[JBV]

I was bored so i started drawing a Gingery style mill in metric!

Work envelope in this configuration is 450*270*150 mm and the weight is ~33 kg so far...

The base, table and Z column is to be cast of aluminium.
The ways is hand scraped, cold rolled steel.
Morse 2 or 3 taper in the spindle and a VFD instead of the belt drive!

I already have a CNC:ed mill but this would be an awesome project. and its nice to have a manual mill that could handle some turning too!

A nice build!

[handlewanker]

Hi JBV, interesting project. This has all the properties of a horizontal boring mill. The bed would have to be a bit longer to accomodate a rising tailstock if it was going to be used as a boring mill, to allow line boring bar support.
In the design, I take it that you are using alluminium to steel for the wearing surfaces? Should work well. I don't like the idea of using alluminium for the table, too vulnerable to abrasion and indentation. I would make the top bit with the tee slots as a seperate iron or steel piece.
Ian.

[JBV]

I'm currently building an induction furnace, by my calculations it should be able to handle around 2 litres of aluminium and 0,5 litre steel/iron. So i tried do get the most of it in the design!

The base is around 2 Litres in my first design, so have to be cast of alu, The spindle head i could make of cast iron, but the table is to big! Perhaps if i make it a bit shorter!

Started to draw a more serious design with more details! A stepper, gibs, integrated leadscrews and a MT3 spindle with drawbar! The spindle motor will be on top of the spindle housing or hanging behind the stepper!

[handlewanker]

Hi, can you give a few details of the induction furnace? Being able to melt iron is quite ambitious for the average home workshop. I had a go at making a furnace for melting alluminium, a year or two back, using electrical elements of two kilowatt capacity, but due to a design mistake the elements, which were buried in the fire clay liner, failed and burned out. I realised afterwards that the elements should have been exposed to the crucible and the fireclay used to prevent the heat getting out.
I am also currently rebuilding a small vertical jig borer to vertical mill standards as the spindle did not have a drawbar, and was only 2MT. The new design of spindle has two 35mm bore angular contact bearings in back to back configuration at the bottom end and one sealed radial ball bearing at the top end.
I am using the R8 collet system instead of the originally planned 3 MT, as I feel it is superior, being able to hold cutters directly in the collet and thus reduce the distance from spindle bearings to cutter.
Looking at your design brings to mind the design of the Kearns horizontal boring mill which I worked on for some years in the '70s in UK.
On the Kearns there is a long cross slide bottom half but the table is shorter and carries a revolving square table on top, the purpose of which is to allow machining of both end faces of a bore. I expect you are familiar with the design.
Ian.

[JBV]

I have build a H-bridge that will be driven by a µC with a lcd and rotary encoder for settings. The H-bridge is to be connected to a transformer from an welding inverter. And after that a tank circuit or the work coil directly!

I have two 35 mm id taper roller bearings and one 20 mm radial, that i was thinking of using for the spindle!

I have no clue about the boring mill design but i will look for some pictures!

[handlewanker]

Hi, I see by your bearings sizes that you have a bore size of 35mm, this will leave you only 5mm wall thickness for 3 MT. There is a problem with the single 20mm end bearing. If the drive is by a vee pulley on the end of the spindle, any subsequent wear, due to drive belt pull, in the 20mm bearing will lead to deflection of the spindle. Two heavier bearings will be better here. You mentioned that you might go for a VFD. If this entailed mounting a stepper motor directly on the end of the spindle housing then this will solve all of your problems. A counter balance weight with pulleys on top of the Z axis column will also be needed to give positive up lift to the spindle housing as in surface grinders.
Ian.

[JBV]

I might have two 20 mm bearings.. I have also been thinking of using a frameless motor for the spindle! But then the housing would have to be bigger!

[handlewanker]

Hi, You would also have to include a method of gaining access to the drawbar for collet holding. In this case it might be better to mount the motor on top of the spindle housing and use two bearings to offset the belt pull.
Have you considered the spindle quill to allow drilling and boring instead of moving the X axis table. In this case the drive belt goes to a pulley that has two bearings to support it and the spindle drive shaft moves in and out on a key or spline, same as a drilling machine, but in the horizontal plane.
Ian.

[JBV]

The drawbar is the bolt at the end of the pulley.. The pulley is attached with setscrew and a flat or a key + nut...

I will put this on hold until i can cast