Thoughts on Removing Flywheels and Keys

| September/October 1996

  • Key shaft

  • Key shaft

Route 1, Glouster, Ohio 45732

Having been a reader of GEM for along time, it has become apparent that many engine men have problems with removing keys and pulling off flywheels without damage. Here are a few ideas that have worked for me, and may well work for others.

Gib keys, the ones with the little 'toe' can often be pulled with the aid of a shop made puller like the drawing. Measure the gap between the flywheel hub and the toe of the key, and use a piece of steel as big as you can fit into the gap. Make the puller as wide as practical. Cut a square notch in the center of this bar which will allow the bar to straddle the key. Carefully measure the spacing of the two draw bolts, and locate these as close to the key as practical, as a close spacing will lessen the tendency to bend the puller.

Drill, tap and fit up two fine threaded grade 5 bolts, using care to allow the bolt heads to pass a wrench. Locate the draw bolts in line with the bottom of the notch in the puller bar. This will locate the line of pull with the top edge of the key, and lessen the tendency of twisting out of the key on a hard pull.

When you have the puller made to your satisfaction, set the puller on the key, and hand tighten the draw bolts. Be sure the bolts bear on a flat part of the hub, as far as possible. On small or chipped hubs, it may be necessary to use a thin piece of steel as a bearing point for the draw bolts. If you anticipate a hard pull will be necessary, chamfer off the first thread to eliminate damage.

When you are ready for a trial pull, lubricate the bolt threads with grease or anti-seize, put a few drops on the end of the bolts and wind a strain on the key, taking care to keep the puller square with the key. Tightening the draw bolts will put a very strong, straight line pull on the key. If the key is too tight and will not loosen, generally no damage will be done, as the puller will bend before any damage is done to the engine. I have driven the key with a copper or brass hammer in an attempt to break loose any rust bond, and of course, soak the key with your favorite 'soak-them-loose' solution.

In extreme cases it may be necessary to heat the hub with an acetylene torch, expanding the hub a bit and possibly loosening it.

For keys without the jib, the problem is a little more spicy. First look on the inside of the flywheel and determine if a driver can be inserted into the keyway, allowing the key to be driven out from the inside.

If this idea is not practical, it may be possible to drill the key, tap threads in it and use a slide hammer to remove it. If this is necessary, use care in selecting as large a size of draw bolt as the key will permit. Since most drilling will be done with a hand drill, be careful to align the drill straight down the center of the key. Make the hole plenty deep and use a coarse thread, as these threads are much deeper than fine ones.

A slide hammer can be made of a bolt, about 16 inches long, or a piece of cold rolled the same sizes with a nut threaded or welded on one end. If your key is large enough to permit a ' hole to be made in it, weld a ' grade 5 bolt to the end of your slide hammer, screw this bolt into the key, and using care not to pinch your fingers, try a few raps, increasing the strength of the impact as your judgment dictates. On mean keys it will help to fit an eye on the end of the slide hammer bolts, and pull a strain on it with a small chain hoist or a come-a-long. This method will put a terrific strain on the key, and will remove all but the most stubborn of them. Obviously, if your flywheel is of the split and bolted type be sure to loosen the bolts and wedge the gap to eliminate the clamping force.

To remove flywheels, belt pulleys, gears, etc. from shafts, it is often possible to use a hydraulic jack. Using the proper size jack for your shaft, locate the head of the ram against the end of the shaft. Loop a chain through the spokes, as close as possible to the hub, and around the base of the jack. Keep the pump of the jack on the bottom side so it will work in a horizontal position. Try to loop the chain around two spokes, if possible, on each side of the jack. Snug up on the jack and render the chain as necessary to achieve a straight pull. Since a jack will have no mercy, use common sense when applying the pressure and do not use enough force to risk breaking the spokes. If possible, two healthy steel bars can sometimes be located behind the wheel and against the shaft and the chains looped around these bars.

I have pulled off some tight fits in this manner, but as with anything involving high pressures, use your best judgment. Keep your nose well away from the work. If the chain should break, it could fly off with considerable force. Practice safety at all times.

A thin coat of anti-seize compound on shafts, keys, bolts and gaskets will allow them to be removed much easier in the future.


Gas Engine Magazine A_M 16Gas Engine Magazine is your best source for tractor and stationary gas engine information.  Subscribe and connect with more than 23,000 other gas engine collectors and build your knowledge, share your passion and search for parts, in the publication written by and for gas engine enthusiasts! Gas Engine Magazine brings you: restoration stories, company histories, and technical advice. Plus our Flywheel Forum column helps answer your engine inquiries!

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