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 Home Model Engine Machinist > 2 Mistakes

01-24-2016, 10:27 AM   #1
1Fitch

Join Date: Jun 2015
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2 Mistakes

Mistake #1

For Christmas my girlfriend wanted to get me a chucking reamer set I had looked at at one one point. Because I have been wanting to cut gears I asked for a dividing head instead. I directed her to the BS1 type that Grizzly sells. I knew there was a problem when I tried to move it and it weighed what felt like seventy pounds. I barely have 6" between centers. A BS0 type dividing head would have been much more suitable for my RF25 mill.

Mistake #2

I have cut a couple of gears using my new (over sized) dividing head. Once I understood the formulas involve for gear cutting and watching Tubalcains videos a few times I thought I had it down. The first couple of good gears I cut were all direct indexed. When I needed to cut a 35 tooth gear is when the trouble started. I'm 46 now and haven't worked with fractions for over 26 years. My calculation was 40/35 = 1 5/40 = 1 1/8 instead of the correct 1 5/35 = 1 1/7! I bolted on a plate with a 16 hole circle and away I went with 1 turn and skip two spaces. When I got to my last gear tooth, I was shocked!
To make this gear blank on my Sherline lathe requires I use riser blocks and care because this is really large for this lathe.

Back to 6th grade math class I go.
Enough of what a dummy I am for now.

Paul

01-24-2016, 04:43 PM   #2
Swifty

Join Date: Mar 2012
Location: Melbourne, Australia
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The dividing head should have come with a chart showing which plate to use and how many turns and holes for the required number of divisions.

Paul.

01-24-2016, 05:46 PM   #3
portlandron

Join Date: Jan 2010
Posts: 221
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Anyone that has ever cut a gear has a few "mistakes"

Regarding the dividing head that's not a mistake. Look at it as you have a dividing head to fit the new lathe that will some day replace your Sherline.

01-24-2016, 06:36 PM   #4
xpylonracer

Join Date: Dec 2010
Location: West Norfolk, UK
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Hi Paul

To save yourself a lot of headaches with which index wheel and number of divisions to use visit Marv's site and check for a simple dividing program, I can't remember the exact program name but there many there to choose from and most have a description, link to the site is
http://www.myvirtualnetwork.com/mklotz/

Emgee

01-29-2016, 03:22 AM   #5
1Fitch

Join Date: Jun 2015
Posts: 11
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Thanks for the replies guys. Swifty, I found the chart you were referring to. I would have never thought to read the directions! Emgee, thanks for the link. There is good stuff there. I appreciate every ones input.

Paul

01-29-2016, 03:51 AM   #6
bazmak
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Some are simple and costly and it hurts at the time

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01-29-2016, 07:21 PM   #7
mcostello
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01-31-2016, 10:32 AM   #8
1Fitch

Join Date: Jun 2015
Posts: 11
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That's how we roll. Learn from our mistakes and keep moving forward. Thank you guys for taking time to read/respond to my post. You guys that have much more machining experience/knowledge than me are always an asset here on the forums.

Paul

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