadrant  Ive just started to clean up the torched areas,   I'm not getting a lot of time to work on the lathe as my casting ingot business is getting out of hand,  I poured 170 lbs of aluminum ingots today.     I'm also working an a pattern set for making jet boat pump intake ports.

Roadie  thanks I'll watch it but they seem to go in the 350 to 500 range.


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## roadie33 (Mar 16, 2015)

I figured since it says for parts it might not go very high.
What happened to that quadrant?
Looks like someone thru it against a wall and shattered it.


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## Rob (Mar 17, 2015)

You might give Atlas a call and see how much they charge for a new one.  It is still carried in stock at Sears for $182 and Atlas usually is cheaper.

http://www.searspartsdirect.com/Cra...007/0009/101/Model-10127440/0247/0728000.html


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## master53yoda (Mar 17, 2015)

when I bought the lathe the prior owner said that the threading gear box didn't work right,  when I tore it down the quadrant came apart in pieces.  what I found in the end was a BB imbedded in the 13 threads per inch gear in the threads per inch section of the gear box. it would work unless you tried to use that particular thread and it would then jam so tight that it wouldn't turn, the quadrant was the weakest point and it broke and released the in-out gear.   It would have been running in the back gears when threading that thread which pushed the delivered torque way up..

I plan on casting a new one in the end but don't have my foundry set up yet for cast iron.  I have other things that i want to spend my tooling money on and have a hard time paying over $100.00 for a part. that i can make.

Art B.


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## Rob (Mar 18, 2015)

Just mentioned calling Atlas as you had mentioned you had been watching eBay.  A lot of folks don't realize that they still support these lathes after all the years.  A lot of the time there price is cheaper for a new item than you can get used for on eBay.  Even Sears marks the price up considerably on the items, in the case of half nuts they double the price.  Atlas sells half nuts new for $35 and a lot of the time they go for double that on eBay.


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## Gunner (Mar 18, 2015)

Some of the ones on eBay are made of brass, too.  Which are easier to damage than the original Zamak ones.


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## master53yoda (Mar 19, 2015)

roadie33 said:


> I figured since it says for parts it might not go very high.
> What happened to that quadrant
> Looks like someone thru it against a wall and shattered it.



I got the Gear box on Ebay   Thanks for letting me know about it, my search that I had setup in ebay didn't pick it up so I wouldn't have caught it myself.    I  got the whole thing for little over 250 shipped,  I can get that back out of the gear box itself.

I think that I'll go ahead and machine the one I'm working on and put it in my Ebay sale stuff somewhere sometime  somebody will break one it will be worth 75 to them.


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## roadie33 (Mar 19, 2015)

Congrats.
Now you'll be back up and turning chips in no time. 
Those Gear boxes are going for $250 - 300 so you should come out good on that deal.


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## master53yoda (Mar 19, 2015)

Gunner said:


> Some of the ones on eBay are made of brass, too.  Which are easier to damage than the original Zamak ones.



I do alot of casting,  I also make a Zamak alloy that i use for alot of stuff, it is based on ZA27,  its  as hard as cast iron and almost as strong, its more brittle then cast iron by about 25%.  its weak point is that it melts at about 925 so you would have to be carefull when up agains High temps.   It makes really good gears as well as cast parts for a lot of things, one of the high points it that it acts as bearing surface due to the 2+%copper that is alloyed in, you can use it as a bearing against a shaft up to about 2500 rpm with oil.

Art B


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## wa5cab (Mar 19, 2015)

That reminds me of a perennial question.  Has anyone ever found believable written proof of which Zamak alloy Atlas actually used?  I've seen it written that it was Zamak 5, but with no substantiation to back up the statement.


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## master53yoda (Mar 19, 2015)

I'm not sure but while I've got mine down I'll either take a gear in and have it scanned or do specific gravity??? test,  wiegh it in water.

I should be able to let you know what Zmak it is.


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## master53yoda (Apr 10, 2015)

I'm having a new continuation of the old problem the the QCGB   I made one good gear box out of my old one and the one i bought off of ebay,  the ebay box bearings for the shaft that carries the selection handles were badly worn as if they had never been oiled.  The gear box that was on the lathe didn't have some of the washers etc.  so i merged the parts.   the interesting thing is that it works just fine and then it binds up and stalls the DC motor, if it didn't stall the motor it would have broken the quadrant again.   I'm finding that if there is no back pressure and it is just carrying the lead screw and the carriage  it runs just fine, but if I'm even cutting a fairly light .020 cut it will bind up the gear box after about 20 to 25 inches of travel using an 8 threads per inch.   at that point i can reverse it and back it up a few inches and then go forward and it will bind up at exactly the same place every time.    I released the carriage feed and moved the carriage to a different location, the new bind up point was repetitive and in a different location on the shaft so I think that eliminated it being a carriage issue.   The fact that it will go the 20 or so inches before it binds again once i go past the bind point seems to me that the problem would be in the thread gear tree right at the output gear,  when i look at it i can't see anything wrong and i cant make it bind at all when hand turning the gear box.    The 20 inches also shortness if I go to a higher thread per inch.  

Any suggestions on where to go next.


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