Please rate these spiders (pic heavy)

[Long Tom]

I bought a 12x36" Logan lathe that came out of a gun shop that was closing up. It had some crusty old tooling; much of it of indeterminate function so far.

I'd like to do some chambering in this lathe in the fullness of time if it proves capable of that.

So, I was very pleased to find spiders for both ends of the spindle in the box of goodies! And here they are. I mounted them up loosely and put a (Kimber) barrel I have on hand in them just for show and snapped a few pics. I'm very interested in your opinion on the usability of these pieces. I have NO emotional attachment here; if you think one or both are crap, please say so! I was planning on making these anyway if necessary. I thank you.

The one on the chuck end of the spindle is steel. I'd like to replace the screws with brass-tipped. It threads onto the spindle nicely.






The spider for the outboard end is aluminum. It's a nice press fit and someone tried hard:





Here's the spiders in the lathe with the barrel in 'em.





Cc: The PM forum

[S.Turf]

Integrating brass or aluminum tips for the adjusting screws is without a doubt a move in the right direction. As far as the square looking fixture goes, my concern would be possible vibrations introduced just by the shape of it. It's possible I guess that it might be balanced but when spinning the barrel @ 1000+ rpm's or so for crowning why take a chance. Keeping vibrations and harmonics out of the equation is always best for a good surface finish.

I guess the first thing I would do is mount the fixtures and see what kind of run out they might have. You mentioned that you were thinking of making your own so that might be a good project plus help you learn the tolerances of your machine, too.

[Harold_V]

Integrating brass or aluminum tips for the adjusting screws is without a doubt a move in the right direction. As far as the square looking fixture goes, my concern would be possible vibrations introduced just by the shape of it. It's possible I guess that it might be balanced but when spinning the barrel @ 1000+ rpm's or so for crowning why take a chance. Keeping vibrations and harmonics out of the equation is always best for a good surface finish.

While I share your concern, that the item is not round makes no difference so long as it has been machined symmetrically around the centerline.

Harold

[Long Tom]

Howdy. Since they are essentially little 4-jaws, and since barrel bored are often not concentri to the barrel anyway, I don't think the TIR of these parts matters one bit (within reason). I think.

My concern was that the outboard spider is very light and maybe somehow that'd be an issue.

I haven't gotten serious about measuring TIR on the lathe itself yet. I measured it at the spindle with the chuck off a few weeks ago and got a few tenth's, but that was just a quick and dirty measurement.

So... do these spiders look about like you'd expect for this kind of thing? The outboard one has to be small due to how this Logan does the back gears.

[S.Turf]

My concern was that the outboard spider is very light and maybe somehow that'd be an issue.

The weight is a non-issue. I have one on the outboard of my Nardini that might even weigh less than yours. It's only purpose is to radially adjust the OD of the barrel to get a couple inches of the bore running true on the other end. I personally use a long stem indicator directly in the bore, in multiple spots, to establish that.

[Long Tom]

S. Turf, that's my plan too. I see that PT&G sells such rods.

Got a 300 WM that is accurate, but has a disaster of a chamber. I may rechamber that as my first project. Or rebarrel it. Also have a .223 that I want to rebarrel to a faster twist.

Ah, the joys of being a rifle loon!

[S.Turf]

S. Turf, that's my plan too. I see that PT&G sells such rods.

I don't use the "range rods" that Dave @ PTG sells. I take my readings directly off the indicator stylus inserted in the bore.

[Long Tom]

With a co-axial indicator?

[S.Turf]

I use an interapid 312B-15 indicator.