4 x 6 Bandsaw wheel aduster block

[Grahame Collins]

Stupidly, I thought I was almost home and hosed in setting up my H&F BS4A Band saw.

Having obtained some Starret bi metal blades replacements for the busted standard one, I was able to get the saw cutting square in both planes . I always de tension the blade after use. I went to retension the blade this morning to do a cut and it there was a resounding crack followed by an inability to gain blade tension.

Oh,crap, I have snapped the blade I thought. Dis-assembly showed that the sliding adjustment block had snapped through the 16mm hole. Given the wheel spindle is 15mm diameter ,this hole serves as the the hinge point for the coplanar adjustment of the idler wheel.

The block measures 25.4 wide and has 16mm hole in its face and some 4 x 4 mm slots on the faces perpendicular to the 25.4mm wide face. There are also 2 other holes ,1 for the 8mm adjuster set screw and one clearance hole to anchor the tensioner spindle. That leaves some very thin cross section when you do the maths.

Obviously no has told the Chinese that while cast iron is great stuff under compression ,it it also exhibits poor strength under tension and shear forces, both which occur in the block under load.Zoom in on the cross section photo and you will see where the edge of the hole has been dressed.That alone makes for a stress point as a crack starter.

I don't think I have over tensioned it as I have not much strength now in my hands and wrists due to arthritic problems.

I will braze it up just to get me by, but in the long run ,I think I want to re -design the block as a steel unit to be stronger.It will be along the lines of a vertical band saw where the spindle is hinged and can only move vertically with adjustment but not laterally.


Somehow the the 16mm hole dimension seems a bit oversize to me ?

[nearnexus]

That's pretty crappy quality Grahame, or penny pinching by the manufacturers.

On my Rong Fu that part is solid steel. Would be pretty easy to make one up out of steel - basic machining.

Also I hear that the vice nut is also cast and breaks real easy on those modern ones. That bit was missing on the Rong Fu so I don't know what it was made from, but I made one out of steel anyway.

Hope you get it up and running soon. I don't de-tension either of my bandsaws, and nothing evil has ever happened.

PS. my Bro in Law saw my cheap BS today, got overly excited, and now he wants one :) So I'm on the hunt for another one, whatever the brand, so long as it costs less than $150 and is in Adelaide.

Cheers

Rob

[Stustoys]

I always de tension the blade after use


Hi Grahame,

I'm not so sure thats needed. I think it comes from wood bandsaws with rubber wheels.(though I've been wrong before)

Stuart

[Ueee]

I've never heard that Stu, but then the saw i used to use was ancient and huge, a little bit of tension on the rubber would probably not have done squat on a 30" wheel.

Shame about the saw Grahame,
Just think you could have the fun of replacing worm gears or finding carbide pads instead....:D

Ew

[simonl]

Maybe it's different with smaller home use bandsaws, but I can't imagine steel merchants or machine shops taking the time to slacken the saw blades in-between cuts or even at the end of each day for that matter. I certainly have no intention of giving mine any such moooshy treatment. It's had over 40 years of hard treatment, I worried if I start that sort of thing then next thing you know it will want to sleep inside at night! :U

Edit: Sorry to hear about the saw. It's never a nice sound to hear when you are tightening something up. Luckily it looks a rather simple part for someone like yourself to fix. The fix will no doubt be better than any original and will last the life of the saw!

Simon

[nearnexus]

Somehow the the 16mm hole dimension seems a bit oversize to me ?

It's interesting you should say that Grahame, as the same thought crossed my mind when I had it all apart to re-sleeve/bush the idler pulley.

Although steel, mine is the same in that the hole is definitely a couple of mm oversized, and I wondered at the time why they had done that, considering tolerances everywhere else are close.

It looks to me that it provides clearance for angular movement when you adjust the set screw to tilt the pulley mounting shaft.

The block that you broke remains parallel by the function of the two mounting strips that lock into each side of it, and only the shaft tilts in the hole.

Rob

[Grahame Collins]

Hi Grahame,

I'm not so sure thats needed. I think it comes from wood bandsaws with rubber wheels.(though I've been wrong before)

Stuart

Hi Stu,
The instruction on the MACC 400 ( my employers new eyetalian bandsaw) says to de tension the blade if the saw is to be left standing idle for any time. Given the correct blades for the work and run in and operated as per instruction it has not missed a beat. Our work structure is that for this machine, use is sporadic.

Like a hand held hacksaw it is possible to induce a curvature in the bow of the saw from the tension in the blade. Given that the cast iron used in this particular Chinese aberration, is probably only marginally stronger the recycled peanut paste, I am taking no chances with it.

Bugger it! I might as well go the whole hog and remove as many bugs as I can.

Changes I have made to date
A new stand, longer wider and higher.
A zeroing block to regain vice jaw square to blade after change back from a bevel cut.( Thanks Rob)
Adjusting threads changed over to tool free operation where possible.
A locking device to keep the bow frame down , when being wheeled about. Thanks again Rob)
A swarf tray
Small gutters to pick up the swarf that the tray misses.
A knurled knob for the blade sheet metal cover
A small amount of machining to allow the tension knob /washer to bear squarely against the bow frame surface

Changes to make
Clean out the gearbox and change to the correct oil. The wrong oil used here can eat into the bronze/brass worm wheel.Any know of a local equivalent gear oil to Mobil SC 634($300 per 20L) that's available in a liter bottle.?
A three arm tension wheel - the original knob is very difficult to tighten with my arthritic hands.
A coolant system
A hydraulic controlled down feed .
a super duper blade wiper for stripping off swarf before in gets to the drive wheel.

If I do a task or two every night who knows I may have a half decent saw before too long.

Grahame

[nearnexus]

Sounds good Grahame.

How did you fix your broken block?

Another mod you may want to consider is an adjustable vise stop screw, for cutting very short lengths.

I think this is a necessary mod.

See my video below for how I did it.

My $85 4x6 metal bandsaw - restoration - YouTube (http://www.youtube.com/watch?v=xAVouUPGxLc&list=UUXGgjDg8p1nJBgHdxPdvkjQ&feature=c4-overview)

Cheers

Rob

[simonl]

Good work Grahame.

Hi Rob,

I have watched a number of your videos but I have never made comment on them. Probably a good time to say that I really find them entertaining and educational. Thanks Rob!

Cheers,

Simon

[nearnexus]

Thanks Simon.

If no body chipped in, there wouldn't be much to see on the internet.

Cheers

Rob

[Grahame Collins]

Sounds good Grahame.

How did you fix your broken block?

Another mod you may want to consider is an adjustable vise stop screw, for cutting very short lengths.

I think this is a necessary mod.


Rob
Rob,
The block has been prepped prior to welding.I have opted to tig it using MMAW stainless as a filler rod.

I have a pair of drop in blocks, both longer than the rear jaw, the front one being drilled and tapped with a rod and knurled knob.I can move them up to the blade and cut a millimeter off if I choose to.
For the moment I have put them down in a safe place and when I find them again will take a pic.


Grahame

[simonl]

For the moment I have put them down in a safe place and when I find them again will take a pic.
Grahame

That so called "safe place" must be getting very crowded. I seem to have a lot of stuff there too!
Simon

[Grahame Collins]

The block is welded but I don't think it will hold the cast is a bit different to weld with tig and did not wet too well. I am making a steel block to a better stronger design.

For any one that interested in the new design, I have some 25.4mm cold rolled square , I will drill holes for the adjuster grub screw and the tensioner. The tilting mechanism is just a 6mm slot in the 25mm square, that takes a flat machined into the end of the 15mm diameter spindle.The flat spindle end will pivot on a M6 shoulder bolt. Only minimal side slop is possible, just up and down movement.It has to be stronger, there's lots more cross section and that is in steel not crap iron.

For anybody that is also chasing the gearbox oil oil for one of the the little sods, I found Penrite 85W-140 a mineral gear oil which Penrite say is OK for copper alloys, so obviously brass well. $14 and some change at Auto barn for a liter ,but the SuperCheap Auto also have it. Also Goggle the Penrite site for a list of sellers.

A question for you ,my machinist friends. I have a face plate for the 12 x 36 that i was going to mount the 180mm ( 7 3/8") bandsaw wheels on to bore and true the saw blade surfaces.
The band saw wheels are 3 legged and the lathe face plate has 8 x 15 wide slots, so the plan was was to screw the wheel to the plate , bolting the plate through 4 opposing slots and tap/slide it the whole shebang into alignment checking it with a dial.

Is this what a real machinist would do or is there a better way to go about the procedure?

thanks

Grahame

[Steamwhisperer]

Hi Grahame,
If it was me I would machine a plug that fits neatly in the hole in the faceplate and neatly into the bore of the bandsaw wheel.
This will help with true original alignment. Clamp the wheel in position then remove the plug out through the back of the faceplate (if possible) and you should be good to go.
This way the bore can be machined true to the outer diameter and vica verca.

Phil

[nearnexus]

There should be enough metal in the pulley lip to mount it using the external jaw set in the 4 jaw chuck.

I considered doing this when looking at options to rebuild my idler pulley centre (I briefly thought about opening out the cetre of the pulley).

In regard to welding the cast, I would have definitely bronzed both sections seperately to get full penetration, rather than use TIG. Anyway steel sounds a lot better long term proposition. Be interesting to see photos of the new design.

Cheers

Rob

[Grahame Collins]

Phil,
I would do as you suggest but there are a few impediments.
One is that the spindle bore of the lathe is 38mm while the bore of the faceplate is 60mm.
The second is getting my mitts on some 60mm+ .The local engineering supplies seems to be suffering cash flow problems as their stocks are are devoid of some essential sizes ie 60mm.

There are other vendors but they are asking a $100 cash buy at the counter. I guess its their way of saying we can't be bothered with small value orders.

The other hope is ring up the scrappy and ask if he sells to the public.Some have rules re PPE

Rob,
I'll post photos when it is finished.

Cheers
Grahame

[Michael G]

Grahame, I think I have a couple of AL slugs around 70mm in diameter, 40mm thick/ long. Would that help any?

Michael

[Steamwhisperer]

Hi Grahame,
Still solvable.
Using a slug of aluminium like Michael has, machine it to suit the bores then set up as normal then machine the slug out as you go.
The slug becomes sacrificial.
You could also use a piece of shaft approximately 75mm long and the same size as the bore of the bandsaw pulley.
Get a piece of 10 mm plate big enough to machine down to 60mm and bore a hole in the centre to take the shaft.
push the shaft through the hole in the plate until it sticks out about 6mm and place a weld around the short protruding end.
Set the shaft and plate up in the lathe and machine the plate outside diameter down to 60 mm.
Machine it out as before after you have used it to set up the pulley.

Phil