Member postings for Andrew Johnston

Small cutters don't work well on my horizontal. Highest spindle speed is 1200rpm. On the Bridgeport I will be running a 10mm carbide endmill in steel at 2200rpm and for cutters less than 6mm on the CNC mill between 3000 and 24000rpm. I rarely use endmills or slotdrills on the horizontal, but when I do they are around 1" diameter. The horizontal mill was designed tor use with relatively large diameter HSS cutters, which dictates the available spindle speeds and feedrates.

Building engines maybe a hobby, but for me it is all about making parts as efficiently as I can. I hate wasting time and/or money.

Andrew

Depends how accurately the ratio needs to be known. To get an estimate just put the lathe in backgear and see how many turns of the drive pulley are needed for one turn of the chuck. Normally the ratio is on the order of 5 or 6 to 1.

Andrew

The chips range from royal blue to a rather pretty gold colour:

Andrew

I can take a video, getting it processed and uploaded is another matter.

Andrew

That's a fair offer, which I am happy to accept. A PM will be sent.

Andrew

Thanks for the offer and from a curiosity viewpoint I would be keen to have a go. But I am very wary about borrowing tools. If I fudge them I feel obliged to replace them and I suspect a 10 insert face mill isn't going to be peanuts.

Andrew

The spindle motor is 2 pole in the high speed range. I don't know about the table feed motor; it isn't even mentioned in my copy of the manual. Both horizontal and vertical modes use Int40 tapers.

Andrew

I' ve measured one phase current. With the mill off phase current was 0.03A, which is an offset in my meter. With the spindle motor running, but no cutting, phase current was 3.6A and taking the same cut as yesterday the phase current went up to 8.6A.

Assuming the mill was pulling the same current on the other two phases that gives a total power draw of about 6kW. The spindle motor in high range is 5hp (3750W) and the table feed motor is 1hp (750W) for a total of 4500W. Assuming both motors were running close to full power that means the power factor was around 0.75 which seems a little low. Anyway, that answers the question about power draw.

I also have a confession to make. When I did the cut today the mill simply went through with very little cutting noise and no fuss at all. The finish was very consistent. Yesterday there was a tiny amount of chatter in a couple of places and the finish varied a bit. Turns out that was because at the end of the cut the milling body fell off the arbor, as the SHCS that holds them together had fallen out. I'm amazed that it caused so little drama and the cut generally progressed as if nothing much had happened. Lesson learnt though; always make use of the workshop gorilla.

Andrew

Correct, the A&S 2E with vertical attachment:

I bought the vertical attachment many years ago on Ebay for £50 but have only recently cleaned it up and fitted it. I also made a M16 drawbar and new drive dogs as one was missing.

Andrew

I have a 3-phase supply for the workshop at 100A per phase. It makes life easier when dealing with two speed motors and rapid reversing of motors. Most of the time the house just runs on one phase. I've got a clamp-on meter so will try and have a look at current draw this afternoon.

In the UK 3kW is about as much as one can draw via a single phase 13A 3-pin plug. However, it is possible to have much larger loads on single phase. I have a 32A single phase outlet in the workshop. My oven/hob is on a 40A breaker and the 10.5kW electric shower is on its own 50A breaker.

The key to taking heavy cuts is not just power but also rigidity. The horizontal mill weighs nearly twice as much as the Bridgeport and is much more heavily built. The Bridgeport is a versatile mill but is quite flexible, in more than one sense. There's also a limit to the power than can be transmitted via the R8 taper, especially as it relies on friction.

Andrew

Update: In response to my last question the seller has stated he has no way of testing the boring head. But he has offered to refund my money plus pay the return postage if I am not happy. Not sure what to do now. Could possibly collect so at least I know where he is. Also I don't really trust the auction site on which the item is for sale in the event of a dispute.

I bought a 25mm insert boring bar for my Wohlhaupter head when boring my cylinders. The shank was simple to turn down using normal insert tooling.

Andrew

The two conventional clamps offer some resistance to twisting, but are there primarily to hold the work down. To reduce the risk of the work twisting I added the offset hexagon clamps. There are two on the left and one (hidden) on the right. The hexagons and offset head screws are commercial items, but the T-nuts they fit into are homemade.

Andrew

Following a recent, somewhat intemperate, thread on face milling, and having just got the vertical attachment for my horizontal mill running I thought I'd give a face mill a real run for it's money.

I used a 7 insert 80mm diameter face mill. Parameters were 420rpm on the spindle and a feedrate of 430mm/min giving a chip load of 6 thou per insert. Width of cut was ~75mm, say 3", and DOC was 2.5mm, say 0.1". The parameters equate to a removal rate of 5 cubic inches per minute. My horizontal mill has a 5hp motor. Cut in progress in some scrap low carbon steel:

I thought the mill might struggle a bit, but the cutter went through like a knife through butter. I'm at a loss as to what I have to do to make the mill struggle on a cut.

Andrew

That is very perceptive, and correct. The little voice is no longer little, but is now hammering on the door and shouting don't buy it!

Following on from the comment by Baz and John a close look at the pictures shows some slight scarring that indicates a possible crash, despite the overall head looking to be in very good condition with nice clean edges and none of the little dings and dents one normally sees. I am assuming spares are not available at any price.

On the plus side it looks to be a lovely head and I am fed up to the back teeth with my R8 import boring head. On the minus side the seller has responded quickly, but has avoided my direct "does it all work correctly" questions with woffle about the slides moving freely. The head has been on the same site, at a higher price, before but was withdrawn by the seller, which is a red flag. Asking price is £600 which I would pay for a fully working head. But not this one; listing ends on Wednesday so I am going to walk away and see what happens. If it dropped below £100 I might take a punt, but not otherwise.

The seller is in Rugby, so not out of the question to visit, but an hour and a half or so each way. Slightly strange selling history too, lots of bench vices, but then the odd large Harrison or Colchester lathe.

Andrew

For my eccentric straps I did the following:

• Face each side in the 4-jaw chuck on the lathe
• Mill bolt lugs to width
• Slit the castings
• Clean up lug mating faces on the mill
• Mill the eccentric rod face
• Drill bolt holes and drill and tap holes for eccentric rods
• CNC mill the fancy curves on the periphery
• Make square head bolts and hexagon nuts

Basic eccentric strap:

• Bore and recess centre for eccentric using a fixture for repeatability; fixture has a central hole for centring same in the chuck

• Drill and tap oil hole

The brass oiler as shown has been binned and replaced by proper wick feed oilers

Andrew

I am looking at buying a Kuroda UPB-3S boring and facing head for use on my Bridgeport. As far as I can see the head is an improved copy of the Wohlhaupter UPA-3, but specifically intended for the Bridgeport; to the extent that "Bridgeport" is engraved on the body.

I have a Wohlhaupter UPA-4 head that I use on the horizontal mill and love it. But does anyone have practical experience of the UPB-3S head and how it performs in the real world? Or even better access to a manual! Unlike the UPA-3 the UPB-3S has two feeds for facing, 4 thou and 8 thou per rev. Does anyone know if these are independent or, like the UPA-4, can be used in conjunction to give 12 thou per rev feed?

The internals look pretty complex, basically epicyclic gearboxes for the feeds, so I am being slightly wary as the seller claims the head and accessories are in excellent condition. But after asking for extra pictures he "discovered" that one of the boring bar holders was broken. That should have been pretty obvious. Again, after asking, he also confirmed that one of the reducing sleeves is missing; no big deal but should have been mentioned. I am wonder what else is hidden?

Andrew

Not if you approach it from a proper engineering perspective and look at the numbers. My 50mm face mill has 5 inserts, at a chip load of 4 thou that is 20 thou per rev. I normally run at 800rpm, giving a feedrate of 16"/min. With that feedrate, a cut 2" wide and 0.04" deep the volume is 1.28 inches cubed per minute. In steel that would require about 1.3hp.

My Bridgeport has an early varispeed head with a 1.5hp motor. Allowing for some loss in the varispeed drive that ties in well with the horsepower requirements. If I push it further the motor stalls. Same for the lathe (3hp); if I push beyond about 2.8 cubic inches per minute the motor stalls. So while the 1 hp per cubic inch in low carbon steel is a rule of thumb it is a good one.

Andrew

I think the elephant in the room just sat on you.

Irrespective of how much money you throw at the problem the metal removal rate will be dictated by the horsepower available and the rigidity of the mill. Running a bigger cutter doesn't help. Some of the chip loads and DOCs mentioned are tiny, well below those for which the inserts were designed.

On my Bridgeport the maximum diameter face mill I use is 50mm. Even then I am limited to a DOC of 1mm or so. On the horizontal I can let rip with 63mm and 80mm face mills and make full use of DOC and feedrates. But the mill has a 5hp motor.

Andrew

Never, not enough room for a seat for a start. Darn cold at this time of year too. Much prefer to sit and cogitate in the design office; like I'm doing now, complete with beer.

Andrew

In my experience that is a consequence of using cheap cutters. Plus a less than rigid setup.

Andrew