Member postings for Andrew Johnston

For full width slotting my preferred milling cutter manufacturer recommends a maximum DOC of 0.5D for 6mm and over, and 0.2D for less than 6mm. For making a nameplate in 1mm thick engraving brass sheet I used a 1mm 3-flute carbide cutter with a stepdown of 0.2mm:

I ran at 24000rpm and a feedrate of 350mm/min.

For similar in steel I used a 0.5mm 3-flute carbide cutter, also running at 24000rpm, but 120mm/min feedrate. Depth of cut per pass was 0.05mm:

The original cutters came from Drill Service, but I broke two of them, both after about an hour of machining, so I was operating on the limit. A change to a cutter of the same spec but from Cutwel lasted the two hour machining time with no problems. So I suspect the 0.2D 'rule' tends to go awry for very small cutters (<1mm) and harder materials.

Andrew

How about putting hydraulic oil in the Volvo?

Andrew

Automotive oils contain additives designed to clear deposits in the engine,and also have specific viscosity characteristics with temperature.

For small, lightly used, lathes it probably doesn't matter much, but I prefer to stick with the manufacturers recommendations. Basically straight hydraulic oils for spindle and headstocks, thicker straight oils for feed gearboxes and specific slideway oils for slideways.

Andrew

These cylinders have a lot of blind tapped holes:

All holes drilled and tapped (using spiral flute taps) on the vertical mill. For cylinder and valve covers it was worth setting up the Tapmatic. For other holes, after drilling, I put the tap in the drill chuck, put the mill in 'neutral' and tapped a few threads deep turning the drill chuck by hand. The threads can be finished later by hand on the bench.

For cast iron I work on a thread depth of approximately 70%, or a little deeper on fine pitch ME threads. All drilling and tapping is done dry.

Tapping by hand is easier with taper hand taps, as the taper helps to align the tap. When tapping by hand I judge perpendicularity in two directions by eye after a turn or so and bias the force on the tap accordingly. I normally only buy taper and bottom hand taps, never use second taps.

Andrew

Not me! As for options it'd be none of them. I use a single 4-way toolpost. Has indexing and no overhang. Works fine for me and is way cheaper. allowing me to spend my cash on more useful accessories. Like high speed threading - that really does save time.

Andrew

I've just had an email from a Glen Farrell with what seems to be a cupalloys email address , that asks to share a document entitled "GS Metal Joining Ltd". It needs a Microsoft login to read the PDF document, so that's me thwarted. Has anyone else had a similar email, and does anyone know what is going on?

Just done a search and the GS Metal Joining website looks remarkably like the CuP Alloys one. So presumably a new company name? Sending a link that requires sign in seems a rather daft way to announce it.

Andrew

I'd try these people:

Wiseman

I've not used them for grinding dies as I have the capability to grind my own, but have bought spare parts from them. Look under PDF price ists for Coventry Die Head Chasers. Prices seem very reasonable.

Andrew

Strictly true, but in the case of an incandescent filament the associated inductance and capacitance will be very small, less than a microhenry and a few picofarads. At 50Hz a resistive model is rather better than reasonable.

The older electromechanical watt-hour meters measure energy consumed, they do not account for VARs. The newer electronic meters do take account of power factor. The case of wall warts is more complex. The current is drawn in pulses so the waveform is nothing like a sinusoid and contains a lot of harmonics. This is a problem for generators, so the power supplies should contain power factor correction circuits these days. These can be passive, ie, a filter, ot active, usually a switch mode supply controlling input current according to the input voltage.

My experience is that my workshop consumes very little power compared to everyday things in the house. The only thing that did make a noticable difference in the workshop was changing five flourescent tubes for LED tubes. I use about 6.5kWh per day, on average, for everything.

Andrew

I can't comment directly on the selected lathe, as I've never used one. I have visited Warco to look at milling machines with a mate who was thinking of buying one, not for me though. Here are a few thoughts, make of them what you will:

In theory a 3-phase motor runs more smoothly than a single phase motor, although the difference is unlikely to be apparent on most lathes. if I didn't have a 3-phase supply I'd go for a VFD and 3-phase motor, followed by a BLDC motor. I'd avoid brushed DC motors, I have one on my mill power feed and the brushes are a PITA. One issue with any of the electronic speed controllers is that at low speed the motor is constant torque, not constant power. If turning a large diameter at slow speed it may not be possible to take a decent depth of cut. Gears/belts provide constant power so torque increases as speed decreases, but they are expensive to provide.

I use micrometers for almost all my measurements up to 18". Calipers only get used for rough work. For micrometers an increment of 0.01mm is fine. Trying to measure to a micron is expensive and probably pointless in the average workshop, amateur or professional. Mitutoyo do a digital 0-25mm micrometer with an accuracy of 0.5um; it costs £1980 including VAT. All of my micrometers are secondhand, mostly bought on Ebay.

When I first started out I bought a genuine Dickson toolpost for my lathe, but never fitted it and never will. I prefer the simplicity and better rigidity of the original 4-way toolpost. If using multiple tools for a job I simply keep a set of shims with each tool when swapping. It doesn't take much longer to swap a tool in the 4-way than with a QCTP. Most of my turning is done with four tools; roughing tool, knife tool, parting off blade and boring bar. Of course some jobs require specials, insert and HSS, but the overall number of tools for a given job is still small. Personally I think QCTPs are a waste of money. A common comment on here is that we are amateurs and have the time to take lots of small cuts. So why is it so important to save a few seconds when changing a tool?

I use a Dickson QCTP on my hydraulic copy unit as that is what it came with, but in general I am taking fairly small cuts:

While a tool needs to be on centre height to cut correctly the degree of accuracy needed is sometimes over-stated. I don't have a centre height gauge, I judge the tool neight by eye against a tailstock centre when setting up. Quick 'n' easy and works fine for me.

Andrew

I agree with Pete, it may well be possible to get away with a narrow spur hear of appropriate size. I also agree with Nigel; if an accurate worm wheel in terms of diameter and tooth count is needed then gashing is essential before finishing by free hobbing. For example, worms and worm wheels (worm wheel is approximately 4" diameter):

Home made hob:

Gashing the blank (note that gashing removes most of the material, allowing the hob to go directly to almost full depth):

Free hobbing to generate the final tooth form:

Andrew

You would be better starting a new thread rather than posting in a completely unrelated thread.

Andrew

The two roller boxes for my repetition lathe both have rollers that follow the tool. Presumably the first op is to turn a small spigot before extending the work to full length. For the two capstan roller boxes I have one has rollers that follow the tool and one has rollers that lead the tool. As Howard says this is more likely to do with the shape of the workpiece and the required cut than ovality of the stock.

Andrew

I don't think the tool will cut a smaller oval. if anything it will cut the inverse. So a wild leap might imply that over several passes the original ovality is reduced.

Andrew

Personally I wouldn't use a tool like that for parting off. They're more of a grooving tool. Carbide parting off inserts will chatter badly if the feedrate is too low. I use power cross feed and a absolute minimum of 4 thou/rev. If you're not confident to let rip then HSS is more forgiving.

Andrew

+1

It requires a lot more thought, extra skills (CAD/CAM) and a detailed knowledge of how the cutting process works. Something that the naysayers are unable, or unwilling, to see.

Andrew

Used primarily for pain relief, but also used in BDSM and other erotic games.

Although the voltages are reasonably high, tens to a hundred or so volts, the currents and duty cycles are low. Thus power ls low and AAA batteries are perfectly adequate.

Andrew

it is 3" scale, but I am pretty sure it is designed from scratch, not scaled up from another design. Ross doesn't do that sort of thing; he ploughs his own furrow so to speak. I've been an avid follower of the build diary on TT. The only downside is that sometimes one feels like following the advice of the late JohnS, ie, take up knitting rather than pretending that I can build a traction engine.

Andrew

I'm lazy and like to keep things simple. If the long rods are 1/8" thick make them from 1/8" material and if the short rods are 1/4" thick make them from 1/4" material. Make each part seperately.

I'd agree with mounting the parts using (CNC) pre-drilled holes. No need to faff about with tabs. In my experience tabs are a PITA, and take ages to clean up afterwards. With each blank mounted using screws in the holes only two simple 2.5D operations are needed. One, slot to full depth in steps appropriate to the diameter of the cutter with mixed climb/conventional milling for speed. For these small parts I'd leave 0.25mm for finishing. Two, a full depth finish pass with curved entry and exit paths, and use climb milling.

There is one caveat, I use flood coolant when machining steel which helps clear the swarf during the slotting operation. It also helps if the length of the blank is chosen so that the slot breaks out at the end, which also helps to clear swarf.

Andrew

Depends on the original frame thickness. If the frames were 5/32" then probably no as the 4mm thickness will most likely be slightly undersize anyway. Otherwise you'll need to change the width of the frame spacers to keep a dimension, mostly usefully outside frame to outside frame, the same as the drawings.

It's what I did on my traction engines when I made the hornplates from 6mm plate rather than 1/4". I just made the axle and 2nd shaft tubes 0.7mm wider so the outside to outside hornplate dimension remained the same.

Andrew

A wirewound non-precision resistor is unlikely to use four bands to determine value. To me the leftmost band looks brown rather than red. So I take the resistor to be as follows, from the left:

Value: Brown Black Gold - 10x0.1 = 1 ohm

Tolerance: Gold - 5%

The rightmost black band could be temp coefficient, in which case it is 250ppm/K, ie, not very good.

Andrew