Best method of boring a bearing housing

I have ordered some 15x35x11.8 taper roller bearings to make one of these things...

based around a length of 45mm square bar but I have realized that, while I know how to cut the bearing housings on the boring bar holder, I will need to cut four housings in the ends of a 200mm 45mm square bar on my old Myford ML7. I'm not bothering with the intermediate holes.

What's the best way of doing this?

I currently don't have a boring head - do I need one or is there a cheap and cheerful way of managing without?

Any guidance gratefully received

Many thanks

Jon

The Cheapest way would be to mount the job on the cross slide at centre height, centre drill and drill progressively larger until the correct size drill goes throughout the bar. Move the bar along using the cross slide hand wheel divisions to give you the correct centre distance then start again with the above method. Repeat for however many holes you need.

Hi Bob,

Thanks for the suggestion.

I think I should have been a bit more specific. I think that I need the bearings to sit firmly in the bar with the ends bored like this...

I think that to maintain alignment, the 35mm holes need to be a snug fit for the bearing shells when they're bored and when the bearings are installed they sit slightly proud of the bar.

Unless anyone has a better idea?

Many thanks

Jon

Edited By Jon Gibbs on 18/05/2015 16:53:55

Packed up and clamped the sq bar crossslide and use a between ctrs boring bar, once you have it set right for the bearing just swap it end for end. It would be easier if the 25mm hole could be larger and I can't see why not as you just need a shallow register for the bearing outer race.

Edited By JasonB on 18/05/2015 16:59:46

Thanks very much Jason.

The 25mm was just a rough guess to highlight the need for the shells to rest on something and could obviously be quite a bit bigger as you say.

Many thanks again

Jon

Hi Jon,

I got the wrtong end of the stick with this one, I thought they were just through holes. Jasons suggestion is a good one, it is a bit of a pain setting the cutter to the right diameter but once set, as Jason says it could be turned around and the other end set to machine a slightly smaller bore for the bearing to register against.

Bob

My thought was to bore them all out to say 32mm all the way through, then set up again and adjust the bar to cut the 35mm hole for one bearing, turn end for end and go straight in with a single 1.5mm cut for the opposite side.

Then set the next bar end up and repeat.

Or if you don't feel you can reset the parts true make a second bar, one for teh through hole and another for the bearing. They are easy enough to make, the one in the photo was just an old 3/4" bolt

Hi Jason,
I think the lathe would have to be run in reverse to do the second side. I thought I would mention this just in case Jon's lathe does not have reverse.

Les.

Hi Jason,

Thanks very much. When you say " turn end for end and go straight in with a single 1.5mm cut for the opposite side" am I turning the boring bar end for end?

Les, my lathe does have reverse thanks.

Jon

Make them out of round bar stock on the lathe then weld then onto a 45mm square box section.

Simples.

Yes turn the boring bar end for end, that way the two bearing holes will be exactly in line.

Through bore the bearing fitting diameter and fit a spacer with a bit of epoxy to keep them apart.

Frank

Welding a round housing to a square bar is ok for a garden trolley,a round housing sufficiently accurate to accept bearings will distort and or shrink when welded ,as suggested above bore through and fit a central spacer,I would secure it with high strength loctite and a pin for added security.Boring housings from each side,which are inline ,takes a lot of skill to get right.

Thanks very much to everyone - I really appreciate all of the replies.

I just realized that although my lathe will go in reverse the catch-plate for the boring bar will be wanting to unscrew from the nose in reverse which makes Frank and Nigel's suggestions perhaps the best for me.

At least I feel that it's within my limited capabilities - My welding is certainly not up to John S's suggestion, although I can see that it would work.

Is there a way to get around the catch-plate unscrewing?

The chucks on my woodlathe achieve this with set-screws onto the spindle nose which is ok for wood tolerances but clearly a no-no.

Jon

Without wanting to do any mods to your lathe spindle nose then you will need to do some thinking away from the box.

There is always the easy option of using a driving centre but they are quite rare to find, not seen one being sold for a while now. You may want to consider making one.

I would make a soft morse taper centre for your spindle taper with a parallel portion sufficient to grub screw a collared catch plate onto ( or Welded ).

Before turning the tapers on the centre, drill and tap the morse end for a suitable drawbar and make one to suit.

A lot of work for a per chance occasion of use but it's an option.

I have a couple of combined self contained catch plates with parallel shanks that can be held in a collet, but you do need a collet set up for your lathe for to use these.

Edited By Malc Broadbent on 19/05/2015 09:16:20

Probably a bodge, but what I'd do : Bore through at 35, make up a press-fit spacer 35 OD, 25 ID, 23 long, press in (and secure with a grubscrew from the side if necessary).

eta: Sorry Frank, only just noticed you'd already suggested this.

Edited By Bob Unitt 1 on 19/05/2015 09:36:09

Hi Malc,

Brilliant! - thank you. I think a few quid on an M10 threaded blank end arbor machined to a 60 degree point would be just as good - perhaps even with a short length of rod poking out to catch the drive dog?

I have an ER32 collet chuck but it also screws onto the spindle nose 

Bob, no problem. 

Thanks again folks

Jon

Edited By Jon Gibbs on 19/05/2015 09:57:52

Or turn a point on a bit of scrap bar held in the 3-jaw, you can use one of the jaws to engage with a suitably shaped drive dog.

Neil

And watch as the chuck unscrews as I would think it fits in the same way as the catch plate and ER32 chuck!

Though thinking about it as the pressure from the ctr will be against the chuck jaws it would not really be able to unscrew without appling a lot more pressure and the bar won't compress

Edited By JasonB on 19/05/2015 10:47:28

Thanks Jason. I went through the same thought process when I read Neil's suggestion

I suppose that also means that the collet chuck might also be ok in practice

...especially if the bar in both cases has a shoulder that means it can't be forced back into the jaws.

Jon