Band saw arm weight

[andrew lynerParticipant @andrewlyner71257]

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.

[Howard LewisParticipant @howardlewis46836]

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

[andrew lynerParticipant @andrewlyner71257]

Thanks Howard

[Nicholas FarrParticipant @nicholasfarr14254]

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.

[HopperParticipant @hopper]

Posted by Nicholas Farr on 30/04/2022 11:00:14:

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

[Michael GilliganParticipant @michaelgilligan61133]

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.

.

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

[SillyOldDufferModerator @sillyoldduffer]

Posted by Hopper on 30/04/2022 11:33:32:

Posted by Nicholas Farr on 30/04/2022 11:00:14:

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

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

[Clive FosterParticipant @clivefoster55965]

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

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Clive Foster on 30/04/2022 17:05:02:

[…]

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

[…]

.

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

MichaelG.

[andrew lynerParticipant @andrewlyner71257]

Posted by SillyOldDuffer on 30/04/2022 15:28:52:

Posted by Hopper on 30/04/2022 11:33:32:

Posted by Nicholas Farr on 30/04/2022 11:00:14:

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

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

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.

[Bill PhinnParticipant @billphinn90025]

Posted by andrew lyner on 30/04/2022 19:53:25:

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

[Nicholas FarrParticipant @nicholasfarr14254]

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

[HopperParticipant @hopper]

Posted by Clive Foster on 30/04/2022 17:05:02:

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

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.

[Anonymous]

Posted by Michael Gilligan on 30/04/2022 13:55:37:

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.

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.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Peter Greene 🇨🇦 on 01/05/2022 02:00:00:

.

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.

.

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.

[Clive FosterParticipant @clivefoster55965]

Posted by Hopper on 01/05/2022 00:18:12:

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.

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

[SillyOldDufferModerator @sillyoldduffer]

Posted by Clive Foster on 30/04/2022 17:05:02:

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.

…

Clive

Yes, but although an adjustable damper might provide more control than a spring, it doesn't answer Andrew's original question – what's the optimum pressure?

A number of posts point to there being a wide range of acceptable settings that depend on variables like:

• the material being cut
• the size and shape of the stock
• number of teeth, their shape, and how sharp they are
• what the blade is made of
• blade speed
• motor power and ability of the blade to deliver it without bending or breaking
• lubrication and swarf clearance
• the goal – cutting speed versus blade life

All these effect the feed-rate, and I suggest are only worth fussing with if the saw spends most of it's time on the same job.

The saw In my workshop cuts something different every time. So I usually run it at the same setting no matter what.   It's set to suit mild-steel, and I've only changed it a couple of times, both when a lot of Aluminium had to be cut. Otherwise, I don't bother.

Dave

 

Edited By SillyOldDuffer on 01/05/2022 10:03:27

[martin haysomParticipant @martinhaysom48469]

with so many variables i doubt that the optimum pressure is obtainable with any machine to be found in our type of workshop. mine is not even adjustable and is never a problem. i just put the job in the saw walk away and do something else.

[Clive FosterParticipant @clivefoster55965]

SillyOldDuffer

As martin says the variety of jobs and materials we see make it a practical impossibility to define an optimum pressure let alone actually set the saw to give it.

Generally not so much down pressure that the blade gets upset or so little that cutting takes "forever" has to do. Plus knowing when a little hand assistance either way is needful. Certainly that was the way I used mine in the days before the Rapidor power hacksaw took over the bulk of the stock cutting work.

Whatever the designers intent the standard spring pressure adjuster is impossibly cumbersome beyond finding and holding a general purpose position that can be used for "most" jobs. There were a few things that I had to accept that mine could not be made to safely cut. Such as thin wall tube.

In contrast hydraulic systems are easily adjustable. So, given appropriate calibration on the adjuster valve, it is little trouble to change settings when changing materials. Obviously it takes a bit of experimentation and note taking to evolve a list that suits your saw and your work. But once its done changing the setting is no harder than changing feed-rate on a QC gearbox equipped lathe. Just like feed rate, choosing from a couple or three settings will do well enough for most jobs but sometimes you need to be more optimal to avoid stripping the teeth from the blade or ending up with a wandering cut.

Optimum is an impossible dream for us but usefully better than an "it will have to do" general purpose setting for jobs when that isn't really appropriate seems quite realistic.

Its usually fairly obvious when the saw is seriously struggling making a swift adjustment desirable.

According to the professionals getting close to an optimum blade pressure / downfeed rate vastly increases blade life.

Certainly when I got mine I ran through several blades quite quickly due to a combination of the down pressure being way too high and the impossibility of correctly adjusting the blade guides correctly. But mine was an early version, got maybe 45 years ago, so the manufacturing standards and quality of blades in the box were much poorer than todays offerings.

Clive

[Anonymous]

Posted by Michael Gilligan on 01/05/2022 05:27:13:

Posted by Peter Greene 🇨🇦 on 01/05/2022 02:00:00:

.

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.

.

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

 

Not the actual quote unfortunately, Michael, but I do have a record of posting this (in another guise) to the forum back in 2014:

"According to a PM conversation I had with the web-maintenance lady (Katie?) some time ago, ………….Apparently, the editor can be configured so that smileys can only be added via the drop-down (thus solving the problem of, for example, quote followed by parenthesis). However users in some other forums here are deathly afraid of mice (presumably they leap up on chairs when they see one). To accommodate them, the editor is configured to insert smileys the old-fashioned way (via keyboard characters) in addition the the drop-down."

 

(Perhaps what I'm remembering is not an actual thread but an offline conversation).

Edited By Peter Greene 🇨🇦 on 05/05/2022 01:57:48

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