[How do I?] Mill The Round Slot For My Replacement Cross-feed Slide?

Here's how I cut the Tee slot on my cross slide I made for my 13" Sheldon lathe.

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This is really great. Went to bed still stumped, and the next morning I have my answer!

Thank you hman and brino! That hole in the bottom is how you insert the captured square-head bolts that attach the compound. For some silly reason it never occurred to to me to use the same hole to insert a t-slot cutter! Like most puzzles it's kinda obvious once you see it, but for some reason I was blind to it before.

It may be a little finicky setting up (a "captive" cutting tool is definitely a first for me) but I'm sure it will work just fine — in fact, I just checked and I don't even have to buy a new cutter. The bolt heads fit just fine in the straight t-slots I already milled.

4gsr: Thanks for the pics. You have your access hole continuing all the way through the part. I don't want to do that on mine, because the heads of the bolts that attach the compound bear on that upper lip. With a hole continuing through the top lip, one of the bolts wouldn't have anything to bear on (the two bolts are diametrically opposite).

You guys just made my day. I should have the whole thing complete in another day or two. I'll post pics of the entire process.

Thank you!
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Rex
 
Rex Walters said:
....I don't want to do that on mine, because the heads of the bolts that attach the compound bear on that upper lip. With a hole continuing through the top lip, one of the bolts wouldn't have anything to bear on (the two bolts are diametrically opposite)......Rex
Click to expand...

See my Tee bolts I made. The finicky one's that were in there originally is what caused mine to fail and have to rebuild. I made them wide enough to straddle the hole created by the Tee slot cutter. The shank on my cutter is too big to pass through a hole. It's almost as big in diameter as the cutting diameter is.

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Wow. Radius-ed t-bolts. Very neat.

My bolts, compound, and cross slide are all in good shape. I just wanted a longer cross slide with t-slots to mount things. I think I'll just use the existing square-head bolts as they are still in quite good shape, and fit nicely into the slots my t-slot cutter makes (fewer parts to make). I may actually make the top slot a little narrower to give the bolt heads as much bearing surface as possible.

Thanks Tom, for the link to the relevant forum. Not sure how I missed that.

Very glad I asked. Lots of good info.
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Rex
 
Rex,

If you wish, I can move this thread to the Logan forum. I had one request from over there to do so.

One thing still puzzles me, though. Your first drawing showed a cross slide for a compound. But your first photo showed what I would consider a typical boring table or milling table for a lathe. One of your posts made me think that you were trying to figure out how to mill one end of the boring table to mount a compound. If so, why would you want to do that?
 
wa5cab said:
One of your posts made me think that you were trying to figure out how to mill one end of the boring table to mount a compound. If so, why would you want to do that?
Click to expand...

[Hi, Robert. You can move this thread if it seems warranted, but I'll also create a separate thread in the Sheldon/Logan/Rockwell forum with pictures from the build as I make more progress.]

Rather than having a separate cross slide for line boring or whatever, I wanted to replace the factory cross slide. As one example, it would be convenient to have a cut-off tool in a rear mounted toolpost while still leaving a turning tool in the toolpost on the compound slide. It's also nice to have a "deck" for something as mundane as attaching an indicator mag base. The rear mounted screw cover that attaches to the factory cross-slide on my old Logan is (annoyingly) both curved and made of something non-ferrous (maybe zinc?).

I think this is the most common way to use that casting from Metal Lathe Accessories. The drawings that Andy sent me with the casting show expressly how to attach a South Bend compound (and Paula in the Practical Machinist Forum did the same). I'm just trying to modify the design to work with a Logan rather than a South Bend lathe.

I've been away from the shop for several days, but after mulling it over in my head I'm pretty sure this will work fine. My plan is to leave the top completely flat, except for a pressed-in 1/2" locating pin for the compound, and the milled circular and straight slots. The original slide has a raised circular area for the compound to ride upon, as shown in my first post, but I can't imagine that being a problem. I haven't measured yet, but I think I can move the pin (and compound) back far enough to allow for the other work-holding attachment points (tapped holes) in Andy's design, but this is about the only thing I'm unsure of at this point.

I also lost about 1/8" of travel on my cross slide when I made larger replacement dials. Rather than making a longer screw or somehow moving the dial back, I'll likely move the compound further back on the casting to reclaim the lost travel. This will mean the round part of the compound won't be visually centered with the round part of the casting, but the compound base fits within the straight sides, so I'll probably just mill off the "ears" (the round part of the casting).

My hope is that most of the time I'll just leave my compound attached, but still have enough room in the back for rigid attachment of tooling or workpieces. When necessary, I can remove the compound to give me more room. If the locating pin ever gets in the way, I can make a flat sub-base out of cold-rolled with a hole for the pin to give me a continuous flat surface

All of this will be clearer with drawings and photos which I will include in the new thread on the other forum. Here's hoping it doesn't end in tears.

73
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Rex
 
Easy peasy. See that big hole in the bottom? Put your cutter through that, from the bottom, shank first. Center and clamp on the RT, then grab the shank in the collet and go from there. When done. Release the shank, remove the workpiece, then remove the cutter out the big hole. It's a little counterintuitive, but once you see it, the penny drops.
 
Yup. The penny dropped for me earlier (see comment #12). Thanks!

Funny how I was blind to it before, since that's exactly how the bolts that hold the compound are inserted.
 
ogberi said:
Easy peasy. See that big hole in the bottom? Put your cutter through that, from the bottom, shank first. Center and clamp on the RT, then grab the shank in the collet and go from there. When done. Release the shank, remove the workpiece, then remove the cutter out the big hole. It's a little counterintuitive, but once you see it, the penny drops.
Click to expand...

That works great if you have a cutter that has a shank smaller than the smaller slot size is. True tee slot milling cutters, such as for 3/8 or 1/2 bolt have shanks diameters of 5/8 and 3/4, that don't work too well in this application. Using a woodruff cutter, which are 1/2" shank, may work, but they are not designed with side cutting clearance. Not having this side clearance will get you an hung up stuck cutter, which will either break off causing grief. Worst yet, destroy what you are cutting on.
 
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