Shop Doc – Should I rebuild my Acme?

Dear Shop Doc,

My Acme-Gridley screw machines have been real money makers over the years, but all that production takes its toll in wear and tear on the machines. Will I be better off doing major repairs to my current Acmes, looking for deals on good used Acmes, or investing in some type of new machinery?

Which Way Should I Go

Dear Which Way,

Acme-Gridley multi-spindle automatics are well designed to be rebuilt or reconditioned, and worn machines can be returned to good running or like new condition by those qualified to perform that type of work. There are different levels of repair to choose from.

For example, you have a 1-1/4” RA6 Acme machine that needs some work. The heart of an Acme is the spindle carrier, which you might start looking at having rebuilt for around $10,000. This includes rebuilt work spindles, new precision spindle bearings, new front and rear retainers and flingers, and new spindle gears, adjusting nuts and keys. The carrier stem is also ground, and fitted to your re-bushed and bored main tool slide. At the high end of your list of options you have a complete machine rebuild, which for all practical purposes is like a new machine. That will cost in the neighborhood of $100,000 to $150,000, depending on your machine and requirements. Compare that to a price tag of $500,000 or more for a comparable new multi-spindle cam machine.

Another factor to consider is that a rebuilt Acme, when properly maintained, can be run hard for 10 years or more before it will require another rebuild. Most single-spindle CNC machines never get that old before they are obsolete or worn out. Acme-Gridley machines come in a wide variety of models, capacities, and vintages. Some machines in service today predate 1950. With sound castings most of these machines are still great candidates for rebuild or recondition, with just a few old models that are obsolete.

A concern for some shop owners today is a lack of experienced machine repair personnel to remove or re-install a spindle carrier, but most qualified rebuilders can offer contracted field service work to do this for you.

Another option popular with some shop owners is look for an inexpensive, worn, late model machine and have it rebuilt. This could be a good option because its mechanical condition is not a concern as long as the castings are in good shape. But even if a machine is examined by experienced personnel when purchasing, the condition of the spindle bearings will largely be an unknown. So it may be a better option to invest money in a machine that you already have and know.

Acmes are well suited for high production part runs, or running a family of similar parts at moderate volumes, but may not be the best choice for small lot runs unless efforts are made to reduce setup times. Attachments are available for Acmes that allow even complex parts to come off the machine complete. In some cases shops are using Acmes in tandem with single-spindle CNC machines, with the Acme blanking the part and then a robot transferring the part to one or several inexpensive CNCs to finish it off. Your production time may be longer, but in the right type of job the dramatic savings on equipment could very well make up for the additional second or two.

Bottom line, your Acmes still have a lot of life left in them, so if you have the right work for them, rebuilding and refurbishing can definitely pay off.

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3 thoughts on “Shop Doc – Should I rebuild my Acme?

  1. David Haviland

    Some of the newer National Acme’s were equipped with ball screws which required frequent repair or replacement because they were undersized. As a ball screw manufacturer, we have successfully replaced these with improved ball screws that ran three times longer before needing replacement. We’ll be pleased to help parts manufacturers with any spindle, ball screw or chuck problem, or any machine rebuild need.

  2. Robert Sarna Jr.

    Dear Shop Doc,

    It sounds like Rebuilding you Acme Gridley is the way to go. Pride Machinery has rebuilt more than 180 Acme Gridleys in 35 years and now with two locations, Anaheim, California and Kanses City, Missouri we can offer even quicker service. Our owner worked on the assembly floor at National Acme in Cleveland during the 60″s and 70’s and has since trained countless set up men, machine operators and maintainence persons around the world. In October 1991 Modern Machine Shop documented our success with servo cross slides eliminating form and shave tools on Acme Gridley’s producing fasteners for the Aerospace industries. Please check our web site for further details.

    Robert Sarna Jr.
    Robert Sarna Sr.

  3. thomas

    rebuilding is the way to go depending on the age of the machine it will likely just need spindle bearings and fork done on your slides as a repairman and rebuilder there are a lot of thing that could be done aslo as a person who has been on both sides of the rebuilding the machins to just needing it to run right because time and production is an issue there are a lot of thing rebuilding companys will charge you for that really does not have to be done so just make sure you get some one that knows what there doing.


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