Slimline Question

[JBCustomPens]

Hey everyone,

I have a question. Why is it that most people think that they can't turn slimlines between centers? Do they think that? I do that all the time, and it is no problem for me.

 

[JeffinWIS]

I do also...with home-made bushings. I make all my bushings with a through hole. Allows putting them on a "mandrel" for buffing. No more blanks getting tossed around the shop from trying to hold them with fingertips while buffing.

 

[mbroberg]

I'm wondering why you believe, "most people think that they can't turn slimlines between centers". I don't believe that is a true statement. I think anyone who turns between centers can turn any style kit between centers.

 

[Craftdiggity]

I wonder why anyone would feel the need to turn a pen kit (that is designed to be turned on a mandrel) between centers. Not that I really care about it, but I just wonder what the point is. I understand it as a kind of "one time thing" to see if you can do it, but as a general rule...

 

[jocat54]

I wonder why anyone would feel the need to turn a pen kit (that is designed to be turned on a mandrel) between centers. Not that I really care about it, but I just wonder what the point is. I understand it as a kind of "one time thing" to see if you can do it, but as a general rule...

Chris for me TBC is so much easier and much more accurate than using a mandrel and I always turn my slimlines between centers with homemade bushings.

 

[Mark]

Chris for me TBC is so much easier and much more accurate than using a mandrel and I always turn my slimlines between centers with homemade bushings.

Not trying to start anything. Seriously... I'm new to this and wandering how it's more accurate? Thx.

 

[jocat54]

Mark it eliminates any out of round that the mandrel might have (bent)--they seem to bend very easily, at least for me.

 

[Mark]

Thanks for the answer.
You still glue and tube them correct? Mount them using bushings, just without a mandrel. I did find a bent mandrel. I started using a mandrel saver and hopefully have eliminated that problem. Thank you John.

 

[jskeen]

I wonder why anyone would feel the need to turn a pen kit (that is designed to be turned on a mandrel) between centers. Not that I really care about it, but I just wonder what the point is. I understand it as a kind of "one time thing" to see if you can do it, but as a general rule...

Well, if you prefer for the turned parts to really be round, like the metal parts of the kits, then turning the tubed blanks between centers eliminates problems with imprecisely machined bushings, mandrels that get warped, flex while turning and otherwise introduce error into your turnings that will ultimately cause your pens to be out of round. Of course, if you don't mind having the centerband proud on one side and shy on the other, mandrels work fine

Actually, It is possible to turn very precisely on a mandrel, but it is much simpler to do so between centers, assuming your lathe tapers are both concentric and properly aligned.

Bushings can make it simpler to turn a barrel to the proper diameter at both ends, but only to the degree that they are themselves concentric and fit the ID of the tubes without allowing them to deviate if the ends of the blanks are not precisely perpendicular to the centerline of the tube. One must also assume that they are the exact same diameter as the corresponding part of every kit you use them to assemble, and that they have not had their diameter altered by sanding or turning over their lifespan. They also tend to cause problems if they are in place while finishing. On the other hand a pair of dial calipers can measure each individual component, and allow you to match the final diameter of the tube to it very exactly, for every kit, and without changing over time.

So it's really just a question of how precise you want your pens to be.

 

[jocat54]

Thanks for the answer.
You still glue and tube them correct? Mount them using bushings, just without a mandrel. I did find a bent mandrel. I started using a mandrel saver and hopefully have eliminated that problem. Thank you John.

Yes, with the tubes glued in. I start by turning a blank to round BTC and then mount it in a collet chuck and drill for the tube (very accurate way of drilling-since changing to drilling on the lathe, I haven't had any drilled off center) glue in the tube and then mount BTC again with homemade bushings and turn until close to bushings and then finish turning using calipers for final size. You don't really even need the bushings, it's just how I like doing it.

 

[jocat54]

Well, if you prefer for the turned parts to really be round, like the metal parts of the kits, then turning the tubed blanks between centers eliminates problems with imprecisely machined bushings, mandrels that get warped, flex while turning and otherwise introduce error into your turnings that will ultimately cause your pens to be out of round. Of course, if you don't mind having the centerband proud on one side and shy on the other, mandrels work fine

Actually, It is possible to turn very precisely on a mandrel, but it is much simpler to do so between centers, assuming your lathe tapers are both concentric and properly aligned.

Bushings can make it simpler to turn a barrel to the proper diameter at both ends, but only to the degree that they are themselves concentric and fit the ID of the tubes without allowing them to deviate if the ends of the blanks are not precisely perpendicular to the centerline of the tube. One must also assume that they are the exact same diameter as the corresponding part of every kit you use them to assemble, and that they have not had their diameter altered by sanding or turning over their lifespan. They also tend to cause problems if they are in place while finishing. On the other hand a pair of dial calipers can measure each individual component, and allow you to match the final diameter of the tube to it very exactly, for every kit, and without changing over time.

So it's really just a question of how precise you want your pens to be.

Very well explained.

 

[larryc]

Just to make sure I'm understanding this thread. I agree that TBC is the way to go but the question seems to be about turning both barrels of the slimlines between centers at the same time. I'm getting the feeling that this problem is not being addressed unless these "homemade" bushings allow turning of both sections at the same time. If this is the case I would like to see pics of these bushings and a little more info on how they are used.

 

[mbroberg]

Just to make sure I'm understanding this thread. I agree that TBC is the way to go but the question seems to be about turning both barrels of the slimlines between centers at the same time. I'm getting the feeling that this problem is not being addressed unless these "homemade" bushings allow turning of both sections at the same time. If this is the case I would like to see pics of these bushings and a little more info on how they are used.

When turning between centers only turn one barrel at a time. In fact, even on the rare occasions that I use a mandrel I only turn one barrel at a time. The shorter the distance from the tailstock to the headstock the better. Any out of round that exists due to a bent mandrel or too tight a tailstock will be minimized. TBC eliminates these imperfections. One other thing, If you use a mandrel stop every so often and rotate your bushings so that if you have a low spot on the bushing it is less likely to show up on your barrel.

 

[Craftdiggity]

Maybe I'm just not all that observant, but the only time I've had finished blanks proud on one side was when I first started out and I tightened the nut on the mandrel too much when turning. It took me months to figure that one out, but ever since, I've used several different mandrel types and I have few problems. I guess I'll pay closer attention next time I turn a pen.

 

[PenMan1]

With wood, I always finish cutting proud, then slightly undersize with sanding, then build back up to correct size with CA. This takes a little bit and I'm finally beginning to realize that it just AIN'T worth all that effort for a $20 pen.... So most of the slims I make now are acrylic.

I have found that if I seperate the slims by lots (meaning groups bought together from the same vendor) that these pieces fit nicely from one kit to the other. I set up three sets of calipers with the first pen kit, put both barrels on a madrel and use the caliper measurement for all the slims I am turning at that time. When I do this, and use acrylic, ommitting the CA, I can make 4 or 5 in an hour. I use the higher end kits (TN and Rhodium) so I have $7 or $ 8 in a pen that will ultimatel sell for $20 or $25.

If I measure each individual slimline kit and put on a CA finsih, my production rate drops to 1 or 2 per hour. Therefore, I have all but abandoned slimlines, especially wood slimlines.

 

[Smitty37]

Well, if you prefer for the turned parts to really be round, like the metal parts of the kits, then turning the tubed blanks between centers eliminates problems with imprecisely machined bushings, mandrels that get warped, flex while turning and otherwise introduce error into your turnings that will ultimately cause your pens to be out of round. Of course, if you don't mind having the centerband proud on one side and shy on the other, mandrels work fine

Actually, It is possible to turn very precisely on a mandrel, but it is much simpler to do so between centers, assuming your lathe tapers are both concentric and properly aligned.

Bushings can make it simpler to turn a barrel to the proper diameter at both ends, but only to the degree that they are themselves concentric and fit the ID of the tubes without allowing them to deviate if the ends of the blanks are not precisely perpendicular to the centerline of the tube. One must also assume that they are the exact same diameter as the corresponding part of every kit you use them to assemble, and that they have not had their diameter altered by sanding or turning over their lifespan. They also tend to cause problems if they are in place while finishing. On the other hand a pair of dial calipers can measure each individual component, and allow you to match the final diameter of the tube to it very exactly, for every kit, and without changing over time.

So it's really just a question of how precise you want your pens to be.

I agree...and also it seems related to how much of a purist the turner is. A lot of the folks on here are seeking perfection....that's fine, it gives them pleasure to get as close to perfect as possible and also means they probably take a little longer turning each pen and don't need to turn as many to spend the desired amount of time in their shop. I might take this up myself some day.

There are also those who like to take a perfectly nice piece of wood and make it look like plastic or glass.... I'll pass on this one if I turn it from wood it's because I want it to look like wood. I already have a couple that folks have a hard time telling they aren't hard surface.

 

[rsulli16]

hi,
I'm a newbie at this,
could you explain how you mount bushings if there is no mandrel? just squeeze them between the blank and the head and tailstock? how does it all stay centered ?
Sulli

 

[jskeen]

hi,
I'm a newbie at this,
could you explain how you mount bushings if there is no mandrel? just squeeze them between the blank and the head and tailstock? how does it all stay centered ?
Sulli

You are correct, the bushings are held in the tube by the live center in the tail stock and the drive center in the headstock. This is another reason a 60 degree live center is critical. The bushings are held centered by the fit between the inside of the tube and the outside of the smaller "step" of the bushing. Most stock bushings will work this way, but the fit between the two, and the length of the step makes it less accurate than most of the custom made ones people tend to use, which have longer "insert sections". Also, the stock bushings only contact the centers on a thin ring at the through hole, where many custom bushings have a machined 60 degree inset to contact the center on a wider area, and that is very precisely centered on the bushing.

 

[rsulli16]

thanks

so the tubes are put in the blanks first then, so the tubes act as a mandrel?
Sulli

 

[edman2]

I too turn between centers. I purchased the bushings for the slimline and comfort style pens from Johnnycnc on this site. He makes bushings that insert into the tube instead of butting up against the blank so it makes for better turning between centers.

I checked the Library and didn't find anything on turning between centers. You would have thought with so many of us doing this that someone would have written an article about this for the Library. So...all you articulate turners with a camera out there...someone write something and put it in the Library!