Single Point Metric Threading On The 618

[David S]

For quite some time I have been looking for metric 12 mm X 1 mm extra fine thread bolts with no luck. I want these so I can use some of the spindle accessories from my Unimat DB200 for other purposes / tooling.

I found out that there are banjo bolts with a 12 mm x 1 mm thread used on some imported cars. Spent a bunch of time yesterday driving around from car place to hydraulic guys, but to no avail.

I have cut imperial threads before on my Atlas 618 before and it sure is a PITA fooling around with the change gears. I didn't think my 618 could cut metric so I got out the book and did a read..WOW it can cut metric threads that are very very close to standard.

So I set up the gears and then read the process. Yikes totally different from cutting imperial threads. Forget the threading dial, never disengage the long feed, and always keep the tumbler engaged forward..do not disengage it. Instead at the end of one pass, stop the motor, put withdraw the crossslide and reverse the motor to back the carriage back to the start. Bring the cross slide back to zero and advance the compound.

I did a trial on a piece of aluminum to see if the gears were correct, and to get the hang of it. Is it ever hard to forget the old habit of disengaging the long feed, cranking the carriage back and engage according to the threading dial.

Everything worked out on the test piece so did the real deal on some 12L14. My old 618 came through again.

The pics show the 4 jaw chuck threaded on as a test and also the face plate.

David

 

[brino]

Hi David,

I didn't know cutting metric were such a change!
It would be hard to break old habits.

Congrats on the success.
Time well spent in the shop.
Thanks for the pics.

-brino

(by the way I like the chip/oil cover for the dial indicator on your carriage stop..........looks like something I'd do)

 

[ogberi]

Very nice! I had to cut a metric thread just before I left on vacation earlier this month. I read up on threading on the SB9A, then ended up just buying the die for it. I like your solution better.

 

[heiko910]

For quite some time I have been looking for metric 12 mm X 1 mm extra fine thread bolts with no luck. I want these so I can use some of the spindle accessories from my Unimat DB200 for other purposes / tooling.

I found out that there are banjo bolts with a 12 mm x 1 mm thread used on some imported cars. Spent a bunch of time yesterday driving around from car place to hydraulic guys, but to no avail.

I have cut imperial threads before on my Atlas 618 before and it sure is a PITA fooling around with the change gears. I didn't think my 618 could cut metric so I got out the book and did a read..WOW it can cut metric threads that are very very close to standard.

So I set up the gears and then read the process. Yikes totally different from cutting imperial threads. Forget the threading dial, never disengage the long feed, and always keep the tumbler engaged forward..do not disengage it. Instead at the end of one pass, stop the motor, put withdraw the crossslide and reverse the motor to back the carriage back to the start. Bring the cross slide back to zero and advance the compound.

I did a trial on a piece of aluminum to see if the gears were correct, and to get the hang of it. Is it ever hard to forget the old habit of disengaging the long feed, cranking the carriage back and engage according to the threading dial.

Everything worked out on the test piece so did the real deal on some 12L14. My old 618 came through again.

The pics show the 4 jaw chuck threaded on as a test and also the face plate.View attachment 100254 View attachment 100255 View attachment 100256 View attachment 100258

David

Hi David,
How did you figure out the gearing?

For quite some time I have been looking for metric 12 mm X 1 mm extra fine thread bolts with no luck. I want these so I can use some of the spindle accessories from my Unimat DB200 for other purposes / tooling.

I found out that there are banjo bolts with a 12 mm x 1 mm thread used on some imported cars. Spent a bunch of time yesterday driving around from car place to hydraulic guys, but to no avail.

I have cut imperial threads before on my Atlas 618 before and it sure is a PITA fooling around with the change gears. I didn't think my 618 could cut metric so I got out the book and did a read..WOW it can cut metric threads that are very very close to standard.

So I set up the gears and then read the process. Yikes totally different from cutting imperial threads. Forget the threading dial, never disengage the long feed, and always keep the tumbler engaged forward..do not disengage it. Instead at the end of one pass, stop the motor, put withdraw the crossslide and reverse the motor to back the carriage back to the start. Bring the cross slide back to zero and advance the compound.

I did a trial on a piece of aluminum to see if the gears were correct, and to get the hang of it. Is it ever hard to forget the old habit of disengaging the long feed, cranking the carriage back and engage according to the threading dial.

Everything worked out on the test piece so did the real deal on some 12L14. My old 618 came through again.

The pics show the 4 jaw chuck threaded on as a test and also the face plate.View attachment 100254 View attachment 100255 View attachment 100256 View attachment 100258

David

Hi David,
I know it is an old post but how did you figure out the gearing for metric on you atlas 618? I can not find anything online nor in any of the old manuals that i have.
What do I need to do to cut metric on a 618?
Thanks,
Heiko

 

[wa5cab]

Heiko,

I'm not David but I can answer most of your questions.

For starters, except for once circa about 1944 or 45, none of the MOLO's printed before 1954 cover threading on the 6", metric or Imperial. Beginning in 1954, coverage of the 6" was added to the rear of Chapter 7 - Threading. And there is a 6" metric chart around page 176 (last page in Chapter 7). Three of the pitches (M1.0, M1.75 and M2.0) require an add-on to the banjo or threading bracket. This was at the time available from the factory but as those three pitches only appear on the chart in the 1954, 1955 and 1957 editions, I doubt very much that it still is available. However, it would be worth a phone call to confirm that and if not, ask whether they still have the drawing. If the do, they should be willing to send you a TIF or PDF of the drawing (but I do not know the part number). If you get that far, send me a copy and I will clean it up and add it to the drawings in Downloads.

I do have one extra original of the Atlas version of the 1955 MOLO, but I paid well over the average cost for it. I would let it go for what I have in it if anyone is interested.

Anyway, MOLO's printed between 1954 and 1988 do have a 6" section in Chapter 7 - Threading.

 

[NortonDommi]

Hi David,
How did you figure out the gearing?

Hi David,
I know it is an old post but how did you figure out the gearing for metric on you atlas 618? I can not find anything online nor in any of the old manuals that i have.
What do I need to do to cut metric on a 618?
Thanks,
Heiko

Hello Heiko,
Here is a little program I have been using for years. I had to make some change gears and I used this to work out what I needed to to all threads I was likely to encounter. It does make you lazy though. You may have to work out gearbox ratios first which is not hard as once you have a base on one set the others for that set are ratios.

 

[heiko910]

MOLO

Hi wa5cab,
I got a reproduction of a MOLO that didn't cover the 6 inch lathe metric thread cutting. I found a copy online that has it. What would you want for your original?
thanks,
Heiko

 

[heiko910]

Hello Heiko,
Here is a little program I have been using for years. I had to make some change gears and I used this to work out what I needed to to all threads I was likely to encounter. It does make you lazy though. You may have to work out gearbox ratios first which is not hard as once you have a base on one set the others for that set are ratios.

thanks,
I will give it a try. I keep seeing 47/37 conversion gears for the 6 inch atlas on ebay but my understanding of the whole gear ratio and the conversion to metric is rather limited. They sell the gears but give no explanation on how to integrate into the gear system.

 

[wa5cab]

Hi wa5cab,
I got a reproduction of a MOLO that didn't cover the 6 inch lathe metric thread cutting. I found a copy online that has it. What would you want for your original?
thanks,
Heiko

Heiko,

The Metric trans-positioning gear pair that Atlas used in their tables are 52 and 44. Which happen to be included in the standard set of change gears that shipped with all of the Atlas and Atlas-Craftsman 6" lathes. So I wouldn't buy the 47/37 pair because (a) you should already have the 52/44 pair and (b) the 47/37 pair wouldn't match the Atlas metric threading tables.

The one extra original that I have of the 1954 Atlas MOLO cost me $54.50 plus postage. As I've written elsewhere, the average price of MOLO's on eBay is about $35.00. I wouldn't have paid that much for one except that at the time it was one of the few that I hadn't yet acquired. I was in a little bit of a rush to complete the MOLO history that I was writing and that issue was one of the few that I still didn't have. If you want it, fine. Send me a PM with your name and address. If you don't want it, no response is necessary.

Alternatively, you can set up a search on eBay as I did, although you can expect a lot of false hits as eBay is more interested in selling stuff than they are in someone finding what they were really looking for. But it may take you quite a while to find what you are looking for as most eBay sellers are clueless as to what keywords to use. About the only thing that most of them will do is to include a photo of the Copyright Page and the front cover. Beginning in 1954, Atlas began including the print history between 1937 and the year that the particular copy was printed. So you would be looking for 1954, 1955 or 1957. And it really doesn't matter whether the front cover is a gray Atlas one or a black Craftsman one as in any year from 1954 on, the only difference between the two versions were the covers. FYI, between about 1939 and 1953, all covers were black Atlas ones. And probably only one year did a few of the ones printed cover the 618. In 10 years of looking, only twice have I found one Copyright 1937 that covered the 618. I don't know whether or not they ever printed one that covered the 101.07301, although I am still looking.

 

[mickri]

One of my projects will require me to cut a 1.80 mm thread. That is a real odd ball thread. I was getting nowhere in trying to figure out what gears I needed to cut that thread until I converted it to threads per inch. To convert to TPI first divide the metric pitch by 25.4 to convert it to inches and then divide 1 by the number you just calculated to get imperial TPI. In my case 1.8/25.4=.0708661. Then 1/.0708661=14.1111. I looked in the manual for the QCGB on my lathe and found a gear combination that would cut 14.1136 tpi. That is only off by .0002% which is close enough for a short thread.