Mazak / Ajax 18x40 Manual - feeds / threading chart

Overland · Jul 24, 2021

I have an older Mazak lathe in pretty good shape, however the chart on the headstock for feeds and threading has been a great place to lay tools in the past. So the chart is not legible !
Would someone who has one of these Mazaks, with a chart in good condition take a close up photo and post it please ?
I'm guessing the same headstock was used on many Mazaks of similar size.
Or maybe someone has a manual with a table in it ......
Thanks in advance,
Bob

muckalee · Jul 26, 2021

I have an enlarged hard copy. Send your mailing address if you want a copy.

Overland · Jul 27, 2021

Thank you.
PM sent
Bob

muckalee · Jul 28, 2021

Putting it in the mail today.

Overland · Jul 29, 2021

Cockeyed threads.

I'm repairing a hydraulic cylinder on a "Metal Muncher" ironworker.
The cylinder rod had pulled out of the trunnion and the owner had tried to weld the cylinder rod into the trunnion (!!!!) and really messed things up.

So I'm making a new piston rod, and welding a bushing in the trunion, to re-thread.
The thread on the cylinder rod into piston, I "measured", not so good eyesite, at 12 tpi. A buddy with a thread gauge took his time to agree, 12 tpi.
12 tpi seems to be fairly common, so I'm quite confident to start on the 2" chrome plated cylinder rod blank I bought ($120).
As discussed above, with a little care I could see the correct settings on my Mazak on the beaten up chart.
The piston jammed on the rod, at about 1-1/2 turns, strange, everything looked good.
Finally decided to put the old cylinder rod in the lathe and check the pitch - not 12 tpi.
Tried 11, tried 13, no good. Looked really carefully on the chart and saw 11-1/2 tpi.
Seems to be just right.
Luckily the blank I bought was 2" too long.
I have another piece of bar I can try 11-1/2 tpi on, to check.

I'm having a hard time believing that someone would spec a thread at 1-1/2 dia, 11-1/2 tpi.

Interesting lesson.
In hindsight, my buddy's thread gauge was only about 1/2" long, so not the most accurate.
Bob

garychipmaker · Jul 29, 2021

I hold a tap along a thread to get a longer gauge.

Overland said:
Cockeyed threads.

I'm repairing a hydraulic cylinder on a "Metal Muncher" ironworker.
The cylinder rod had pulled out of the trunnion and the owner had tried to weld the cylinder rod into the trunnion (!!!!) and really messed things up.

So I'm making a new piston rod, and welding a bushing in the trunion, to re-thread.
The thread on the cylinder rod into piston, I "measured", not so good eyesite, at 12 tpi. A buddy with a thread gauge took his time to agree, 12 tpi.
12 tpi seems to be fairly common, so I'm quite confident to start on the 2" chrome plated cylinder rod blank I bought ($120).
As discussed above, with a little care I could see the correct settings on my Mazak on the beaten up chart.
The piston jammed on the rod, at about 1-1/2 turns, strange, everything looked good.
Finally decided to put the old cylinder rod in the lathe and check the pitch - not 12 tpi.
Tried 11, tried 13, no good. Looked really carefully on the chart and saw 11-1/2 tpi.
Seems to be just right.
Luckily the blank I bought was 2" too long.
I have another piece of bar I can try 11-1/2 tpi on, to check.

I'm having a hard time believing that someone would spec a thread at 1-1/2 dia, 11-1/2 tpi.

Interesting lesson.
In hindsight, my buddy's thread gauge was only about 1/2" long, so not the most accurate.
Bob

A tap held along the thread makes any error easier to see than using a short thread pitch gage

muckalee · Jul 30, 2021

sounds like you are working with previous field repairs where a pipe coupling was welded in or the trunion was rethreaded with a pipe tap. Since you are making the repair bushing and the rod, make them both 12tpi.

Overland · Jul 30, 2021

Thanks Muck,
I had to replace the cylinder rod. It was original, but really trashed by welding attempt.
So started the piston end, the 11-1/2 tpi nonsense.
The trunnion end I can do what I want as I have to cut both threads.

I'm not sure I have a big tap like that, but one of those obvious suggestions when its pointed out. I'll check.

Thanks,
Bob

muckalee · Aug 1, 2021

So, you are using the oem nut? i would bet my next born that the threads are 12tpi, not 11 1/2. Many times I have seen a pipe plug, 11 1/2 npt screwed in to a 12 tpi port in reservoir on equipment. If you dont have a 1.5- 12 tap, I would make a sample piece more than the length of the rod threads and make sure the nut will engage the length needed and not lock up about one inch down the rod. If the nut is actually 11.5 tpi, the nut bind up at about or at 8 turns on the 12 tpi rod. If someone had a tap, 11 1/2 NPS, the nut may have been rethreaded to 11 1/2 tpi.

Overland · Aug 1, 2021

Once bitten, twice shy, so I got a piece of scrap and cut a thread 1.5 dia, 11-1/2 tpi.
Fitted into the piston beautifully.
Maybe I'm not reading the gearbox handle position markings correctly, but as long as I'm consistent, should be fine.

Overland · Aug 1, 2021

View attachment 325778 View attachment 325785 View attachment 325784 View attachment 325786 View attachment 325787

The first photo on left shows clevis and end of old cylinder rod I had to cut off to dismantle cylinder.
Next photo shows other end of cylinder rod that goes into piston. This is the infamous 11-1/2 tpi thread.
Middle photo shows clevis, bored out to take bushing, and end of new cylinder rod, to be threaded to suit bushing. Bushing will be welded into clevis.
Next pic shows "Threading/feeds" table on lathe - hard to read !
Right hand pic shows lever at #6 for 11-1/2 tpi thread.

The original problem was that piston rod pulled out of clevis. The owner tried 4 times, over a period of years to weld the rod into the clevis, hence horrific state of piston rod.

I'm having trouble loading images, hope you can see them.

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