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Length of skive for leather belt to drive grinder

I am about to make a leather drive belt for an old universal grinder and think it ought to be a glued joint so as to run smoothly. It seems reasonable to me that the length of the skive depends on the thickness of the belt and I was thinking that 5 to 10 times the belt thickness would be good. But I looked on the internet and found everyone talking about the length in inches and more inches than I thought was necessary. The belt is about 3/16 's thick so 5 times that would be about an inch and ten times it would be just under 2 inches.

So does anyone have experience with making leather drive belts with relatively short skived joints? Is making the skive 10 times the belt thickness reasonable?

I happen to have some kevlar roving and was thinking of laying in a little of that in the glue joint. Not a whole lot, but maybe enough so that about 50% of the joint is covered with kevlar. I seriously doubt that anyone has experience with doing that, but would appreciate comments on why that is a good idea or why it is a bad idea. The kevlar would be oriented so the strands are running the length of the belt , not across the belt. My thought is that the kevlar would prevent stretching which might make the glued joint stronger.

Now there has been a lot of discussion about asking questions in RCM, so if you do not want to spend any time in answering these questions, feel free to not reply.

In searching the internet, I found some stuff the Tee-Nut had written, but did not find his web page on flat belt drives.

Which reminds me. Tee-Nut used to drink New Castle Brown. i recently had some Brooklyn Brown which I enjoyed even more than the New Castle Brown. But both are good stuff in my book.

Dan

Reply to
dcaster
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" snipped-for-privacy@krl.org" fired this volley in news:965b46a0- snipped-for-privacy@t5g2000yql.googlegroups.com:

Dan, that seems really short. I had an old F.E. Reed lathe for years, one that powered off an overhead line shaft. I have made several belts for it, both for the main drive and for the longitudinal feed.

The belting manufacturer recommended something around 5-6" for a 3/16" thick belt, but some of the old texts I read had you making the skive of a length such that it would pass half-way around the largest pulley in the system, regardless of what length that was. I tried both at one time or another, and both always worked; so I presume the shorter skive is satisfactory.

But my 'shorter' skive was a whole lot longer than your longest 10X figure.

I also used alligator clip unions, and they worked just as good, but of course with the repeated clickity-click (which some old machinists told me sounded like a mother's lullaby to them! )

LLoyd

LLoyd

Reply to
Lloyd E. Sponenburgh

3/16" thick leather should have a skive closer to 6"
Reply to
Steve W.

"Steve W." fired this volley in news:kl9uda$20f$1 @dont-email.me:

Dan, that's now two for 6".

Lloyd

Reply to
Lloyd E. Sponenburgh

Machinery's Handbook 22nd (1985) says 4" for leather belts less than

4" wide. MH 10th (1941) shows 5" for 1-2" wide. 6" for 3-4" wide. No mention in either of belt thickness, which surprised me. I imagine the recuction in length has to do with better glues.

There's no mention of splicing leather belts in the 26th ed.

Reply to
Ned Simmons

Two FE Reeds (one Inc. circa 1880s, one Makers, which I assume is earlier) and a Faye & Scott here.

Unless you are running an antique display that needs to be properly antique to some time before the clip lacing (what Lloyd calls alligator clip unions) they are superior in practical use, IMHO. They run smoothly, and you don't have to cut the belt or take the spindle out if you need to move the motor or tool (or just the tool, if you are adequately antique to have a lineshaft bolted to the ceiling beams to go with it - none of mine do, and it would be hard to replicate unless I found an old one that hadn't been ripped out for scrap or run without maintenance before being left to rust for 80 years...)

Depending on how your clips fit the belt, they make either no noise (belt surface keeps the clip, sunk into the belt just a hair, off the pulley surface) or a small clicking noise if the clip is at or above the belt surface.

Skiving and lacing (you might be gluing without laces?) is more of a home project than clips are, so that may make it better for you if you don't have a good belt shop handy. I looked at doing it, but found that a belt shop that could handle flat belting was not really all that far away. Your "old mill services" availability may vary, but you also may need to look a little to find it even if it is there.

Reply to
Ecnerwal

Ecnerwal fired this volley in news: snipped-for-privacy@news.eternal-september.org:

yeah..., I just could NOT bring that term into my head. Yes, LACING.

The smaller belt on the longitudinal drive of that F.E. Reed was skived, glued, and SEWN. (only a little 3/4" belt, so not much to glue on)

LLoyd

Reply to
Lloyd E. Sponenburgh

A LOT is going to depend on what you use for glue. You're loading the joint mostly in shear, which is usually the worst direction for most glues. The 1" wide belt for the SB 9" has a joint about 6" long. A long skive is always better than a short one, more surface area for the glue. Belt thickness is irrelevant. I wouldn't be putting in anything besides glue in that joint and you need to make sure the two halves fit very closely. Last new belt I made up, I used a block plane to do the shaving and tacked both halves to a board to plane them side by side. The glue recipe I found in an old machinist's helps and hints book would have made decent model airplane cement, so I got a tube of Ambroid and used that. Lasted 20 years until I had to break the belt joint to dismantle the lathe to move it.

Stan

Reply to
Stanley Schaefer

Picking nit : Actually, shear is the strongest direction for most adhesives in most circumstances. It may not be with rubbery adhesives, depending on their bulk tensile strength. With a thick glue layer, bulk tensile strength becomes shear strength. With a thin one, it usually is not. The limit in those cases usually is adhesion.

I don't know what's used for bonding leather belts these days, but the reason for long skives, as you say, is to give a lot of shear area. If they're going to give way, it's generally at the ends of the lap, because the peel strength of most adhesives is inferior to shear strength. The specific load (load per unit area) is highest at the edge of a lapped joint of flexible material.

A key example is the way they rivet-bond aluminum aircraft skins. As with a leather belt, the limiting factor is lifting (peeling) at the flexible edges. Most of the strength of those joints is the adhesive in shear, but they put some rivets along the edges to prevent peel.

Reply to
Ed Huntress

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