Electrical Newbie....please help!

Your are suffering from basic mechanical problems. First off the small pitch of a threaded rod requires a high RPM to achieve rapid motion along it. This high RPM has to overcome the resistance due friction from a less than ideal material match between the basic threaded rod and the nut that is running on it. A typical machine tool would have a pitch something like 2.5mm, 3mm, 4mm. These allow rapid motion with lower RPM. They also have a better material than stainless steel and the mild steel threaded block. Typically machines have well made, polished, stiff leadscrews and brass or bronze nuts for low resistance. CNC machines tend to use ball nuts and matching ball screws to reduce the friction as much as possible to achieve the high transit speeds you are trying for. Secondly the U channel is also stainless. Stainless steel is not usually used for sliding surfaces because there are usually better options.

A typical router does not rely on metal to metal sliding surfaces, they may use bearings as wheels to give low resistance to movement. Mills and lathes have lubricated flat contact surfaces that are carefully made for low friction. This complexity is justified as it is a one off cost that fixes friction problems. Remember that once you actually start using what you are designing there will be additional forces acting on the sliding parts and these will increase the friction of all sliding surfaces. By not reducing all this friction you may get something that will move when not doing any work but stalls the moment you try to use it on a workpiece. Ian P mentioned whip in a long slender rod spinning at 1000rpm. Even a small amount of whip will increase the friction inducing forces. This is why at low rpm the effort needed to turn the rod and move the carriage is low but at high RPM it stalls.

Martin C

Edited By Martin Connelly on 20/05/2023 07:44:06

To select a suitable motor or drive system by you will need to ignore factors such as 'D shaft' and 'drill body clearance' (is that because of length?) and concentrate on working out the overall power requirements (and as Martin has just so eloquently explained) the actual mechanics of the rig.

My understanding of what you describe as 'cordless drill replacement motor' would be a small permanent magnet brushed motor with a shaft about 4 or 5mm diameter. Even if you could couple that shaft to your 12mm leadscrew its never going to have enough oomph to do anything but just spin it, as soon as any load is applied to the nut it will just stall. Cordless drills get away with physically small motor because they incorporate reduction gearing between the motor and the chuck.

What you actually want to use the rig for, matters to no one here, but if we knew a little more about the weight of the moving carriage and what force the cutting tool 'sees', plus pictures of the setup, then I'm sure you will get some good advice here.

Ian

I think you might have problems with the rigidity of your proposal even when you have solved the movement bit. As a wood turner you will know how a good finish is achieved.

Can I ask why you want to do this? For long pieces I have a long tool rest on my wood lathe suported by two clamps instead of the normal one, which give a solid rest for the chisels, this is simple gives feel to the job and works very well .

As Ian says more information would be good for all of us trying to help.

Good Luck with your project

Pete

Edited By Pete White on 16/06/2023 07:50:10

Reading this thread again, it occurs to me that you might be trying to reinvent the wheel:

Metal working lathes already have a lead-screw arrangement to move the cutting tool carriage along on purpose built accurate low friction slides.Those lead-screws are turned by a reduction gearbox which multiplies the torque from a big 1/2 or 3/4 horsepower motor.

Maybe easier to adapt a metal working lathe for woodworking?

You say that a battery drill does turn your shaft but it physically won't fit. Can you not engineer some sort of offset drive using a toothed belt and two toothed pulleys so the battery drill can be mounted alongside at one end of the lead-screw instead of in-line at the end?

People here have added motors to move their X/Y tables, but they typically use big stepper motors, (and toothed belts). You could try searching for those topics.

Hi

Car batty for psu is Good, but use a holder that allows you to TOUCH one of the connectors to a terminal during testing, that way you have INSTANT disconnection,.

Loads SINK as much current as they want, no need to worry that a High current supply will damage the load (unless you have a short circuit)

Make sure your wires can carry the current your motor needs.

How about using an Ammeter in series with the supply? But finding a cheap >10A meter may be tricky.

How about a flexible drive or belt drive between the drill and the shaft to get clearance?

George

I fear that a lack of both electrical and mechanical knowledge may well doom this project ! A stainless leadscrew spinning at 1000rpm may well pick up(gall) and destroy the whole thing risking hurting the operator as well ! I would try to engage the help of someone suitably competant in the field. Analogies with metal cutting lathes are largely pointless as few have a bed of 5', lead screws are 20mm or more, and winding a carriage end to end in 1min is power travel not cutting. An accurate description of the project, it's goal and ideally a few pictures of what you have so far would enable us to offer better advice. Good luck. Noel.

Someone up post suggested not bothering with all the electrical stuff. The Wadkin R S Pattern makers lathe is hand feed with not hassle, built to run all day as well. Might give you some ideas?

Have a look here

You have recieved alot of suggestions and really we have no idea exactly what you are trying to achive. You discribe a jig and are actually making a lathe nearly. How about roughing out the piece and then using a router to finish to size, google router lathe.

Edited By Pete White on 16/06/2023 14:02:28

There has been plenty of advice and guidance given so far on this topic and I think it is pointless adding more and more until the OP gives some more information.

On the face of it the original enquiry is a genuine request and one which forum members here are more than willing to assist with but until 'Steven Brown 1' re-appears we may as well leave things dormant.

Ian P

Re reading the thread, if the objective is for the cutting tool to cover 1.75 M i(I think that 5 feet was mentioned somewhere) in 2 minutes, tha M12 threaded rod will be rotating at 500 rpm.

To me that seems pretty fast, from the point of view of safety.

A piece of 12mm studding, is likely tyo whip, evn if held in bearings at both ends.

And the warning about stainless galling is well made.

Also the actual workpiece will need to mbe rotating at an even higher speed, unless a screw threas dinish is required.

Normally, one would be looking to produce a smooth finish, so the Leadscrew, which is what bthe OP wants, will be rotating dar slower than the workpiece..

Given the 2 minute travers time, does the OP REALYY want a worlpiece rotating at somethging like 10,000 rpm?

is the machine even capable of that?

As Ian P says, the OP needs to define the objective first of all, and then to consider means of achieving it with the equipment and machinery which is available.

Howard

The OP seems to be talking about trying to make dowels a different way to everybody else.

.

I would suggest you give that a try, Stephen

… if anyone objects, the Moderators can soon delete any objectionable link.

MichaelG.

I think Ian .P, three up post said it, but I am still in waiting to see what it is all about, love a mistery, usually have to be content trying to work out what the Mrs. is "trying" to tell me? lol.

Edited By Pete White on 16/06/2023 18:38:22