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Need help identifying belt size of my LC30 A milling machine

C

crustyrusty

Member
I purchased an LC-30A machine off of an estate and have always thought the belts on it weren't quite right. I have found a manual for the machine but it doesn't seem to specify belt size and I am not really sure of the best way to measure belt size seeing as there is lots of movement between the idle pully tensioner and the tensioner on the motor. Any help Identifying the belt size would be greatly appreciated. Attached are labeled pictures of the belts currently on the machine and the machines name plate
 

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I believe on the mill I own First LC-30 (same name plate as yours), when @Dusty replaced the belts the sizes in the manual were not the correct ones. My mill also has the two idlers and a front pulley and a motor pulley. I find the belts that Dusty installed very tight, like a heck of a fight to get them off tight. They are all B type. I can confirm the sizes tonight if you want. I believe @6.5 Fan also has the four pulley version. @6.5 Fan can you confirm?
 
The belts that were on my mill when I got it from @Dusty were: B32 front to idler, B26 from idler to idler, and B24 from idler to motor. I since changed the idler to motor to a link style belt (size B) to give a little extra ease in changing belts. I am working on a three phase motor with VFD for it currently. Working on making a piece to install new bearings on an old motor I picked up a while back.
 
Taiwanese belts don't match up to the numbers. Sweet. I thought to change the First Rope belts to some quality ones, That didn't work out. I know different brands can be different lengths, but this was crazy. The belt makers call belts "Matchmaker", now, but I wasn't so sure about that. I have been retired for 10 years, so maybe the learned how to make belts the correct length now. I suspect Chinese are worse.
 
Downwindtracker2 said:
Taiwanese belts don't match up to the numbers. Sweet. I thought to change the First Rope belts to some quality ones, That didn't work out. I know different brands can be different lengths, but this was crazy. The belt makers call belts "Matchmaker", now, but I wasn't so sure about that. I have been retired for 10 years, so maybe the learned how to make belts the correct length now. I suspect Chinese are worse.
Click to expand...
No. The worst is the rubber. The present world champion for auto-fail rubber is India, Chinese comes in second.
 
This might not even be relevant to the discussion...but if I may toss my 2 cents in as a parts guy...
I'll use Gates as an example (I had the most experience with them in the auto parts world)
Customer would come in with a belt off something, we'd measure it with a tape on the outside circumference.
Let's say it measured out at 22 inches. An " A " series (1/2" top width) belt would be an A20.
if it was " B " series, it'd end up as a B19.
I got stung more than once with this, as some folks would give me the measurement, then the width.
It was genuinely just a lack of experience on my part.
I learned to ask "did you measure, or did you get the # off the old belt?"
 
Changing belts was one of those common millwright tasks . In imperial sizing we have the "L" series, fractional horse power,I almost never saw these, the old industrial "A" "B" "C" ,then the modern industrial "3V" "5V" "8V" . The cross sections and widths are different.The sheaves are made to match these . The little motors on our machine tools mostly use "A". With metric, yes, there are metric belts, I didn't encounter very many, so I just used the numbers. In the old days belts, not so long ago, were sized at the factory, 50 being perfect, 49 short and 51 long . When using multiples, we would have to figure out stretch . That's where the claim of Matchmaker come from, BTW. Setting up drive belts is pretty critical.
 
To elaborate on my post, @Downwindtracker2's comment about the Taiwanese belts not matching North American belts is accurate, I believe. I have a Taiwanese lathe and milling machine, both built in 1989. The lathe appears to have its original belts, while the Sanwu-branded belts on my milling machine are most likely original as well. However, the Napa-branded belt is definitely not original obviously.

I'm beginning to suspect that the Napa belt was purchased to make belt changes easier, as it doesn't match the correct belt width and I suspect it to have a slightly larger circumference than the factory belt. Both my lathe and mill use belts labeled B34, and in fact, both belts on the lathe are also labeled B34 one Belt on the Mill is a B34

I went to Gregg Distributors and bought the belts listed by @YYCHM for my mill, which matched the specifications in my manual. I also purchased two B34 belts for my lathe. I started with my lathe because it was in desperate need of new belts. I removed the B34 from the motor and replaced it with the new B34 from Gregg Distributors, but it was way too big. Even with the full tension adjustment, it wouldn't fit.

Next, I removed the B34 from my mill and tried putting the new B34 from Gregg Distributors in its place, but it was also too big. However, when I put the original B34 from my mill on the lathe, it fit perfectly.

I know the logical next step would be to measure the belts and buy the correct ones based on those measurements, but at the time, my thinking was that by purchasing the belts specified in the manuals, I could eliminate any doubts about whether the current belts were actually the right ones. I was hoping for a one-trip solution (but, of course, it never works out that way, does it?).
 
From what I can tell so far, these Taiwanese belts off of my old Taiwanese machines have an inside circumference 2" less then what's labeled on the belt
 
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Belt Sizing Issue on Older Import Machines – Findings and Solution

I’ve been dealing with a belt sizing issue that seems to be common on older import machines, including my King Canada 1440 lathe, which is from the same era as my LC30 milling machine. Once I have the time to purchase new belts and swap them in, I’ll update this thread to confirm my findings.

Modern B-Series Belt Sizing (Using B-28 as Reference)​

  • B – Refers to a "B" section v-belt, which is the "Classic" v-belt style. The top width is 21/32" (0.656"), though it’s often referred to as a 5/8" (0.625") belt. The thickness of the belt is 13/32" (0.406").
  • 28 – Refers to the inside circumference of the belt in inches. For B-section v-belts, the outside circumference is typically 3 inches larger than the inside circumference. Therefore, the outside circumference of the B28 belt would be 31 inches (28 + 3).
  • 29 – Similarly, for the B29 belt, the inside circumference is 29 inches, and the outside circumference is 32 inches (29 + 3).

Comparing with My Chinese B-28 Belt​

The belt from my Chinese machine is sized quite differently. I’ll use the Chinese B-28 belt (from my milling machine) as a reference:

  • Belt label: B-28 (as specified in the machine manual)
  • Belt inside diameter: 26"
  • Belt outside diameter: 29"
From this, I can see that the inside and outside circumferences of my old Chinese B-28 belt follow the same pattern as modern B-series belts (the outside circumference is 3 inches larger than the inside). However, the number on the belt (B-28) does not directly match the inside circumference, unlike modern B-series belts, where the number typically corresponds to the inside circumference.

Conclusion and Sizing Adjustment​

Based on this, I believe that if you subtract 2 inches from the belt sizes specified in the manual, you'll end up with the correct B-series belt size. Here’s how the sizes work out:

  • Front Belt: B-34 → B-32
  • Idler Belt: B-28 → B-26
  • Rear Belt: B-29 → B-27
Once I replace the belts and verify the results, I’ll update this post to confirm my findings.
 
Good Work !

For belts to work well ,both sheaves have to be in the same plane. I have always found getting the motor to sit right under belt tension to be large pain in the *** . But It Must, if you want the belt to last and be effective in transferring power. A old timer showed me his method, two straightedges, one on each sheave, they should swing onto each other exactly. Lacking two straight edges that are the same, I would hold or clamp the straightedge to one sheave and swing it down to the edge of the other sheave, it should touch at TDC. Then repeat for the other sheave. It's not as quick or as accurate as the two straightedge method.

Roller chains on the other hand, so long as they are in the same time zone, they will wear in.
 
Downwindtracker2 said:
Good Work !

For belts to work well ,both sheaves have to be in the same plane. I have always found getting the motor to sit right under belt tension to be large pain in the *** . But It Must, if you want the belt to last and be effective in transferring power. A old timer showed me his method, two straightedges, one on each sheave, they should swing onto each other exactly. Lacking two straight edges that are the same, I would hold or clamp the straightedge to one sheave and swing it down to the edge of the other sheave, it should touch at TDC. Then repeat for the other sheave. It's not as quick or as accurate as the two straightedge method.

Roller chains on the other hand, so long as they are in the same time zone, they will wear in.
Click to expand...
Downwindtracker2 said:
Thanks for the great information! Something I recently discovered with my 1440 lathe while "leveling the bed" is that tightening the belt tensioner or "clutch" actually throws off the alignment, causing the lathe to cut a taper—assuming I leveled the bed with the belt loose. I'm not sure if this indicates an issue with the spindle bearings or if it's normal for belt-driven heads, but I wasn’t thrilled with the discovery.



To illustrate, if I place a bar in the chuck and mount an indicator on the end, I can observe the needle move about .0015" when I tighten the clutch. I’m still not sure if this is normal, but I plan to start a discussion about it soon. For now, to minimize the issue, I’ve re-leveled the bed with the clutch engaged.
Click to expand...
 
That wasn't me with that second quote. My lathe is just a 12x24. back geared belt drive BusyBee labeled Taiwanese generic. When I changed the bearings I left two tenths clearance in. That's what I found when I pulled them. That is a bit tight I think. I'll keep them oiled. My belts are inside the box. But the headstock castings are Not real robust, kind of thin I think, so they could flex. Yes, even cast iron will flex.

At work we had a deflection guage for belt tension but I only used it a couple of times and then went by feel. Some machines with high power, the tension was very tight, they needed it. But for our little machines, basically what you have been told is good.
 
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