4 spur center

ralphtaff · Post by **ralphtaff** » Wed Mar 25, 2009 11:25 am

I have a problem with the 4 spur center staying on in the wood.it keeps spinning on the wood. this happens on all the wood i try. i hade a school wood shop teacher look at my center and he said it was ok, i made sure it was on real good. could i have that much wobble in the shaft of the markv that it is causing this?

greitz · Post by **greitz** » Wed Mar 25, 2009 11:33 am

Maybe the wood you're using is so hard that the spurs can't dig in deep enough? Rick Davis showed us that for very hard woods, you might need to saw two perpendicular slots in the end of the blank to get the spurs deep enough.

Gary

beeg · Post by **beeg** » Wed Mar 25, 2009 11:36 am

Did you have a pilot hole for the point?

JPG · Post by **JPG** » Wed Mar 25, 2009 11:37 am

greitz wrote:Maybe the wood you're using is so hard that the spurs can't dig in deep enough? Rick Davis showed us that for very hard woods, you might need to saw two perpendicular slots in the end of the blank to get the spurs deep enough.

Gary

OR not 'driving' it in far enough. Cross sawing WILL help. Drilling a (small)pilot for the point MIGHT help. Are you putting enough pressure from the quill?

ralphtaff · Post by **ralphtaff** » Wed Mar 25, 2009 9:12 pm

Who knows? i thought so but maybe not. i have done all of the above. a teacher at the school i work at has a shop smith and he does not have any trouble with his on the same type of wood. we both get it from the junk pile at the school. he is going to let me use his spur center and see if maybe i need a new one. i just did not want to buy a new one then still have the same problem. will let you all know what i find out.

beeg · Post by **beeg** » Wed Mar 25, 2009 10:43 pm

Do the points of both centers line up?

charlese · Post by **charlese** » Wed Mar 25, 2009 11:10 pm

ralphtaff wrote:I have a problem with the 4 spur center staying on in the wood.it keeps spinning on the wood. this happens on all the wood i try. i hade a school wood shop teacher look at my center and he said it was ok, i made sure it was on real good. could i have that much wobble in the shaft of the markv that it is causing this?

Sorry Ralph, I haven't had this problem whenever I follow Shopsmith's written instructions. (I have occasionally tried to get away from these steps, but the center slips, as you describe and I have to go back to the basics.)

They say to first drill a 1/8" hole in the center of each end of the blank. The hole should be 1/4" deep. Second saw perpendicular slots that cross at the pilot hole. I will use either the bandsaw or a Japanese pull saw to make these slots. These slots should be about 1/8" deep and wide enough to accept the 4 spurs.

These instructions cannot be found in PTWFE, but in the Shopsmith Instruction Manual. (in the White plastic notebook)

I turn hardwoods, but if turning pine, spruce or Western red cedar, I would try to get by without the slots, but would drill the holes.

ralphtaff · Post by **ralphtaff** » Thu Mar 26, 2009 10:05 am

after reading all the posts at several different forums imayby my problem is the speed. To make a long story short, i have one speed to change speed i have to change pullys so with a 2 inch pully at the motor and a 4 inch pully at the shaft i get about 862 rpm that does good on the ring master and out of round bowls about 8 to 10 inch. so for a spindle i am probably to slow? what say you all.i can reverse the pullya and get 3450 rpm, wouyld that be better? or to fast?i have 1.75 pully,2inch,2.5inch,4inch and 6inchpully.

foxtrapper · Post by **foxtrapper** » Thu Mar 26, 2009 11:18 am

You can cut spinning slow. But, slow or fast, you cannot cut too aggressively. I suspect you're digging in too aggressively with your tool, causing the spur to slip and skid.

woodburner · Post by **woodburner** » Thu Mar 26, 2009 11:42 am

Are you turning on a SS MarK V? By your comments in previous posts about belt changing I will guess you are not.

Without knowing the actual type of lathe you are using, it makes it hard to help you with the right answers.

For me, except for hard woods, I use a rawhide mallet to drive the spur into the wood. No drilling holes and such, its not needed unless your wood is very hard. You also want to make sure you have enough tension on your wood between the headstock and tailstock. But make sure you are not putting too much tension on the piece. This will cause the spur center to strip out and cause the problems you are having.

I doubt going to slow is causing your problems, unless you are having lot of catches with your chisels. Starting your lathe to fast with the spindle mounted can cause the spur drive to strip through the slots due to all the torque being released all at once, and cause the piece to fly off the lathe. This is a dangerous practice and should not be done. Starting at a slow speed and working your way up is the correct and safe way so you can check for vibration, etc.

Also, you didn't mention if you are having a lot of catches with your chisels. This also will cause your piece to come loose from the spur drive. Make sure your chisels are sharp. Dull chisels can cause a lot of problems and are more dangerous to use from a safety standpoint. If your chisels are sharp and you are still getting a lot of catches and dig ends, it might be time to work on your woodturning techniqes themselves.

Your problem just might be not knowing how to use your chisels properly. Best advice I can give you for that is you should consider taking some woodturning classes. You should contact a local woodturning club in your area. They usually have a member or two who enjoy teaching beginners the basics and passing on there knowlege.

To find out if there is a woodturning club in your area, check out the AAW (American Association of Woodturners) website. They have listings of all the clubs in the states and overseas with contact information.

Hope this info helps and have fun turning.