spiral balance

Quick Learner from maryland

Jun 9, 2023 6:32 pm

I'm not sure how exactly to measure the length. Is it the external plastic tube or the internal metal tube?

Also my diameter is 1/2 inch. Would you recommend the 3/8 in or the 5/8 as a replacement?

Finally can you confirm if the tip is actually blue and not green?

Thanks

3 user uploaded images

8 Replies

Bob from SWISCO

Jun 11, 2023 8:44 pm

Thanks for posting. The outer tube is what the diameter and length should be measured by. With these old plastic sheaths sometimes this admittedly gets a bit difficult. I would use as as undamaged an identical balance as possible from the house to obtain these measurements. I suspect this tip is green, but let's determine the diameter for sure before proceeding. We'll be able to determine everything from there.

Quick Learner from maryland

Jun 12, 2023 8:35 am

I just measured the diameter of the outer plastic sheath with calipers. It looks to be 0.5 inches. What would you suggest?

Tom from SWISCO

Jun 12, 2023 11:39 am

No tilt window spiral balance is made with a 1/2" diameter, to my knowledge. Our only options are the 3/8" Series 900 and 9/16" Series 600. Yours is very likely the 9/16" version, but you should triple check to be 100% sure.

Quick Learner from maryland

Jun 12, 2023 5:45 pm

I've attached the measurements I've found. When I set the calipers to 9/16ths, there is more wiggle room that what I would expect. What do you think?

3 user uploaded images

Tom from SWISCO

Jun 13, 2023 8:50 am

That could be on account of the tube being worn out and warped from its original shape. Either way, the two sizes I mentioned above are your only options. There is nothing between 3/8" and 9/16".

Looking at your calipers, my personal choice would be the 9/16", but you'll have to make the final judgment.

Quick Learner from maryland

Jun 13, 2023 9:26 am

Just to confirm, your recommendation is a 9/16" diameter, 21" length, and green tip?

What are the costs of getting this wrong? Will a 9/16" perform just as well where a 3/8" is supposed to be used? Or are there some aspects of a 3/8" that I will not get by choosing to go with a 9/16" instead?

Tom from SWISCO

Jun 13, 2023 12:40 pm

The S600-21 doesn't have a green tip, it's only made with a blue tip. That may very well be what you need but I would advise weighing your sash on a scale to verify that it falls in that weight range of 10 through 20 pounds. You can see a chart on the S600-21 store page that tells you how much weight each option supports.

The risk of buying the 3/8" balance is that it might be too small and too weak, and the risk of buying the 9/16" balance is that it might be too big and won't fit. They're not made to be interchangeable and I wouldn't advise using one to replace the other. This is a strictly binary choice.

As mentioned above, I would personally go with 9/16". I still think your original tube is just misshapen after years of use so you probably won't get a 100% accurate measurement, even with digital calipers. You just have to compensate for that using your best judgment. If it makes it any easier for you, it's definitely too big to be 3/8", so in my opinion you just have to decide if you think the 9/16" is worth trying.

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