You are using an out of date browser. It may not display this or other websites correctly.

You should upgrade or use an alternative browser.

You should upgrade or use an alternative browser.

- Thread starter GrahamJ46
- Start date

Just curious on what you want to do with the CSV file? I have exported a WTP summary before. The main use was when designing a bowl from a board. Row number, outside and inside diameter were the only data I needed.

It would be interesting to see your spreadsheet with the calculations. I just use the segment edge length calculated by WTP.I do some processing to derive the fractional setup blocks for the distance to the blade for the Segeasy sled.

I also use a seg easy sled. To set the distance for the stop block for the segments I use a digital caliper. I set the distance on the readout, do a first cut on a thin scrap piece of wood, use the caliper and mark the segment length on the scrap, then place the scrap against the segeasy fence and align the mark to the blade and the stop block. I will then do a test cut and measure. Fine tune the adjustment if needed and then all the segments.

Unless I am missing something there is no need to do any test cuts. The distance to the blade can be calculated via:

Ring OD x tan(180/number of segments) x cos(180/number of segments)

Having done the calculation I work out the combination of fractional setup blocks to make the calculated distance. I then use that to set the distance and cut away! I have a Segment PRO output which uses both a regular report and a report where the board width is grouped after optimizing. I use both reports to produce the above and a cut list. See attached.

Ring OD x tan(180/number of segments) x cos(180/number of segments)

Having done the calculation I work out the combination of fractional setup blocks to make the calculated distance. I then use that to set the distance and cut away! I have a Segment PRO output which uses both a regular report and a report where the board width is grouped after optimizing. I use both reports to produce the above and a cut list. See attached.

WTP and SP program uses chord length instead of actual arc length for calculating SEL.

(diameter * pie) / number of segments = sel.

Many turners use this formula for determining segment edge length. This is accurate enough when you consider the ring will be turned down to the final diameter. I personally make a ring .128 to .25 larger than planned and turn down do diameter.

Definition in WTP help section states:I understand. So when WTP & SP state OD what is it, corner to corner or chord to chord? To allow for turn down I have added to the OD when designing.

Outside Diameter = the maximum diameter of the ring once turned perfectly round.

I am not a math wiz. WTP/SP uses the basic formula I have already posted. Even Malcolm Tibbets in his books use the same basic formula. I have found that WTP/SP calculations create the ring diameters I want to build. Tangent calc is more accurate but the difference is not critical for something that is going to get turned down to desired size.

What the math (spreadsheet or software) does not account for is glue line, slight variation in segment sizes, etc. What may start out to be a 6.0 inch dia. ring may end up actually being slightly larger due to the glue up. I have found using the software many years the plans have been accurate to meet the design needs of the turning.

If you want more information I would suggest you send Lloyd an email.

Happy turning.

Happy New Year. Let's hope that it is much better than 2020.