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View Full Version : _ Home Made: Delrin 120 tooth change gear for 14x40 lathe...



iMisspell
06-09-2013, 06:30 PM
Started a thread acouple weeks ago asking peoples opinions on how much quieter a Delrin gear would make the lathe.
Well i got around to making one and im so happy i did (and didnt screw it up :) - moving that indexing pin 120 times was a real chore for me).
Some time down the line im gonna make a recording of the two different gears, but boy it made a pretty big difference.... its not dead quiet, but if you disengage the feed gear box and flip on the spindle and then reengage the gear box theres only a "small" sound (not sure how of word that) of gears spinning.

I think the gear came out real good (only the second gear ive ever made so i might be alittle biased :) ) - the tooth profile meshes well with both a 60 tooth and 30 tooth gear and the "flat" on the top of the last tooth cut and first tooth cut are almost perfect (dont have a comparator to check).

Have not threaded anything with the lathe yet, but it runs smooth and much more quieter then before... it also seams nice that i will not have to get an absolute perfect mesh as before with the metal gears.... Just hope it holds up for a long time to come.

You can read more and see some more pics of the process i took here:
http://site.thisisjusthowidoit.com/metalworking/19-lathe/pm1440e-lb-lathe/31-delrin-120-idler-gear

http://i1284.photobucket.com/albums/a570/iMisspell/Projects/Metal/Gear_Cutter/DCP_1559_zps644a2fcd.jpg (http://s1284.photobucket.com/user/iMisspell/media/Projects/Metal/Gear_Cutter/DCP_1559_zps644a2fcd.jpg.html)

TR
06-09-2013, 07:02 PM
Wow what an excellent idea. I will try the same. Thanks for posting.

Peter.
06-09-2013, 07:43 PM
Nice job. It'll hold up. I made a similar gear for my lathe spindle drive a few years ago and it's been holding up just fine, with much greater loads than your changegear will ever see.

Evan
06-09-2013, 10:16 PM
Very well done. Making gears seems much harder than it really is. It is one of my most favourite machining jobs.

iMisspell
06-11-2013, 01:27 PM
Thanks every one...


... Making gears seems much harder than it really is...Making the gear was not bad at all (just need to pay attention :) ), but understanding how to make a gear, the correct radius for the cutter, tooth height, etc... is a whole nother story for me. For the application im using this for - getting it really close (and not perfect) will fit the bill (i have yet to thread with it tho). I think there is a bit more "science" to gear making then most other parts of machining if you are doing it from scratch/the ground up.

But boy... does this thing sound good :)

_

mikem
06-11-2013, 01:40 PM
Is there a difference between the white and black delrin?

Peter.
06-11-2013, 02:05 PM
Not enough to worry about - the black doesn't show up grubby finger prints. I didn't actually use Delrin I used regular acetal, partly because it was cheaper and partly because they had stock in a size closer to what I wanted.

cameron
06-11-2013, 02:14 PM
Is there a difference between the white and black delrin?

I don't know about Delrin, but white acetal turns yellow with exposure to light. Also , I think the black may be more UV resistant.

iMisspell
06-11-2013, 02:17 PM
Is there a difference between the white and black delrin?Funny you ask... the other night i email Matt (owner of PM Tools, who i bought the lathe from) and we talked about the color alittle... I dont know much about Delrin, but from what i have read and the info on the McMaster-carr site (which is where i bought the raw from) there are many different kinds, the word 'Delrin' is kind of like saying Stainless Steel (there are different series), again i don't know alot about this. In the past i bought some Delrin whihc was dark brown which i used for making a left handed nut for a lead screw in a X-Y table, the brown stuff was "high wear resistant" but no good for shock, the stuff i made this gear from was high wear resistant and good for shock and they (MasterCarr) said it was used for gear making. I would not take my word for this but if you plan on using Delrin, i would research your use and the correct stuff to get... I choose white over blank cause it was acouple bucks cheaper ;)

Evan
06-11-2013, 02:49 PM
As has been pointed out in numerous other posts Delrin and acetal are not the same thing. They have different properties in strength, chemical resistance and casting/extrusion performance. They are similar and for many purposes can be interchanged. They are also used to make plastic alloys with many other plastics and may also be filled with a variety of fillers to produce various enhanced properties. The same is true of most plastics. With acetal/Delrin the colours are just that and make little difference to performance, if any. However, there is black acetal that is carbon filled to produce a static free material as it has low enough internal resistance to discharge static on the surface. "White" acetal is just "natural" with no colourant added. That is what the raw resin looks like.

When buying acetal or Delrin ask which you are getting. If they tell you it's all the same thing find another supplier. While it may not make a difference to your application it shows they do not know their plastics or don't care.

The name Delrin is a Du Pont trademark for homopolymer acetal resin. Generic "acetal" is a copolymer acetal resin.

Peter N
06-11-2013, 05:31 PM
Delrin and Acetal are exactly the same thing because 'Delrin' is an acetal, as is 'Tecaform', 'Ultraform', 'Celcon', 'Hostaform' and others.

The difference - as already pointed out - is that Delrin is a homopolymer acetal whilst the others are co-polymer acetals.

mikem
06-11-2013, 05:34 PM
In the flyer that I just got from Enco, it says on page 60, natural -- high natural lubricity, black--normal lubricity. I wonder what that means?

cameron
06-11-2013, 07:15 PM
Delrin and Acetal are exactly the same thing because 'Delrin' is an acetal, as is 'Tecaform', 'Ultraform', 'Celcon', 'Hostaform' and others.

The difference - as already pointed out - is that Delrin is a homopolymer acetal whilst the others are co-polymer acetals.

You mean they're exactly the same thing, but different?

Forestgnome
06-11-2013, 07:15 PM
Congrats on the gear! I looked at what you went through to make a gear cutter, and have a suggestion. Since you went to the trouble of grinding an HSS tool to the profile to make a cutter, you could have done the other side of the HSS tool and you would have had a single point cutter to cut the gear with. Plus if you make a single-point holder correctly you don't have to fuss with grinding a relief.

Evan
06-11-2013, 09:33 PM
Delrin and Acetal are exactly the same thing because 'Delrin' is an acetal, as is 'Tecaform', 'Ultraform', 'Celcon', 'Hostaform' and others.

That's like saying that Hydrogen monoxide and deuterium are the same thing because they are both forms of water.

If you are processing tomato juice you really don't want Delrin in the pot. Generic acetal is fine.

Peter N
06-12-2013, 02:38 PM
That's like saying that Hydrogen monoxide and deuterium are the same thing because they are both forms of water.

If you are processing tomato juice you really don't want Delrin in the pot. Generic acetal is fine.


But that's exactly my point Evan (not that I know what those are or can be bothered to check - I'll take your word) they are both Water, just as a Jaguar a Mini are both cars, or as 4140 and 1018 are both steels. You wouldn't say " Don't use 1018, use steel instead" would you? The term 'Generic Acetal' covers both co-polymers and homopolymers.

Polyacetal, Polyformaldehyde, Polyoxymethylene (Homopolymers and Co-Polymers)- call them what you like - they are all from the family of Acetals. You can't call Delrin a non-acetal because it IS Acetal.
Acetal co-polymers have exactly the same main long chain molecule and structure as acetal hompolymer (of which Delrin is only one of several available) but have an additional ethylene oxide structure added into the chain randomly, and this gives them different properties.
In a nutshell, Homopolymers are generally stiffer with better mechanical properties and Co-Polymers have better chemical resistance and are more heat stable during processing.

But don't take my word for it (again...:D:D), what do I know? I only spent 3 years at University studying Polymer Engineering and my entire life running techical injection moulding businesses, and I get grumpy when the incorrect nomenclature is used.
Bit of light reading here:

http://www.ptonline.com/columns/how-do-you-like-your-acetal-homopolymer-or-copolymer

https://en.wikipedia.org/wiki/Polyoxymethylene

http://www.asahikaseiplastics.com/products/tenac-tenac-c-pom.html

Evan
06-12-2013, 06:11 PM
but have an additional ethylene oxide structure added into the chain randomly, and this gives them different properties.

In other words, it is a different material. It's how you get around a patent.

They are both plastics but not with the same molecular structure. They have the same atomic constituents but arranged differently and the properties are different. They are made by different chemical processes using different precursor chemicals. I am NOT calling Delrin a "non-acetal" but instead a particular type of acetal which is Du Pont's idea, not mine. The two types are not the same material.

Hydrocarbons all have the same atomic makeup too but they are not all the same. We have different names for the different types and we do for acetal family materials too. Delrin is a brand name for a specific type of acetal. Generic "acetal" is not used to refer to Delrin except as a general class of plastics, which is incorrect usage as it is not properly specific. Generic acetal has come to mean the copolymer of the acetal class and Delrin DOES mean the homopolymer as that is what was patented. It is also used by Du Pont with qualifiers to refer to various combinations of the homopolymer with other materials as is commonly done with Teflon, another brand name.

The main point of my post is to point out that if you ask for Delrin you should make sure you actually receive Delrin. If I ask for Delrin it is because I want a particular property that generic acetal does not possess.

Incidentally, I have been working with plastics since I was child. I still have my original Mattel Vacuform machine from about 55 years ago. I have been studying plastics since.

BTW, I also get grumpy when somebody selling plastics doesn't know the difference.