Author Topic: Simple Dividing Head  (Read 19394 times)

Offline swilliams

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Re: Simple Dividing Head
« Reply #15 on: October 27, 2013, 01:43:35 AM »
So I made a boring bar and a clamping strap,





and finished off the boring on the topslide. The front face was squared up with a flycutter before I took it off the topslide.



above the cotter after the boring. I'll cut it in half next.



and the spindle in place after some more turning.

cheers
Steve

Offline steamer

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Re: Simple Dividing Head
« Reply #16 on: October 27, 2013, 02:54:40 AM »
Looking great man!    I see your going to use it on top of the compound?...at least you can set the angle with the protractor!

Dave
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Damned ijjit!

Offline swilliams

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Re: Simple Dividing Head
« Reply #17 on: October 27, 2013, 03:44:13 AM »
Thanks Dave

Yep, will use it ontop of the compound for the odd bit of drilling PCDs. Main use will be in the milling machine vice though. Yep can tilt the compound if necessary (I keep calling it the topslide), probably won't end up doing that much though.

Steve

Offline Don1966

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Re: Simple Dividing Head
« Reply #18 on: October 27, 2013, 03:48:31 AM »
Looking good Steve and you never know when you'll be using it on the lathe. Nice to know you can though, great work bud.  :ThumbsUp:

Don

Offline Ginger Nut

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Re: Simple Dividing Head
« Reply #19 on: October 27, 2013, 04:46:49 AM »
I like what I see and sticking my chair in the corner to watch this WiP even tho I have been following Doubleboosts on his Utube channel I need to learn as much as I can quickly. I know doing is better way to learn. :facepalm:

Offline swilliams

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Re: Simple Dividing Head
« Reply #20 on: November 02, 2013, 02:26:42 AM »
Thanks Don and Ging

I've done more stuff.



Cutting the thread on the back for the thrust nut come indexing plate.



turning the outside of the nut. It's made out of hex because I got some hex just over 2" AF from a scrap metal place cheap.



So now the nut is set up on the rotary table with a spacer between it and the table



Then I cut 24 slots in with a 1mm module gear cutter. It's the cutter you use for cutting a rack, so the sides will be very close to straight with a 20deg angle between them.



So here's the nut mounted on the back with various holes. 3 holes for grub screws with copper pads under them to secure the nut and a number of other holes just spotted. This means I have marks for dividing 3, 4 and 6.

Next will be boring out the 3MT taper at the front of the spindle.

May post more later if I can get it together.

Cheers
Steve

Offline Don1966

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Re: Simple Dividing Head
« Reply #21 on: November 02, 2013, 02:41:46 AM »
Hi Steve, I have had trouble using the copper pads to lock my VDH. It seems to slip even when I have them fully torqued. What I did with my Myford nose spindle attachment was to mill three flats on the shaft and then lock it in place, no more slipping.

Don

Offline swilliams

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Re: Simple Dividing Head
« Reply #22 on: November 02, 2013, 03:13:09 AM »
Interesting Don! I'll see how it goes, I could always put some weak loctite in there.

Offline swilliams

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Re: Simple Dividing Head
« Reply #23 on: November 03, 2013, 12:58:27 AM »
So I had a interesting problem pop up and learnt a thing or two on the way, but more on that shortly



Above is my setup for boring out the 3rd MT in the spindle. It's held against the centre in the headstock with some cable ties and the front is in the fixed steady. This means it is running dead true with the axis correctly in line. Just putting it in a 4 jaw chuck won't do that so reliably.



So the Morse taper turned out running dead true, but not so the thread  :toilet_claw:  My lathe doesn't use the register to locate sideways, rather it locates on the thread and the face behind it. After much head scratching the problem dawned on me. The thrust face on my lathe's leadscrew is not true, I presume it is worn. The spindle pitch is the same as the leadscrew and so the end effect is that the thread is just like it was cut out of true.



So here's the spindle set up running true in the 4 jaw with a small backplate screwed on. Because the face has already been turned true, it doesn't matter if the axis isn't dead on line. The backplate has had it's OD turned in place on the lathe, so that is what I want to run true, i.e. I can test it. After some careful planning and measuring with a dial indicator I was able to juggle the tumbler gears and remove the high spots off the offending area.

I realise this is complicated and I've skipped over it pretty quick, but I don't want to write a huge essay on it. If part needs clarification I'm happy to answer questions though.



So here it is, the finished spindle complete with thread that results in the chucks running true. Anyway I'll have to add fixing up my leadscrew to my "to do" list.

Cheers
Steve

Offline steamer

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Re: Simple Dividing Head
« Reply #24 on: November 03, 2013, 01:20:14 AM »
Great job on that Steve, that's the way to do it.   

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Don1966

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Re: Simple Dividing Head
« Reply #25 on: November 03, 2013, 02:17:35 AM »
Hi Steve, I get the part about the lead screw, but not quiet sure what all you have said. I am glad you were able to sort it out. I probably would of never figured it out, lack of experience. Looks like it came out great bud.

Don

Offline swilliams

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Re: Simple Dividing Head
« Reply #26 on: November 03, 2013, 03:01:12 AM »
Thanks Dave and Don

Don, I'll try and do a sketch later on to show what's going on.

Steve

Offline swilliams

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Re: Simple Dividing Head
« Reply #27 on: November 04, 2013, 11:22:55 AM »
So here's a small sketch to try and explain the problem a bit better



The tool oscillates side to side, relative to where it should be, once per rev. This is because the thrust face on the leadscrew is not true and because the leadscrew has the same pitch as the spindle nose. It's only the "Face A" that the chuck registers on, so due to the angle on the tool the error translates and becomes equivalent to the nose running out of true. Effectively just like what would happen if you used an inaccurate 3 jaw chuck to hold the job in.

I've now pulled the gearbox off my lathe and have the leadscrew out. The thrust face is on the gear and there is a small amount of wear, say 1 thou tops. But the gear face butts up against a machined surface on the gear box that isn't round. I think I can see where it is going wrong. I'm going to face the outside of the gear down a little and leave a smaller diameter for the thrust face. This reduced diameter will be against the machined surface all the time and should fix the problem.

Hope this makes sense,
Steve

Offline Don1966

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Re: Simple Dividing Head
« Reply #28 on: November 04, 2013, 01:29:20 PM »
Thanks Steve it is very clear. Are you going to show us photos of the problem and the fix?


Don

Offline swilliams

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Re: Simple Dividing Head
« Reply #29 on: November 04, 2013, 09:47:28 PM »
Will do Don