[Runner4404spd]

has anyone looked into, boring out the bearing seats on the 9x20 spindle. ideally, i need a lathe that has a 1.5" bore. basically double what hte stock 9x20 has. i don't mind machining a new spindle but i was wondering if the original head casting has enough material to bore out the bearing seats for larger bearings.

[acondit]

Runner4404spd,

I looked at that option earlier and my recollection is that there isn't enough beef in the existing casting to bore out the bearing bosses an additional 0.75 inch radius. Additionally the larger bore bearings actually require more than just an additional 0.75 inch radius.

I was toying with the idea of doing a new headstock casting. I am afraid the work and cost are more than any reasonable person would be willing to bear. I would guess that the pattern for a new headstock would be about $1500-3000 worth of time. And the castings would probably cost $100-200 each, if done in the US. Then one would still have to do the machining.

I ended up buying a HF 12x36 (HF33274).

All that said, I am looking at having to downsize my shop, which may mean selling my 12x36. I would still like to have the larger spindle, so once I get some of my other projects done I may explore this some more.

Alan

[Geof]

How about this approach, make outrigger bearings housings for the existing headstock?

What I mean is remove the existing bearings and make a bearing housing that has a large diameter section bored to take your new larger spindle bearings and then a smaller diameter that is a very mild press fit in the original bearing hole in the headstock. This will move your chuck out by whatever the width the outrigger housing is, probably 3/4" or so. It will also move the drive gear on the back end of the spindle out so some work will have to be done adapting the gear train.

I think advantagea to this approach are that you could make all the parts on the machine you are modifying, you would not need to machine the headstock and if things did not work as planned you can go back to the original condition.

[NC Cams]

An alternative would be to fabricate via welding a housing from plate stock in concert with either billet and/or tubing for the bearings to support the spindle.

Once you do the fabrication/welding, double draw (anneal then normalize) the welement BEFORE you machine it. Once normalized, the thing should be pretty stable/tough and durable.

We have lathe bed that was made up of a combination of weldments in concert with hardened/ground iron castings bolted to it. Naturally, a casting would be "easier" to create for a production part. HOwever, a well done billet and/or weldment should readily suffice for hobby and/or even production shop needs.

[Runner4404spd]

Nc Cams, thanks for the great suggestion. the 9x20 has a 62mm bore for the bearing races. with them removed there is a small lip for a swaft shield to sit on leaving about 2.25 of open space. this is great news. adding a bearing holder on either side of the head will allow me to put a spindle with a 2" bore through there. i will keep everyone posted as the project progresses.

[Coops]

how did you make out, I am interested to know if I can open the bore frm .75 to 1" + thx.