Oversize Hole!

[Smifffy]

I'm slowly and steadily working away at my driving/coupled wheels. So far I have faced off the back of each and I am now drilling and boring the axle holes, by clamping the back of the wheel against the faceplate (which has been skimmed). 5 out of six done so far.

I'm boring the axle hole to be a push fit on the shouldered axles and will then cut a recess (cotton reel style) on the axles for the loctite (as per advice on here).

However, I've managed to bore one of my holes 0.05mm oversize which is making it a sloppy fit. No real problem as I just machine an axle to the same size - in fact, I was going to bore the last wheel oversize too, so that I have a pair and can then have one oversize axle.

My issue arises with the rest of the machining operations on the wheel. My intent is to face the fronts and cut the flanges and treads with the wheel mounted on a home made face plate with a mandrel turned to the bore size. I will then complete each operation on the set of wheels - i.e. turn each wheel's flange, before moving on to each wheel's tread, etc. This way, I can ensure everything is the same size.

But now I have at least one oversize wheel axle bore, I'm not going to be able to do this as I will need two different sized mandrels.

I hope all of this makes sense ?

If so, any suggestions on how I go forwards ?

Cheers.

Mark

[cotswold]

May 1, 2008 6:58:24 GMT Smifffy said:

....
But now I have at least one oversize wheel axle bore, I'm not going to be able to do this as I will need two different sized mandrels.

One mandrel - two sizes? Start with a mandrel to fit the bigger hole then skim it down (without removing from the face-plate) for the smaller holes?

[Tel]

Make the mandrel to fit the big 'oles, do them and then skim it down to fit the others - easy peasy.

[dickdastardly40]

If you would prefer all the same size, bore the hole in the oversize one out and fit a sleeve with the bore on size.

[Smifffy]

I thought about doing the "big hole" one first and then turning the mandrel down accordingly. But i was hoping to be able to, say, take a final cut on the tread on one wheel, swap it fo the next wheel, and do the final cut with everything as was, etc. till alll wheels treads were cut. That way I would be certain that all diameters will be exactly the same.

Dickdastardly, can you expand on your suggestion. I guess it's simply a case of bore the hole out to a suitable size then fit a sleeve (Mild Steel ?) and re bore accordingly ? The axle bore is 17.44mm - how big should I make the spindle ? Again, do I just need to loctite it in ?

As always, may thanks in advance.

Mark

[dickdastardly40]

I think the size (wall thickness) of any sleeve you could fit will depend on how much 'meat' you have between the size you have to bore the wheel to, to fit it and the spokes.

Say your spokes start at a diameter of 30mm this will give 6.28mm 'meat' to work with. If you made the OD of the sleeve 20mm, you'd have 5mm left before the spokes started and a wall thickness of 1.28mm.

If your spokes start at a smaller diameter you'd have less to work with and you'd have to decide the best size against strength and utility.

It may be this method is not the best for this application but I've got around oversize holes by fitting sleeves or bushes before.

You could loctite the sleeve in place, hold it mechanically by drilling and tapping the join between the two and fitting a grubscrew, shrinking it it or soldering. Lots of options.

Al

[chris vine]

Hi Mark,

It is well worth using the mandrel to allow you to swap the wheels often so that you can do just one operation at at time on each wheel.

My mandrel which I use for this had a nose diameter of .5" but I fit little sleeves onto it to fit the job in hand. In your case you could just make two sleeves, a good fit on the mandrel and one to fit the correct wheel hole and one to fit the oversize one.

The result will be so invisible that if you had not mentioned it here, nobody would ever know!!

Chris.

[dickdastardly40]

I like that idea for the sleeves on the mandrel, however to work in this instance if Mark leaves the oversize wheel as is, the sleeve for this job will have a wall thickness of .025mm which might be a bit difficult to make.

Al

[Smifffy]

...ahh! Now Chris, that's a cracking idea and it's what I will do :-)

Thanks again guys, as always, you've been a great help.

Mark

[Smifffy]

I think Chris meant to make the Mandrel smaller than required and then make two bushes - one for correct size and one for oversize.

It would be a challenge to make a 0.025 thick bush :-)

[brozier]

Hi,

The other option is to bore out the other 5 to match and just have the one madrel.

Not that I've ever made that mistake oh no! ;-)

Cheers
Bryan

[Smifffy]

...I thought about that one too, but I don't think I will be able/capable of getting the wheels correctly centered on the faceplate again. I'm only playing with 0.02mm (less than a thou) on the radius.

[dickdastardly40]

May 1, 2008 9:11:37 GMT Smifffy said:

I think Chris meant to make the Mandrel smaller than required and then make two bushes - one for correct size and one for oversize.

Re-reading Chris' post it makes perfect sense, my bad!

[weldsol]

As you are using Loctite then may consider knurling the one axle shaft this should bring back your fit.

[Smifffy]

Weldsol, it's not the fit on the axle that is my concern. It's the ability to finish off all the wheels on a mandrel in the lathe.

[freddo]

This may seem silly, but why not overbore all the other wheels to match?

[weldsol]

May 1, 2008 13:55:41 GMT Smifffy said:

Weldsol, it's not the fit on the axle that is my concern. It's the ability to finish off all the wheels on a mandrel in the lathe.

OK sorry after re-reading (it's an age thing )your post go for the smaller mandrel with sleeves that seems the most logical

[Smifffy]

Hehe Weldsol, it's meant to be the young that are impetuous !

I do appreciate your suggestions though :-)

This site and the input from you guys really is invaluable - I would not have made it this far without the great input from all here.

[kingsteam9]

Just to chuck in my five penn'orth. I I've got to ask why go to all the trouble of sleeving the oversize bore? Just start with the oversize mandrel and then turn down to fit the smaller sizes as suggested earlier. Then, and this is the important bit - leave final skimming of all wheels until after you've loctited them onto their respective axles. Set up each axle between centres (I'm assuming you're putting centres in each end), and then if you move the saddle to the tailstock end you can take a final skim cut to bring them all to the same finished diameter in turn at the same crosslide setting. You'll need to swap the axles end for end between centres but that's easy enough. That'll also take care of any slight runout (but you won't have any will you :-) !!)

cheers
Robin

[Smifffy]

...ahh, my axles are 3/4" silver steel. I have put centres in them, but I'm not 100% certain that they will be dead on. Having typed that, it's just made me think - will they be 100% centered by definition ? I turned the shoulders after having set the axles up in the 4 jaw.

If I had turned the axle from stock between centres then I would be comfortable with this approach.

However, I do like the sleeve bush approach, so that's what I'm going to go for - unless you guys convince me otherwise :-)