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Doc Nickel
01-06-2014, 11:44 PM
I need to replace this gear out of my QCGB, for obvious reasons. :D

http://docsmachine.com/2014/gear1.jpg

However, gears and their proper nomenclatures are not my forte`. Apart from knowing it has (had?) 24 teeth, fits a 1" shaft and is nominally 1/2" wide, I don't know what to look for by way of pressure angle or... pitch diameter?

I'm hoping I can find an off-the-shelf gear I can bore/key to fit in there, but I need to know what to order. I don't know if these photos will help or not, but I'll be happy to get additional measurements if necessary.

http://docsmachine.com/2014/gear2.jpg

In addition to the above, the teeth measure approximately 0.112" wide (more or less at the base) and going from the peaks of two adjoining teeth to the 'valley floor' is approximately .148".

Doc.

Optics Curmudgeon
01-06-2014, 11:56 PM
Looks to me like you have a 14DP 24 tooth 14 1/2 degree pressure angle gear there. Not so common a pitch any more, but searching for 14DP gears may get you something.

John Stevenson
01-07-2014, 04:16 AM
I agree

Doc Nickel
01-07-2014, 05:57 AM
Well that's no help. :D Nothing in 14DP listed on McMaster, MSC or the recently-noted Amazon Supply. Heck, nothing even on eBay.

And, naturally enough, I have some 36 Brown & Sharpe involute cutters, but not the one I apparently need. (If I have this right, 14DP, 14.5 degree PA, #5 cutter for 21-25 teeth. I have #1, #2, and numbers 6 to 8. Though no pressure angles listed.)

Looks like I'll either have to order a cutter or make a single-pointer.

Why doesn't anyone carry extensive replacement parts for seventy-year-old marques that have been defunct for 20 years. :D

Doc.

haroldmulder
01-07-2014, 06:04 AM
Here is a cutter I believe that you need on Ebay
http://www.ebay.com/itm/NOS-Decovich-Tools-2-1-2-Dia-Involute-Gear-Cutter-14-DP-14-1-2-PA-12-T-5-/350609192223?pt=LH_DefaultDomain_2&hash=item51a1efb51f

Harold

J Tiers
01-07-2014, 08:51 AM
Eh.. use a number 6 and make it. Might be a bit noisy, but should work. Won't be perfect. It's at the wrong end of the range, a #4 (26 -34) would be closer

Or, buy the right one and make the gear.

Seems like the P A should be listed on the cutter...

Timleech
01-07-2014, 09:15 AM
Seems like the P A should be listed on the cutter...

Usual rule, AIUI, is that no marked PA means 14.5 degrees.

Just like no marked form on Coventry die chasers means Whitworth form ;)

Tim

John Stevenson
01-07-2014, 02:23 PM
Doc,
Thought you might have scored as the 14 DP struck a chord. Drummond lathes use 14DP @ 14.5 PA as change wheels and a while ago I was involved in a project with these machines which involved some gears.

So dug around and found the relevant tin, rack 5, bin 3, where I had placed it 12 years ago. Like tree rings to date trees I use spiders webs :o

However no such luck unless you want 27, 21, 16 or 13.

http://www.stevenson-engineers.co.uk/files/14dp%20gears.jpg

You could have had one of these FOC if it had been the right size.

TGTool
01-07-2014, 03:35 PM
Usual rule, AIUI, is that no marked PA means 14.5 degrees.

Just like no marked form on Coventry die chasers means Whitworth form ;)

Tim

Like the zoology rule I guess, "If there's nothing on the tree, it is the chameleon that you see."

Tony
01-07-2014, 03:40 PM
try Stock Drive Parts:
https://sdp-si.com/

techonehundred
01-07-2014, 05:39 PM
This wouldn't happen to be a Sheldon lathe would it? If so look at this gear. It might be worth sending an email to get him to measure the diameter. http://www.ebay.com/itm/Sheldon-Lathe-Feed-Tumbler-Gear-L-1612-24-Tooth-/231130544944?hash=item35d0743b30

lane
01-07-2014, 06:45 PM
Been their done that.You not going to find a store bought gear that pitch,I have looked . Lots of old lathes used 14 DP gears ,but you will have to make it . i have a whole set of cutters in 14 DP just because of that . If you cant find something . PM me and I will make you one .

J Tiers
01-07-2014, 07:29 PM
Usual rule, AIUI, is that no marked PA means 14.5 degrees.

Just like no marked form on Coventry die chasers means Whitworth form ;)

Tim

Maybe.... these are all marked, I think every one I have is marked....

http://img.photobucket.com/albums/0803/jstanley/tooling/gearcuttersPA_zps0c2c2a82.jpg (http://smg.photobucket.com/user/jstanley/media/tooling/gearcuttersPA_zps0c2c2a82.jpg.html)

John Stevenson
01-07-2014, 07:36 PM
Jerry,
now look for one that isn't marked and tell us what angle it is ?

J Tiers
01-07-2014, 09:07 PM
I don't have any not marked.... that I know about.

But I'd have to probably do some pretty tricky measurements to get a good number.... although 14.5 and 20 look like different numbers, they no doubt look pretty close when you go to measure a small gear tooth.... I'm not sure I have adequate measuring "stuff" to even try it. And don't even ask me to do that with a 48DP gear.... :D

Interesting question though.... you mean it as a joke, but I suppose it is do-able.. You'd have to find the pitch diameter, and determine what the tangent line to the tooth is at that diameter (pitch line), and then compare that to a radius... getting the angle between.

I think I'll stick to reading the nice number off the cutter, thank you very much!

Doc Nickel
01-19-2014, 05:21 AM
Okay, I ordered a cutter off eBay, listed as a 14DP, #5, for 21-25 teeth. No pressure angle listed, but I assumed it would be 14.5 as per the above statements. However, comparing the tooth profile to the existing gear shows what I'd consider a reasonably significant mismatch:

http://docsmachine.com/2014/gearcutter.jpg

So what happened? Did I get the wrong cutter? Are the gears a different pressure angle? How would I determine the correct cutter? Am I overlooking something?

Doc.

John Stevenson
01-19-2014, 06:28 AM
Doc, the gear cutter work in bands. you have got a 21 - 25 but want to cut 24.
However the cutter is only truly accurate for it's lowest count - 21. If you look at the profile is pretty good except for the tops of the teeth.

If this was a 21 you would expect more radius there.

Get a file and radius the tops of two teeth slighly and then check the fit and I think you will find it a lot better.
As an aside to assist this they do make hlaf size cutters but they are quite rare today.

Personally For what it's going to be used for I know you will get a decent profile for them to run together.

Doc Nickel
01-19-2014, 07:25 AM
Actually, I was more worried about the width at the base of the teeth. The cutter looks like it'd produce a cut maybe 20-25 thou (by eyeball) narrower than the original gear. Would that be an issue?

Would I be better off grinding a single-point cutter based off the original gear?
Doc.

j king
01-19-2014, 08:57 AM
Hey Doc. Had similar problem identifying a gear the other day.It is a metric gear for a cat poop box cleaner.Not mine but a friend's. He couldn't find a gear so I offered to help.I have some cutters but not the correct one so I single point cut it. I ground a tool and single point cut it.I know you can easily do it too from work I've seen you do.
Only took 2 hours lol! Pissy little thing.
http://img.photobucket.com/albums/v24/ikimjing/Mobile%20Uploads/1390049742_zpsc64b9b28.jpg (http://smg.photobucket.com/user/ikimjing/media/Mobile%20Uploads/1390049742_zpsc64b9b28.jpg.html)

Paul Alciatore
01-19-2014, 02:32 PM
That looks like an awful lot of error. Is that cutter actually labeled, in a professional manner, as 14 DP Or could it be a 16 DP? Perhaps the label means 14 degrees (as in a 14.5 degree pressure angle).

I do not think it will make an acceptable gear for you. I also think you would be a lot better off making a single point tool yourself. Surely you can match the tooth profile better than that. Perhaps start up with the round disk method and touch it up a bit from there.

Perhaps you could post a photo of any markings on the cutter.

Doc Nickel
01-19-2014, 05:04 PM
Is that cutter actually labeled, in a professional manner, as 14 DP Or could it be a 16 DP?

-Actually, no, and that's what's concerning me. The markings are part original stamping, part hand-engraving. "14P" is part of the original stamping, then there's an engraved "2", a stamped "1" and then "to 25 T" is hand engraved. Then there's another stamped "I" followed by an engraved "nvolute" followed by an engraved capital M. The maker's name is UTD Co, Athol, Mass, which is a trace of stamping that has been "filled out" by hand engraving. The opposite side just has a part number, 141600, hand engraved, and probably by a different device than that on the stamped side.

I bought this cutter since the other two on eBay at the time were in either Canada or Australia. It was only $27 with shipping, so if I got the wrong one I'm not too worried about it.

Maybe I should try again? :D

Doc.

J Tiers
01-19-2014, 05:14 PM
UTD would have MADE it correctly, but for what?

Looks like it was maybe made to a contract, hence the part number. In that case, no telling... could be anything, but the "Involute" should mean it was intended for spur gears,

There is another type that is made for cutting bevel gears. It has a narrower profile, to fit through the small end of the gear. Not an issue for bevel gears, since you will be setting it over to cut the other side of the toothspace, but not so good for spur gears.

Timleech
01-19-2014, 06:01 PM
There's a well-known tool supplier in the UK which used to offer gear cutters at a good price. Maybe still do. Some (I bought a couple, years ago) had clearly been surface-ground to remove the original markings and had new markings crudely etched in. I think they were probably old Circular pitch cutters which had been remarked with the nearest DP or Module size.

Tim

John Stevenson
01-19-2014, 06:43 PM
There's a well-known tool supplier in the UK which used to offer gear cutters at a good price. Maybe still do. Some (I bought a couple, years ago) had clearly been surface-ground to remove the original markings and had new markings crudely etched in. I think they were probably old Circular pitch cutters which had been remarked with the nearest DP or Module size.

Tim

Yes bought some supposedly 20DP 14.5 PA for the Myford, one handn't been clean up on the grind and it was just visible, MOD 1.25 20 degree PA

There's a guy on Ebay at the moment with loads of gear hobs in like new condition, only problem is none of the markings mean anything.
He's not a rip off merchant, I have bought loads from him but all popular hobs. These are what's left from a job lot and he knows he's going to get stuck with them

Richard P Wilson
01-20-2014, 04:00 PM
There's a well-known tool supplier in the UK which used to offer gear cutters at a good price. Maybe still do. Some (I bought a couple, years ago) had clearly been surface-ground to remove the original markings and had new markings crudely etched in. I think they were probably old Circular pitch cutters which had been remarked with the nearest DP or Module size.

Tim

If its the guys I think you mean in the South West, then I too bought some 16DP cutters from them a few years ago, and was slightly puzzled by the crudely etched on markings. Having said that, they are supposed to be 16DP 14.5 degree PA, and gears cut with them mesh perfectly with original Raglan gears, so I can only suppose that they are indeed what its says on the tin. What the purpose of grinding and remarking was, I have no idea.

Richard

Timleech
01-21-2014, 05:25 AM
If its the guys I think you mean in the South West, then I too bought some 16DP cutters from them a few years ago, and was slightly puzzled by the crudely etched on markings. Having said that, they are supposed to be 16DP 14.5 degree PA, and gears cut with them mesh perfectly with original Raglan gears, so I can only suppose that they are indeed what its says on the tin. What the purpose of grinding and remarking was, I have no idea.

Richard

Some CP sizes are not far off common DP or Module sizes, for instance 3/16" CP is 16.75 DP, probably close enough to 16 for most Home Shop purposes, also 1.52 Module, and who is going to want to buy a stock of CP cutters?

Tim