Thread: Thiel model 17 metal bandsaw

Continuing with the strip down to get to the worn pinion shaft bearings.

Handwheel on the input shaft was easy - just a grub screw and then puller to slide it off the shaft.

The flat belt pulley had a 1/2" grub screw in it. A bit unusual, and it was actually clamping on this weird key arrangement that I've never come across before. There's even a female thread inside the key piece to allow it be extracted from the pulley.



Behind the pulley was a retainer plate. I was hoping that it was retaining the shaft, but turned out to be only for a gland packing type of seal.



At that point it was obvious that the only way out for the input shaft was for this large plug inside the column to come out.




It turned out to be a very substantial plug and bronze bushing complete with oil wick. The shaft is in great condition, and while there's some slight wear on the drive gear it will no doubt see me out.



Steve

Finally - the pinion shaft itself, but it still wasn't obvious how it came out.

Found a small grub screw under about 2mm of paint and removed that. Tried to tap the shaft out to push the large plug/cap out in a similar way to the input shaft, but it was solid.
Turns out it is only a cap, and I managed to pull it out with the aid of a large magnet to grab it.

That revealed a retaining collar (LH threaded), the drive gear and woodruff key, and a ball thrust bearing:




Sure enough, the bushes and shaft are quite worn, but looks like there is enough meat in the shaft that I can turn it down to remove the damage and just ream the new bushes to suit:



Steve

I'd thought the big foot pedal on the front of the machine was to mechanically engage the chip blower pump, but turns out its for a conical clutch for the main drive wheel input.
It must have got too hard to adjust the clutch, as someone has installed a locking pin between the large drive gear and the shaft.





I'll see if I can get the clutch fixed as I think it would be a useful feature.

Steve

Got the output shaft repaired today. Shaft turned down slightly to clean up the worn areas, new bronze bushes made and reinstalled.
Also refitted the input shaft.

Here's a photo showing the gears of the two shafts and one with the blanking plug fitted - complete with grub screw to retain it.





Steve

Apart from the thrust bearings on the drive shafts, the only rolling bearings I've found are on the blade wheels.
The upper ones feel nice, so just going to give it a good oiling and not mess with it other than that.

The bearings in the lower one were definitely dirty with old oil and crud, so I threw them in some solvent in the ultrasonic cleaner.

After 5 mins the solvent had turned to mud.



Into some clean solvent, and another 5 mins in the cleander didn't do much more. All gleaming now though:



Steve

Still not sure why they bothered with a bolted front flange on the lower wheel, but here's a photo of it all cleaned up:



And the other side with the drive gear:



Refitted - you can just see the oil hole in the top of the shaft that feeds the 2 bearing races, and the plug in the end of the shaft where its been blanked after drilling the axial gallery:



Steve

The lower thrust guide is the only fabricated part I've found on the entire machine. The body consists of a simple bracket that has a steel boss for the rotating part to run in, and and simple adjustment that bears against the rotating shaft.

The rotating part is a short shaft with a large flat flange on the front to bear against the back of the blade.

I didn't take any before photos, but the rotating part was seized solid and the blade had cut into the front about 0.5mm deep.
Thinking I'd just give it a quick clean up on the lathe, I chucked it up but soon realised it was DAMN hard. The cheap WNMG insert took a bit of a hiding - particularly with the interrupted cut from the slot that had been worn into the piece, but I managed to get it 99% cleaned up using 3 edges. You can just see the slight remains of the original deep slot.




I also added a lubrication hole to the boss so I can get some oil into it



Steve

It lives !!!
Well, sort of....

Got it wired up and running today. Replaced the cable from the wall to machine on/off switch as it was badly perished. The cable from switch to motor was fine so left that alone.
The drive belt was slipping a lot and it only took light cutting pressure to stop the blade completely. I took the belt off, cleaned it up a bit and gave it a light spray with contact adhesive, then wiped it off and left to dry for about 10 mins. That has definitely improved it, but I need to make a new belt for it.

I have had a slight setback though. The blade seemed to be going VERY slowly - even on the highest speed. I did some rough calcs on the RPM and blade speed and it seemed to be in the ball park of what was on the machine's chart.
I checked what speed new bi-metal blade is meant to run at, and its around 200 m/min for general steel - that's with coolant though so I'd need to reduce that a bit since its running dry.
Anyway - working with the 200m/min - with the 300mm wheel that comes out around 212 RPM.

Highest speed I've got (as measured with optical tacho) is 53 RPM.

Bugger. I guess the machine was built a long time before bi-metal blades were born.
I can only see one practical option for getting a 4x speed increase out of the old girl, and that is to replace the motor and countershaft gears with a more direct geared belt drive. Seems a shame to remove that beautiful reduction gear drive, but with the solid cover it won't be obvious.
Currently the gears give a countershaft speed of 213 RPM with the 1430 RPM motor.

I think it would be good to get the countershaft up around 1000 RPM which will give a highest blade speed of ~250 m/min and a lowest of around 70 m/min. Should be a useful range I think.
Obviously shaft lubrication becomes a bit more of an issue but I'm happy to oil it when I use it.

Anyone care to give me a sanity check on my musings?

Steve

I've finally solved the mystery of the moving weight inside the column (photos in post #13).

Its to provide auto-feed!!

The cable attached to the weight should come out the back of the column and connect under the table to a fore-aft rod with a block on the front - at the edge of the table.
The block has provision to add a second part to get higher than the table surface, with a sort of pushrod to push on the work.

First photo shows the cable exiting the column and going in under the table:



This one of a larger model Thiel shows the block and pushrod setup.



Guessing you fit the top block, adjust the pushrod and then pull it out to raise the weight in the column. Insert your workpiece between pushrod and blade and let the weight provide the feed force.

Steve

Originally Posted by OxxAndBert

...The blade seemed to be going VERY slowly - even on the highest speed. I did some rough calcs on the RPM and blade speed and it seemed to be in the ball park of what was on the machine's chart.
I checked what speed new bi-metal blade is meant to run at, and its around 200 m/min for general steel - that's with coolant though so I'd need to reduce that a bit since its running dry.
Anyway - working with the 200m/min - with the 300mm wheel that comes out around 212 RPM.

...

I think it would be good to get the countershaft up around 1000 RPM which will give a highest blade speed of ~250 m/min and a lowest of around 70 m/min. Should be a useful range I think.

Not sure about sanity at this end, but here goes -

The numbers I use for cutting speed for HSS are 30m/min for MS, Alloy steel & CI about half that (so say 15m/min) and for Al something like 3 times that, so around 90 to 100m/min. My understanding is that the bi-metal cutting teeth are HSS, so 200m/min sounds way too fast.

You won't kill a blade by running it a bit on the slow side, but too fast and it is history.

I'd be checking that speed again and finding out whether you really need to go that fast. As you have a blade welder on there, are you better off just making up and using carbon steel blades anyway?

Michael

Thanks Michael. Your 30 m/min figure is very valid - ie speed for HSS tooling. I hadn't considered it from that point of view and was focused on working backwards from the published blade spec.

The recommended speed for the blade is definitely around the 200 m/min range. My blade is made from Arntz "M42 Sprint" stock. 10/14 variable tooth count, zero rake.
Here's a snip from the Arntz catalogue:



On a horizontal saw with flood coolant it would fly through, but I can't find any info in the catalogue on how much to reduce the speed if running dry.

I checked the speed range on a couple of commercial vertical saws, and they are roughly from 20-100 m/min so that lines up pretty well with your speeds.

With my highest speed around 50 m/min I could probably use a bit more (ie double) for aluminium, but otherwise its about right.
It cuts nicely so I'm just going to run it as-is and see how this blade lasts. Beats the heck out of using a hacksaw and much nicer to use that a thin cutoff disc in an angle grinder

It took about 40secs to do one cut about 10mm long through this 15mm thick MS.



Steve

Hi Steve, Guys,

I do hope that its not wanton vandalism, destroying a useful gear like that.

Happy New Year Guys.

Originally Posted by BaronJ

Hi Steve, Guys,

I do hope that its not wanton vandalism, destroying a useful gear like that.

Happy New Year Guys.

That "gear" was purely a test piece, seeing what happens when you use the wrong number cutter for the actual tooth count

Steve

Hi Steve,

Ahh, the fabled 16.5 tooth gear.

I've yet to have a play at making gears.

Although you have just given me an Idea ! Thanks.

Originally Posted by BaronJ

Hi Steve,

Ahh, the fabled 16.5 tooth gear.

I've yet to have a play at making gears.

Although you have just given me an Idea ! Thanks.

When my stuff ups give people ideas it scares me!

No, not the fabled half tooth (but I do have examples of that too!!).
From memory it was cut with a cutter meant for much lower tooth count gear, so has a lot wider gap between tooth tips. You end up with the correct root but a very thin tip and about as useful as an ashtray on a motorbike.

Typically 8 cutters in a full set, cutter #1 does 12-13 tooth, #2 14-16 tooth, #4 21-25T and so on up to #8 which does 135-rack.

Steve