Spider for my G0602/0752Z 10 x 22

[WobblyHand]

Emboldened and chastened by my recent mini-lathe spider project, I decided I would try making a spider for my 10x22 lathe. I bought a chunk of 4340 (don't ask me why, I don't know what I was thinking) that was 2.25" in diameter, which matches the OD of one of the spindle jam nuts. I cut off a piece about 1.75" long and faced it on a lathe. I used TCGT inserts on this, simply because I was too lazy to change them for TCMT. I have loads of TCGT inserts. It seems the TCGT has worked fine. This surplus 4340 has a ratty exterior, but it is dark and I'm not sure if I will turn it or not. To turn it, I'd need to make a mandrel, and I'm not sure I want to bother. I drilled it to 7/8" in two steps. After that , I will bore it.

My lathe spindle has an M39 x 1.5mm thread. On my mini-spider, I just copied the OD of the spindle thread and made a male screw for a pattern. Apparently I didn't measure it well enough and it didn't fit correctly, causing me some grief. So this time, I think I'll measure the pitch diameter and then make a male pattern to match. It's really a good idea to do this, especially with a metric thread. Even though you can detach the chuck, it's a bit of a trouble re-syncing the thread. Much better to use a male pattern test piece (if it is the correct size!). Of course I don't have a 1-2" pitch micrometer (have a 0-1") so I'll have to fiddle with thread wires - if I can find them.

The spindle bore is 26mm (measured previously), so the bore of the spider will be no smaller than that. Like the first spider, I didn't start out with a drawing, so I think my next steps will be to make a drawing, and to find some reference that gives me pitch diameter of an M39 x 1.5 metric thread. Found the pitch diameter specs at Engineer's Edge. https://www.engineersedge.com/hardware/metric-external-thread-sizes2.htm

I found my handy dandy 1 wire spreadsheet and put in the values to calculate the nominal 1 wire measurement for an M39x1.5 6g external thread. IF I got it right, I calculate out a nominal value of 39.273 mm (1.5462") over 1 wire using a 0.040" wire. The male form should be turned down to 38.968 mm max and 38.732 mm min. Yeah, so 39mm which is 1.5354" which isn't a convenient stock size for me. Well, I'll rummage around and see if I can find something. In the interim, I need to do a drawing.

In any case, I need to simply do a 1 wire measurement on the spindle thread and duplicate it for the pattern...

 

[WobblyHand]

Completed a drawing. I'll post it later, I'm at my RPI4 shop computer. Same design as the mini-lathe version, but hopefully there's enough room to do the hole pattern without jaw interference (crossing his fingers). Bought two 3" long 3/16" carbide end mills. The one I was using before was only 2" long.

Found a piece of 1-5/8" 12L14 on the shelves - perfect for the male pattern! Redid my numbers and determined that a nominal 1 wire measurement for a M39x1.5 should come out to 1.5456" (39.259mm) using a 0.040" wire. My wire actually measures 0.03965". I measured the spindle threads on the lathe and got with 1.5458". Which is right in the ball park. In any case, that's the number I have to match to. Sawed off 44mm of the 12L14 stock and will thread it with a 1.5mm pitch on my G0752Z.

 

[verbotenwhisky]

My PM1236 came with a spider....

 

[WobblyHand]

A little more progress. Made the male pattern thread. Figured out the nominal major diameter and turned to that diameter. Did a scratch pass with the threading tool and checked it. Even though I coded my ELS, I still check things, there's always the possibility of human error.

With that out of the way, proceeded to single point the threads. I used the 1 wire method and kept cutting and measuring until I hit the same value as the measured spindle thread (using the same 1 wire technique). When I got the value, I simply spun on the nut. No muss, no fuss.

With that out of the way, I proceeded to drill out the hole to 1" diameter. Then I will bore it to 26mm (give or take). It can be larger, but the spindle bore itself is 26mm.

At lower speeds, the VFD on my lathe can't deliver the torque needed and the motor would stall. It took a long time to drill the 42mm, but it is done. Quit for dinner, and the fact that a line of severe thunderstorms were moving through.

 

[WobblyHand]

My PM1236 came with a spider....

My used lathe did not... So I needed to make one.

 

[WobblyHand]

Bored the 1" diameter drill through hole to 26.05 mm. The drill hole was a bit rough. Bunch of scarring in the drill hole, maybe due to excess chips. Was trying to bore to 26 mm but hey, as long as it is bigger than 26 (the spindle bore) it is fine.

Used a 1/2" carbide bar (old Circle Machine bar, think it is a QCBI) with a triangular insert with a 0.002" nose radius. Cuts nice, even in this 4340 stuff. The last pass was 0.050 mm off the radius. I was only running at 150 RPM and I think a 0.05mm feed. Definitely a slow (boring) process.

Next step will be to bore a 15.5 mm long section to the nominal minor diameter of an M39 x 1.5. It's on the order of 37.23 mm, but I have to double check that. I'll work on that tomorrow.

 

[verbotenwhisky]

A little more progress. Made the male pattern thread. Figured out the nominal major diameter and turned to that diameter. Did a scratch pass with the threading tool and checked it. Even though I coded my ELS, I still check things, there's always the possibility of human error.
View attachment 497288View attachment 497289
With that out of the way, proceeded to single point the threads. I used the 1 wire method and kept cutting and measuring until I hit the same value as the measured spindle thread (using the same 1 wire technique). When I got the value, I simply spun on the nut. No muss, no fuss.
View attachment 497290View attachment 497291
With that out of the way, I proceeded to drill out the hole to 1" diameter. Then I will bore it to 26mm (give or take). It can be larger, but the spindle bore itself is 26mm.
View attachment 497292
At lower speeds, the VFD on my lathe can't deliver the torque needed and the motor would stall. It took a long time to drill the 42mm, but it is done. Quit for dinner, and the fact that a line of severe thunderstorms were moving through.

Looks good.

 

[verbotenwhisky]

Bored the 1" diameter drill through hole to 26.05 mm. The drill hole was a bit rough. Bunch of scarring in the drill hole, maybe due to excess chips. Was trying to bore to 26 mm but hey, as long as it is bigger than 26 (the spindle bore) it is fine.

Used a 1/2" carbide bar (old Circle Machine bar, think it is a QCBI) with a triangular insert with a 0.002" nose radius. Cuts nice, even in this 4340 stuff. The last pass was 0.050 mm off the radius. I was only running at 150 RPM and I think a 0.05mm feed. Definitely a slow (boring) process.
View attachment 497299
Next step will be to bore a 15.5 mm long section to the nominal minor diameter of an M39 x 1.5. It's on the order of 37.23 mm, but I have to double check that. I'll work on that tomorrow.

I like working with 4140 and the per-hardened 4140-HR, works nice and if you are making a tool that will stay with you then spurging for the good stuff is worth it. Nice work.

 

[WobblyHand]

I like working with 4140 and the per-hardened 4140-HR, works nice and if you are making a tool that will stay with you then spurging for the good stuff is worth it. Nice work.

What are the specific words or descriptions for getting the correct "version" of 4140? Not familiar with the terminology. Pre hardened 4140 HT? Buying from McMaster is pricey, so I get forced (not really, but there's budget pressure) into looking on eBay and places like that. Lots of creative words used so don't want to buy the wrong item.

 

[WobblyHand]

Had time to bore out the area for the threads. Came out ok at 2 tenths oversize compared to nominal.

Need to break the edge, put in a small chamfer at the 26mm section so the stock will be guided into the bore. Used this set up. Probably should have choked up on the bar, but it did fine. Was only taking off 0.25mm at a time. It was interesting that I could do a cut of 0.05mm (and under) and the finish became shiny.

Have to clean up the shavings and set up for the threading. Will use a A12-NEL2 bar with a top notch insert and thread from the inside out. I've done a lot of internal threading that way. A lot easier! Since the insert is pointing to the back side the lathe is in reverse. The compound is moved to 60 degrees, but towards the chuck. I'm cutting a right hand thread, to match the male piece made earlier in the project. Here's a better view of the tool.

I'll use the threading tool to cut a groove. Wished I had the correct inserts (a grooving tool) but haven't procured any. So I'll make do with a groove with slanted walls. I'll single point the threads in the morning, it's too late for me to concentrate. I find single pointing requires me to have high levels of attention, particularly if threading metric.