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Cincinatti Traytop Metric Conversion

Holescreek

Titanium
Joined
Aug 27, 2004
Location
Centerville,OH
An upcoming project requiring 1.5mm thread pitch forced me to take a look at my lathes again. At one point in time I considered buying an import machine for metric threading capability but I couldn't bring myself to do it.

Browsing the Traytop PDF manual online I saw that metric threading was possible with just 2 additional gears. My 12.5x18" traytop has been super noisy since the day I purchased it with high pitched ringing from the worn out change gears. The

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The original setup has a 33 tooth gear on the spindle, a 120 tooth idler and a 66 tooth gear on the gearbox shaft for a 2:1 ratio spindle to gearbox. The manual states that for metric threading the 33 tooth spindle gear is kept but now drives a 127 tooth gear pinned to a 120 which drives an 88 on the gear box. I opted to go with 16DP 14.5 PA gears because there is a large tooth count selection available. I knew I'd have to be creative mounting them, the new gear OD's are much smaller that the originals. The spindle gears had to be bored out and welded to adapters and the 33 tooth gear in a 16DP size isn't a whole lot larger than the OD of the spindle shaft. Also (due to the smaller diameters)I had to make a new banjo to provide swing for adjustment.

After thinking about it for a bit I decided to change things up a bit. Instead of switching between the 66 and 88 on the gearbox I decided to eliminate the 66 altogether and leave the 88 in place, but switch between a 33 and 44 on the spindle. I also run the 127 tooth gear as the primary idler and leave the 120 pinned to it for metric use. So now for inch threading I run 44-127-88, and for metric I run 33-127/120-88.

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I found a photo of a metric chart on the LathesUK site but I didn't get the same results with my lever positions. One difference I noticed was my A-B positions are marked opposite of those in the photo on the net. So using my DRO to give table movement per spindle revolution I created a new chart for my lathe.

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I've for several hundred dollars tied up in gears but now the lathe runs very quiet, has metric capability, and was a whole lot cheaper than buying a new lathe.
 
I should add that the biggest PITA about switching the machine from inch to metric is swapping the clutch and idler caps on the opposite side of the gearbox.

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There is a very small 1/8" D key in the shaft under the clutch cap that needs to move with the cap. if you don't shove a rag under the shaft and fill the space in the back of the hole the key will fall down into the gearbox never to be seen again. the key is so far back in the hole and my fingers don't fit so I have to move the key with a hemostat.

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The other thing required is removing the left end cap of the gearbox and moving a gear cluster from the top shaft to the bottom shaft.

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The manual states that the changeover should take an experienced operator about 15 minutes. Seems about right.
 
Side views, just because I have them.

Inch:
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Metric:
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Spindle gears:

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Backside of the new Banjo with steel insert for the idler stud:

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Spacers for the 88 tooth idler gear:

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metric tray top

Sir:
My end cap does not require my removing the key - can swap because the 7/16 bushing is set back far enough in the cap to clear the keyway. Can post some data if needed. The metric chart in the sales brochure is closer to yours. Are the original gears pressure angle 20 degree? Can you change the left side gear without removing the shift rod? Bob
metric chart .jpg
 
Sir:
My end cap does not require my removing the key - can swap because the 7/16 bushing is set back far enough in the cap to clear the keyway. Can post some data if needed. The metric chart in the sales brochure is closer to yours. Are the original gears pressure angle 20 degree? Can you change the left side gear without removing the shift rod? Bob
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With regard to the small key clearing the cap, I only found a key on the shaft with the clutch cap so I moved it with the cap. If I hadn't already had two keys fall out and drop back inside the gearbox I might be tempted to try leaving one in place.

I had to remove the inner shift rod from the lever when moving the gear cluster to the lower shaft. It's easy enough to remove the cluster from the top shaft without taking the rod off but there is just not enough geometry to put it on the lower.
 
I had a chance to look over your gear chart tonight and I'm happy to have gotten so close to the factory numbers. I apparently made a mistake on AC-7 in my chart when I was typing it in from my notes. Thanks for posting it!

The gear chart shown in a photo on the LathesUK site doesn't match either of our charts, perhaps it was from a 15" or larger model.
 
traytop metric transposing gears

this was an interesting read about the change over for metric threading reversing the caps on the quick change gear box. I have a 18 inch gap bed traytop and had to make the 127 tooth gear and the 66 tooth. I used the Kearney trecker astronomical dividing attachment for the 127 tooth gear. can you reverse the feed rod in motion similar to a monarch lead reverse lever? I think mine is supposed too according to the manual thanks for listening and have a good new year ed
 
Yes the caps are swapped without needing to remove keys - in my 1953 version. The feed rod simply operates to electrically put the motor in forward neutral or reverse in the non clutched 1953 version. In metric threading the half nut stays engaged.
 
img012 copy.jpgMr. Holescreek:

Had this proof made up today while doing my imperial chart (mine was missing)can have a mylar with adhesive backing sheet with 2 prints made if you need ?
Ed could do metric 18" while at it. Bob
 
View attachment 217134Mr. Holescreek:

Had this proof made up today while doing my imperial chart (mine was missing)can have a mylar with adhesive backing sheet with 2 prints made if you need ?
Ed could do metric 18" while at it. Bob

I printed out and laminated your chart before Christmas, it's been hanging above the lathe ever since. Thanks! I won't be switching between in/mm very often, I just wanted the capability for an upcoming project. It was an interesting undertaking, I got to learn something and the lathe is so much quieter now I can even hear others talking while it's running. -Mike
 








 
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