Member postings for Raglan Littlejohn

GRBL is open source software that you can load onto an Arduino or similar. To use it, you load a program, Universal Gcode Sender, into any windows pc. The pc is connected to the Arduino with a usb lead. Universal Gcode Sender will import g code from Fusion360. Universal Gcode Sender will give a preview of the tool paths. It will communicate with GRBL via usb, and drip feed the g code to the controller in the Benbox (presumably a micro controller like the one in the Arduino).

I've used GRBL in a simple cnc router setup, with GRBL loaded onto an Arduino Uno, and with an inexpensive driver board which plugged into the Arduino and ran the stepper motors. This worked very well. It's limited compared to Linuxcnc or Mach3, but I think it will do everything you need on a cnc router.

The accurate hole drilling will not be a problem for GRBL. The mechanics of the machine itself will be the limitation on accuracy. Hopefully someone else who has one of these machines will comment.

John

I loaded grbl onto an Arduino a couple of years ago. I used the instructions from NYCNC https://www.youtube.com/watch?v=1ioctbN9JV8.

Some DC equipment is +ve earth. If the original psu is -ve earth, and the new equipment is +ve earth, this is the sort of problem you would get. I'd put the motor on an insulated surface, and check with a voltmeter.

I've looked up Ivan Laws method of doing this job. It is described in chapter 10 of 'Measuring and Marking Metals' one of the Workshop Practice Series from Tee Pubishing. I'd be interested to hear what people think of this method.

I would do as Duncan suggests, but I would make the coupling rods first. Next make the discs the same diameter as the coupling rod bearing holes. The axle boxes can then be fitted on the locomotive packed up to the same height. The discs can then be adjusted on the axle boxes so that the coupling rods fit . On an 0-6-0 I would fix the discs for the middle axle in the correct position relative to the frames etc, then adjust the first and third axle discs to fit the coupling rods. The discs can then be used to align each axle box for boring as mentioned before. I think I saw this method in a book by Ivan Law.

Murray,

I'm looking at upgrading to a modern VFD, as I would like Vector Control. Thanks for the link. I was impressed by Inverter Drive Supermarket, the easy start guide they produced for the LS Starvert iC5 1.5kW was excellent. They also have manuals for all their products, and the prices look competitive.

John.

Hi Nobby,

Thanks for that. I thought that picture might help to show how quick it is to set up.

Another picture of Nobby's method. The cross slide stays engaged, just follow the template with the dti using the crosslide handle. The only work involved is cutting out the template and mounting it in the tailstock chuck.

Nobby's idea is ideal for this job. I did a similar set up for a model loco smokebox door. Use slow power feed (sliding), and keep adjusting the cross slide to follow the template. you have to keep watching the dti, and try to keep the needle in the same place. Best to work from the middle of the template, as you have to wind the cross slide in to keep up. If you get behind with the cross slide you just stop cutting, and don't spoil the job.

I looked at one a few years ago, the owner was thinking of selling but no price was mentioned. They look to be very nice machines, any problems are covered in lathes.co.uk. I don't think you can go wrong at that price despite the rust.

I did a saddle tank for a Sweet Pea loco, brass, with copper ends. I tinned all the joints, clamped it all together, and tried to solder it using ordinary plumbing solder (lead based). It was the hardest job of the whole locomotive build (the boiler was bought in). As I soldered one seam, another would open up. I managed it eventually, but Duncans idea sounds the best way. I would also use plenty of rivets to try and keep the seams together. It would be a lot easier to just rivet//bolt it all together, then use some sort of tank sealant, say Petseal. If it can cope with petrol, water in a saddle tank should be no problem. Good luck whatever way you do it.

John.

"Not that I doubt the technical knowledge and excellence of my esteemed forum colleagues - but you have to try things for yourself, no?"

Iain, I think you've hit the nail on the head here. You've found something not right (tapered bore), asked questions etc, had concerns about chuck alignment, and tried different things. You've now had a good result, and know your lathe is ok. You also know a HSS boring bar can produce a parallel bore. Excellent result.

As you suggested, have a go on your cylinder with the new hss boring bar. Just make the piston a bit bigger to fit the finished bore.

Regards,

John.

Clive,

I understand your concern re using the ball bearing carrier linear rail in this application. It's a pity they are so sensitive to tilting. I guess they are designed to fit under a moving table (typical application, cnc router), so most of the force is from above, not from the side. Looking at the link in the first post, http://www.dzcues.com/taper_bar.html, I see he uses a Heim link to compensate for vertical misalignment. He also looks to be using a high end carrier. As you suggest,the u channel carefully made looks the best solution.

John.

This looks an excellent idea from Thomas. MGM12 400mm linear rail including one linear rail block is £16.56 from Banggood. Additional blocks are £6.30. I would be tempted to use two blocks. They should be low friction, smooth running, and accurately made. This will save a lot of machining work in making a taper attachment, the main parts needed will be a platform, a couple of brackets to fit to the lathe bed, and a bracket to connect the cross slide to the linear blocks. As long as you make sure the blocks cannot tilt in use, I cannot see any problems.

"3 Take an 8 inch piece stick it as far back into the chuck as far as it will go, face the end and centre drill the end with a No 3 or 4 centre drill. Pull out the bar so you are holding it with about 1/2 an inch, support the end with a revolving centre and lock up the tailstock."

I did something similar to this when I was learning to use my lathe. After facing and centre drilling a round bar, I loosened the three jaw chuck and pulled the bar out three or four inches. I then supported the end of the bar with a revolving centre. Unfortunately the drilled centre in the bar was no longer running true, and I ruined a nice little revolving centre that came with the lathe. that was an expensive mistake, I don't forget those. If using this method for testing make sure the drilled centre is running true before engaging the running centre.

I just realised the knurls should be in a spiral. Will have another go.

Here is some some knurling done in Design Spark Mechanical. This is a free program based on Space Claim. It's limited in the file types that it can import/export, but I find it easier to use than Fusion 360.

https://www.gumtree.com/p/van-truck-hire/hiab-hire-crane-hire-worcestershire-gloucestershire-warwickshire-lathe-pallet-anything-considderd/1181666787

I noticed this one on Gumtree, might be worth checking out.

Hi Emgee, Thanks for your that. I'd forgotten that mine was a Mk2, and the Mk3 could do arcs of any radius. It was still a very nice little machine, and all the electronics still worked despite being about twentyfive years old. I did manage to connect an old TV to it to moniter the g code, but I entered it all on the machines key pad.

John.

Thanks for the link to your cnc conversion. These write ups are very useful for those of us contemplating a cnc conversion. The work involved in recording your project must have been considerable. I'm interested to know how the Leadshine drivers/motors perform. They seem much smoother and quieter than standard steppers. I also like the idea of using belt drive to the steppers. I made up a simple cnc router last year, and getting good alignment of the steppers to the feedscrews was difficult. The belt drive overcomes this, as well as allowing more flexibility in positioning the steppers. I had an Emco Compact5cnc lathe, and this used a 1 to1 belt drive for the steppers.