Joining plastic drive belts

[brianw]

This may seem a trivial subject, but to me it is becoming serious.
I can’t get my plastic lathe drive belts to stay stuck together. I’ve tried heating a knife and then putting each half either side of the knife and removing the knife. I’ve also tried heating both ends in a flame and then pressing them together.
Every time I try they work for a while, then in the middle of using the lathe they spring apart.
Is there something I’m doing wrong? It may be that I’ve got some cheap plastic that doesn’t weld easily or it may be that there is some trick that I’m unaware of.
If any of you know of a way to get the ends stuck together reliably then I will be very glad to hear about it. If it works, I will be eternally grateful.

[Bob Tascione]

Hi Brian,
I’m not up on the different plastics used for belting but normally don’t have problems with them although I do on occasion have one come apart while turning.
You may already be doing the following but if not it may be of some help. If you are doing it this way then maybe this will be of help to others that may read this in the future.
I first overlap both ends of the belt by a half inch or so and slice through them both at about a 45 degree angle. By slicing through both at the same time you are assured an even match when melting together. Also the diagonal cut gives more bonding surface area rather than a straight cut. I then heat a thin piece of steel (usually an old hacksaw blade) and place both ends of the belt on either side of the hot blade. Rather than pulling the blade out I slide the belt ends off of the blade bringing them together. In this way I have a second or so to make a fine adjustment for the match. I think the diagonal cut will give you a much better hold.
Others may have a better method that works for them that they can post up here. This pretty much solved my problems so hope it helps.

Bob

[arutha]

Hi Brian,
Bob has pretty much covered it but I would also add I have had a few different types of that green belt material and some are much easier to join than others. This seems to also be the case if it has been lying around for ages.The softer textured stuff from China is very easy to join compared to the stiffer/harder green belting.
Paul.

[willofiam]

Adding to what the 2 brilliant men above have already said…….. I avoid “pressing” the ends together, too much pressure and you squeeze out the melted material, I have had good luck by sliding the ends off of a hot razor blade (which I mount in a vise) and letting them touch with very little pressure.
Have fun. William

[bernie weishapl]

Pretty much it has been said. I put a kitchen knife in a vise, heat it red then let it cool slightly. I put the belt on either side and slide them off together. Light pressure is the key as the others have said and not to hot because then it will burn the belt.

[david pierce]

Brian,
If you go to THE WATCH REPAIR CHANNEL on Youtube there is a video on how to correctly weld a belt, however, I switched to O-RINGS several years ago and never looked back. Once you know the diameter of the belt (length/Pi) you can order one of similar thickness from an industrial supply house. I usually buy them from MSC but McMaster-Carr also sells them and I know McMaster-Carr sells world wide. I have found that no matter how perfect the weld looks there is always going to be a difference at the seam. O-Rings are molded in one piece and are seamless, so they inherently run smoother than the welded belts.
david

[Bob Tascione]

First Happy Birthday David! (I saw it posted on the main index page along with your age!)
Not to give you a hard time on your birthday but since I’ve already posted on this and am assuming from your post that the way we are doing it would be the incorrect way…well, why not?

go to THE WATCH REPAIR CHANNEL on Youtube there is a video on how to correctly weld a belt

Really? That’s THE Correct way? Okay.
I won’t defend the angled cut that I mentioned works great for me since many people have different ways of doing things that may work better for them. I can certainly respect Marks choice of welding the ends together if it works for him. Although some of us up here no longer do it that way but rather heat and slide the belt ends off of a blade or thin piece of steel to meet for the bond. I have to ask though…should I have been dissasembling the headstock/spindle to install these belts all these years too as it’s shown in the video rather than just wrapping it around the spindle and then welding it?
Here’s the link to the video for those interested.
https://youtu.be/uTBaUcVBqqc
Bob

[brianw]

Thanks to all of you for your very helpful advice.
The plastic that I have is quite hard, so I think I will buy some more.
However. Using an angled cut, a hot knife held in a vice and leaving it to set for half an hour instead of using it straight away seems to have done the trick.
I can now use the lathe without fear of a sudden interruption caused by a breaking belt. Fantastic.
I didn’t dismantle the lathe to fit it though. I threaded it through before joining. I think Mark just likes taking things to bits and putting them back together again.

[chris mabbott]

I’m gonna throw a curve into all the good info given so far..

I buy solid belts, then I disassemble my lathe, service it, inspect etc, install the one piece belt and reassemble the lathe…

I destroy one of the pre made belts every 5 years, so not bad.. I actually found this method by chance, because I blew a joined together type, then I was stuck so….
These last forever it seems..

You can also purchase tiny V belts which on this application, last for an eternity and work well..

[bernie weishapl]

Happy Belated Birthday David.

[david pierce]

Bob,
I have joined belts both with angled cuts and butt welds. Both methods have worked for me but neither produced as good of a final result as a solid seamless belt. It is a good idea to take the spindle apart and clean the crud out of it at least once a year anyway, so why not use that golden opportunity to install a good quality O-Ring belt. As Chris said the belts last for years.
david

[arutha]

If anyone is interested I have an old pillar drill which is very sensitive and extremely accurate. When I got it the rubber belt was in such poor condition I had to throw it away, it was only then I realised I didn’t have any green belting material long enough. I joined two pieces together to make a piece long enough so this belt has 3 welds and has been running like that for the past two years. The motor on it gives much more power than a standard watchmakers lathe so it just goes to show when done properly and if you have good belting material to start with it is not an issue.
I agree with stripping down the lathe and giving it a good service but I want to do that when I have time for it, not because the belt has broken and not half way through making a balance staff!
Just another few cents
Paul.

[Bob Tascione]

It is a good idea to take the spindle apart and clean the crud out of it at least once a year anyway, so why not use that golden opportunity to install a good quality O-Ring belt. As Chris said the belts last for years.
david

Got to run to town this morning so will try to add more to the list when I return but off the top of my head;

1. Personal preference and choice…
I don’t share the same enthusiam over these belts to the extent where I would consider changing to O-Rings or any other continuous rubber belt a ‘golden opportunity’ but rather a step back in time. At least for me.

Here’s why in most cases I prefer plastic belting:

2. Simplicity in quickly implimenting creative new set-ups for more advanced watch and clock parts making…
Quickly making belt length changes when needed without having to measure, order and wait for a belt to arrive that restricts working distance between pulleys.
Real application example: This past Saturday I made up a plastic belt for my rounding up tool and two plastic belts for my hand cranked lathes requiring a total time in labor of probably less than 30 minutes. After messing with the rounding up tool a bit I realized that the tools’ belt tensioning system, which is just a slide carrying the hand crank wheel with a belt groove along it’s perimeter that can be moved in or out to change the distance between pulleys was adjusted a little too long for my comfort. I only needed to clip out about a 2 inch section and re-weld making it a perfect fit for me. An adjustable leather belt would have also allowed for this modification. If I chose to use a continuous belt I would still be waiting for the first rubber belt to arrive. If I had need to lenghen rather than shortening it I could have made up a new belt within a few minutes from my stock on hand and then used the older belt as ‘material’ for a future belt application. Another instance of a needed alteration on that same day was with the two hand cranked lathes. After moving them from a bench to a lower table (as you know I’m in the process of modifying my shop which is pretty much an ongoing process) I realized that the crank wheels were now much too low as my sitting height position had then changed. Again it was a simple and quick fix to shorten the plastic belts. Adjustable leather belts would also have made for an easy change. As of today Thursday I would most likely still be waiting for the rubber belts days later with the older rubber belts being rendered useless unless a future set-up called for their length.

3. Ease in belt changes due to breakage…
Belt breakage is far down the list for me of “reasons necessitating a belt change”. Breakage does occasionally occur but this is normally within a few minutes of test period and is always due to my having done a crappy job on the weld which could have been avoided by paying better attention. When this does happen I’m back in action within a few minutes. If it does break later though, which all aged belts might do and which almost always happens while turning something (of course) then it’s a simple matter of running a new belt around the pulley, cutting and welding back up without having to disturb your setup or workpiece. No reason to remove your work for the change which for obvious reasons is very undesireable. Leather belts can also be installed this way. Continuous rubber belts must be installed by removing the spindle/pulley assembly as well as disturbing the workpiece. Also if the belt is a very short one, making it difficult to weld due to space, the entire headstock can be slipped off of the bed, layed on its side on a flat surface and manipulated in such a way as to allow for melting and welding of the belt without disturbing the work piece if held in a collet or chuck.

4. Inexpensive to keep and maintain a stock of different metric diameter and length sizes on hand for immediate use. I have a very small investment in a reasonable range of belt stock…
.
5. Relocating of motor, countershafts, tensioner height and location, adding new accessories off of countershafts such as pinion polishers, grinding and milling attachments etc. etc. or whatever my imagination might come up with is made simple to drive with these belts..
Would be surprised how often machines must be resituated around the shop when space is limited.
Take a look at some of the shops of AHCI members like Dufore etc. and you will see green plastic belts driving many of their machines. I can search, find and post some links up here if you have any trouble finding them. Check out some of the shops belonging to watchmakers doing high end restoration and parts making work and you should see the same. There’s a good reason that these belts are so popular. When prepared correctly they are smooth running and very dependable. It does take a little time to get the hang of producing good welds that run smoothly without bouncing at the meld points but it is something that can be mastered fairly easily through practice. My feeling is they make life much easier for the watchmaker who’s serious about doing work beyond parts changing and simple lathe operations. If you plan to set up a lathe in one permanent location with no future expectations of possibly altering motor to machine distances or using countershafts etc then the O-Rings should serve you very well.

6. Easy to thread belt through captured spindle/pulley systems eliminating the need to dissasemble that part of the machine…
As you know from past phone conversations I have tried the O-Ring belts and find them smooth running but not very versatile. I also find the plastic belts very smooth running.

Got to head out but will give this more thought when I get back home David. I’ve answered your question although I think that it would have been even more meaningful to have asked this of Mark since he not only disassembled the headstock providing “that golden opportunity to install a good quality O-Ring belt” but then proceded to install a plastic belt. (In all fairness to Mark he may have a perfectly good explanation or reason for doing this or may even have had an ‘Oh Crap!’ moment having realized he forgot to place it over the pulley first).

I would now like to pose a question to you.
Why WOULD you use that golden opportunity to install a good quality O-Ring belt when you could use a more versatile plastic belt? Can you give a brief merit list?

Adios for now,
Bob

[david pierce]

Bob,
I did bring this up to Mark Lovick about one year ago. If you go to Youtube and watch his belt changing video you will see that he kept my post as his top comment. I do not know if he switched to seamless belts or not but people tend to stay with tools and techniques that have worked well for them in the past. I do not have the years and years of watchmaking experience that you have and tend to experiment with tools, techniques and processes more than a seasoned professional would. Sometimes I find things that I feel work better than the accepted and approved process, and sometimes I do not. When I find something that I feel works well I tend to share it with others. When a process does not work well I discard it and move on to something else.

There are some things with these machines that I like better than the accepted trends such as induction motors and step pulleys as opposed to universal motors with speed controllers. I like the heavier cast steel machinery, with steel sliding bearing surfaces, better than diecast aluminum machinery. I like ball bearings better than sleeve bearings. For all but the very smallest shaft diameters I prefer ER collets. Last but not least I prefer seamless belts over welded belts for several reasons as stated in previous posts.

My countershafts have swivel adjustments on them that have, so far, provided the necessary tension adjustment for the belts, and I have not had a problem maintaining the proper belt adjustment. When a belt needs to be replaced I can replace it with the exact size that was there. The initial setup and installation may prove to be a bit more challenging but after that the replacements are easier to install.

The bottom line is that if someone is comfortable with the process they are using, and it works for them, they will
probably stay with it. If someone else comes up with a different way to do something hopefully it won’t be taken as a slap in the face.
david

[chris mabbott]

Hey guys do you think you could keep it to 10k words or less please, it’s a real beeatch to read these long posts on a phone screen, and I keep loosing my place 😆 😆

[Author]

Posts