Chester Conquest Mill Spindle

I’m stripping down my mill to replace the bearings and fit a belt drive. The spindle is out but the key for the plastic gears is firmly stuck in the keyway, it needs to come out to remove the inner race from the bottom bearing. Not shown on the assembly drawing is the black disc behind the bearing race, I assume this is a spacer. Is it safe to put a tube behind the disc and whack it? And what’s the best way to get key out, I can’t grip it with a wrench and it doesn’t shift when hit with a chisel. Any advice welcome.

Usual way to remove the key if you don't want to destroy it is to drill and tap a hole in it and jack it out with a screw. If the key is long put one in towards each end.

If the spacer is metal, perhaps a little heat applied to it will allow it to drop off. Otherwise putting the shaft into a tube supporting the spacer and hitting the end with suitable protection.

Try not to mangle it! I usually manage to grip such keys in a milling vice. It will probably need an equal thickness spacer to keep the jaws parallel, or perhaps even a slightly thicker spacer to ensure gripping along the inner side of the key. Start with it really tight, once it slips off, the chances of success reduce. A vice with rounded jaws is hopeless.

Another possibility is vice-grips or a mole wrench. Again, probably needs to be the genuine article to have much chance, and again as tight as possible. Tap shaft with a copper mallet, or if not available, apply hammer via a piece of aluminium etc to avoid bruising.

You could try clamping the exposed key in a vice and tap shaft upwards with a copper mallet. As already suggested, drill and tap one end of the key and jack out of key way.

Good luck.

Another vote for using a milling vice to grip the key.

I have a small vice which, with the aid of a spanner, will grip the key sufficiently for the vice to be tapped with a soft blow hammer to gently drift the key out undamaged.

I always use a pair of side cutters pliers to remove keys….never fails. Use pliers parallel with the shaft grip the sides of the key and lift it out…

As this photo

Having destroyed the outer parts of the bearing, ideally clamp a bearing puller tightly into the groove of the inner race, and use the puller to drag it loose. Once it begins to move it should be easier to remove completely.

In this way, the plastic spacer will be unharmed.

If you haven't got a bearing puller, it would be worth making one.

A disc that is a tight fit in the groove, cut in half, and tapped for two extension legs, a cross piece and a fin thread forcing screw.

My Sykes Pickavant bearing puller, capable of dealing with quite large bearings, uses a 3/4 BSF thread.

Probably 1/2 BSF (16 tpi) or UNF (20 tpi) would be adequate The finer the thread the better.

You can exert a lot of force with a screw thread! Look at your car jack

Howard

Typos galore!

Edited By Howard Lewis on 14/01/2022 08:47:31

Subject to the mangling it looks like a rounded one that lifts out

You hit one end with a non mangling item and the other end lifts up

Better still, following Ian Parkin's method is to grip the key as close to the shaft as you can get with a pair of nail pincers and lever it out from one end. They have the advantage of parallel gripping and will not damage the key in the process of extraction.

Regards

Brian

All the above said, if some annoying tech has assembled the shaft with bearing fit you may need to apply a fair bit of heat to remove the key or bearing inner.

I’d grind the bearing through taking care not to cut into the shaft as soon as its through it will slip off

If the key is a Woodruff type, as Ady1 says, tapping on one end with a soft drift should tip it it up to the point where a better grip can be obtained to pull it out.

The problem with taking an angle grinder to the inner race is going to be avoiding damage to the spacer. So a very long angular cut will be needed.

The heat from grinding, before going right through, may be enough to expand it and help to prise it loose.

Howard

This was the key fitted in the new three phase motor for the Tom Senior light vertical. The pulley had to be bored to a larger size and there was not enough wall thickness to add a keyway. So I removed the new key from the motor shaft and milled it down flush and put 2 locking grubscrews in the pulley, adding the location bores in the key for good measure. The little screwhole is a 6BA to jack out the key if required. Any size of screw would be able to jack out the key, and do not worry if the end of the drill just touches the spindle. The jacking screw would have to have the first couple of threads removed, as the tap will not reach the bottom of the key, having a plug (bottoming) tap would come in handy here. Your key will be a straight one as the spindle is hollow.

Try Rob's milling vise method first.

Edited By old mart on 14/01/2022 12:28:20

Edited By old mart on 14/01/2022 12:31:22

i use a 1 mm cutting disc. stop just short of the shart then put a blunted chisel in the slot then give it a tap with hammer to crack the bearing race it will then fall off

I don't think the OP is worried about getting the bearing off, its the key, which will have to be removed before a new bearing is fitted.

Many thanks to all who offered advice. The answer is … none of the above.

The key was 5mm wide and deep and very soft, it was no longer required because I was replacing the geared drive. Side cutters give an incredible grip - what a good tip - but I still couldn’t budge it. Drilling and tapping holes didn’t work for me either - the 6BA jacking screws just sheared. I tried M4 and realised that if I drilled just shy of the 5mm about 5mm in from the ends of the key, I could knock the small end off with a chisel, when I did that, I could whack it out without damaging the spindle. After that I could easily knock down and remove the inner ball race and the spacer (which is metal)

I should say that I did not “destroy” the bearing, is just fell apart when I gently used a screwed rod to wind the spindle out of the casting, it must have been very worn - hence new angular contacts.

Thanks again for all the help.

Not the first bearing, by any means to disintegrate when the machine is stripped or removal.

Modern packaged hub bearings for cars seem to be designed to do just that. But since the task is to replace them anyway, as long a the remains can be removed, it does not matter. Sometimes the remains can be lightly ground and used as a dolly for fitting the new bearing.

The main thing is that you succeeded without damage to anything else, so that the upgrade can proceed without need for extra repair / replacement.

Howard