PSI lathe frustrations

[blame]

hey guys

been playing with the PSI lathe i got off of ebay here awile back

i'm alittle frustrated with both the tailstock and the psi 4" util chuck
the tailstock doesnt apply very much pressure instead it slips on the bed so looking at it i found you could tighten the nut on it there for increasing clamping pressure so i thought but now the nut is bottemed out on the threads and still it slides. it wont even drive the spur point into a pcs of soft maple whats up with that?

and psi chuck works great if i use it from the start but if i use the face plate or the spur point when i put the turning into the chuck its always out of round

and which is better clamping on the inner id or outer id of a turning?
i tried to turn a small 8 inch bowl i used the face plate to rough it out then used the chuck to try to hollow it out first using the inner dia of the chuck jaws the after it flung off the lathe breaking the tang off the bottom of the bowl i then drilled a 1 1/2" hole 1/2" deep to try the outer dia of the chuck jaws same thing bowl flung off the lathe also tried both the #1 and #2 jaws the #1 jaws held better then the #2 but still had to play catch with the lathe LOL
so what am i doing wrong? do i need to just keep play catch so to speak or??????

thanks in advance for any help
blame

[bmyers]

Sorry to hear about your troubles. Don't give up! I think you just need some minor adjustments.

First, perhaps a washer between the nut and the bed will help your tailstock grab a little better. Make sure it's assembled correctly, there may be a washer there already but in the wrong order.

There is no single right method for your jaws. General rule is clamp whichever way you can apply the most pressure without breaking your workpiece or the jaws. If you think of an egg, you can't break it by sqeezing it but a little baby chick can bust out easily. So, squeezing hollow circles together is generally better than pushing them apart.

For small bowls, you can use the face plate with the blank screwed into it or you could use a center screw and clamp that into your PSI chuck. Turn the outside of the bowl and when you get to the bottom, make a 1/4" deep dovetail recess for the foot of the bowl. That means the spigot gets slightly bigger as it gets farther away from the bottom. Make it 2 inches in diameter (or the approximate size of your #2 jaw when expanded a little bit)

Now switch to your #2 jaw and rechuck the bowl, expanding the jaws to grab onto that dovetail cut in the bottom. Hollow out the inside of the bowl.

If you have the "jumbo" jaw with the adjustable rubber pieces you can rechuck the bowl again to turn away the recessed dovetail cut for a more refined look to the foot of the bowl. With practice, sharp tools and a light touch you can make the dovetail recess more shallow and less noticable and still not have it go flying across the shop.

BT3 Member kwgeorge has some great pics and movies out there. Check out this one on tennons and spigots. You want to make a spigot and grab that with your PSI chuck.

http://www.theturnersshop.com/turnin...t_and_s_1.html

And the rest of his site too. It's very good stuff.

HTH,
Bill

[blame]

thanks for the link bill i'll check it out

[DonHo]

I have the PSI lathe and haven't had to adjust the clamp on the tailstock so I'm not all that familar with the adjustment process but I think it's addressed in the manual, it you don't have the manual let me know and I'll try to post what my manual says about it.

As for the chuck, I can't figure why you shouldn't be able to start a bowl on a face plate then switch to the chuck and still be centered if you cut the tenon or rebate while the blank is turning on the lathe, I do this as regular practice. It may be that you didn't square up the foot of the blank and thus the rebate or tenon wouldn't be square and cause the blank to set sligntly at an angle which would cause it to wobble.

I also don't think the PSI chuck has dovetailed jaws, so it should get a better grip with straight walled rebate or tenon. I will just add that if you are using a rebate (griping from the inside) you should be sure to leave plenty of thickness in the wall of the rebate, I have busted out a couple of thin walled rebates when I've had a catch. On the other side of the coin I've also twisted off a tenon which was too thin in the same way.

Good luck,
DonHo

[Tom Miller]

To fix the tailstock slipping on the bed -- check the mating surfaces to make sure they're clean of everything including wax, finish used in previous turning projects, dust, etc. (Maybe a good wiping with mineral spirits or naptha.) If that doesn't do it, you can always stick some 320 grit sandpaper to the bottom of your tailstock.

I'm guessing your chuck may have some runout -- I've experienced that to some degree with my PSI utility chuck. To determine for sure (and the actual amount of runout), chuck a cylinder and measure with a dial indicator.

If you have runout, you can learn to deal with it, or get rid of the chuck. When I reverse a turning with such a chuck, I just plan to cut a little more to get back to round.

Regards,
Tom

[kwgeorge]

Hello Blame, I think I would offer a few things to you.

First off the tailstock is really only meant to assist in holding the piece in the lathe. You should not be using it to drive a spur center but rather should do that with a mallet prior to mounting the spur in the lathe. You will find it a lot easier to remove the spur drive from the headstock later. In reality the live center should be just snug enough to hold the piece secure. If you feel your tailstock still moves to easily then you need to adjust the bolt between the lathe bed ways. If this still don’t get you were you want to be you could as suggested clean the ways and the matting surface on the tailstock and alternatively you could rough up the ways just a bit with a stiff wire brush. I do not recommend putting anything under the tailstock where it mates the bed ways as to do so would alter the centers alignment. You could however if alignment was a problem.

On the chuck, there are many things you need to get in the habit of doing and dealing with a chuck is one of them. The first thing you need to do is verify that the chuck is going all the way onto the spindle and seating against the rear of the spindle. If it is not than you will need to add a washer. Next if your chuck has a spindle size adapter you need to make sure it is screwed all the way in and seated. Now onto mounting the work piece, it matters only to the type of task you are trying to accomplish as to if you use a Tenon or Spigot (also referred to as Rebate) what does matter is where the piece is seating on the chuck. Either way you are mounting the piece should be resting on the face of the jaws and never touch the back of the jaws.

Some other things you can check for is metal burs from manufacturing sill remaining in different parts of the chuck including between the jaws and the slides and so on.

Ken

[blame]

hey guys thanks for all the great replies

as far as the tail stock goes i used DonHo's advice and added a washer under the special washer that was already there problem solved thank you for the idea DonHo

now to the chuck

i really hate this one , i'm still having the same problem as before when i chuck a piece after using the face plate i always have to go back over the work pc again . this is how i have been making the Tenon i use a 1/2" skew chisel that i have ground to a 15 deg ang
first i cut it down to about 2" in dia. then i straiten out my skew and cut it for the ang.
the tenon is a 1/4" in length once that is done i then chuck it into the psi chuck when i think it is seated correctly but there always off

any ideas ?

the other thing that has been a frustration is when i'm working on hollowing a piece its breaking the hold the chuck has on the tenon it seems to make no difference how tight i tighten the chuck it always seems to break its hold when i get about an 1 1/2" into the hollowing process i try to take as light a cut as i can even down to where is just dust coming off the 3/8" bowl gouge. my gouge is sharp i've been using a leather strop on it
its sharp enough to cut paper from just its own weight ( a friend of mine is a knife maker and i took all my lathe chisels to him and had him sharpen them cost me $35 for 21 chisels) do i need to use a different tool rest once i get and inch or so into the piece or ?
maybe thats what i need to do. i'll have to make a round bar rest out of 3/4 " bar stock

dunno i 'll try it and see what happens
blame