Homemade 6" linisher

[Jonesy]

Hi again.

Around 15 yrs ago I made two 6" x 24" belt linishers. One for wood and one for metal. Although they worked I would describe them as adequate at best.The belt tensioning system I designed was pants and the tracking was almost non existent. But they have served me well for that time so they couldn't have been too awful.

I think the main problem was that the rollers were not crowned (and they were so far out of true!!!).

Anyway, I'm now building 2 new linishers from the remains of my old faithfulls that have now been stripped.

So, which roller do I crown? The driven roller, the slave roller, or both?

And.. how much of a crown should I put onto a 3" dia 6" wide roller?

And... what profle should the crown take (if that even matters)?

I can taper on my small lathe.

Gratefull for any advice.

Thank you.

[brian Rupnow]

High point in the center of both rollers. Taper off 1 1/2 degrees from the center towards the outer edges..

[boslab]

I found offsetting the tailstock and turning the roll between centres or centre and Chuck at a push, though it’s rash to turn a stub centre held in the Chuck, if you don’t mind resetting the tailstock after ( I don’t but some seem to have trouble getting it reset, I figured the more you do it the better you get) after turning to halfway both sides I hit it with a tube polisher ( that was a handy thing, must make a new one) or a thing I was shown in work, a sanding bow, basically something springy like an old drain rod or tent pole, bent to a curve with a strip of Emery tied between, crude but safer than wrapping Emery round a spinning shaft, think the longest one I made was about 6’, (imagine a home made bow and arrow but the string is Emery cloth or more recently the open mesh roll
mark

[chipmaker4130]

Most of those I've seen have a flat drive roll and crowned 'feed' roll (the one that guides the belt toward the platen). Seems to me that you might end up 'herding cats' with multiple crowned rollers.

[Galaxie]

I have always heard that having all pulleys crowned is best, but also that one crowned pulley is sufficient in most cases. I think Machinery's Handbook still has a section on flat belt pulleys.

[chipmaker4130]

I have always heard that having all pulleys crowned is best, but also that one crowned pulley is sufficient in most cases. I think Machinery's Handbook still has a section on flat belt pulleys.

Well, that's good to know since I hope to get one built this year!

[Bob Engelhardt]

I have always heard that having all pulleys crowned is best, but also that one crowned pulley is sufficient in most cases. I think Machinery's Handbook still has a section on flat belt pulleys.

Except the contact wheel - I don't think that you would want that crowned. I only have 1 wheel crowned & it works fine. It happens to be the motor wheel, because that is also the "feed" wheel.

[Jonesy]

Thank you all for your input.

Today I took the belt off the toy linisher where I work and had a look at the mech. It's only a 4 inch belt, Both rollers are crowned. No more than 1/2mm each side of center. And it's a radius crown. Nice and smooth.

The slave roller tracking ajdustment is so simple it's brilliant. Why didn't I do something as simple instead of my franken-adjuster? DOH!!

My problem with re-using my existing rollers is that they are only 1mm section, and significantly out of true. By the time I've trued them I doubt there will be enough metal left to machine the crown. I completely overlooked this scenario.

But, I've got other stock laying around to make a better job of this so new rollers it is!!

[Galaxie]

Machinery's Handbook 27th edition says:

Flat Belting: Pulley width is usually about 10% larger than the belt, and for good tracking, pulleys are often crowned by 0.012 to 0.10 inch for diameters in the range of 1.5 to 80 inches.

Flat Belt Pulleys: Pulley face widths are nominally the same as the width of the belts they are to carry. Belts may be made to center themselves by use of crowned pulleys. The usual amount of crowning is 1/8 inch per foot of pulley width.

It also says that when you have a "riding idler" close to a driving pulley, the idler should not be crowned, and the adjacent pulley should have very little crown. This applies in areas where the "curvature of the belt changes rapidly".

[metalmagpie]

When we (lakeside53 and I) built our 2x72 belt grinders, we looked into the issue of how much to crown a pulley. We concluded it really shouldn't be much. I think we shot for .012" crown only on the feed roller. The belt will soon take on the profile of that crown, so keep it to about half the thickness of a belt or less.

Using the 1/8" per foot over a 2" pulley would yield .021" so we were pretty close to what MH's rule of thumb suggests.

I personally would reuse your old pulleys but bore out some stock and press it over your old wheels to make the rim thicker. You could even experiment with using a hard plastic, although I'd use the same material your existing wheels are made of.

metalmagpie

[Jonesy]

Made a little progress on this. Made new driven rollers using 4" plastic waste pipe. Wall thickness section is about 1/4" so nice and sturdy, and turned some 1 1/2" thick drums from ply to mount the rollers on. As these are the driven rollers I've not crowned them.

The slave, or feeder rollers, are the old 3" metal ones with 25mm shafts. I struggled to crown them on my tiny lathe. I tried to put centres in the ends of the shafts but couldn't do it with any accuracy. So putting the tailstock off centre and turning betrween centres was out.

What I did, and I know it was a poor operation, was to mount a 25mm bearing in place of the tailstock, offset by about 2mm, and hold the shaft in the 3 jaw with copper soft jaws to allow for the skew. Then I was able to straight taper the bearing end, about 1/3 the length, down to about 1mm taper. Then flip the piece and repeat.

Then used a long length of emery to smooth it all out. By my standards this turned out pretty good!

[BCRider]

Most of those I've seen have a flat drive roll and crowned 'feed' roll (the one that guides the belt toward the platen). Seems to me that you might end up 'herding cats' with multiple crowned rollers.

The 6x48 belt and disc sander I have used to be like that. Belt seemed to have wanderlust. I finally took the the darn thing apart and removed the crown from the drive side and gave the double cone idler a bit more of an arc to the cross section and from then on it's stable as could be wished for.

So I vote for only ONE crowned element which is adjustable and the other(s) made straight.

[Jonesy]

The 6x48 belt and disc sander I have used to be like that. Belt seemed to have wanderlust. I finally took the the darn thing apart and removed the crown from the drive side and gave the double cone idler a bit more of an arc to the cross section and from then on it's stable as could be wished for.

So I vote for only ONE crowned element which is adjustable and the other(s) made straight.

Well that's what I'm going with so fingers crossed.

Managing to grab an hour or 2 each day on this so hope to test soon.

[larry_g]

Made a little progress on this. Made new driven rollers using 4" plastic waste pipe. !

Be ready for some static shock.. You may have to put some conductive grounded wipers on the roller to dissipate the static electricity that can build up. Learned this the hard way.

lg
no neat sig line

[Jonesy]

Be ready for some static shock.. You may have to put some conductive grounded wipers on the roller to dissipate the static electricity that can build up. Learned this the hard way.

lg
no neat sig line

Thank you. I know my plastic extraction pipes get a lot of static so worth looking into.

In today's couple of hours I fabricated the true-ing adjustment... or part of it anyway., and the clamps to hold the slave rooler shaft .

Everything is in mirrored duplicate as this is 2 verical linishers side by side off a single drive.

It's getting there.