Metric Gears and Racks, I'm lost.

A

alphonso

Titanium

Joined

Feb 15, 2006

Location

Republic of Texas

• Dec 28, 2020

• #1

Large Italian built lathe. Crank and gear for tailstock are missing. Near as I can tell the pitch/module(?) is .511/13mm. Measuring from crown of one tooth to same point on next tooth. WTF have I got here? Have about 2.375" clearance between rack and lead screw.

 

L

Limy Sami

Diamond

Joined

Jan 7, 2007

Location

Norfolk, UK

• Dec 28, 2020

• #2

Going by your info You have probably ?????? got a MOD 13 rack & pinion, .......IME Italian m/c tool builders love to be awkward and ''brew their own'' my Induma mill has 5tpi leadscews on 30mm dia

 

johnoder

Diamond

Joined

Jul 16, 2004

Location

Houston, TX USA

• Dec 28, 2020

• #3

alphonso said:

Large Italian built lathe. Crank and gear for tailstock are missing. Near as I can tell the pitch/module(?) is .511/13mm. Measuring from crown of one tooth to same point on next tooth. WTF have I got here? Have about 2.375" clearance between rack and lead screw.

Click to expand...

No tooth count yet - but lets say it is 12 teeth and Module 4 - makes a 48 mm pitch dia - a little less than 2"

As to what the pitch eyeballs, that same gear would have 12.56 mm "looking" pitch

It would help to post a dimension from center of what the gear mounts on to mid depth of rack tooth

 

A

alphonso

Titanium

Joined

Feb 15, 2006

Location

Republic of Texas

• Dec 29, 2020

• #4

Pulled segment off tail stock end of machine to get (maybe) better measurements. Doesn't appear to have any wear. Kinda surprised that there is 4 or 5 thousandths difference in overall height in the 22 inch long segment. Width of rack is 1.525.

John, not sure what you are asking, base of rack to (sort of) pitch line? 1.071.





Limi, yes there are a number of strange things on this lathe. Operations are a wee bit different from what I am used to.

 

johnoder

Diamond

Joined

Jul 16, 2004

Location

Houston, TX USA

• Dec 29, 2020

• #5

John, not sure what you are asking, base of rack to (sort of) pitch line? 1.071.

Click to expand...

Your picture added to



In other words, you have some sort of bracket bolted to TS and it has a bore in it for said axle. You need to know a vertical dimension from the C/L of that bore up to the point indicated on the captioned rack photo

Twice that dimension is pitch diameter of gear you need - and will be evenly divisible by some number of teeth that are Module 4 sized

I am sticking to Module 4 for the time being since its pitch is only .008 less than what you came up with .352 + .1535

The other possibility is that the Italian gents used .500" circular pitch instead of anything metric

As can be seen on your rack sketch, your new gear will be 20 degree pressure angle

For reference, here is what the "bracket" looks like on my 20" Heavy Greaves Klusman

 

A

alphonso

Titanium

Joined

Feb 15, 2006

Location

Republic of Texas

• Dec 29, 2020

• #6

I guess I wasn't clear in my original post. I do not have the tail stock bracket, gear, axle or handle. I want to know what pitch of gear will be compatibale with the rack. The bracket, size and number of teeth of the gear can be determined when the pitch of the rack is known.

i have English/imperial/American pitch gages and none of them fit the rack. 6 pitch is a little course, 7 pitch is a little fine. Have metric/module gages coming. Just thought I could get a head start from the group.

 

johnoder

Diamond

Joined

Jul 16, 2004

Location

Houston, TX USA

• Dec 29, 2020

• #7

Here is a 12 tooth Module 4 for not much - maybe a pace to start. Its O.D will be near 2 1/4

Catalog | K Standard Pinion Gear - Module 4, Full-Depth Tooth, Pressure Angle 20deg (Katayama Chain) | Katayama Chain | MISUMI

have fun

 

A

alphonso

Titanium

Joined

Feb 15, 2006

Location

Republic of Texas

• Dec 29, 2020

• #8

Well, metric/module gages arrived. It appears that M4 is the pitch. The root of the gage matches the crest of the rack. However, the rack has truncated teeth. According to a downloaded CAD file and the gage, the tooth height is .346, not the .278 measured on the rack.

Now to find a gear that will fit in between the rack and the lead screw, then make a bracket.

BTW, the Misumi link requires registering to read CAD files/order product and is not sending out verification email. Will find a gear elsewhere.

 

P

Peter Neill

Stainless

Joined

Apr 30, 2006

Location

Suffolk, England

• Dec 29, 2020

• #9

Some easy reference information here, may help you determine what size gear you need to mate with the rack.
Select Module size, click go, and you'll get a PDF with OD, PCD, and number of teeth.

HPC Gears Spur Gears Products

 

Mtndew

Diamond

Joined

Jun 7, 2012

Location

Michigan

• Dec 30, 2020

• #10

Here is another site that seems to have a lot of info on gear dimensions,maybe this will help?
Technical Gear Info | Omni Gear & Machine Corp.

 

EmGo

Diamond

Joined

Apr 14, 2018

Location

in the middle of the edge of the center

• Dec 30, 2020

• #11

alphonso said:

The bracket, size and number of teeth of the gear can be determined when the pitch of the rack is known.

Click to expand...

Alphonso, everything in involute gearing is derived from the rack, so since you have a rack, it's a pickanick mr ranger sir. For pitch, just measure from any feature to the same feature on an adjacent tooth. There's your pitch.

Pressure angle likewise, it's the angle between a vertical and the side of one tooth.

If you gotta rack, you're set, buddy.