How Tight Should Keyways Be In New Axles?

[Dan B]

I am on my second pair of new axles. The keyways on the first pair were not machined correctly so they sent me a new pair. The keyways on these measure .245-.246”. The Ford drawing specifies .247-.248”. This doesn’t sound like much of a difference but axle keys are nominally .250”.

The keys fit in the new axle shafts very tight and need to be seated with a hammer. Is this normal? I have not actually tried to drive them home because I do not want to damage the axles in case I decide to send them back. I realize that my original Ford axles are probably worn a bit but the keys fit in them snug, not forced fit.

I am hesitant to dress down the keys because the hub is probably already worn and I do not want play there.

Any ideas?

[RajoRacer]

Search the Forum - this matter has been discussed in depth !

[Walter Higgins]

I have taken to milling the axle to my liking. If the keyway in the hub is a bit loose you can even get standard "oversized" key stock from McMaster and sweeten up the fit a little more yet. Being a light tap fit is ideal but not to the point it is necessary to pound them. That is asking for trouble further on down the road.

[Dan Hatch]

This why everyone needs a lead or Babbitt hammer. Dan

[RajoRacer]

No way you're going to beat in a key several thousands bigger than the keyway !!!

[Scott_Conger]

Walter said exactly what I'd say. This is an old story that should not still be read about and frankly for the other precision parameters and specs involved in their manufacture, the fact that a single axle remains on anyone's shelf that doesn't meet an industry spec regarding keyways, much less a FORD drawing is shameful. If this simple detail cannot be gotten right, what else is wrong and when will it show up? I am very sorry to hear you're fighting this, but if you keep this axle, Walter has the solution.

[Dan B]

Search the Forum - this matter has been discussed in depth !

I can’t find where it’s been “discussed” but I see several posts from you saying that you had to file down the key to get it to fit. This was from a couple years ago and looks like the axles haven’t changed.

[Dan B]

Here’s a pic from the first set of axles received. Both were the same. I’m this close to putting the originals back in.

[Walter Higgins]

Thanks to Scott for the kind words. Some know that I Iost more hair sorting through this recently. The nice thing about the axles you're using is that they are consistently wrong and the outer keyway seems to be the only real issue with them. In all other respects they are pretty nice. I tried a set from a different manufacturer trying to get away from this issue and they were all over the map with several dimensional issues that made them unusable. So far as I know the ones you have in-hand are the best available.

I was going to post documentation photos that I took at the time but the forum software doesn't like the dimensions and I don't have my easy resizing software since a recent hard drive crash. With four axles in-hand all the the keyways were 0.247 when checked with gauge blocks. The key stock I used was 0.251. In the end I think I left the keyway about 0.0005-under after taking an equal amount of material off of each side. That made for a nice tap fit in the axle and took care of some of the issues with the hubs I was using.

[RajoRacer]

Here's one thread - I don't know how to do multiples ! I'll be baaaaccck !

http://www.mtfca.com/discus/messages/70 ... 1502761591

[RajoRacer]

And another - viewtopic.php?f=2&t=1692&p=15554&hilit= ... way#p15554

[Dan B]

Thanks Steve! I’m usually really good at searching for old forum posts but this is the first I’ve seen these.

I took a fresh look at the situation this morning. After some gentle dressing of both the keyway and key edges, I was able to achieve a fit that seems to be satisfactory. The keyways themselves still seem to be undersized. I am not a machinist nor do I pretend to be, but it seems that even someone untrained like me should be able to take a reasonably good pair of dial calipers down that slot and measure the same width throughout. That’s not the case here. I don’t know how this is possible on something that you would think is precision machined. The keys themselves also leave something to be desired. There is some variation in the width along the length of the key and the end where it is cut was very slightly mushroomed.

In any case, I think I got them where they need to be. On two parts that should be made to industry specs on precision equipment, I would not expect the extra effort but what do I know?

[RajoRacer]

I ended up ordering undersize 1/4" key stock from McMaster-Carr and dressed it down - nice snug tap-in fit.

[Mark Gregush]

You don't want to dress the whole sides of the keys, just the area that fits in the groove. The part that fits in the hub has to stay the same. I wonder if these are made to fit the key stock that's available? Some of the keys being sold are under size by one of the major parts seller suppliers.

[Walter Higgins]

I am not a machinist nor do I pretend to be, but it seems that even someone untrained like me should be able to take a reasonably good pair of dial calipers down that slot and measure the same width throughout. That’s not the case here. I don’t know how this is possible on something that you would think is precision machined. The keys themselves also leave something to be desired. There is some variation in the width along the length of the key and the end where it is cut was very slightly mushroomed.

In any case, I think I got them where they need to be. On two parts that should be made to industry specs on precision equipment, I would not expect the extra effort but what do I know?

That keyway is shallow and not easy to measure with calipers which is why I used gauge blocks. I didn't find any of the four that I did to have variation along their width or any other out-of-squareness. It's a problem and it's irritating that a lot of these things we buy can't be used right out of the box, but the trade-off is this is one of the few cars where you can get anything this cheap. Other cars where you have to have this stuff custom made one-off, you can get it done by the right shop and it will be perfect when it come back, but it won't be just $100 bucks, either.

[Dan B]

You’re right about that Walter and the parts supplier I bought them from was easy to deal with as always and made things right. I’m sure you can guess who it is.

[Walter Higgins]

Yep, we are fortunate in that respect that we can usually get satisfaction without having to lodge a complaint that disappears into cyberspace through some automated program.

That said, cutting something at 0.250 doesn't cost any more than 0.247. My suspicion is there were a lot of these made this way in a single run and the inventory is still working down or the manufacturer is just plain bullheaded. What would be ideal with parts like this is if the manufacturer of the axles also supplied the keys so everything worked together and I know I would be willing to pay for more for that.

[Willie R]

Just checked my new axles and new keys. No go...250.00 with shipping and still don't have a good set up.