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Gallery, Projects and General => Project Logs => Topic started by: vtsteam on August 15, 2013, 06:41:27 PM

Title: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 15, 2013, 06:41:27 PM
I really could use a boring table for my lathe, so today I made a pattern to cast in iron. It will replace the present cross slide for boring. Maybe also for turning if I make it similar to the Myford style slide.

The size of the pattern is 8" x 4" and is about as large as I can comfortably cast with my present crucible -- with a little leeway. I put a relief down the center so I don't have to cut as much material away for the dovetail slide. I considered also casting in some recess for T-slots but decided not to.


(http://www.vtsteam.com/BoringTable/BoringTable1.jpg)


Title: Re: A boring table for a Craftsman 12" lathe
Post by: mattinker on August 15, 2013, 07:07:40 PM
Nice to see the follow up starting!

Regards, Matthew
Title: Re: A boring table for a Craftsman 12" lathe
Post by: ieezitin on August 16, 2013, 08:57:25 AM
V----

I have the 12" craftsmen commercial 70ies model. I am curious of the fixture you have on your Atlas lathe to receive this boring plate fixture. I have wanted to add one to my own unit. Please while you document this build give some nice shots of the saddle.

My biggest gripe i have with American style lathes is they have no slotted beds on the saddle. I also have a Logan 820, it too has no standard fixture for a boring table.

This feature makes the lathe from the factory so much more versatile.

Will be keeping a keen eye on the thread.

Thank you.


Anthony....
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 16, 2013, 09:41:12 AM
Thank you Mattinker!  :beer:

Here you are ieezitin:

(http://www.vtsteam.com/BoringTable/BoringTable2.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: ieezitin on August 16, 2013, 11:44:00 AM
Thanks for the photo...... i assumed you already had some sort of fixture already.

Are you just going to dove tail the new table and lock it in place or are you going to connect it to the cross-slide screw?

Anthony..
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 16, 2013, 12:31:45 PM
Anthony, it will be dovetailed with gib, and It will be connected to the cross slide screw just like the present cross slide.
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 16, 2013, 07:53:22 PM
Not much time to work on machine stuff today as we're getting ready to take a family car trip to Tennessee to visit friends.

I did a little work on the pattern because I really want T slots but didn't like the small amount of material between the dovetail cut underneath and the slots on top which would go crosswise. I really needed a thicker pattern. But a thicker pattern would require a lot more iron and I really feel I'm close to the limit of my crucible, after gating and risering is figured in.

What to do? I finally decided reluctantly to just fasten steel strips on top of the casting for the upper surface of the tee slots, but to mill the lower slots themselves in the casting. This would give me another 1/4" of metal between the dovetail slot and the tee slots.

It also meant I could cast in the lower slot sections, and in fact that would actually lighten the casting and require less metal. So today I milled in some slots and re-finished the pattern. First coat of paint was drying when I too a picture below, just before dark.

This will mean slightly more complicated molding since there will now be a parting line along the side of the pattern. And all sections above that had to have draft in the opposite direction -- so I had to add that. And greensand cores in both drag and cope -- but nothing too deep, so I don't think it will be a problem.

Unfortunately I'll have to wait until we get back to cast the table, so it will be awhile before I can continue here. Anyway, a little progress:


(http://www.vtsteam.com/BoringTable/BoringTable3.jpg)


Title: Re: A boring table for a Craftsman 12" lathe
Post by: mattinker on August 17, 2013, 05:08:52 AM
Have a good trip!

Looking forward to the next instalment

Regards, Matthew
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 27, 2013, 03:41:06 PM
Thanks Matthew!  :beer:

Back now, ready to make chips.

This morning I started the furnace, and set up the patterns for casting -- here checking spacing, which was kind of tight in my moulding boxes.


(http://www.vtsteam.com/BoringTable/BoringTable4.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 27, 2013, 03:42:54 PM
I rammed up the drag and turned it. Here you see my runner and sprue basin, as well as the table pattern.



(http://www.vtsteam.com/BoringTable/BoringTable5.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 27, 2013, 03:46:38 PM
The pattern needed to be coped down around the edges to the parting line. The riser is now in place, as is the tapered sprue dowel on top of the pouring basin. The sprue dowel has a small prass peg to fit in the basin.

The arrangement is a bit tight -- it would be better in a bigger flask. I haven't cut gates yet. The pattern has been blacked with plumbago.


(http://www.vtsteam.com/BoringTable/BoringTable6.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 27, 2013, 03:52:53 PM
I forgot to take more photos until after the pour. Here is the shake out. Pretty good casting, except for that big hole in the middle. It had sand in it and I think a bit of the greensand core had collapsed here. It's in a spot that won't interfere with the part build, and won't be visible in the final table but its a shame to have it mar an otherwise good looking casting.

I decided not to re cast the table -- I want to move on with the steam engine project and I need this boring table to do that.

(http://www.vtsteam.com/BoringTable/BoringTable7.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 27, 2013, 03:59:58 PM
Here is the table after roughing it in for further machining -- some minor flaws came to light besides the hole. These are shallow.

This face of the table gets a steel plate over it. It will be the upper surface. The tee slots are made by slotting that plate.

The recesses under are where the grooves are here. These will first be machined out square and to proper depth. I'll first fill the flaws with metal filled epoxy before machining.

The table was machined with my homemade carbide cutter detailed elsewhere. Quite pleased with the job it does on rough castings.


(http://www.vtsteam.com/BoringTable/BoringTable8.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 28, 2013, 06:21:58 PM
Not much time today, but filled flaws, milled the slots. and cleaned up ready to add the top plate.


(http://www.vtsteam.com/BoringTable/BoringTable9.jpg)


Title: Re: A boring table for a Craftsman 12" lathe
Post by: ironman on August 28, 2013, 09:48:41 PM
 Years ago I made a table for my lathe.

 The only regret I have is that it was a total waste of time drilling and tapping all the holes, they are never in the right place when you what them. A far better idea is to drill the holes for every job.

 If you look closely at the table casting you will see slag inclusions and blowholes.

The table was used to bore a steam engine cylinder between centres.
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 28, 2013, 10:18:57 PM
Thank you for that ironman!  :beer:
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 30, 2013, 09:05:34 PM
Here I've widened the central groove with my new homemade milling cutter. I left a couple shoulders near the corners to serve as references when I cut the dovetails:


(http://www.vtsteam.com/BoringTable/BoringTable11.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 30, 2013, 09:35:22 PM
Cutting the dovetails:


(http://www.vtsteam.com/BoringTable/BoringTable12.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 30, 2013, 09:39:44 PM
First one done:

(http://www.vtsteam.com/BoringTable/BoringTable13.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on August 31, 2013, 06:51:09 PM
I finished the other dovetail cut today removed the new table from the mill vise and laid it on the lathe saddle, to pretend it was functional. I tried setting the 3/8" steel plate on top and then the cross slide.  Pushed them up to the tailstock center to see if there was enough clearance for setting the tool height, running things back and forth to see how it all went. Of course without a gib or slide screw nut it wasn't much of a try out, but it was fun imagining. I probably would have made turning noises except for the fact that my wife might have been walking by outside!  :)

So next thing to do was make a gib strip. I knew I had a 3' length of brass strip somewhere about the right size, but when I located it, it was the right thickness -- 1/8" but not wide enough -- 1/4".

Probably ideally it would be made of cast iron, but I didn't have anything suitable to saw out of old castings, and I wasn't about to fire up the furnace just to make some iron stock for a gib. So I rummaged around in a brass and bronze scrap barrel I bought  at auction a few years ago and found a 9" long strip of what looked like bronze, about 1" wide and 3/16" thick.

Kind of soft, and had what looked like pores. I don't think it's sintered bronze, but not sure just what it is. But seems like it would have good bearing qualities, and anyway it was about the right size so I cleaned it up on the mill and thinned it down to 1/8". I'll need to miter the edges and slitting saw it to size tomorrow. But that's about as far as I got before being called away to entertain in-laws.  :(


(http://www.vtsteam.com/BoringTable/gib.jpg)



(http://www.vtsteam.com/BoringTable/gib2.jpg)

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 02, 2013, 06:11:36 PM
After reading a negative comment elsewhere about bronze as a material for gibs and thinking about the difficulty of finishing the edges in this soft easily bent strip, I decided to go with a steel gib instead.

I also decided to cut it out with a slitting saw from a wider strip to cut down on bending forces and to saw both edges out while clamped in the angle vise.

Here I'm slitting the gib stock -- the upper edge has already been cut:



(http://www.vtsteam.com/BoringTable/BoringTable14.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 02, 2013, 06:13:41 PM
And trying the gib in place on the boring table:



(http://www.vtsteam.com/BoringTable/BoringTable15.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: tom osselton on September 03, 2013, 02:13:33 AM
Looking good  vsteam
Title: Re: A boring table for a Craftsman 12" lathe
Post by: RussellT on September 03, 2013, 04:29:55 AM
Well done.

I couldn't have got that far and not tried it on the lathe straight away.

Russell
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 03, 2013, 07:37:55 AM
Well done.

I couldn't have got that far and not tried it on the lathe straight away.

Russell

In-laws again! They arrived just as I was cutting the last 1/4" I kept at it, took a photo, and then ran up to the house to change and wash up!  :(

Tom, Russell, thanks!!  :beer:
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 03, 2013, 10:19:15 PM
Spent a little while today adjusting the gib -- had to mill a small amount off because even though the table fit on the saddle and the proper surfaces were in bearing, the gib was slightly cocked. It was just a couple thou too wide. So without gib screws it leaned, which allowed the table to set down on the ways and look right, but not be right.

Anyway, clocked the gib in the vise on the mill and skimmed it 5 thou. After that everything fit well and it was time to drill for gib screws.

I wanted 4 but I didn't want them to end up where they would interfere with the table surface hold down screws (yet to be added). So they needed to be located roughly where the present channels are milled into the table. This meant 3 screws or 5 screws, and thinking 3 were too widely spaced, I went with 5. Kind of overkill but, well, it certainly doesn't hurt anything.

Drilling:

(http://www.vtsteam.com/BoringTable/BoringTable16.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 03, 2013, 10:27:10 PM
I checked the original cross slide gib screws and found they were 1/4"-28 -- fine thread. Pretty tight clearance to the bottom of the slide -- not a lot of meat there -- the dovetail is 5/16. But enough I guess, so I followed suit.

Picked up the little trick from DoubleBoost's videos of running the mill with the tap in it, switching off and lowering the quill into the hole to start the thread. Worked great. Thanks John!  :thumbup:



(http://www.vtsteam.com/BoringTable/BoringTable17.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 03, 2013, 10:34:48 PM
And finally today, added screws, set the table on the apron, tightened for light contact, and proceeded to slide, then yank at the table. Sliding went smoothly, no movement when I tried to force it to the side, not a click. Nice solid fit.

The screws are a little short for adding lock nuts and taking up wear in the future, so I'll have to head back to town tomorrow to pick up longer, ones. But all in all, well pleased today.


(http://www.vtsteam.com/BoringTable/BoringTable18.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: awemawson on September 04, 2013, 02:22:30 AM
Excellent result Steve. Not only looks good but is good :wave:
Title: Re: A boring table for a Craftsman 12" lathe
Post by: tom osselton on September 04, 2013, 05:54:41 PM
Very nice this is one project I will have to do my clausing doesn't have the slotted table either or a follow rest thanks for showing!
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 04, 2013, 06:21:54 PM
Thanks Andrew, Tom  :beer:

Today was hole day. Whole lotta holes.

I took the scale off of a 3/8" thick piece of steel plate which will cover the casting and will eventually be milled for the top groove of the t slots. I lined it and the casting up on the mill and spotted screw locations:


(http://www.vtsteam.com/BoringTable/BoringTable19.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 04, 2013, 06:25:29 PM
Then started drilling tap size:


(http://www.vtsteam.com/BoringTable/BoringTable20.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 04, 2013, 07:12:27 PM
Then drilled the clearance holes:


(http://www.vtsteam.com/BoringTable/BoringTable21.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 04, 2013, 07:16:13 PM
Then the countersinks:

(http://www.vtsteam.com/BoringTable/BoringTable22.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 04, 2013, 07:20:23 PM
Then began tapping holes:


(http://www.vtsteam.com/BoringTable/BoringTable23.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 04, 2013, 07:23:51 PM
And this is where I left it by supper time. Ten down, eight to go:



(http://www.vtsteam.com/BoringTable/BoringTable24.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: awemawson on September 05, 2013, 02:46:05 AM
I think that you need to put a self reversing tapping head on your Christmas present list. I'd lend you one but you're miles away!
Title: Re: A boring table for a Craftsman 12" lathe
Post by: PekkaNF on September 05, 2013, 05:30:42 AM
Today was hole day. Whole lotta holes.

Whole lotta of holes. Whola lotta....


You must have reached some soth of zen state of mind at certain point of threadin :lol:

Pekka
Title: Re: A boring table for a Craftsman 12" lathe
Post by: black85vette on September 05, 2013, 08:38:25 AM
Looking great so far.   I also miss not having a table on my Atlas 12".   You always come up with cool solutions and then execute them well.  :clap:
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 05, 2013, 08:52:00 AM
Andrew, Pekka, B85V, thanks!

It's not so bad, maybe an hour and a half. No boss and nobody's paying me. Probably the only time I'll have to do this particular thing in the rest of my life. It will yield a boring table that I built myself.

What I find difficult is concentrating enough not to make a mistake -- working from my head without a drawing or CAD, using this mill drill with lots of backlash and no DRO makes it challenging. In a small way, challenge equals fun. I guess that is zen!  :med:

Now mowing the lawn....... that's tedious!

Title: Re: A boring table for a Craftsman 12" lathe
Post by: dsquire on September 05, 2013, 01:11:43 PM
.
.
Now mowing the lawn....... that's tedious!

Steve

Isn't that what goats are for?  :lol: :lol:

You're making a fine job as usual.  :clap:

Cheers  :beer:

Don
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 05, 2013, 05:50:20 PM
Thanks Don! Grass? Don I think sheep -- not an animal husbandry type, but I think goats eat brush...... So does a Deere   :lol:.

Today's attack on metal object:

Holes all tapped, in fact one too many -- that central one needed to be drilled out to 3/8 to fit the lead nut:


(http://www.vtsteam.com/BoringTable/BoringTable25.jpg)


Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 05, 2013, 05:51:24 PM
Then it was time to start milling the slots:


(http://www.vtsteam.com/BoringTable/BoringTable26.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 05, 2013, 05:52:18 PM
Slots all done:



(http://www.vtsteam.com/BoringTable/BoringTable27.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 05, 2013, 05:55:48 PM
Skimmed it all with the homemade carbide fly mill, and set it up on the lathe to see how it all looked. The nut I have to duplicate (from the lathe's cross slide) with a little modification to suit the height of the boring table is sitting on the back. You can also see a T-nut being tried in one of the slots. It fits really nicely. Another good day.


(http://www.vtsteam.com/BoringTable/BoringTable28.jpg)


Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 06, 2013, 06:35:09 PM
To make the nut I need an acme 10 TPI internal threading tool. I found elsewhere on the forum instructions for making threading tools on the lathe, so I thought I'd try it.

Here's my first effort:

(http://www.vtsteam.com/BoringTable/BoringTable29.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: tom osselton on September 07, 2013, 02:42:22 AM
I remember those have not tried them yet though they should be perfect!
Title: Re: A boring table for a Craftsman 12" lathe
Post by: chipenter on September 07, 2013, 03:26:52 AM
I think it would be better to make a tap , as it is square thread or half a tap similar to a D bit , http://www.rdgtools.co.uk/acatalog/ACME_TAPS__LEFT_HAND_.html the link shows a tap with square grooves milled along the length .
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 07, 2013, 08:57:32 AM
Tom, Chipenter, thanks -- always looking to try new things (to me). And this site is a great resource for that. Hope I'm contributing something in return. :nrocks:

Chipenter, a tap would have been my first choice, especially since I'm sure I could use it again in the future. But a quick check of the usual machinery resources here in the U.S. showed acme taps of this size (1/2"-10) were approximately $100  :bugeye:
I wonder if they are made of platinum?

I'd seen a youtube vid of a roughly made acme tap, but I don't have acme threaded rod on hand, so would have to order that. Also it can't be hardened, though in this case I'm not cutting steel.

I'm very curious about the tooth shape boring bar turning method -- it's fun and I have drill rod on hand.

Missed the link last post, here it is:

http://madmodder.net/index.php?topic=3523.0

I can see several improvements I could do to my technique after this first one -- mainly to increase stiffness:

1.) the bar should be as wide as possible -- to fit the internal starting diameter of the nut.
2.) the bar should be as short as possible with just enough clearance to pass through the nut and a little bit more to stop the carriage in time.
3.) the cutting profile should be as short as possible, with just enough clearance to clear the cut.
4.) although I have tempered to appropriate colors in the past for boring bars, I believe this one should be made like the OP suggested, dead hard, to maintain the highest sharpness through the cut.

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 07, 2013, 11:05:15 AM
Thinking about the above, for a 1/2" x 10 TPI thread, I think I'll try this:

1.) start out with stock equal to the nominal diameter -- in this case 1/2".
2.) turn the end button and shank to a depth of 3/8"- which yields about 125% tooth depth
3.) after making the flute flat, grind off the outside turning tooth profile for clearance.

I think that will make a much heavier shank.
Title: Re: A boring table for a Craftsman 12" lathe
Post by: awemawson on September 07, 2013, 11:53:47 AM
Steve,
A rough and ready tap for single use can be made easily from mild steel, then case harden it. Turn a length of rod to the acme profile you need, taper one end for a lead in, mill four slots axially to provide cutting edges, then case harden it.

This will give a tap with no 'back relief' - so will be easiest to use if you first rough out the female thread by boring, then finish with the crude tap.

If you have no case hardening compound, a reasonable substitute is ordinary table sugar. Heat the steel, plunge into sugar bowl whilst wife is not watching, remove, dip in clay slurry, then heat to cherry red. Keep at heat for a couple of minutes, then plunge vertically into water. The clay slurry markedly reduces the oxidation. Keeping vertical reduces distortion.

Many a set of wire cutters were hardened this way by POWs in WW2

Title: Re: A boring table for a Craftsman 12" lathe
Post by: chipenter on September 07, 2013, 03:40:11 PM
Drill rod makes excellent taps , the easiest way I have found to cut acme threads , is to make a parting tool to fit the thread from round high speed steel , and twist the tool to match the rake of the thread , and a very small in feed .
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 07, 2013, 06:35:28 PM
Those are both really great tips. Thanks Guys! :nrocks:
I suppose I could make the acme rod to then make the tap.


Before I read the above today though, I already made up a second internal threading tool and set up the lathe for thread cutting. I haven't cut anything yet and will try some test pieces tomorrow. I guess I'll see that through, one way or another. But now have a plan B with the tap tips.

Also, I should admit, Andrew, I have an unused can of Kasenit sitting on a shelf.    :palm:


Here's today's and yesterday's cutters compared. I had to grind down the shank of the new one by hand because I had hardened the cutter already and found I didn't quite have enough clearance in the bored hole size -- .420" -- even though the shank was .375. The tooth pushes that out, of course  :doh:  :

(http://www.vtsteam.com/BoringTable/BoringTable30.jpg)

Title: Re: A boring table for a Craftsman 12" lathe
Post by: chipenter on September 08, 2013, 03:27:54 AM
I made one of Bogs tools and found that there was not enough clearance for a coarse thread , and had to grind the front back for 1 1\8 x 11 tpi faceplate , took me a while to figure it out lol .
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 08, 2013, 08:38:10 AM
Even if this new tool works out, I gotta try making a tap, the way you guys suggest, too. I'm sure it will come in handy, and I have the materials for it, plus the lathe is set up for cutting 10 TPI. It just sounds like fun to me. And I want to try that hardening recipe. Maybe I'll do 3 of them -- then I can try Andrew's hardening mix, try Kasenit, and also do a drill rod version. Cool!

But I better check out what I'm planning with the internal tool -- I didn't have an acme gauge -- and had to find the info for internal cutting in a couple different places here's what I think I'm supposed to do....

1/2" x 10 TPI:

Width of cutter tip was turned to .032"
Angle of sides is 29 degrees
Diameter of hole to be bored in the nut .420"
Diameter of full cut .520"

Please let me know if any of this is wrong!  :wack:

Thanks!
Title: Re: A boring table for a Craftsman 12" lathe
Post by: awemawson on September 08, 2013, 10:07:20 AM
Steve, I seem to remember that ACME is usually symmetrical, so you can use your existing lead screw as a gauge for grinding your tool, just slightly truncate the male and take the female a tad deeper.

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 08, 2013, 10:26:18 AM
Thanks Andrew. The tool is made (turned to sizes and hardened)  plus I'm sure the cross slide leadscrew has some wear by now so I think this way is probably more accurate -- I just want a check on my math for the tool tip width and the bore for the nut if anyone knows for sure, before I start wasting metal  :zap:
Title: Re: A boring table for a Craftsman 12" lathe
Post by: awemawson on September 08, 2013, 11:18:27 AM
Always use the ends of a lead screw for sizing as they will have had virtually no wear, which gets concentrated in the active portion (usually the middle)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 08, 2013, 06:12:06 PM
A lot of mistakes today -- one of those days.

List of mistakes:

The first and biggest blunder was misinterpreting a drawing in an online diagram and thinking the half angle was 29 degrees for acme threads instead of the full angle. Therefore the two cutters I had made yesterday were scrap.

The second was finding an 12" piece of 1/2" drill rod and deciding to use that instead of the newer 3' stock. I made up a new cutter with the correct 14-1/2 degree half angles, milled the flat, and then attempted to harden it. No go! It just wouldn't harden. Not sure what it is but it isn't drill rod -- or how I even came to have it -- it appears precision ground, not cold rolled, and certainly not hot rolled. But just wouldn't harden.

Third problem: So then I broke out the Kasenit to try case hardening, just for the heck of it. Did that twice, but the depth of case wasn't impressive.

Fourth problem: decided to just practice with what I had on a piece of aluminum (former sprue). The lathe was already set up for cutting 10 TPI. But the new cutter just wouldn't cut.

Edge seemed sharp, so I guessed there wasn't enough relief under the cutting edge. I had cut the flute flat (?)  about ten thou under the center of the diameter, but that didn't provide enough relief.

Since the case was so thin, I was able to just file more relief under the cutting edge, and finally the cutter began to work. It was pretty much the end of the day, but it was good to see swarf coming out of the scrap piece as it turned and the thread deepening with each pass.

Fifth problem: I hadn't bored a reference land at the start of the hole to indicate when threads were at full depth, and i don't have a piece of acme rod to test (the cross slide screw was being used!) so I just stopped cutting the thread at an arbitrary point. Here's a pic of the practice piece.

Tomorrow I will make one more new cutter from new drill rod, and file clearance in before hardening. Long day today, but by the end, the beginnings of an internal acme thread from a homemade cutter. So not so bad after all.  :ddb:


(http://www.vtsteam.com/BoringTable/BoringTable31.jpg)






Title: Re: A boring table for a Craftsman 12" lathe
Post by: dsquire on September 08, 2013, 07:05:08 PM
Steve

Now that you have all those out of the way you can get down to some serious work tomorrow. It happens to all of us occasionally if we are honest enough to admit it.  :D :D

Cheers  :beer:

Don

Title: Re: A boring table for a Craftsman 12" lathe
Post by: chipenter on September 09, 2013, 02:46:02 AM
Did you cut from the chuck out of from the back of the blank inwards , I only ask because I have not cut a left hand thread yet ?
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 07:35:26 AM
Don, thanks for the encouragement!  I'm ready to cut serious metal today!!  Or as serious as I ever get.    :)  :beer:

Chipenter, no, I cut from the tailstock end into the piece, right to left.


Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 07:37:53 PM
Did you cut from the chuck out of from the back of the blank inwards , I only ask because I have not cut a left hand thread yet ?

I was kinda confused byt this, and the link to the taps you gave earlier -- left hand taps. Why all this left handed talk? So today I decided to check my cross slide screw. Sure enough a left hand thread.  :doh:

The Gingery lathe I built had a right hand thread for everything -- naturally because it was made out of common all-thread. I just assumed the Craftsman was the same. .........Wrong!

I'm not sure if I'm up to plan F yet, but feels like it. Luckily a lathe threading tool can cut either way, unlike a tap. Although it is handed -- inside vs outside cutting.

Anyway, started on the new tool.


(http://www.vtsteam.com/BoringTable/BoringTable32.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 07:44:47 PM
This time I decided to reduce a portion of the shank to .315, while leaving the bulk at .5. I realized it would fit my boring tool holder, and didn't need to fit the .375 slot in my regular lathe tool holders. The 5/16" section seemed to be the maximum diameter possible to provide clearance for backing out of the groove and returning the tool to start while threading, based on my other tools.


(http://www.vtsteam.com/BoringTable/BoringTable33.jpg)

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 07:48:51 PM
Fluting the cutter. This time I milled to the center, and decided I would add more relief later, rather than milling below center.


(http://www.vtsteam.com/BoringTable/BoringTable34.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 07:52:24 PM
I also milled off some of the excess at the back side of the cutter:


(http://www.vtsteam.com/BoringTable/BoringTable35.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 07:56:27 PM
After milling. There is still too much material on the end. Additional relief needs to me removed under the cutting edges because the relief angle is too shallow.


(http://www.vtsteam.com/BoringTable/BoringTable36.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 08:00:35 PM
I blued the cutter edge and gradually filed it away, watching the blue mark:


(http://www.vtsteam.com/BoringTable/BoringTable37.jpg)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 09, 2013, 08:47:52 PM
When I got close to no more blue, I switched to a bench stone and took the last of it off. Then it was time to harden the cutter. This went without a hitch with REAL drill rod, and a file couldn't scratch it. I left it full hard, as none of my earlier trials yielded a broken cutter -- screw cutting happens at slow speed with light cuts and they aren't interrupted. Maintaining the keenest possible edge is important, so that was my choice.

I left cutting edges at both sides of the tool for the time being, since I though I'd try cutting a tap with the outside facing lip. After that I planned to grind it off so the cutter could fit the bore when internal threading.

Cutting a tap proved impractical with this tool. The boring tool holder was in the way of either the chuck or the tailstock since this is a tool designed to be aligned parallel with the bed.  1/2" tap stock had too long an overhang to be solid enough on my lathe without support by the tail center.

Low speed chatter was the result when trying to thread drill rod. It left a horrible finish. Much better would be a conventional lathe tool, ground to do a 29 degree thread. You would have a shorter tool extension, plus support by lathe centers. So after fooling around for an hour or so I finally gave up and ground off the extra lip.

I did a practice piece in both aluminum and brass, left hand internal threads, and finally chucked up in the 4 jaw the stock I intend to use for the actual leadscrew nut. A old scrap block of either brass or bronze, I'm not sure yet what it is. I'm thinking bronze -- need to clean it up more to see the true color. It's acting like bronze -- maybe even aluminum bronze as it was quite tough to drill.

I figure I've got two chances with this block -- the hole I drilled is near one end. If I screw up screwing, I could try again at the other end -- it's long enough to cut off the mistake and try again.

By the time I had the first hole drilled it was supper time -- time flies. I'll have to bore to  ,420" tomorrow, and then cross fingers it'll thread right this time.....

The cutter after hardening:


(http://www.vtsteam.com/BoringTable/BoringTable38.jpg)


Ready for tomorrow:


(http://www.vtsteam.com/BoringTable/BoringTable39.jpg)

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 10, 2013, 02:42:17 PM
The day's about half over and I still haven't cut that nut. A bit frustrated. I tried one more test piece -- seemed perfectly cut, no mistakes, put a bore on the end to tell when cut to proper depth, reverse thread 14-1/2" degree grind, new cutter, etc. But it wouldn't screw onto the cross slide lead screw.

I decided I wanted to measure that screw, but it's well buried in the cross ways. I tried removing it but it's trapped by the the drive gears, and to fully remove It I'd have to loosen what appears to be a 1-5/16" hex on the support spigot. I don't have a wrench that size.

Then an Idea! What about the compound slide screw -- could that also be a 1/2" 10 TPI acme? Yes indeed! And I can get it out much more easily. Finally I have it, and measure the OD which is a thou under 0.5" -- that's okay. And the thread depth which was about 0.407" also good. I was cutting the thread to .420 and .520.

So I tried the nut. Weird--  it cocked sideways and wouldn't screw on. Eventually dawned on me that the compound slide has a right hand thread, and the nut was left hand to suit the cross slide :doh:

So the lathe has a left hand thread on the cross slide and a right hand screw on the compound slide. No wonder I sometimes get mixed up turning dials. Well, then, I thought, you did make a right hand nut by mistake yesterday, try that on the compound screw.

But no, something is wrong, and so far I'm not sure what. But finally I have a sample of the acme thread that I can check the cutter profile against. I can also use it to make a conventional lathe tool in case I finally have to resort to making a tap.

Man what a time waster this has been!  :bang:


Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 10, 2013, 06:43:20 PM
(http://www.vtsteam.com/BoringTable/BoringTable40.jpg)


I checked the threading tool against the compound slide's acme thread and the fit was really good. No play at all and the end of the cutter bottomed out perfectly in the thread. So the profile wasn't the problem.

I had a feeling that the thread wasn't deep enough -- even though I thought I was cutting to .520", maybe I wasn't

I decided to try one more scrap piece of aluminum, and this time not only cut a register in it, but also blued it so I could see for sure when the cutter touched the outer bore. This one took a lot longer to thread -- which was a hint that the others were indeed too shallow.

When it was done I also measured the inner bore -- I had bored .420, but when measured after threading, it was .410. I think the aluminum burred outwards -- I used a round file to bring it back to .420.

When I tried it, the scrap piece threaded on the acme screw -- finally! Well, most of the way. I think the thread was still a little shallow at one end. So I realized I probably needed to make a few more spring passes to clean up the end of the thread. Small holes like these necessitate slender boring tools, with a fair amount of spring. The fit was quite good otherwise -- no apparent backlash when wiggled. So I think I have the problems all  figured out.

This would all be a lot easier if I'd had a piece of left hand acme rod to test the piece as I threaded it. I could just thread until I had a good fit, rather than watching a register. With the register method, you only have one shot to get it right, because you have to remove the nut from the chuck to try it on the lead screw. It can't be threaded any deeper on the lathe after that.

Anyway glad to have some answers to the problems.
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 11, 2013, 09:18:56 AM
Before starting this morning, I thought I'd give myself some extra insurance by calculating what the compound slide should read when the thread is fully cut. Well, in an ideal world anyway.

Because I'm cutting this thread using the compound set at 14.5 degrees, rather than the straight in method, each division on the compound does not equal the actual distance cut straight in.

To calculate the difference, I figured it would be the inverse of the cosine of 14.5 degrees times the tooth depth I want to cut.

The inverse cosine of 14.5 degrees is 1.033 and the tooth depth is .05" so 1.033 x .05 = .0516". Round that to the nearest thousandth and it's .052" So as a check on the depth of cut, I should be turning the compound slide in a total of .052" on its scale. If I've done that, and I'm also starting to cut my register on the part, I should be at full depth of cut.

Fingers crossed!
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 11, 2013, 04:31:22 PM
(http://www.vtsteam.com/BoringTable/BoringTable41.jpg)


Finally!

It took one messed up hole when I got out of sync threading, but there was enough stock to make two. I'll cut the mistake end -- the square one -- off and fit the other to the boring table.

Man that was a lot of work for one nut!     :Doh:  Well at least I learned a lot....   :coffee:

I may try again to make a tap, as long as I have the lathe set up for threading.
Title: Re: A boring table for a Craftsman 12" lathe
Post by: awemawson on September 11, 2013, 04:57:37 PM
Well done Steve. It all came right in the end due to doggedness on your part.
Title: Re: A boring table for a Craftsman 12" lathe
Post by: dsquire on September 11, 2013, 07:37:56 PM
Steve

I knew that you were going to stick with it until you had it dancing your tune. Fine job.  :D :D

Cheers  :beer:

Don

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 11, 2013, 09:30:17 PM
Thank you gentlemen!  :beer: The table itself was easy, by comparison!


This threading exercise has got me thinking about it still.

Here's one idea I'm wondering about:

Now I used the cutting method where the topslide is set over to the half angle. Ostensibly that reduces the wedging action of the cutter for our smaller lathes, and allows them to cut on the leading edge of the cutter and the tip (in an acme thread).

I was using a turned cutter profile. It has no relief under that forward edge. And the interior groove it is cutting presumably bears hard against that lack of relief, since the angle of the thread goes aft and under the cutter. Relief here would need to be pretty steep to even just parallel the thread edge.

The topslide was set over 14-1/2 degrees towards the headstock -- because you gradually withdraw the topslide to cut the thread.

Now what would happen if I had angled the topslide the same amount but in the opposite direction? Wouldn't that cut easier, because the trailing edge presents the opposite situation -- automatic relief in relation to the square cutter edge? Can you cut on the back side of a threading tool vs the front?

questions, questions........

Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on September 11, 2013, 09:35:20 PM
(I built a lathe sharpening fixture for a disk sander at this point -- which went on for quite a few posts -- that has been moved to a separate thread here: http://madmodder.net/index.php/topic,9051.0.html . I'll finish up the boring table project here.)
Title: Re: A boring table for a Craftsman 12" lathe
Post by: vtsteam on January 07, 2018, 10:55:13 PM
Restored the photos in this thread which had broken links due to Photobucket.