Member postings for AJAX

Agreed - very noisy but effective. It might be worth noting a small compressor will not keep up and the needles will mark softer metals.

Understood, but that doesn't resolve the problem of an exposed metal heatsink that is in close proximity to mains voltages with no apparent regards to safety. Clearance between the incoming live and heatsink is minimal with no attempt at insulation.

Yes, I agree it should be mounted in an enclosure. But what happens when the VFD is mounted in an earthed metal enclosure? The heatsink currently floating above 50VAC would then be shorted to ground. Or how about an internal fault which brings the (unearthed) heatsink to mains potential? Seems dodgy to me.

The seller offered an 80% refund. I replied and said I'm expecting a full refund.

No, I didn't buy the one you are thinking of.

Yes, I agree with your comment about safety. I will be reporting this one.

Just tested the heatsink. 52VAC with respect to mains PE (ground). Not happy with this.

Well that's a coincidence! I'm wiring up a qdm 750 right now.

£50 for the VFD

I guess more than a few of you have purchased cheap imported VFD units. I bought one last week but now I'm looking at wiring it up I have had a closer look. No protective screen behind the PCB and heatsink, and the heatsink is not connected to ground. If there is a short to the heatsink it could be lethal.

I didn't rate 3d printers much until I recently tried printing change gears for my lathe. They are excellent!

Andrew, do you suffer any nuisance tripping with the Siemens VFDs? I considered getting one but the documentation states to avoid nuisance tripping an RCD must be type-B 300 mA. The RCD serving my garage is only 30 mA and I do get occasional nuisance tripping with a Eurotherm VFD.

As mentioned earlier, I decided to go for the simple and secure option with a turned "shaft" mounted in the central hole and then cross drilled and tapped. I won't bore you with the details as it was an easy job requiring just a couple of new parts and the height adjust screw being shortened. I used brass for a bush and aluminium (type unknown) for the shaft as that's what I had in the junk box. The tilt adjust mechanism now feels rock solid and I have confidence it cannot easily fail.

5/16" was my original assumption and subsequently confirmed by measurement. I believe these Walker Turner bandsaws were made in the USA in the 1930s / 40s and that must have an influence on the threads we can expect to see.

Thanks for your contribution

Posted by AJAX on 26/01/2021 22:43:18:

I've had a few more thoughts about a possible solution. If re-tapping / threading the hole is a problem then I could take an entirely different approach and turn a plug that fits in the centre hole (see photo below) and cross-drill and thread that plug. It's not quite as simple as it sounds, as the centre hole is used for the height adjustment, but that shouldn't be too difficult to modify either.

I will probably be back...

As promised, I'm now back after having another look at the tilt and height adjustment.

The easiest, cheapest and strongest solution will be as mentioned above. I will turn a cross-drilled and tapped shaft to fit in the centre hole. The tilt adjust screw can then go through the existing dodgy thread before passing through the newly tapped shaft.

The hole is bored to accommodate the height adjustment screw and a spring (adds tension to the bandsaw blade), but springs can be easily added to the rods either side and then all I need to add is a small bush. I tried a couple of valve springs from my junk box and it worked fine, but stiffer springs would probably be even better.

It's actually much easier than I had thought.

I'll try to get it done one evening later this week.

Thanks, Neil.

I've had a few more thoughts about a possible solution. If re-tapping / threading the hole is a problem then I could take an entirely different approach and turn a plug that fits in the centre hole (see photo below) and cross-drill and thread that plug. It's not quite as simple as it sounds, as the centre hole is used for the height adjustment, but that shouldn't be too difficult to modify either.

I will probably be back...

Thanks for the helicoil recommendations. I've never used one before but I knew they exist.

Measuring the internal diameter of the threaded hole (the "minor diameter" indicates about 7.64 mm. There's probably less than 1.5mm material to one side. I'm assuming the original screw was 5/16 BSW.

I just watched a YouTube video to get an idea about how a helicoil could be used. He drilled and tapped the hole, then installed the helicoil. No shortage of taps here but I'm not keen on enlarging the hole.

Are helicoils suitable for a through-hole? The screw must pass through the threaded section.

Any suggestions?

Something else I forgot to add:

Would filling the hole with JB weld, drilling and tapping be a viable solution? I'd much rather fill it with metal.

I have an old Walker Turner bandsaw that I'm finally getting around to repairing. I have all the parts but there's one thing I would like to fix before reassembly. The top wheel has an adjuster for tracking and it appears that someone stripped the thread and/or used an M8 screw. I don't trust the thread enough and don't want it to give way during use. Failure might lead to the top wheel making sudden manoeuvres.

Here is a closeup of the tapped hole. As you can see, there's not a lot of material to work with. It is diecast something (pot metal?) that goes with the era. The rest of the machine is very solid cast iron.

Thanks

I agree, the bed design is unusual and not like anything else I can find. The cross slide looks like a boring table.

Apologies for the poor quality images. Can anyone identify this lathe? It looks a bit Britannia-esque and I have trawled the usual websites with no success. I'm told it has a throw of about 14".