Question: I am attempting the oft-mentioned but apparently seldom-documented Taig headstock to 4th axis conversion. I have chosen to use an anti-backlash worm gear at 64 pitch, with 140 teeth, for a 140:1 reduction and 56000 steps/rev at half-step with a 200 steps/rev stepper, with 0 backlash! My question is, will a 64 pitch brass gear stand up to the task? Is 140:1 too ambitious? I've never built anything that takes significant torque before. I have never seen anyone use anti-backlash worm gears save for these people at 72:1, do they work well? http://www.kdntool.com/_sgt/m3m1s1_1.htm
And of course, anyone with links or information - any little bit helps!

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So, I've got a converted Taig (XYZ). Up until a little while ago, I thought I was happy, and then I saw this and thought of how completely insufficient my machine was for all the things I've never used it on before. All I can think of now are parts that require a 4th axis...:
http://members.shaw.ca/mryankey/4th%20axis.htm
I've always put away the idea of having a 4th axis since I don't have the budget for it, but I have seen 3 examples of the headstock to axis conversion (only 1 documented that I could find), and I think I can do it.

I'm ready to fire on the following parts:
$71.40 4-jaw self-centering chuck (Taig part #1060)
$60.25 Headstock & standard spindle (Taig part #100-00 or 200-60)
$6.00 Headstock mounting plate (Taig part #200-48)
$52.53 64-pitch 140-tooth Anti-backlash worm gear (SDP/SI part S1B86A-P064B140S)
$17.50 Worm (SDP/SI part S1D96Z-P064SS)
_____________________________________
$197.68 Total (w/o motor, versus $270 for the Sherline 3700CNC w/o motor)
I already have some pieces, but I priced them out for the benefit of those who don't. Buying your gears from Nordex instead of SDP/SI will save you ~$10, but you have to register (free) to see their prices. If you don't use anti-backlash gears you can save another ~$20, and about another ~$10 if you go down to about 72:1 ratio.

So I just have to make the NEMA 23 stepper mount (I'll post the 3d model later, nearly done) and fabricate an adapter to fit the anti-backlash worm gear (.25" bore) on the 5/8"? spindle. I can't just bore it out like a normal gear since the anti-backlash gear is composed of two halves. The worm itself is pre-bored to .25" in which is standard size for the motor so it will slip right on.
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If you can afford it, the Sherline rotary table is a great unit. From a pure performance perspective they just can't be beat. If you are just wanting to try a build yourself for fun or just to save some bucks, thats great though!

I have seen a couple done on the Taig headstock before, some without worm gears. There was even a guy on Ebay selling brutally simple and really cheap to construct rotary axis units made from these, by using the headstock and the stepper sitting parallel to each other. There was a plate drilled to mount to the back of the headstock and to the front of the motor, leaving them to sit side by side. Timing pulleys were then attached - small one on the stepper and larger one on the spindle - and connected with a really short toothed belt. For this application I cannot imagine backlash to have been an issue, though a tensioning idler would be a no-brainer to add to this idea if you felt the need. This may not have enough resolution for you, only having a reduction of more like 4:1 or so.
As for resolution, is the resolution you are talking about necessary for what you are doing, or maybe even desirable? Better resolution always sounds good on paper, but even at only the 72:1 reduction of my regular table, I sometimes have a problem keeping proper feedrate for my tools. Too many steps/rev and the steppers just might not be able to spin it fast enough for you. This is why I also keep a 10:1 on hand when needed.
Don't know what it is you will be doing with it, so just something to keep in mind and consider in your calculations .

I can't comment on the specific item about which you have questions but I can comment on KDN Tool. I bought a Pinnacle Mill from KDN in March-basically a converted X2- the quality is top notch. This machine has given me NO PROBLEMS WHATSOEVER and continues to amaze me with what it can do. The reason is simple. Ken at KDN puts these machines together with great care and with a complete understanding of the component parts and how they interact. I would not hesitate to purchase the 4th axis from KDN. Actually I didn't know KDN offered this product and I'd probably buy one if I didn't have a powerboat and two kids in private school. Bottom line - KDN stuff is old fashioned quality.

Thanks for the replies. 72:1 is definitely enough for me, but I figured why not go for the best resolution while I'm at it. I already have the headstock, so it is about half the cost of the Sherline.

The KDN looks good, but my primary reason for excluding it is that it is too small (The supplied chuck is 3-jaw 2"), and since I would need to replace it, the cost would be ~$400. Plus, look carefully at their gear picture - it is the same picture used at SDP/SI in their anti-backlash worm gear category! (https://sdp-si.com/eStore/Direct.asp?GroupID=210) Somebody didn't source their photos properly, tsk tsk(heh). So I'd be doing the exact same thing as them.

I think I may get the 100:1 48 pitch combo instead, since it is the largest pitch SDP/SI has...
S1B86A-P048B100S (https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=15220&GroupID=210) and S1D94Z-P048SS (https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=46961&GroupID=211)

{EDIT} KDN is probably using S1B86A-P048B072S (https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=54573&GroupID=210), so I guess 48 pitch will work. I'm still waffling on whether to get the 64 pitch...

{EDIT2} Nordex sells the 100-tooth 48 pitch antibacklash worm gear as
KFX-E7-100 (http://nordex.com/pc1717_12419) ($48.12) with the matching worm as KAS-A1-2 (http://nordex.com/pc1638_12067) ($12.30) vs. $49.29/$15.90 for SDP-SI

Hello all,

I got my order from SDP/SI. I am glad I went with the 48 pitch, as it is just at the limit of what I think would be appropriate in CNC duty.

I will now post my files in 3DM and DXF format, but read the description first:

I made my mounting plate out of 0.25" aluminum today, but the thickness is not absolutely critical. There is room for adjustment (sliding side to side to allow for different thicknesses of worm wheels) where it mounts to the headstock. There is also room for up and down adjustment where the NEMA23 motor mounts to allow for different diameter worm wheels. So this mount can be used for pretty much any combination of worm and wheel.

Notes:
- I used a .125" end mill to cut the bolt slots (They are .200" wide) and a .25" to do everything else.

-That cut out area on the bottom slot is to allow access to the clamping screw.

-Whatever thickness you make your plate, remember that the NEMA23 motor needs a 1.5" diameter recessed area around the shaft to fit into. On the model I made mine .08" deep and 1.6" dia, but I think the standard says .06". You could just cut all the way through, but I think that would reduce the strength of the mount the way I have constructed it.

-The mounting plate extends about half an inch / ~15mm below the headstock's bottom. The headstock must be elevated at least this high above the table when it is mounted. Just stick something underneath the dovetail mount when it is put on.

-I found that the ridges on the headstock make the lower t-slot area stick out just a bit farther than the top t-slot protrusion. You may want to account for this on your plate by pocketing away a little on the backside, or adding a shim under the top area. I don't really think it matters that much.

Someone sent a message saying that the zip wasn't working, so here's another one. This one has a NEMA23 motor and all the gears and adapters in it, so it is easy to see how everything fits together.

Hi,

Make sure you check out

http://www.jeffree.co.uk/pages/divheadmk2.html

It is a fully documented project for converting a Taig headstock to a 4th Axis.

Cheers,

Peter.

I'm seriously considering this! The first link too the Taig conversion looks amazing. It looks like it should be on the Taig! It's awesome looking.

I like the design too!


-Jason