Fosdick radial arm drill acme elevating nut - material choice?

Working on a 40's or 50's Fosdick hydraulic radial arm drill. It's the 8', which is biggest in their lineup. When I arrived the nut was worn and tripping the anti-drop mechanism. So I pulled the nut out to machine a new one, and discovered it was made of cast iron. I've never seen that before. Every drill press, knee mill, lathe and horizontal milling machine I've ever repaired has had a bronze nut. The shop I use for all my ACME nut work hasn't seen cast iron either, but suspected it could be a wartime machine. Acme nuts are typically a bronze alloy, silicon bronze perhaps.

I found a book on ebay, but it does not specify the material. So we went ahead and made the new nut out of the same material, cast iron. I dressed the galled portions of screw thoroughly in the lathe, and checked the fit of the new nut along the full length of the screw dry. Was very smooth. Went ahead and oiled the screw and nut with heavy oil and put it back together. I did not use the typical ISO 68 Vactra #2 way oil. The machine tag specifies a much heavier oil, 140-160 SUV at 210 f, which crosses to an SAE 140, or ISO 460. I went with Mobilgear 600 XP460. This stuff is thick like honey. There is an oil pot surrounding the top side of the screw. I filled that pot and let it sit over the weekend, then filled it again. It's a total loss system so it just drips past the threads and onto the machine base.

Testing did not go well. We ran the machine and elevated the nut a couple feet. Was some squeeling and chatter. I mechanically disabled the column clamp to eliminate that as an issue. Ran it up and down a bit more, which was ok, then no more movement. I put my hand on the elevating screw above the nut and it's physically hot to the touch. Way too much friction! The oil is full of particles, and this is after 30 seconds of use. Looks like lapping compound.

Now we're in a bad spot. In my mind, this nut should be made of bronze. Even dry bronze won't gall this badly, regardless of what type of oil is used. Looking for advice from the more experienced guys.


FYI I also went through the hyraulic system and had the motor and valve gone though. The hydraulic system is building pressure per the spec in the manual.

There are a lot of grades of cast iron, I have seen acme nuts made from cast before but it was dark gray and full of graphite...phil

Bread,
I have 2 large NEW Acme Elevating Nuts with a 2-1/4 OD x 2.5 TPI. They are Bronze, identified as for a Giddings & Lucas HBM. If the thread is right you could modify the base to fit. These are for sale for less than the price of the bronze to make them. Fives group wants 3473.00 for one. I'll take way less.
spaeth

Thanks spaeth. Those won't work for this machine, but I'll keep that mind. I do work on Giddings and Lewis as well as Lucas horizontal boring mills from time to time. On the Fosdick, the nut iself is driven rather than the screw. A bit unusual, and costly to replicate.



Unbelievably, I found another shop who has a hydraulic Fosdick radial arm drill, and they allowed me to inspect the elevating nut. It's also made of iron, not bronze. They don't run oil on the screw but rather grease. So I suspect my binding issue is a combination of a new nut on a worn screw. The thread profiles don't match. I'm going to wipe the oil off tomorrow, unload the arm with the overhead crane and run some heavy grease on the threads. I was going to apply some EP2 with moly, but I've got also got some open gear grease that will stick to anything.

Bread,
Can you get a new length of Green Bay Acme threaded rod to fit your new nut. I've not bought anything from them in years, but their prices were always very fair and they had plenty of standard and special sizes.
I have more info on the G&L nuts if you ever need one.
spaeth

I can have a new shaft made locally if it comes to that. Nicholson Engineering in Tacoma specializes in ACME threading. They actually used to make the factory G&L nuts. The top 18" is unthreaded, with some snap ring grooves machined on it.

I'll try the grease tomorrow. If that fails a new shaft will likely be the next step. I was trying to save the customer any additional cost, but if that's what it takes to do it right then that's what we'll have to do.

Typically on a G&L or similar HBM, a new nut can be installed on a worn table or elevating screw without issue. I think the key differences are that bronze is more forgiving (slippery), and there is much less load on the threads. The table just needs to be pushed around, and the headstock is counterbalanced. An 8' radial arm drill on the other hand has its full weight resting on the nut. This machine in total weighs 26k lbs according to the book.

Make a nut from 464 Naval bronze. That would be a slightly higher yield material than cast iron and a bit less friction to deal with.

You can go to nook and buy what you need , or send me a msg, I have a new not needed 8 ft pc of 2 1/4 inch acme rod with 2 brass nut to fit...Phil

I have always used 954 Aluminum-Bronze for Acme nuts.
Go to McMaster Carr and they have good information
about the different alloys of Bronze.

-Doozer

spaeth said:

Bread,
I have 2 large NEW Acme Elevating Nuts with a 2-1/4 OD x 2.5 TPI. They are Bronze, identified as for a Giddings & Lucas HBM. If the thread is right you could modify the base to fit. These are for sale for less than the price of the bronze to make them. Fives group wants 3473.00 for one. I'll take way less.
spaeth
View attachment 317822View attachment 317823View attachment 317824

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And I though 16,000.00 was out of line for a set of Cincinnati 1D pulleys was out of line from Fives

Doozer said:

I have always used 954 Aluminum-Bronze for Acme nuts.

-Doozer

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Yep, that's what we use typically. This is the first time I've ever seen one made of iron. Ductile iron in this case.

swatkins said:

And I though 16,000.00 was out of line for a set of Cincinnati 1D pulleys was out of line from Fives

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Dealing with Fives can be a pain. Typically if you can get it made locally, it will be cheaper. As far as ACME nuts, order these from Nicholson Engineering in Tacoma. It will be a 1/3 less, but he's going to want to have the old nut to work from. Keep in mind the price of bronze is through the roof right now. I'm having an elevating nut made for a 6" G&L, and the chunk of aluminum bronze cost a grand to my door.

Id have a go with moly dag as the lube ....this is moly powder with just enough oil to make it fluid......this has cured a lot of seizure situations for me ,including a slewing ring for a truck crane that was making a horrible racket...like parrots fighting....completely silent and no more chatter.......however ,I wonder if your cast iron was a doped SG/ ductile iron?....unsuitable structure for bearing surface?

Bread,
I forgot to mention the Giddings & Lewis Elevating Nut is part #10456,(Fives #M.000.2417) Not sure which models and years of machines it fits. 350T I think. You are right on about that bronze price, pretty steep.
spaeth

john.k said:

Id have a go with moly dag as the lube ....this is moly powder with just enough oil to make it fluid......this has cured a lot of seizure situations for me ,including a slewing ring for a truck crane that was making a horrible racket...like parrots fighting....completely silent and no more chatter.......however ,I wonder if your cast iron was a doped SG/ ductile iron?....unsuitable structure for bearing surface?

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Hmm never seen that stuff. I'll have to check it out. I did use the open gear grease and the machine was able to elevate the arm over parts of the screw, but still not fully. Had to use the overhead crane for assistance, and it did pull a burr in places. We're going to make a new screw. It would seem in a high load elevating situation the thread faces need to be perfectly smooth.

spaeth said:

Bread,
I forgot to mention the Giddings & Lewis Elevating Nut is part #10456,(Fives #M.000.2417) Not sure which models and years of machines it fits. 350T I think. You are right on about that bronze price, pretty steep.
spaeth

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Ok great. There are a few 350T's in my area. A couple mechanical shifted, and one electric over hydraulic over mechanical shift (nightmare to work on when these get old). I've done the table nut's on two of them, and I'm sure the lead screws will need to be done at some point in time.

You may be able to reverse the screw ,and use the unworn side......I d also research the different kinds of cast iron to use.....one called 'meehanite' seems to be used for leadscrew nuts.......Ive got a fair sized radial I just moved into my new shed ....hoping the elevation still has a bit of life left in it.