Question about Ammco Combination Disc/Drum Brake Lathe

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I bought an Ammco 4000 brake lathe and the arbor was not installed in it. The one they gave me has surface rust on it. It will not fit into the spindle either. I'm not sure on got the correct one. What is the procedure for the arbor replacement

Posted by Jeremy Owen on


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alex hidell

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A standard arbor which you should have been provided with should look like this...

I bought an Ammco 4000 brake lathe and the arbor w - section-gp0qxwy22y1qrfiy42l4xkcn-4-0.jpg

The standard arbor size is 1 inch.
A used arbor is okay--but if it has rust on it, you should remove the rust with a wire-wheel mounted on a bench grinder (and be sure to use eye protection because fast spinning wire-wheels routinely throw off wires).

Any arbor (especially new arbors) have to be lapped into the spindle using a fine lapping compound which can be easily found at auto parts stores.

Apply a small amount of lapping compound onto the mating surface of the arbor and insert it into the spindle with the machine turning. Hold the arbor tight and let the lapping compound grind away for about 40 seconds.

Remove the arbor and reapply another small amount of lapping compound--repeat the grinding process one more time. Remove the arbor and using a rag clean the lapping compound from the arbor.

Clean the lapping compound from the outer spindle seat. The outer seat is easily accessed--the inner seat of the spindle is harder to access. This is cleaned by doubling a rag over the threaded end of the arbor. Holding the rag, insert the threaded end into the spindle and clean the inner seat.

Turn off the machine and insert the arbor into the spindle. Insert the spindle "draw bar" (which you should also have) through the hole in the drum gear box (Infimatic gearbox) on the right hand side of the machine.

Holding the drive pulley, tighten the draw bar.

Next you have to check the arbor run-out using a magnetically mounted dial indicator as shown....


Mount the dial indicator on the machine's twin cutter (tightened down) and crank in the disc-feed carriage until the dial indicator can make contact with the arbor.

Start the machine. The arbor run-out should be no more than 1 1/2 thousandths. If the run-out exceeds greater than 8 thousandths it cannot be straightened. Arbor with slight run-out problems can be straightened.

(Note: If the dial indicator vibrates too much to get a reading--you will have to manually turn the machine using a wrench as described below).

First try loosening the draw bar, and rotating the arbor 180 degrees and then re-tightening the draw-bar. Many time this will solve the problem or at the very least lessen the run-out or bring it within spec.

If the arbor is still exceeds spec, then you have to straighten it. To straighten an arbor, manually turn the machine with the "Ammco wrench" (which you should also have) using the nut on the draw bar. Turn the machine until you find the high spot (straight up), then remove the dial indicator to prevent damage.

Using a copper dead blow hammer, give the arbor a modest whack, and then recheck the run-out. Repeat the process until you manage to get the arbor within spec.

Please note that straightening an arbor using this method will sometimes break the arbor off. You are rolling the dice when straightening an arbor--but this is the nature of the animal. Even brand new arbors sometimes need straightening.

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Posted on Mar 29, 2015

  • Tim Hofstetter
    Tim Hofstetter Mar 29, 2015

    Very good answer! Kudos!



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Ammco 4000 longtravel g/box adjustment not working properly,variable speed adjustment works slowly,then when increased starts to work backwards

What you are referring to is called an "Infimatic" gearbox, or drum-feed gearbox.

The problem lays inside most likely with the clutches.
They are worn out, and possibly other components are worn and broken. Feeding backwards means something has gone terribly wrong--and it needs to be fixed immediately for the machine to operate properly.

These gearboxes are not easy to fix properly--they are literally like a puzzle inside. Our shop employs a infimatic gearbox specialist and we are one of the few shops who can rebuild them to factory spec.

A brand new Infimatic gearbox will run you over $1,300.00 plus tax and shipping from an Ammco depot.

You can ship a broken Infimatic gearbox to our shop for a complete rebuild to factory spec.

For more information...

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Can,t get the front brakes off

If its a disc brake set up there are bolts holding the calipers to the steering knuckle. If its a drum setup, then the star gear that pushes the lower portion of the pads out may need to be backed off. Tap around the drum to break lose any rust, corrosion build up


Not enough rigidity, wrong speed, wrong feed rate, wrong depth of cut, wrong or dull tooling...


Most likely you have a stripped out "disc feed screw."
This is a common problem I see several times a month in the field.
The stripped out portion of the screw is near the end of the feed range obviously.

If you need parts or more questions answered....

Buy Sell Used Brake Lathes Brake Lathe Parts

Instructions for changing an ammco 3000 brake lathe to a 4000. Parts needed?

Yes, an Ammco 3000 brake lathe can be converted over to a 4000 model--most any year 3000.... preferably the later years after 1970.

The problem with some of the early 60's models is that the cross-feed bore is not perfectly perpendicular to the spindle.

If you convert one of these models, you will cut the rotor at an angle and then jam the machine.

Later models can easily be converted.

You will need...

1) A complete disc feed gearbox.
2) A driven pulley (the big one) set-up for a with a pin drive.
3) A complete spindle lock assembly for the Infimatic gearbox.
4) Possibly need a longer guide bar for the cross-freed. If you have a round guide bar, this is possibly long enough. If you have a "Double-D" guide bar (flat on each side), you most likely will need a longer bar.
5) A complete twin-cutter, with tool guides, tool holders, knobs, etc.

We have all the parts you need for a conversion--or we can convert it expertly for you...

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Replaced belt on 4000 lathe and now I have no fast feed.

I think that you really need to source the manual for that machine.

How do I change the belt on my ammco 4000 lathe?

I am a brake lathe technician.

To change the drive belt on an Ammco 4000, you must first remove the 90 degree angle PTO (power take off) gear assembly which is driven off the back of the big pulley. Two small allen head screws hold it tight.

Pull the PTO gear assembly out of the disc-feed gearbox. If there are colored shims between the gearbox and the PTO assembly, you must make sure not to loose. If they drop off, be sure to replace them with a dab of grease.

Rotate the red knob at the back of the machine and the motor assembly will unlock and rotate upwards. Replace the drive belt.

To adjust the drive belt tension properly--loosen the 3/4 inch nut on the back of the machine, and the motor will drop down. Tighten the 3/4 inch nut and then rotate the red knob back until the belt is taught.

Replace the PTO gear assembly--making the rotating part with the protruding pin is centered on the big pulley. Tighten the allen head cap screws.

Turn on the machine. If the PTO is making noise--you have not correctly is correctly. Repeat the centering process until the machine runs without rattling or vibration.


Hi, we have a AMMCO 7750 brake lathe, the problem is runout in the ARBOR we have replaced the arbor but still have the same result. We are unsure of hat is causing this so any help or advise would be...

First off--your model Ammco is their "El-Cheapo" model.
Yeah, they work, when they work that is.
I doubt that your problem lies within the spindle bearings. But it could-- I suggest that you tug on the spindle to see if you get any back and forth end-play, or up and down play.... if so, you are screwed. This machine is not worth the effort, money and time fix this problem.

As for the arbor...

This model uses the same arbor that the better 3000, 4000, 4100, 7000 and 7100 models.

Every time you replace an arbor (new or used) you have to...

A. Lap the arbor into the spindle using lapping compound (just like lapping valves in a cylinder head) The lapping compound is then cleaned out of the spindle and off the arbor, then...

B. You then have to check the "runout" with a dial indicator. These are obtained cheaply at Harbor Freight FYI. With the dial indicator mounted (magnetically) on the twin-cutter check the arbor run-out. The runout (two inches from the spindle) should be no more than 1 1/2 thousandths. One thousandth or under is optimal. Any reading over 8 thousandths cannot be straightened.

C. If the run out exceeds 1 1/2 thousandths, you have to then straighten the arbor.

To straighten the arbor you will again need the dial-indicator and a heavy copper hammer....

With a wrench on the end of the draw bar (far right on the end of the drum gearbox), rotate the machine (counter clockwise) until you find the high spot on the arbor (carefully watching the dial-indicator).

Remove the dial indicator and give the arbor a whack with the hammer (not too hard if this is your first time) when the high spot is directly straight up.

Install the dial-indicator and check the run-out again.

Sometimes you will get it on the first whack--sometimes you will have to go through an ordeal until you get the arbor in spec.

And remember--sometimes you can bust the arbor completely off on the first whack. They are hardened and allegedly tempered, but some are more hard than others. If it breaks off--tough luck. You need to get another arbor.

I have personally straightened arbors more than 30 thousandths out (once)... and I don't want to repeat that ordeal. Sometimes arbors cannot be straightened (bent in strange ways) and cannot be straightened.

When loosening a rotor, do not allow the work to dump onto the arbor. This is the main reason they go out of whack.

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