Today in the shop (turning problem)

reible · Post by **reible** » Mon May 19, 2014 12:08 am

Here is the situation, I've been working on making some pendants but today I ran in to an issue that has me pretty much stopped in my tracks.

Forward

I purchased a faceplate that has a center hole and a series of "off-center" holes. I have this mounts by way of a 3/8" stud that is mounted in a shopsmith router chuck by way of a 3/8" to 1/2" adapter. That faceplate then has a series of screw holes that allows the secondary plate to be mounted in any of the 24 locations available. Don't worry pictures are coming.

To the secondary plate has screw holes to mount a waste block. Like other projects the waste block becomes the place the project is mounted for turning. So first I true up the block so it runs round and flat. Then I turn the area where the pendent will mount, a smaller area so I can tape the project piece down but still get my fingers in to remove it (held on with double side tape).

As mentioned here are the pictures:

[ATTACH]25069[/ATTACH]
This is the collection of parts.

[ATTACH]25070[/ATTACH]
When assembled it looks like this. Note the "0" and "0" are lined up.
This is where I trued up the block and have it ready to mount the pendant.

[ATTACH]25071[/ATTACH]
This show the front or working face.

[ATTACH]25072[/ATTACH]
The pieces have been rotated 180 degrees.

Problem

This attachment is normal sold with a MT2 to 3/8" drive for use in more conventional lathes. I'm using a cut off bolt which I made to turn bottle stoppers and that sort of thing. It has worked well for that and in fact I have made two of these for convenience. I tried both of them.

In this video things are setup and working pretty much the way it is expected to work.

https://www.youtube.com/watch?v=wFk890juj5k

The lathe is running at 1000 rpm and I would have no problem making a pendant and in fact I have.

In this video the index was changed so it is 180 degrees from the previous setting.

https://www.youtube.com/watch?v=WXkWkZn8BPk

As you can see it is wobble time, this would be very difficult to do any fine turning with it this way.

I stepped back to just the faceplate for this video.

https://www.youtube.com/watch?v=DBD36l-bO5M

Indeed the issues is clearly presenting it self already.

So as of right now the indexing is not functional except at "0" "0".

My problem is which part is causing the issue. It could be the bolt but the faceplate seems to run pretty well on it side edge.... the faceplate could either be drilled a bit off or the face might not be flat.

I plan to contact the seller but I though I give you guys a shot at providing some input. I'm no lathe expert so maybe you will see something amiss.

Worse case I guess I could have an adapter made, 5/8" shopsmith to 3/8" x 16........

Ed

greitz · Post by **greitz** » Mon May 19, 2014 12:37 am

Ed- the Shopsmith lathe screw center has a hole that's a little too small for a 3/8" x 16 screw, but maybe you could bore it out a bit?

Gary

rcplaneguy · Post by **rcplaneguy** » Mon May 19, 2014 9:35 am

Would something like this help?
http://www.ebay.com/itm/LATHE-HEADSTOCK-ADAPTER-w-1-2-20-THREADS-FITS-5-8-PLAIN-SHOPSMITH-SPINDLE-NEW-/291116179326?pt=LH_DefaultDomain_0&hash=item43c7e05f7e

JPG · Post by **JPG** » Mon May 19, 2014 10:35 am

In all three videos the base plate(attached to the drive screw/shaft) wobbles.

If you are truing the mount block with the secondary plate set to '0', then when set to 180, the wobble of the base plate will be doubled since the mounting block was 'trued' to a wobbling base plate. The greater od of the mounting block will increase apparent wobble further.

Measure the od of the screw and the id and od of the sleeve.

I believe all the wobble is due to runout between the 1/2" router adapter and the base plate. A bent screw would be culpable as well.

I have two observations which lead to two questions.

1) Is there a cone like projection on one end one the base plate which mates with the concave cone shape in the end of the secondary plate? Orrr, is there one on the mt2 mount you are not usingf?(I now see it is flat on the table)

2) The mounting block is threaded in the center bore. Relevant or not?

terrydowning · Post by **terrydowning** » Mon May 19, 2014 11:55 am

I don't get it.

Why are you setting the indexed plates 180 degrees out?

dusty · Post by **dusty** » Mon May 19, 2014 12:51 pm

Ed, I assume you initially trued the block with it attached to the faceplate and the faceplate aligned 0/0. I further assume that if you return to that setup, the vibration goes back to normal.

If that is the case, it seems to me that somehoe the black simply gets off center to the faceplate.

I'll be watching to see what turns up.

rpd · Post by **rpd** » Mon May 19, 2014 1:44 pm

I would be suspicious of the 3/8 stud/washer/nut/adapter assembly. A one piece machined arbor would be a better way to go.
Tapmatic 1/2" Straight Shank Arbor with Threaded Mount, 3/8"-24 Thread

[ATTACH]25074[/ATTACH]

JPG · Post by **JPG** » Mon May 19, 2014 1:55 pm

rpd wrote:I would be suspicious of the 3/8 stud/washer/nut/adapter assembly. A one piece machined arbor would be a better way to go.
Tapmatic 1/2" Straight Shank Arbor with Threaded Mount, 3/8"-24 Thread

[ATTACH]25074[/ATTACH]

BINGO!!!!!!!!!!!!

reible · Post by **reible** » Mon May 19, 2014 3:49 pm

Thank you all for your responses! I'm having a gardening day so thus far I have just done a skim read of the reply's.

I have looked at the screw centers I have made, they both pass the roll test as best as I could tell. Anytime threads are involved it is more difficult to view none the less with a back light I see a pretty uniform pattern. This does not mean that they are not the problem.....

The indexing is every 15 degrees and it does not take long before the issue starts showing up. Yes it is very pronounced when you are 180 degrees out which is indicative of the possible issues.

I think it might be well for me to have a special shopsmith version made to order, one that will eliminate issues on my end, thus either solving the problem or moving it to the faceplate.

I'll be back tonight to digest what has been written.

Ed

reible · Post by **reible** » Tue May 20, 2014 12:24 am

Today was a washout of shop time, to much gardening to do. I'm hoping it rains for part of tomorrow so I can have more time to look at this situation.

To answer the two questions, the cone looking hole is for a screw that would attach say a bottle stopper directly to the plate. This is how some bottle stoppers are done, the bottom is done first then threaded and attached via a 3/8" x 16 tpi mounting stud.

The mounting block was threaded so I could turn the back side flat, step one in the process. The block is then turned so the flat sits against the second plate where the 4 screws mount it. The faceplate is then attached to the second plate via a set of screws. This is when the block is turned true and the step is made on the front. The 3/8" x 16 screw doesn't come in to contact with the block except for the original flatting process.

Does that make sense?

Ed

JPG40504 wrote:In all three videos the base plate(attached to the drive screw/shaft) wobbles.

If you are truing the mount block with the secondary plate set to '0', then when set to 180, the wobble of the base plate will be doubled since the mounting block was 'trued' to a wobbling base plate. The greater od of the mounting block will increase apparent wobble further.

Measure the od of the screw and the id and od of the sleeve.

I believe all the wobble is due to runout between the 1/2" router adapter and the base plate. A bent screw would be culpable as well.

I have two observations which lead to two questions.

1) Is there a cone like projection on one end one the base plate which mates with the concave cone shape in the end of the secondary plate? Orrr, is there one on the mt2 mount you are not usingf?(I now see it is flat on the table)

2) The mounting block is threaded in the center bore. Relevant or not?