drive spur and setting up between centers

[Jeff Jilg]

I do a lot of turning, and a lot of roughouts as a result. To load a roughout I typically get a decent surface on both sides of the wood where contact will be made. Then the piece is mounted on the lathe between centers. A 4-spur drive with 2" spurs in a chuck is used to drive the piece.

Since the wood is green it's soft. Pressure is initially applied with the tailstock. Then I lock the spindle and rock the piece back and forth a bit to drive in the spurs. Then the tailstock is tightened more. This is repeated until the spurs bite into the wood. I used to use a 1" drive spur but it usually becomes a drill bit on the large pieces I rough out.

What do y'all think of this practice? The practice was also recommended by a well known turner who did a 2 day seminar at our local club. Will this prematurely wear out the spindle bearings? Or are those spindle bearings getting a good workout from the lateral force of the tailstock anyhow?

I've got over 2,000 hours on the PM3520 already, so those bearings have lasted this long! So far there's no discernable play in the bearings. :cool2:

 

[Mark Mandell]

Start-ups

Jeff,

When I started turning, I would mount by face plate and use the TS for extra stability. In the post-JET/Stubby era (and a weekend with David Ellsworth) I bought a spin-on 4-spur drive center and now start pieces between centers. This allows me to move the orientation of the piece to better balance the grain to the shape. However, before I put the piece on the lathe, I use a dead-blow urethane mallet to set the drive spur into the face grain of the blank to save wear and tear on the tailstock. With the spur well seated in what I want to be the center of the bowl, adjustments in grain orientation are easy to do by just shifting the contact point of the live center. Although those shifts will tend to "unseat" one or two of the spurs, a bit of pressure on the TS resets them, and I get very little slip on the spur.

I would think that the wiggling you describe would be harder on your tailstock than on the headstock bearings. I would anticipate that the wiggling will flex the quill shaft in the TS casting and eventually you'll get compression of the casting allowing play in that bore which will then tend to induce vibration in the piece because the spin axis will shift at the TS end as a cut is made. I would minimize this by using as little extension on the TS quill shaft as possible and also by tightening the quill lock which I see many turners ignore. This would also mean moving the TS in instead of just extending the quill.

Mark

 

[Jeff Jilg]

Good points Mark. I hadn't thought of the potential problems to create quill play. While the headstock bearings can eventually be replaced, reworking the tailstock would be a lot more expensive.

Like you I used to start every piece attached to a faceplate. Basically it took too long, and also it was difficult to establish the best grain orientation....as you've stated.

Currently I'm using a 4 spur drive bit that fits into the oneway chuck. The spur is fine, but they should have designed a set screw with it. I accidently spun it a couple of times within the chuck jaws. Mostly it has made a mess of the teeth in that jaw set and the grooves in the spur. The other disadvantage of this system is there is too little room to use a mallet (off the lathe) to drive the spur. Doing so would include malleting the fingers (ouch).

The spin-on drive spur you have sounds interesting but I haven't seen it in the catalogs. Does it come in a 2" width, and who markets it? thanks...Jeff

 

[Mark Mandell]

Spin-On Drive

I got mine, made by Stubby, from John Jordan when I bought my lathe. The spurs are 2" across. You can get a similar drive ("Texas" style) in 2, 4 or 6 flutes from Bestwood Tools from their site at http://www.bestwoodtools.com/ although their flutes are 1-1/2" wide for $80. I've spoken to some who prefer the 2-flute version for rough-outs. Don't think the 6-bladed model would be much use as there wouldn't be enough wood between the blades to hold well; too likely to spin and lose grip.

They also sell a spanner wrench and "pound handle" to fit their drives, but since the piece has machined flats for a wrench and I use a non-marring mallet to set the teeth, those seem an unnecessary ($30) expense.

Mark

 

[hockenbery]

Hi Jeff,

I start almost all of my bowls and hollwforms between centers from green wood. I usually drive a 1" spur center into future opening of the hollowform or the bowl. Once in a while I use a 1 1/4 inch spur center.

I almost never have the spur drive spin as long as I remember to do the 3 things required to keep it from not spinning.

1. I keep the spurs sharp so that they will cut into the wood when struck. If the teeth get too short get a new center. They should bite in 1/4 to 1/2 inch.

2. I make sure to drive the spur center into solid wood with a wooden mallet with the spurs set at 45 degrees to grain so that they seat evenly.
If this is the bark side I keep a 1 1/4" drill bit in the drill press to bore the hole for the spur drive. The spur drive needs to be in faily solid wood and bark will usually just spin away.

3. I keep the tail stock tight by continually tightening it.
With cutting pressure and vibration both of the centers dig deeper into the wood and I need to take up the slack by tightening of the tailstock. I don't tightent the ram in place so that I can always just turn the tailstock crank.

I don't see any problem using the wiggle tighten method. I've seen it done successfully on blanks of modest size.
However in my opinion it takes a bit more time to get a good seat and it isn't practical for big blanks. Some of my blanks weigh over a hundred pounds which I can't wiggle and I'm not sure I'd want to wiggle a 40 pounder.

With Punky wood getting something that resembles solid wood to seat the spur can be a challenge.

Happy Turning,
Al

 

[Jeff Jilg]

Thanks for the comments Mark and Al. At this point I'll pursue the $80 4-fluted spin-on drive from Bestwood Tools.

The stock for that part is machined from 2" round stock. So I don't understand why they cut the flutes down to 1.5" dia. But that's probably big enough. This solution will allow me to drive the spur into place with a soft mallet prior to turning.

 

[-e-]

response from oneway

jeff: i use the method you describe on my oneway and posted your message on the ow forum ... here's kevin's response:

'''There are no problems except it doesn't work very well. Get a 4 inch faceplate. Find a bolt that will go through the screw holes. Sharpen the end of 4 bolts and then put them in from the backside and then hold it in place with a nut. The faceplate should now have 4 sharpened bolts sticking out that you can use as drivers. If you want to be able to adjust your piece easily use only two bolts. The points will dig deeply into the wood without using a lot of pressure and will drive much better tna a sput, especially board grain.
regards
Kevin\
...."

therefore, although this technique may not work as well as the one kevin described, it DOES NOT harm the lathe !!! ... so nice to hear the lathe is not as fragile as other's might be.

 

[Jeff Jilg]

Thanks -e- that's a good idea from Kevin. I had seen something like this on a website some time ago and had forgotten about it.

I like the idea because there seem to be 3 advantages:

• the sharpened bolts won't dig in very far, even on the green wood chunks I roughout
• it would be real tough to generate enough force to get them to drill into the wood like a spur
• the solution is basically free, or at least cheaper than the $80 spin-on spur drive I was considering

I'll try the technique this week with one of my faceplates. If it works well, then I'll setup a dedicated faceplate for this method.

thanks!!

 

[Mark Mandell]

Bolts

Hey, Jeff,

Remember to run a nut on each bolt BEFORE you sharpen it so you can recut the threads when you remove the nut.

M

 

[arbud]

screw it

Idano, lads, I start my bowls using the screw center in the Nova chuck. I drill an 11/32" hole about 1/2" deep and screw on the blank. I find that the centrifical force tightens the piece to the jaw face; I've had only 1 come lose.
However, I can only turn up to 14 3/4" dia. inboard. You people with 20" swing lathes might have a "launching" problem. Send me your lathe and I'll check it out for you, I wouldn't want any of ya to get hurt. 😀

 

[Jeff Jilg]

Thanks Mark - I've done that trick multiple times....namely messing up the threads then trying to get the nut on it. Thanks for the reminder.

Bud - a flatbed truck should be pulling up to your place any second. You can fine tune my mustard colored lathe for me :cool2:

 

[hockenbery]

getting the grain right

One of advantages of using a spur center is that it allows me to adjust the grain of piece so that I get a nice pattern in the bottom of the bowl or on the surface of a hollow form. I like grain to form parabolas and hyperbolas centered in the bottom of my bowls or cirlces in the center when I find a flat sided tree that lets me put the rim on the bark side.

Using the 4 bolts or the screw center you need to be really really good with the saw to get the grain aligned in the blank.

Al Stirt uses 2 bolts so he maintains adjustment in one plane. He ups his odds on the other plane by cutting his blanks with the sawn edge parallell to the bark using a milling attachment on the chain saw. He also adds a bolt in the center to use for aligning the blank if it has a matching center hole.

Phil Brown is the best I've ever seen using a screw center. He gets spectaular grain patterns but he is a master at cutting blanks. He spends a lot of time laying out and cutting his blanks. He comes to the cutting site with a framing square, plumb bob, and lots of chalk. I can gennerally cut a truck load of blanks in the time it take Phil to cut 3 but he will get more money for his 3 bowls than I can sell my truck for.