4 Prong Spur Drive

[Don Stephan]

While teaching a recent spindle turning class, the students were using a wooden mallet to "seat" their 4 prong spur drives into the end of 8" long 2x2 SPF (spruce-pine-fir) spindle blanks, soft wood. Of course they positioned their blanks on the worktable directly over a 4x4 leg resting on concrete. I first demonstrated, and no matter how hard I whacked the end of the 4 prong spur drive the spurs only entered the end of the blank about 1/32". Having encountered this repeatedly over the years I've looked at a number of spurs. The bevel angle, although not acessible for a measurement, always looks to be about 45 degrees or greater. Anyone else feel the bevel angle on four prong spur drives is too large?

Anyone try to grind a more acute angle on the spurs? If so, what was your experience please.

 

[Brian Gustin]

IMHO, 1/32" should be plenty enough of grab - if you're experiencing stops/spin-outs on spindles on that then tools need sharpened or technique needs adjusted. Doing a spindle, should have no troubles even using a standard cup drive which has no prongs at all for someone who has mastered sharpness and technique (presentation of the tool to the wood, etc.) Only real reason to drive your spur center into the wood is to avoid stressing your bearings on the headstock, IMHO.

 

[Ronald Diamond]

Uh

 

[Larry Copas]

For spindle work, I normally use a cup drive center. Just tighten up the tail stock and start turning, no pounding necessary. If I were to use a prong drive it would be a two prong. Far better than 4 prong and again no pounding necessary. Just tighten the tailstock and turn. Normally have to re-tighten the tailstock after the first couple of passes but than I'm good.

 

[hockenbery]

Ditto to @Larry Copas
Pieces remount perfectly, i can flip the piece en for end,
if I’m doing a layout with the index wheel I can loosen the tailstock an line the face I want up with zero.
Great for multi-center work.

I usually put a pencil mark for center and put the cup center pin on the mark.
If I want a precise center I mark it with an awl put the center pin in the awl hole.

Also if you get a brain cramp and slide the tool rest into the spinning work, the wood will stop, the cup drive will just spin, and damage to spindle will be minimal.

Teaching students to use a cup drive takes about 12 seconds.


If I’m doing spindles and have to use a spur I will cut a center cross 1/8” deep with a bandsaw on the end of the blank.

I use spurs almost all the time with bowl and hollowform blanks.

 

[John K Jordan]

I know people who make two bandsaw cuts on the drive end of the blank to grip the spur. (Oops, I just glanced up and saw where Forum MVP hockenbery just mentioned that.)

I've never modified a spur drive center.

Actually, I quit using the spur drive centers long ago. I use 1/2" or 1" Steb centers with spring-loaded points. I rough out blanks with a skew, I'll teach but almost never use a spindle roughing gouge in my own turnings. If someone is turning a spindle and needs a spur center to keep it spinning they might consider working towards trading force for finesse..

 

[Jon Rista]

I switched to steb centers as well. That spring-loaded point and the plethora of teeth are quite handy. I don't think I've pounded a spur drive into anything in a couple of years. I do use a roughing gouge, but like John said: finesse. My gouge is ultra sharp, and I don't try to do what many turners do...where they just shove it in and rip the blank down in seconds. I take a little more time than that, and it works out just fine.

 

[R Henrickson]

I use only cup (safety) and steb centers for both ends of a spindle. If there should be a catch or other problem, the spindle merely slips rather than doing something more dramatic. As noted above, if the spindle slips, you've done something wrong, and the slip protects you. The one minor exception is when I turn very long and thin (e.g. 1.5" diameter and 30" length), I mount one end in a chuck for a bit more stability.

 

[Roger Wiegand]

Sharpening the prongs will just make them better able to split the blank. I too went over to cup drives a number of years ago and have never looked back. With the big one that Robust sells I've turned 100 lb bowl blanks between centers without any problems. I no longer own a spur drive, and don't miss it.

I also tried Steb drives a while ago and found, perhaps counterintuitively, that their holding capacity was much lower than a continuous rim. In my hands they ended up acting like hole saws more often than not, especially in green wood.

 

[William Rogers]

I also only use the safety center. I will use the steb center on spindles, but likely 95% of the time I clamp it in my O’Donnell jaws.

 

[Don Stephan]

I can finesse truing rough spindle blanks, but often don't have time to do so and keep up with work needs. So roughing out often has to be without finesse so detail and final cuts can be finessed.

I'll order a 1 1/4" morse taper stebcenter to complement my two smaller onces, and I'll try reducing the bevel angle on a spur drive.

 

[John K Jordan]

I can finesse truing rough spindle blanks, but often don't have time to do so and keep up with work needs. So roughing out often has to be without finesse so detail and final cuts can be finessed.

I discovered I could rough turn spindle blanks a faster with a skew than a spindle roughing gouge. I prefer to use a 1" or 1.25" skew. The "trick" was starting a little bit from one end (for example the right end) and make what might be considered a shallow cove or taper into the corners then follow through down the grain to the right end. Move over a bit to the left and make similar cove-like cut then repeat. Before running too far to the left end, turn the skew around and repeat the process headed towards the end this time. Repeat, then cut off the hump in the middle. By then the blank is completely round or nearly round and needs only a bit of touch up.

As long as there is no catch, with a sharp skew there is very little force on the blank.

Something like this is far easier to show than describe but I don't even have a video. I did see a video here recently of a gentleman using a very similar method with the skew.
Oh, I remember, it was John Kananis in this thread, watch how fast he roughs square blank with a rounded skew:

The thread:

Turning a Snowman with the Skew

I hope you enjoy, it's a quick watch. View: https://youtu.be/EQJPCjQDwy0?si=_vUDi1K9yObZzeoj

www.aawforum.org

Or on YouTube:

View: https://www.youtube.com/watch?v=EQJPCjQDwy0


Since I started roughing like this I rarely use the spindle roughing gouge for roughing except to demonstrate to students who may still need a bit of skew practice to be comfortable. I have a couple of Thompson spindle roughing gouges, a 5/8 and a larger one (1"?), but use them less for roughing and more to shape curves on spindles. These are "U" shaped with the sides straight and parallel for a bit. This lets me start a cut with the rounded part to shape a curve then twist over to the flat for a smooth cut where I want a taper or cylinder. I use the 5/8" Thompson without a handle since the shaft is 5/8" and makes a comfortable short handle.

JKJ

 

[Doug Rasmussen]

Steb center? Hadn't heard of it until now.

Never had problems with spur centers. For offset center turning wouldn't the spur be needed? Mark one spur on the center as an index point and also mark that spur's location on the wood so if re-chucking was needed the wood could be put back in and indexed correctly.

 

[John K Jordan]

Steb center? Hadn't heard of it until now.

Never had problems with spur centers. For offset center turning wouldn't the spur be needed? Mark one spur on the center as an index point and also mark that spur's location on the wood so if re-chucking was needed the wood could be put back in and indexed correctly.

I use Steb centers on nearly all spindles and often for tailstock support on other things.
One thing I really like about them is the spring-loaded points. I turn a lot of thin spindles and would hate to work without the 1/2" centers.

These are 1/2" Steb centers, drive and live. I also have the 1", would like to get the bigger versions some day.



These are my 1" and 1/2" drive centers.



JKJ

 

[hockenbery]

Steb center? Hadn't heard of it until now.

Never had problems with spur centers. For offset center turning wouldn't the spur be needed? Mark one spur on the center as an index point and also mark that spur's location on the wood so if re-chucking was needed the wood could be put back in and indexed correctly.

I prefer cup centers. On napkin rings i can easily use the cups to put a particular grain pattern on a face of a multi center turnin.
Spur drives don’t recenter well even if you match the spur locations
They aren’t well suited to placing centers near the edge of the work

Turning 3 faces is common multi-center turning. I mark the three centers on each end at the same time.

I do 3 sided napkin rings in a demo
Mark centers, Mount spindle, turn the faces with each of the 3 center pairs,

 

[Doug Rasmussen]

This is a little different type drive center.

The large piece to the left is to put a 90 degree point on your workpiece. Then with a little practice you get so you push the pointed piece into the spinning chuck at the right. The chuck has sharp 90 degree tapered threads which the work screws into. It screws in surprisingly tight, enough that you can turn shorter work with no tailstock support.

When the turning is done give it a whack with a soft mallet to dislodge it. This can all happen without turning off the spindle. Sometimes you see production turners in the 3rd world who don't turn their lathes off.

Both these pieces mount to a 1-8 threaded spindle, the chuck is a little over 2" diameter. Of course, this setup can work with a tailstock for long spindles.

 

[Don Stephan]

For thin spindles (think magic wands) John Jordan kindly shared in a post making a #2 Morse taper on one end, and use the headstock spindle to turn the spindle blank. Minimal contact by the tailstock center pin is all that's needed to keep that end from wobbling.
Same friction drive concept, without the two pieces of hardware. But thanks for sharing.

 

[Jamie Straw]

Spur drives can get beat up with groups of students, variable skill levels, using them. At our last club meeting, I became very interested in the Axminster Friction Drive set The Program Director was doing multi-axis demo, large maple stock (~4" x 22" or so) using a French bedan. Whether he was aggrasively taking down stock or doing very fine shaping cuts, those little friction drives+center did great, even with the wonkiness of the multi-axis situation. He's been using them for years, apparently.

 

[hockenbery]

Spur drives can get beat up with groups of students, variable skill levels, using them. At our last club meeting, I became very interested in the Axminster Friction Drive set The Program Director was doing multi-axis demo, large maple stock (~4" x 22" or so) using a French bedan. Whether he was aggrasively taking down stock or doing very fine shaping cuts, those little friction drives+center did great, even with the wonkiness of the multi-axis situation. He's been using them for years, apparently.

Those are a very nice pair of cup centers. :-( They are out of stock

They don’t seem to have a #3 taper on the live center as an option.
Be great on the midi lathe.