Between Centers

[W.C. Turner]

Hello,

Recently, I've tried larger blanks between centers, about 15" dia., weighing about 21 pounds. I use a dead blow hammer, off the lathe, to pound the drive center into the blank. When I try to mount the blank on the spindle, invariably, the drive center will pop out, or, I have to re-arrange the blank to be more balanced, blank is hard to hold with only 1 arthritic hand, etc. Then, in order to get the blank mounted, I just crank the tailstock live center in, to hold the blank on. I saw John Jordan do it like this in his "Bowl Turning" video. He even said "It wasn't necessary to pound the drive center into the blank". Although, I don't think the one in the video was 20 pounds.

1) How do ya'll get the spur drive center to stay in the blank without it falling out the first time, & without placing unecessary force on the tailstock?

2) This is about the 3rd. large blank I've tried like this. I've noticed a grinding sound(kinda like the sound of my arthritic joint bones grinding together), appears to be coming from the spindle. I don't think I placed any abnormal stress on the tailstock that would damage the bearings. Does this sound like a bearing problem?

Thanks in advance for any replies.
W.C.

 

[Bill Boehme]

Use a Forstner bit in a hand drill to make shallow holes at each end of the blank. About 1/2" or so is usually deep enough as long as it is in solid wood. And the size of the bit needs to large enough to esily clear the drive center and live center.

Bill

 

[bbrussell]

Like Bill said drill a flat bottom hole to house your drive center. I suggest, instead of using a drive center, use a steb center.

 

[JimQ]

Or a 2 prong drive center.

JimQ

 

[Ed Koenig]

I suggest you consider mounting a lifting device over your lathe bed such as a small block a tackle. If you're struggling with 20lbs, you will certainly be in trouble with 50lbs or more. Also, devices used for lifting engines from cars work well.

Try drilling a small hole just large enough for the center point on the spur which will allow better penetration of the spurs. If that doesn't work, use a chisel to deepen the spur slots.

I like two prong spurs for natural edge blanks that aren't too large.

When I work with large blanks, I always use a faceplate. Plane the surface where the faceplate sits using a hand plane. If you have a planer large enough to accept big blanks. that's even better.

It's not the tailstock you have to worry about, It's the headstock. Cranking to hard on the tailstock puts unnecessary pressure on the bearings in the headstock. After tightening the tailstock, back off slightly to relieave the pressure. After mounting stock between centers, you should swing the work piece and it should not bind. It should swing freely.

Ed

 

[dkulze]

I'd be careful, with that grinding sound. Try tightening and loosening the tailstock just a bit while it is spinning. If the grinding sound changes, you got bad bearings. You can also wiggle the drive spindle a bit and see if there is any play. Either way, a grinding sound is a baaaaaaad thing.

To keep the drive spur in, use a couple of drops of CA glue (superglue). This is quick and will give you the tiny bit of grip you need to not have it drop out. It will break loose easilly as long as you don't use huge amounts of glue.

Have fun,
Dietrich

 

[MichaelMouse]

Still prefer the security of pin chucks or pin jaws, personally. Especially with wetter wood, where the spurs can tear easier. If the blank is going to be used as a bowl, you can even take the tailstock out of the way after rounding and make your hold of choice on the tail end. it's effectively the same as boring that hole to hammer the spur center into, as far as loss of wood is concerned.

 

[spinsdawood]

About the grinding sound, how large is your lathe?
Jim

 

[W.C. Turner]

About the grinding sound, how large is your lathe?
Jim

I have a PM3520A.

 

[pfduffy]

Ruff Blanks

Still prefer the security of pin chucks or pin jaws, personally. Especially with wetter wood, where the spurs can tear easier. If the blank is going to be used as a bowl, you can even take the tailstock out of the way after rounding and make your hold of choice on the tail end. it's effectively the same as boring that hole to hammer the spur center into, as far as loss of wood is concerned.

Hi, MM, Could you amplify your comments on the use of pin chucks and/or pin jaws? Not sure what pieces of tooling you are referring to and how they are used. Thanks, Phil
For WC; suggest you check to see if the belts are tight on the head stock and if the live center is heating up badly. You should be able to touch the bearings and if the heat is too high the live center bearings need to be replaced. Phil

 

[MichaelMouse]

It's a tenon in a 1" mortise. If you bottom the nose of the jaws or chuck in the recess, it can't tilt perpendicular to the axis of rotation, and is held in position by either expanding the jaws or wedging the roll pin. I use the tailstock to ensure proper registration, and can hang 16x7 soaking wet maple on an 1 1/2" pin chuck. The jaws can only go about 7/8 deep, so anything much over 8 x 4 takes a fairly delicate touch.

I leave the pillar in after hollowing on green stock, because a quick ream with a forstner gives me a properly centered piece to re-turn to circularity.

Quick Pictures.

 

[MichaelMouse]

When I work with large blanks, I always use a faceplate. Plane the surface where the faceplate sits using a hand plane. If you have a planer large enough to accept big blanks. that's even better.
Ed

Fix the piece to be mounted on a board to make it easier to slide around on the drillpress table, then set the drillpress depth stop and bore overlapping Forstner holes to flatten the area for faceplate attachment. Lots easier than sweating it down with a scrub plane.

 

[Hugh]

For a lifting device - A friend of mine has a bad back and turns fairly good sized bowls. He does not like to pick up large chunks of wood to mount on the lathe. What he did is buy a Harbor Freight electric chain hoist and mounted it over his lathe. He said it cost around $100. His has a 4 -6 foot length of rail for the hoist to run on. I am not sure how he attaches the chain hoist to the wood - but that should not be too hard to figure out a way.
Hugh

 

[W.C. Turner]

Update

I think I may have discovered part of my problem.

I changed the belt, on my PM3520A lathe, over, from the high range, to the low speed range. I didn't get to try it out much yet, but, I think it should spin the larger heavier, blanks much better.

I've been using the high speed range for most everything, & just thought about the low range.

W.C.