#14697

Hello, Is there any tricks to take the slow out of the main arm hinge? I pulled mine apart to fix something else and now notice there is side to side movement when arm is down.? May have always been there but I didn't notice it.??

#14698

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On 3/9/2019 10:22 AM, moto52000@... [4x6bandsaw] wrote:

?

Hello, Is there any tricks to take the slow out of the main arm hinge? I pulled mine apart to fix something else and now notice there is side to side movement when arm is down.? May have always been there but I didn't notice it.??

Posted by: moto52000@...

? Depends on where exactly where the slop is . Could be as simple as replacing the pivot pin if it's worn , might need to be reamed out and either bushed or have a larger pin installed . A lot depends on what tooling you have available and your level of expertise .
? --
? Snag

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#14702

Yes there ways, though not easy.?

BUT this is the MOST important factor in your saw cutting square (esp vertically down).? So much so, that you have to fix it or get rid of the saw (unless you don't care whether it cuts square, but then you'd ever want to fix it).

To cut square the pivot shaft MUST be parallel to the workpiece in both front elevation (i.e. horizontal to the base of the vice - not easy to measure, therefore not easy to set correctly) AND in plan view (i.e. looking down from above - effectively parallel to the back of the vice, which is always easy to do).? The back of the sawblade also has to square to the pivot in front elevation and plan view.? Although they're related, they have different adjustments available and don't really concern you when re-bushing the pivot.?

Because the pivot shaft is set-screwed to the sawframe side of the hinge, the wear is only in the ears of the base. With luck you may need to only do the bush next to the blade, which is normally the one that wears first.? However ANY slop on the bearings translates to un-square cutting. Turning the pivot shaft end for end may get any shaft wear into places it doesn't matter. If you want your saw to cut square within 'thou' the pivot shaft alignment must be parallel within the same amount.? The 2 are flip sizes of the same coin.

The ways I know are:

1. Milling off the ears and bolting on replacement pillow block style bearings -? has been done and there are photos in the Photo section of the site. The pillow blocks need only be square steel bar reamed to 15mm diameter of the pivot shaft. You can ensure parallelism of the bearing mount to the saw base when setting up in the mill.??

2. If you don't have machine tools, then drilling and/or filing out the base ears until they're sloppy enough to accept a bronze or brass bush will work.. Because the worn hole is oval, drilling it out dead size for the bush may not get it It is aligned with vice base and back.? Try drilling dead size and measure the alignment before easing it open any further. You can ensure alignment in a sloppy hole by using 3 set-screws in each ear (one up from underneath and the other 2 in from the back and front).? Once aligned the gap between the bush? and the cast iron base ear is injected with epoxy resin from a hypodermic syringe through an additional hole from underneath so it flushes the air out. An o'ring on the shaft either side of the ear will stop the epoxy squishing out the sides. Suitable diameter bushes are available from engineering supply places like McMasterCarr.com, though you'll have to cut them to length.? You might get lucky and getting a bush that's twice as long as you need and can just cut it in half.??

The only relatively simple method of measuring whether the pivot shaft is parallel to the vice base casting is to cut some 4'x1" soft pine or fir joinery timber (dressed all sides, it winds up under size but that doesn't matter):

mark one of the 1" edges with a pencil or marker pen (so you know which way up the piece was when cut)?
grip it 4" face vertical in the vice, so 1" edge sits flat in the vice base, with about 1/4" ready to be cut off and mark line upwards (get used to doing it the same way all the time, as you will have to do it many times before its right..
?cut off the end of it by lowering the saw through the wood by hand so it take at least 10-12 sec to make the cut (the blade teeth are rasping the wood to the shape the pivot geometry makes it).? Discard this piece.
?turn the wood over 180 degrees (now mark line is against the vice base), again about 1/4" to be cut off, exact length is not important.
?cut the piece off in same 10-12 seconds as before.? This is the test piece.
?measure the thickness of each end (with digital calipers is best) and subtract one measurement from the other??
?ONLY if the pivot shaft is parallel to the vice base will the measurements be the same and the difference between them zero. Otherwise it will be tapered, either toward the mark line or away from it, depending on which end of the pivot shaft is higher than the other.
less than 25thou" taper is ok for most general engineering work, less than about 10thou" is good for accurate work but is not worth adjusting further as you're just as likely to overshoot as much in the opposite direction, obviously parallel is best.

Hope it helps - jv

#14703

Thank you for replying.? My issue should not be due to worn out pivot pin or ears.? It was cutting well before I messed with the pivot to install a hydraulic down feed control. It seems to be an adjustment.? I think I'm going to tear it all down and see how the pivot looks then reassemble. I noticed some oil on and around the drive wheel so I will replace the seals and bearings at the same time. I almost want to buy another saw as backup, having this saw down makes me realize just how much I use it.? ?

I plan to buy parts (bearings, seals etc.) from Grizzly?since I've heard? HF shipping takes a long time.? Do you think these parts should fit? My saw was purchased new at HF in 2011.??

Thanks again.

Glen

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#14705

It should not be worn, but then things often are not what they should be.??

Are you talking about sideways movement of the sawframe and pivot shaft through the ears in the base, not slop in the base's pivot bearing itself?

Normal assembly procedure is to use the supplied cylindrical spacer on the pivot shaft between the base ear and the sawframe on the RHS, then push the pivot arm onto pivot shaft, up hard against the base ear on LHS, and then tighten the set screw in the pivot arm eliminating any sideways movement.? This also sets the angle of the sawframe to make the blade back square to the vice table.

If you removed the pivot arm itself (which people often do to put the hydraulic downfeed cylinder horizontally on the LHS of the machine), then you may not have pushed it on the shaft far enough when bolting back together and that would allow axial movement of the pivot shaft (and also create a little off-angle in the blade back, making the saw cut away from the vice, if it was cutting square before you disassembled).?

If there is no axial movement of the pivot shaft, but the sawframe can still be moved sideways, then almost certain you have a worn bearing in one or both of the pivot ears on the base. Press your finger onto the pivot shaft and base ear together and move the head to create the movement you're calling slop, and it should be apparent where its coming from. RHS is normally worse than LHS.? Let us know the outcome?

The HF manual shows an oil seal on the outside next to the drive wheel.? I'd replace that first if its leaking oil

without changing the bearings as they can be troublesome to replace.The bearing next to the drive wheel is nearly always the one to fail as it doesn't get as much oil as the inner one. Unless you've been having problems with the blade tracking off the drive wheel, its probably ok.

No real experience in swapping?parts?between brands, but seals and bearings are all metric and pretty std with the exception of the guide-roller bearings which are all over the place between brands. You can get seals and bearings from any bearing supply place.? They're normally 6202 (35mmOD x 15mmID x 11mmW) with a 35x15x7mmW lip seal -??jv

#14706

Thanks JV,? I used a clamp to help push the pivot in all the way before tightening the setscrew and that seemed to resolve the issue.? Several test cuts and all seems good now.??

I still have to fine tune the blade guide bearing but it's cutting acceptable for now.? How much pressure on the blade is recommended? I've seen recommendations anywhere from light as in you should be able to rotate the?bearings by hand to as tight as possible.? ??

Glen

#14707

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Glen, take a look at the attached document.

?

CarlH

?

Show quoted text

From: moto52000@... [4x6bandsaw]

Sent: Thursday, March 14, 2019 10:07 AM

To: 4x6bandsaw@...

Subject: [4x6bandsaw] Re: How to remove slop from arm pivot

?

Thanks JV,? I used a clamp to help push the pivot in all the way before tightening the setscrew and that seemed to resolve the issue.? Several test cuts and all seems good now.??

?

I still have to fine tune the blade guide bearing but it's cutting acceptable for now.? How much pressure on the blade is recommended? I've seen recommendations anywhere from light as in you should be able to rotate the bearings by hand to as tight as possible.???

?

Glen

[email protected]

#14708

Hi moto?

Sorry I didn't get back to you earlier, I've been out of the country.

I take it you're talking about the blade-to-guideroller clearance. There are 2 different schools of thought on? this, the manufacturers and the users. The only thing they do agree on is that you should NOT run the bearings tight on the blade (i.e.steel bits are bending to let the blade pass).? This causes the bearings to fail and cracks the blade by acting like an english-wheel.?

Manufacturers say set the clearance at zero to 2thou" max. and that its the most important setting on the saw. Users say the guide roller bearing fail too quickly when set like that so recommend 7 thou" +/- 2thou" as you saw in the article Carl sent you.? There arguments to support both. I believe the right setting lies in combining the best of both.

The arguments go like this:

The blade cuts in the direction its pointing.? Once the blade is set up to cut square, the more rigidly its is guided the better and longer it will cut square, which is why industrial bandsaws use carbide slipper guides set with next to no clearance.?

Why should a 4x6 be different? Because the roller guides can roll swarf chips through the nip between the blade back and the guide rollers, especially the ones? just after the cut. When there is no clearance, if a chip goes through, it will send a shock load through the balls and races of the bearing, the force spike is enough to damage it.? This reduces the life of the bearing enormously.? User experience shows that set with zero-2thou" clearance the side guide bearings fail regularly and often, hence John Pitkin's recommendation to run ~7thou" clearance.? It is many times worse if you use cutting fluid (as you must do when cutting aluminium and should do on high grade steels) since lots of chips stick to the side of the wet blade and roll through the nip. On the other hand if you only cut mild steel, which falls away from the teeth, swarf hardly ever gets to be rolled through the nip and zero-2thou" setting is easiest to set and maintain and is OK to use.

Since I cut a lot of aluminium and brush on kerosene, up until now I've always used 5 thou" clearance. Its not that easy to get a consistent 5 thou clearance and the angle of the blade changes as the clearance changes, so this is much harder to set up to cut square.

But I found when cutting multiple pieces of aluminium that, even when set to cut square initially, I'd slowly loose vertical squareness of cut.? Thin plates of squished aluminium swarf were building up on the sides of the blade and on the surface of the guide rollers.? When the buildup was scraped off (needed a chisel to do it!) it cut square again.?

The reason it cuts out-of-square is as follows.? When you run wider clearance, the blade is slanting across the gap between the 2 rollers, The angle of slant gets less as the swarf builds up on the blade and rollers. The blade will then point away from the vice (the only direction it is free to move), and so it cuts away from the vice.??

This angle change is less if the rollers are set with zero - 2 thou clearance, but the buildup still occurs and you english-wheel the blade and the bearings run tight on the blade, destroying them.?

I believe the best way is to set the blade with 0-2thou" clearance? for best support and easiest setting, and make sure no swarf can get to the nip between the blade and guide rollers by putting a blade scraper in front of the bottom guide roller.? If you check out the document called 'Liquid Coolant Lube on a 4x6 Bandsaw.pdf' in the Files section of the site you'll see the 2 different types I've made.

Hope that helps - jv

?

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#14709

Hi Glen

Just been pondering your reply to removing the slop.

You shouldn't have to use a clamp to get the pivot arm snug against the base pivot ears.? At least not so much that there is any bending/tension in the pivot arm. Cast iron doesn't like tension or bending, though its great in compression.

You can check whether it is by releasing the 5/16" bolts that fix the pivot arm the the sawframe casting and see what happens.? Use a scriber to mark across the joint so you can see which way it moves when you release the bolts. There is quite a bit of slop in that joint, as its the primary adjustment to get the bandsaw blade to run at 90 degrees to the pivot shaft.

1. If it just slips inward along the slots (which is what I'd expect if you've pulled the bottom of the pivot arm across with a clamp) then you will (most likely) have restored the original setting.? Use? an engineers square in the vice to line up the blade as square to the vice back (which should be parallel to the pivot shaft before you start) and re-tighten the bolts. That will make it cut squarer vertically down in metal, though you may need to tweak the angle of the guide brackets to make the blade square to the vice table in front elevation to get it exactly right.?

2. If the joint springs apart or doesn't move, there's not much you need do.? It just means the pivot shaft hole on the sawframe ear is not quite aligned with the one in the pivot arm.? Just re-tighten the bolts while using the engineers square to maintain alignment, but at least you'll know that its in the best position - jv?