Band saw arm weight

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But as gesture of goodwill, I will point you to a discussion elsewhere: **LINK**

https://www.mig-welding.co.uk/forum/threads/clarke-cbs45md-6x4-metal-cutting-bandsaw-modifications.58019/page-5

MichaelG.

I have had one of the same generic type of bandsaws for six months or so now. Used it extensively cutting 3/4" steel plate as seen in my recent thread on Myford Lever Action Tailstock Design and Build. It seems the "correct" setting for the spring adjustment is by trial and error and varies somewhat depending on the material being cut and its thickness. Blade tension can make some difference too. Obviously cuttng a piece of 4" x 1" flat bar will be different from cutting a piece of square tube with 1mm wall thickness.

In the end I have arrived at a setting that generally works but if the machine sounds like it is starting to shudder or work too hard, I might either lift the arm a bit to take some pressure off, or wind the spring up a bit. Conversely if it's cutting a bit slow or rubbing a bit, I might gently push the arm downwards add some weight to the blade, or adjust the spring to suit. Mostly, once you get the "feel" of it to your satisfaction, the spring can be left alone and the saw left to do its job unattended once started.

One thing I did do was follow the advice of the manufacturer of the new blade I bought and tighten the spring up to use less pressure on the blade until it is "run in" a bit. Definitely helps. Good quality aftermarket bimetal blade is streets ahead of the standard item. And you can run the saw on the fast speed to cut steel with it, saving a lot of time. I think from memory mine is a 14-10 variable pitch blade and seems to work on steel and aluminium just fine.

So in a nutshell, a bit of trial and error and a bit of gumption will get you there.

Edited By Hopper on 29/04/2022 07:34:21

I think Hopper summed it up nicely. As most of us are unlikely to make more than two similar cuts in a row its best to just find a setting that works reasonably well on the type of cuts you make and stick with that. For a single cut its likely to take as long to look up and change settings to suit blade, material, section, etc than it is to make the cut.

Luckily my Femi has constantly variable manual feed pressure so I don't have to worry about weights and springs.

Yup, Suck it and see. KISS principle.🙂🙂

Vertical down-force will vary with arm angle (likely by about a third?) from tallest cut to virtual break-through.

Downward pressure at the cutting point will vary dependent on the area (and the angle), which can easily be be an order of magnitude.

Thanks for sticking with me, guys. My issue has been more with the way that the user manual presents its information. It would have been so easy to use a term like"arm weight, unsupported by the spring" instead of assuming that was obvious, But it's not all that obvious to someone who is looking for some definite advice / instructions. I get it now.

All the other factors like arm angle and length of cut in the workpiece are sort of obvious but I guess that the 'optimum' loading force is on a very broad curve so it's not too clear cut.

On the subject of the forum software, I hadn't previously come across those stupid 'automatic smileys'. It's a pointless facility because there are real smileys available. But that's just further example of the tiredness of the existing system. Things have changed a lot since the software was built - not least, the cost of data storage. ME could perhaps be looking for a new host with more up to date ideas (and possibly cheaper rates). The 'quaint' display theme is quite attractive and wouldn't need to be changed much.

Have had one of the generic Chinese 4.5" bandsaws (Warco rather than Clarke / Machine Mart ) for many years.

There is no counterweight.

The load on the blade is applied by the adjustable spring tension My experience is that applying too much load will cause the cut to curve away from a vertical straight line.

So if in doubt err on the side of "less" rather than "more"

It will pay you to spend time setting up the saw, setting the guide rollers, (The rollers are mounted on eccentric pins so that the rollers can be adjusted to just bear against the top and sides of the blade.

Jacques Maurel designed and made a simple tension meter. I made one and following his advice set the tension.

Having set the tension, adjusted the guide rollers and the tracking, it would then produce a straight vertical cut, allowing pieces as thin as 1.5 mm to be cut. On one occasion the difference in thickness was a never expected to be repeated 0.025 mm!.

Once set up, blades seem to last a lot longer, to wear out rather than break.

If you open brackets and don't leave a space between the last character and the closing bracket, you will get those infernal "smileys".

HTH.

Howard

Thanks Howard

Hi, I can't see why you would get a smiley when you don't leave a space between the last character and a closing bracket Howard, (I don't seem to get them) Maybe it has something to do with the browser you use.

Regards Nick.

if you put a " and ) together you get "

Or something like that. It is the combination of things like  : and ) together you get and ; plus ) = and :O that cause smileys. Dates back to the stone age of the 1990s before there were smilieys and those symbols were a secret internet cool dude code meaning the emotions the smileys graphically depict today. So always put a space before a closing bracket and you will not get a smiley. : )

Edited By Hopper on 30/04/2022 11:35:57

Nick

Have a look at this old thread : **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=172073

and the older one one that I linked from it.

MichaelG.

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The number [and uselessness] of available ‘Keyboard Shortcuts’ provided by Micro$oft is astonishing.

https://support.microsoft.com/en-us/office/use-emoticons-in-lync-for-mac-c1f07009-bbc4-4fba-87d7-564c01647b43?ui=en-us&rs=en-us&ad=us

Edited By Michael Gilligan on 30/04/2022 13:59:11

Of course all us Internet veterans disapprove strongly of dreadful modernisms like graphical screens and mice. Back in the day, real computer men didn't have any of that namby-pamby wet-worm technology that today's snowflake wimps can't do without. It was character forming! The internet worked on text terminals paging 24 lines of 80 characters each, in any colour you liked as long as it was green. Or a teletypewriter, about 50 characters per second flat-out, plus ear defenders.

Here's what the forum looks like in a proper browser (lynx), albeit in shocking Technicolor, which we knew at the time would never catch on:

As for images - here's the FreeCAD cotton-reel, done properly the old-fashioned way!

Maybe the internet is better today, but I shall never admit it!

Dave

Getting back to the original question there seems little doubt that the best solution is an adjustable hydraulic damper set-up allowing the rate of fall to be set to obtain a suitable cutting pressure on the blade.

Various designs have been published over the years.

I imagine an old car suspension damper might be a good source for many of the components. Unfortunately I'm not aware of a source for how to modify the piston to give the requisite flow to control of down-feed and full flow when lifting back into position.

Its reported than a motorcycle steering damper of the adjustable type can be made to work well.

May be relevant to note that the larger version has hydraulic downfeed control and is generally considered a workmanlike device that "just works".

Fundamentally the spring system is flawed engineering but better than nothing. Its primary virtue being low cost. Essential in a device that has to hit a relatively low price point. Big brother is over double the cost. The effetcive hydraulic downfeed control doublets being a significant contributor to the difference.

Clive

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As per the discussion that I linked at the top of this page

MichaelG.

A real trip down memory lane. I imaging that 3D printing would not be a favourite.

I daren't do a smiley for fear of offending people.

Good to see this evidence of tact on your part, Andrew - decidedly belated, but welcome nonetheless.

Edited By Bill Phinn on 30/04/2022 20:46:34

Hi, thanks everyone for explaining about brackets, gaps and smiley's etc., guess Howard didn't give the full reason. I've never really used a computer before 1999, when I bought one off the company that I used to work for, when they did a major upgrade to their servers and all the computer terminals across every site and it came with this CD ROM in case there were year 2000 issues, which thankfully wasn't needed.

When I got it home and rigged it up and turned it on, I thought now what do I do with it and it only had the default programmes that came with the OS, so I played around with it and learnt how to do all the basic opening and closing etc. and I think Paint was the first programme that I started to get the hang of things with.

Regards Nick.

Edited By Nicholas Farr on 30/04/2022 22:42:36

But wouldn't a hydraulic damper system still need adjusting each time to suit the job in hand? Cutting a piece of 4" x 1" flat bar will need less damping than cutting a piece of 2" square tube with 1/16" wall thickness, won't it?

But if the larger machines have a damper as standard, it might be easier to adapt one of those to the smaller machines than using motorbike dampers, which are usually a bit pricey too.

IIRC there was an even earlier one way back when the website lady explained that keyboard wizzes in other forums here needed to be able to to enter smilies etc using keystrokes only. For that reason the site was configured to allow it (rather than turning off that option) resulting in the rest of us generating inadvertent smilies.

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That’s not quite how I remember the ‘explanation’ Peter … but as I couldn’t easily locate that particular thread, I decided to just illustrate the ‘mechanics’ for Nick.

If you can find the actual quote, do please post a link pro bono publico

MichaelG.

The shop made versions all seem to have some sort of valve for adjustment. In principle it would seem no great problem to arrange a divided dial and calibrate the set up. Hang a chart nearby or stick a label on the machine to give the setting for different materials and size. If you needed more than one turn then copying the Bridgeport quill downfeed scale system with a ruler alongside calibrated in one turn units would not be too difficult.

However its not exactly super critical. Folk like us won't notice the difference between dead nuts right and close enough to work well. I seem to recall one of the home brew versions having a needle valve with 4 turns of useful movement "graduated" in half turns as being close enough.

The motorcycle steering damper folk can just count clicks on the adjuster. The common 70 mm stroke, 330 mm long ones from "China Inc" in various brands and colours are around £30 - £40 which isn't stupid expensive. Ohlins et al are priced for the racer boys so not appropriate. My experience of high end Ohlins, Japanese factory and cheapy import from 30 odd years back was that they were all equally poor at their proper job on a bike but all had similar damping abilities against simple movement.

Depends on the damper design too. There are types with a very savage velocity / force curve giving little variation in movement speed over a wide range of applied forces. So the arm drop won't be too fast on thin materials but for thicker stuff the extra resistance to cutting slows things down enough that the downforce per tooth is still reasonable.

Clive