Lathe Chuck Wrench and Toolholder Threads

It only is that way, because it is easier to make. You need a 0.35" square key.

Nick

According to Martin Riggins :

Don't sweat it. Make the square to match that smaller dimension. The pinion square holes are made by drilling to a little over the across-flats size, and then pushing a single-toothed broach into the hole to trim out the corners to near square. That is the only place where the wrench actually contacts when it is being turned, anyway.

If you get a square multi-tooth broach (for broaching through holes), there is a secondary size marked on them for the pilot diameter, so it produces similar shaped holes to what you have -- though those were obviously *not* done with a through-hole (multi-tooth) broach, as you can see the metal removed by the broach folded into the center of the hole at the bottom -- but the principle remains.

You don't mention which size toolholders these are -- but then I don't remember the thread pitch on the holders which I have, so that does not really matter to me.

My Series-200 (BXA) sized Phase-II toolholders had metric threads. I actually re-threaded them with an inch tap so the same screws and T-handled Allen wrenches would work as for the genuine Aloris holders. That was a bit of a struggle as the holders seem to be hardened (or at least case hardened), and I think that my nice gun tap is rather dull by now. :-)

Enjoy, DoN.

Thanks. It seems I'll be getting a 3/8" and filing it to size. Not a big deal but I wanted to make sure Burnerd didn't use some funky wrench before I wrecked one messing with it.

Martin

Thanks, that's just what I'll do. But I'll have to start with a

I wondered what that was at the bottom of the hole.

Just so you know (because I'm sure it's keeping you up at night ) they are BXAs.

You know, I wouldn't have thought that would work well considering the sizes but that just goes to show me that I need to stop theorizing and get out there and do it.

It wouldn't have been cheaper (but I'll grant not as convenient or sano) to get a 5mm T-handle for the Phase IIs?

Thanks for your explanation on everything, Martin

According to Martin Riggins :

It is strange. Perhaps it is a way of making sure that you either go to them for a wrench, or you make one from scratch. :-)

Hmm ... calculating the diagonal of a .350" square, I come up with 0.495". That is pretty close to a 0.500" diagonal, and converting that back to the square gives me 0.353" I'll bet that it was originally calculated to be made from 1/2" diameter stock, even though it really is made from larger diameter stock to minimize the torsion spring when tightening or loosening the chuck.

You can see similar things in the bottom of socket wrenches, especially the cheaper ones where they don't bother to break the chips out before plating the wrench.

It results in a bit of thread error, which is why the final few turns are the hardest.

Possibly. But to be honest, I checked the toolholders rather too quickly, and figured them for inch threads until I encountered the difficulty at the bottom of the holes. By then, I had already sent off an order to MSC for a box of a hundred (or was it a gross) of the inch screws, and I was determined to make them work. It was only after I got some genuine Aloris holders that I realized the benefit of having the same wrench for them all. (And perhaps using an inch Allen wrench in a metric socket is one of the causes for the reputation of easy to break screws in these. :-)

Best of luck, DoN.

Maybe i can help with metric / SAE problem . Thread gage over 6 or more threads will clearly show even the smallest difference between SAE and Metric .

A cars spark plug is so close 14mm 1.25T 9/16-16TPI either works , but you can still tell the diff' with a thread gage over 16 threads . You can see it with a eye loupe magnifier .

BTW My old belt drive lathe had a 16T LS but a 12T clock gear , I replaced it with a 16T , then i could sync all integral threads , 1,2,3,4,5,6 etc ... It had 120T and 127T to cut metric threads Wish i was rich to afford CNC .....