I have an 8" Palmgren rotary table. The table is marked with 180
divisions, or 2 degrees per division. The crank has 100 divisions. One
turn of the crank turns the table 9 divisions, or 18 degrees, making one
division on the crank .18 degrees. Nothing appears to be direct reading.
Is the design screwy, or do I not know the proper technique?

Kevin Gallimore

axolotl wrote:
I have an 8" Palmgren rotary table. The table is marked with 180
divisions, or 2 degrees per division. The crank has 100 divisions. One
turn of the crank turns the table 9 divisions, or 18 degrees, making
one division on the crank .18 degrees. Nothing appears to be direct
reading. Is the design screwy, or do I not know the proper technique?

Kevin Gallimore

Sounds like a 40:1 worm , which is a standard ratio - mine's 90:1 which
makes each turn 4°. Do you have index plates with it ? I can't remember the
calculation offhand , but with the plates you can divide a circle into
however many segments you want - think "gearcuttung" , where the degrees
don't really matter but the number of teeth does .
--
Snag
Learning keeps
you young !

On Sun, 02 Jan 2011 16:53:01 -0500, axolotl
wrote:

I have an 8" Palmgren rotary table. The table is marked with 180
divisions, or 2 degrees per division. The crank has 100 divisions. One
turn of the crank turns the table 9 divisions, or 18 degrees, making one
division on the crank .18 degrees. Nothing appears to be direct reading.
Is the design screwy, or do I not know the proper technique?

Kevin Gallimore
==========
Try asking Palmgren.

see
http://www.palmgren.com/contact_us.php
and
http://www.palmgren.com/index.php?cPath=13_14

or 800.621.6145 773.265.5740 (fax)

-- Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

On Jan 2, 4:53*pm, axolotl wrote:
I have an 8" Palmgren rotary table. The table is marked with 180
divisions, or 2 degrees per division. The crank has 100 divisions. One
turn of the crank turns the table 9 divisions, or 18 degrees, making one
division on the crank .18 degrees. Nothing appears to be direct reading.
Is the design screwy, or do I not know the proper technique?

Kevin Gallimore

That sounds like a non-standard rotary table. If one turn turns the
table 18 degrees, than the rotary table has a 20:1 gear ratio. Not
what I would expect. 40:1 is what I would expect.

The MSC catalog has Palmgren rotary tables listed, but they are all
40:1 gear ratios. Would you mind checking one more time what the gear
ratio is? I just find it hard to believe that your rotary table has a
20:1 gear ratio.

Dan

On 1/2/2011 6:08 PM, wrote:

That sounds like a non-standard rotary table. If one turn turns the
table 18 degrees, than the rotary table has a 20:1 gear ratio. Not
what I would expect. 40:1 is what I would expect.

The MSC catalog has Palmgren rotary tables listed, but they are all
40:1 gear ratios. Would you mind checking one more time what the gear
ratio is? I just find it hard to believe that your rotary table has a
20:1 gear ratio.

Dan,

I just went down and double checked. Twenty revolutions of the crank
gives one revolution of the table. Perhaps it was a compromise in
cranking speed; the table has no way to decouple the worm gear and shift
the table by hand. It is a horizontal only table similar in appearance
to the No. 86 made in the fifties. The age is unknown- it was a Cabin
Fever purchase.

Kevin Gallimore

--Palmgren is known for making crap. Think of it as a boat anchor
and get something better for precision movement.

--
"Steamboat Ed" Haas : Steel, Stainless, Titanium:
Hacking the Trailing Edge! : Guaranteed Uncertified Welding!
www.nmpproducts.com
---Decks a-wash in a sea of words---

On Jan 2, 6:55*pm, axolotl wrote:

Dan,

I just went down and double checked. Twenty revolutions of the crank
gives one revolution of the table. Perhaps it was a compromise in
cranking speed; the table has no way to decouple the worm gear and shift
the table by hand. It is a horizontal only table similar in appearance
to the No. 86 made in the fifties. The age is unknown- it was a Cabin
Fever purchase.

Kevin Gallimore

Thanks for looking. I am not sure why they would have used 20:1
gearing.

Dan

On 1/3/2011 2:30 PM, Jim Wilkins wrote:
On Jan 2, 6:55 pm, wrote:
...
I just went down and double checked. Twenty revolutions of the crank
gives one revolution of the table. Perhaps it was a compromise in
cranking speed; the table has no way to decouple the worm gear and shift
the table by hand. It is a horizontal only table similar in appearance
to the No. 86 made in the fifties. The age is unknown- it was a Cabin
Fever purchase.

Kevin Gallimore

To make N divisions on the table you turn the crank 20/N times

table crank
2 10
3 20/3 = 6 full + 66.7/100
4 5
5 4
6 20/6 = 3 full + 33.3/100
8 20/8 = 2 full + 50/100
and so on.

To mill a hexagon, like a bolt head, you'd start at zero and cut a
flat. Turn the crank twice plus 33.3 marks and mill the second flat.
Turn two full revs and stop at 66.6 for the third. Next turn two full
revs and advance to zero (=100) for the fourth, etc.

I wrote a spreadsheet that lists all the full and partial turns for up
to N = 100 for my 40:1 table.

jsw


Good idea. I'll make one up and post it on the door of the cabinet that
holds the table.

Thanks,

Kevin

On 1/3/2011 3:07 PM, Brian Lawson wrote:
On Sun, 02 Jan 2011 18:55:08 -0500, axolotl
wrote:

SNIP
it was a Cabin Fever purchase.

Kevin Gallimore


Hey Kevin,

Not real sure what their return policy is, but you could always take
it back next week!!VBG

At this point I have gotten my money's worth out of it. Just couldn't
figure out why it was made the way it was.



ps...are you going??

If the creek doesn't rise and there is no threat of snow (we got 30-odd
inches in a single snowfall last week). I will be there with my two
beautiful girls.

How about yourself?


Kevin

On 1/3/2011 12:07 PM, steamer wrote:
--Palmgren is known for making crap. Think of it as a boat anchor
and get something better for precision movement.


Palmgren is certainly cheap and cheerful. It will serve, however, until
I find a Troyke at a small multiple of the price I paid.

Kevin