Change gears - pressure angle

Reeltor

Active User
Registered
Joined
Nov 18, 2014
Messages
741
Standard involute gear cutter in a Bridgeport on a 7/8" arbor. For those not familiar with gear cutter nomenclature, this one is No.7 (in a series of 8) with 20 Diametrical Pitch (abbreviated as P here and as DP on other gear cutters) and it cuts gears with 14 to 16 teeth. The full depth of cut is 0.108". The pressure angle is not marked on this cutter. We had to cut a gear with the cutter to determine what pressure angle the cutter was. We got lucky and this one was the correct 14.5º which is what we needed. In my collection I just happened to have this single cutter, acquired some time over the last 30 or so years from an unknown source. The arbor holding the gear blank is unusually long because there is a bad bearing in the dividing head causing runout. By using a long arbor and keeping the cutting near the tailstock, we've reduced the runout of the arbor. I'm still shopping the used market for the #4 cutter in the 20DP series to do the 32 tooth gear my friend needs.
View attachment 227603 View attachment 227604 View attachment 227605


Thank you for the photo, from the shot that you had of the gears sitting on your mill it looked like some type of endmill was being used. Do you have any issues using the (milling) arbor with the unsupported end? When I cut some 4DP gears on the horizontal mill, I had to do everything I could to increase rigidity. On the 4dp cutters you are going just over 1/2" depth of cut.
 

RWL

Active User
Registered
Joined
Nov 11, 2011
Messages
225
The cutter is mounted on a stub arbor held by 3/4" end mill holder. If the cutter had had a bor of 1" instead of 7/8" I could have mounted it on my 1" R8 stub milling arbor with less stick out. With the 20DP cutter I've had no vibrations with this setup. It was a rather smooth cut. When we go to cut the 32 tooth gear, which is larger in diameter, we're wondering if we'll get some vibration from the arbor holding the gear blank. Time will tell.
 

lowpass5

Registered
Registered
Joined
Feb 24, 2017
Messages
11
Nice to see you are able to make what you need to repair the lathe. When I needed to replace the transfer gear on my Rockwell 11", I bought a stock unhardened gear off ebay and machined it to size.

I too had a couple of stripped gears in the QCGB and was able to find used replacements through the Rockwell Lathe Yahoo groups. Would recommend joining the group and posting your parts needs. There are a fair number of knowledgeable folks on the forum that can help you with the machine.

The Rockwells are great lathes.
 

RWL

Active User
Registered
Joined
Nov 11, 2011
Messages
225
Within the past day or two, the gear that my friend needed showed up on ebay. A 20 DP #4 gear cutter also appeared. My friend bought the gear cutter and we anticipate making some of the 32 tooth gears next. We'll make an extra or two of the 32 tooth combined gear in the hopes of recovering our expenses.
 

Jim D.

Registered
Registered
Joined
Jul 25, 2020
Messages
5
Hello,

I know this is a long shot after 3 years, but do you still have any of the mated 16/32 tooth gears for sale?

I have restored a 1968 Rockwell 10" and have 2 of these gears worn in the gearbox. I would buy 3 of them from you depending on price.

Thanks for your consideration.

Regards,
Jim D.



We'll make an extra or two of the 32 tooth combined gear in the hopes of recovering our expenses.
 

RWL

Active User
Registered
Joined
Nov 11, 2011
Messages
225
I think we made an extra pair and I think my neighbor has them since I don't. I'll check with him.
 

RWL

Active User
Registered
Joined
Nov 11, 2011
Messages
225
My neighbor says he has the gears. Check your messages here at hobby machinist for other details. If you need more than one pair, we'd have to set things up again and redo our calculations.
 

Jim D.

Registered
Registered
Joined
Jul 25, 2020
Messages
5
Hello RWL,

I'm wondering if you got the email I sent you directly. I'm not familiar with using forums and now I can't seem to find the message you sent the other day.

Thanks,

Jim D.
 

RWL

Active User
Registered
Joined
Nov 11, 2011
Messages
225
I didn't get any email from you. The messages on PM are accessed by clicking on the little envelope in the upper right side of the banner at the top of the page.
 

wa5cab

Downloads Moderator
Staff member
H-M Platinum Supporter
Joined
Dec 25, 2011
Messages
9,197
FWIW, the Xenforo PM (Private Message) system is called "Conversations". That buzz-word may have originated with Yahoo. Or at least that's the first place that I recall seeing it.
 
It can take up to an hour for ads to appear on the page. See our code implementation guide for more details. If you already have Auto ad code on your pages there's no need to replace it with this code
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock