metalworking request/favour

[thetyreman]

I was wondering if somebody on here could make me something specific

I recently bought a bandsaw which I overtensioned which stripped a bolt so I've been thinking of making a new part for it.

It would be made from 18mm brass rounded rod and in the dead centre of it need a thread tapped to fit an m8 1.25mm pitch thread, so all I'd have to do was use this to replace the old part and I can buy an m8 bolt and some m8 size threaded rod to attach a handle to it and this will be my new way of tensioning the bandsaw.

what happened was I put a 1/2" blade on it and it couldn't take the tension and it stripped the bolt and the metal part that the bolt goes into, I think this is partly to do with the original part not being well made enough or engineered, but to be safe I will now only use 3/8" blades and no wider.

final dimensions would need to be 38mm long, 18mm diameter with the m8 thread tapped through the centre all the way through.

in exchange for doing this I could repay you in money or some kind of woodworking item like a dovetail box,

regards,

Ben.

 

[Lons]

It's a pretty simple job Ben even easier for anyone with a metal lathe but is it possible to drill out the existing and tap it to say M10 and then you can use M10 threaded rod to make what you suggest?

 

[thetyreman]

It's a pretty simple job Ben even easier for anyone with a metal lathe but is it possible to drill out the existing and tap it to say M10 and then you can use M10 threaded rod to make what you suggest?

unfortunately not because of the thing that bolt has to go though, it's a steel bar with a square hole in it that should fit the square part of an m8 bolt perfectly, there's also a spring going over the bolt that would only really fit m8 size, I don't fancy having to get or make a new spring as well.

 

[Trevanion]

Must've been a pretty weak material to strip in the first place! If you buy an M8 bolt to go into brass don't buy anything that's coated with something like galvanized or chrome as it can cause a dissimilar metal reaction with the brass after a while of being tensioned and it will be stuck solid, I've seen it happen before! Ideally, you'll want a high-tensile blackened bolt (which is also the strongest option) which is basically just bare steel, which is fine. I reckon with 38mm of thread, the brass shouldn't strip out anytime soon so you shouldn't have to worry too much about having a stronger material there.

I can do it for you if you want, I've actually got some 20mm brass chucked up in the machine right now from something else I did at the weekend :lol:

 

[sunnybob]

use a welder to almost close the hole and re drill and tap back to the original size

 

[chaoticbob]

Ben, this rang a faint bell and a look in my bits box turned up a length of 3/4" (19mm) brass round with an M8x1.25 hole threaded to about 40mm deep in one end - can't remember why I made it! If you're not sorted already I can cut off the threaded bit to 38mm - turning down to 18mm diameter if critical would be the work of minutes. Yours for postage.
Bob.

 

[Trevanion]

Ben, this rang a faint bell and a look in my bits box turned up a length of 3/4" (19mm) brass round with an M8x1.25 hole threaded to about 40mm deep in one end - can't remember why I made it! If you're not sorted already I can cut off the threaded bit to 38mm - turning down to 18mm diameter if critical would be the work of minutes. Yours for postage.
Bob.

It's almost like it was meant to be :shock:

 

[thetyreman]

here are some pictures to help explain why it happened I hope,

as you can see the metal part is designed to fit the red plastic handle so it's hollowed out, the greatest point of stress when you tension it up is where the bolt meets the air. p.s I cut the bolt incase you were wondering why it doesn't reach the top in the pics.

I've included a rough sketch of what I plan on doing, will stainless steel bolts be ok with brass? I'm presuming it won't stick trevanion, this was the one I plan on ordering https://www.ebay.co.uk/itm/CARRIAGE-BOL ... 1438.l2649
the collar in the bolt has to fit in the square, hope that makes sense.

chaoticbob that sounds perfect! I will send you a PM and pay you for postage no problem, can always give you a bit more for material costs as well. I am truly amazed at the generosity and kindness of certain members on here, very grateful.

 

[thetyreman]

a few more pics.

 

[Robbo3]

If things don't pan out you could adapt an M8 connector. £1.82 for 10
- https://www.toolstation.com/connector-nut/p86819

 

[novocaine]

funny enough I did the same with my titan saw.

the handwheel is rubbish, it's not that the machine cant tension a 1/2" blade (as evidenced by the fact that is what's on mine at the moment)

I used an M8 connector nut and a spanner as already suggested.

might make a new hand wheel at some point.

 

[MikeJhn]

As a further refinement, how about a cam and lever to de-tension the blade after use?

 

[Trevanion]

I've included a rough sketch of what I plan on doing, will stainless steel bolts be ok with brass? I'm presuming it won't stick trevanion, this was the one I plan on ordering

I'm no expert on the subject but I think brass and stainless should be ok as far as dissimilar metals are concerned. I think my main concern with a stainless bolt would be thread galling though, as stainless has a serious tendancy to sieze in place when it's tightened up because of the oxide layer being taken off thus cold welding itself to the part it's threading into, I've had it happen to me on a couple of occasions on stuff that I've done up and undone a few times. I'm not sure if it would happen with a brass nut but it did happen to me with cast iron. This video goes into it:

[youtube]HC4KiulYs68[/youtube]

Another problem is that you can't really get coach bolts in anything other than coated steel and stainless steel :?

Also, here's a handy chart I've stolen from google for dissimilar metals:

 

[Robbo3]

As I've posted in other threads on this forum, the wear cause by tensioning is a common problem on Elu 3401/3501/DW738 & other small bandsaws.
Whilst trying to find a better solution I came to the conclusion that it was just as easy to renew the tensioning bolt, every year if needed, as the parts are so cheap.

 

[thetyreman]

As I've posted in other threads on this forum, the wear cause by tensioning is a common problem on Elu 3401/3501/DW738 & other small bandsaws.
Whilst trying to find a better solution I came to the conclusion that it was just as easy to renew the tensioning bolt, every year if needed, as the parts are so cheap.

I bought 10 of the carriage bolts because it works out so much cheaper so if it lasts 10 years I'll be happy

 

[chaoticbob]

Ben, this rang a faint bell and a look in my bits box turned up a length of 3/4" (19mm) brass round with an M8x1.25 hole threaded to about 40mm deep in one end - can't remember why I made it! If you're not sorted already I can cut off the threaded bit to 38mm - turning down to 18mm diameter if critical would be the work of minutes. Yours for postage.
Bob.

It's almost like it was meant to be :shock:

It was slightly weird - I remembered seeing a bit of brass in the short parts bin with what might have been M8 thread in the end, screwed in a bolt, lo and behold it was indeed M8 and went in about 40mm.
Reading further comments about this being a problem with other machines I wondered if an Acme or trapezoidal screw might be a better solution. I had a look at my own saw (Record 350, very much a hobby machine) and that's what they use for the tensioning mechanism. It must be an one of those areas where manufacturers cut corners.
Robin

 

[thetyreman]

Ben, this rang a faint bell and a look in my bits box turned up a length of 3/4" (19mm) brass round with an M8x1.25 hole threaded to about 40mm deep in one end - can't remember why I made it! If you're not sorted already I can cut off the threaded bit to 38mm - turning down to 18mm diameter if critical would be the work of minutes. Yours for postage.
Bob.

It's almost like it was meant to be :shock:

It was slightly weird - I remembered seeing a bit of brass in the short parts bin with what might have been M8 thread in the end, screwed in a bolt, lo and behold it was indeed M8 and went in about 40mm.
Reading further comments about this being a problem with other machines I wondered if an Acme or trapezoidal screw might be a better solution. I had a look at my own saw (Record 350, very much a hobby machine) and that's what they use for the tensioning mechanism. It must be an one of those areas where manufacturers cut corners.
Robin

recieved the part today, thanks robin, delighted with it, absolutely perfect and exactly what I wanted, that was super fast!

 

[chaoticbob]

Glad you're happy - I have to confess thinking that as I should turn off the mill finish from the nominal 19mm bar I may as well swipe it down to 18mm in the process, and was dismayed when it came out as 17.96 :shock: .
I'd be interested to hear how the epoxy joint between the wooden handle and threaded rod holds up. I'd thought about something similar myself for a project, but wasn't confident that glue would be strong enough.
Robin.

 

[Lons]

I should turn off the mill finish from the nominal 19mm bar I may as well swipe it down to 18mm in the process, and was dismayed when it came out as 17.96 :shock:

Shoddy, you need to calibrate your micrometer :wink: :lol:

I'd be interested to hear how the epoxy joint between the wooden handle and threaded rod holds up. I'd thought about something similar myself for a project, but wasn't confident that glue would be strong enough.Robin.

Just fix a reinforcing pin through.

 

[thetyreman]

I'm still thinking about a better way to hold the handle in place, I will try the epoxy first and see how it goes, my plan is to epoxy in an insert into a piece of wood, glue some brass thread into it then glue that into the top of the brass shaft, if anyone has a better idea I would like to know, will have to see how it holds up, not all of the parts have arrived yet so there's time.