Atlas 10F V42

[timmeh]

On Saturday, finally got around to putting the Atlas back on it's screw jacks after rearranging the workshop a while back.
On Sunday, power was out for a while, musta got bored, i dunno....



Now I'll have to clean up reassemble. While its apart, I'll make some changes, do a bit of fixxy and get some better photo's of some previous repairs/mods.

Bit of history as I know it, purchased about 2011 from an elderly gent in Mandurah, W.A.
Had suffered a major crash somewhere along the line, the change gear banjo has been repaired, the fwd/rev gearbox had quite a lot of bentism and the toolpost is now only a plinth with a 4way turret.
So far, the motor has been replaced and a fwd/rev switch installed, new spindle made, fwd/rev gearbox straightened and some improvements applied, compound adapted from another lathe, along with quite a few other repairs and modifications.
I'll try to remember them all.


Already found something a little odd, Bolts/Holes for attaching feet to bed appeared to be 1/4"U.N. to me(Course for headstock end and fine for tailstock end).
Closer inspection of the bolts says otherwise, with the course bolts measuring 6.75mm O.D. and the fine bolts at 6.7mm O.D.(1/4" is 6.35mm). The T.P.I. for the course bolts seems to match NC 20 but the T.P.I. for the fine bolts is nowhere near NF 28, maybe 26 T.P.I. not sure yet.
Are these a special made by Atlas?

 

[wa5cab]

Tim,

I have no idea why anyone would have used coarse thread bolts on the headstock end and fine thread on the tailstock end. Unless it was wartime shortages. But my best guess is that the coarse threads are 1/4" BW or BSW (20 TPI) and the fine are 1/4" BSF (26 TPI). Why the diameter is a few thou over 0.250 I don't know. Can't be something like BA as 0BA diameter is 6MM and there is no fine and coarse. If you still have the bolts, check the width across the flats. BW bolt heads are larger than BSF which are larger than both UNF and UNC (which are the same). 1/4" BW hex head is 0.525" max. My 1943 Machinery's Handbook doesn't seem to list dimensions for BSF heads. There was once an A.S.M.E screw thread series with the #16 having an OD of 0.268. But the pitches listed are 22, 20, 18 and 16.

 

[timmeh]

O.K. Have done a bit more ground work, definitely "off the shelf" or mass produced bolts. Confirmed that coarse thread is 20tpi and fine thread is 26tpi. Diameters are, as near as i can determine with a .05mm dial vernier, course 6.77mm(somewhere in the vicinity of slightly on the high side of midway between .266" and .267") and fine 6.71mm(a bees butt hair over .264")
The hex headed bolt is 7/16 AF. I have come across a few oddball threads/diameters/pitches on fasteners and various components. I suspect you may be on the right track with wartime shortages, short on standard stocks and all that's available is specials(fasteners) for military purposes perhaps?
It's possible that these sizes won't show up on a standard thread chart.

Bit of a bummer, if one has a problem the next size up is 5/16, not a lot of meat left there after that.

 

[wa5cab]

7/16" across the flats of the hex head and 26 tpi and nominal 1/4"
diameter doesn't match anything that I can find. All that I can suggest is that if you have all of the original bolts, use them. If the problem is that you don't have enough of them, you have four choices. Locate and purchase 1/4" hex head BSF for the fine thread and 1/4"-20 UNC hex head for the coarse. Make the missing ones. Drill out and tap for a larger available size. Drill out and tap for a larger helicoil for some nominal 1/4" or 6mm diameter size.

 

[timmeh]

I don't think 1/4" bolts would even take any tension in these holes, the coarse ones might tear the crests off. .014" to .016" is a bit much, no matter which way you might going on a fastener that size, i.e. clearance or interference.
These fasteners are definitely mass produced and way to big for 1/4" threaded hole.

One of the fine bolts here must not have been tapped right through(centre, at the end of the bed), has damaged the end of the bolt. A little troublesome coming out, more so going back in. It's in for now, but don't know how long for as I had run a 1/4" fine tap through the hole to clean up(OOPS) before checking sizes properly.
Plenty of time yet to decide... fix one/fix all. Tis but a hiccup.

Still, there is a lot to ponder. Why fine and coarse, why that way around(I would have thought vibration would have been more of an issue at the h/stock end)?

Original plan was to fit some riser blocks between feet and chip tray/legs to give a little more clearance under the bed. Maybe modify the chip tray a bit to install a drain and catch can for oil and such.

 

[wa5cab]

I've never actually had my hands on an Atlas 10". only on several of the 1/2" way 12". What is the minimum thickness of the material that the tapped holes go up through? And are the holes approximately centered in it? The smallest bolt whose tap drill would probably clean up the 20 and 26 TPI threads would be 5/16"-24 UNF or M8-1.0.

Are the rest of the threaded fasteners on the machine all either UNC or UNF?

One solution if the web is too thin for the size of tap drill that would clean up the holes would be to step over about 1/2 inch and drill entirely new holes.

 

[timmeh]

Are the rest of the threaded fasteners on the machine all either UNC or UNF?

I believe so.

One solution if the web is too thin for the size of tap drill that would clean up the holes would be to step over about 1/2 inch and drill entirely new holes.

That may be a little difficult. The pads at each hole and either side of the outer end hole are a bit over 1/2" I guess. Repositioning might be asking for more problems. Not out of the question to upsize the holes, just doesn't leave a lot of material left at the edge of the rectangular opening on feet or bed.
I've managed to get it back together without modifying, will have to keep an eye on the damaged thread/hole. Thickness of material/length of thread around 1/2".

 

[wa5cab]

And if those are two of the holes in the bottom of the bed visible in the lower right corner of the photo, they don't appear to be centered in the sides of the bed. Unless the top of the bed is wider to the outside than the thickness of the side wall below it.

 

[timmeh]

The two holes at the 'inner' end of the feet would not have a problem, there is plenty of room. The outer holes break through right next to the vertical section of the bed casting. The hole at the tailstock end is the only one that's a bit iffy.
The fine thread bolts are considerably longer than the others and longer than the thickness of the material(approx. 5/8") they are fitted to. The bolt/hole that has the issue hasn't been tapped far enough and the thread on the bolt is damaged.
Upsizing is possible, but have to be careful, don't need to do it yet... thanks lucky stars...

Anyway, on with the important stuff. Bit of panelbeating on the chip tray and... Turned out great, until I tried to press the centre for a drain hole, top and bottom dies weren't quite lined up. Bit of a mess, but still usable. Not going all out for coolant, just catching and reclaiming oil.

 

[timmeh]

Almost forgot, the riser blocks are done too. Makes everything a little on the high side now so will have to make some shorter screw jacks. Much easier to clean up now.
Started off with the access holes on the inside, found that it all fits together much better with holes on the outside. Done.