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Member postings for Mark Davison 1

Here is a list of all the postings Mark Davison 1 has made in our forums. Click on a thread name to jump to the thread.

Thread: Does a 1600rpm bantam have a single v belt?
15/04/2019 19:05:33

I'm primarily interested in getting access to speeds above 800rpm which is the max with the current single phase motor. The low speed is fine. At the moment I've order exactly the same size pulley, but may also order a slightly larger one as (I think ) you're suggesting

15/04/2019 06:51:07

Not sure, don't recall seeing a date on the data plate. They (i bought two) are 90 frame as opposed to imperial, with moulded plastic fans and fan shrouds. Dual voltage as standard. Saw it run on a 400v rotary converter before I bought it and all seemed well. Nothing ventured nothing gained. Worst case I have to cough up for a new one, which is what i had previously intended to do anyway.

15/04/2019 06:10:25

Thanks everyone

14/04/2019 20:49:26

Does anyone know if the 2 speed / 1600 rpm Colchester Bantam came with a single or double V belt. I'm about to fit a 2 hp 230v 3 phase motor/VFD in place of my single phase 1hp motor (800rpm machine with a single belt). I would have gone for 3hp but I got an old but unused 2hp cast iron Brook Crompton for a really good price).

Manual seems to suggest it is only a single pulley.

Thread: First attempt at threading on a bantam - all didn't go well
12/01/2019 16:23:09

Machine still works. I dismantled and cleaned the NVR/contactor. There was a loose wire which I suspect was at least part of the problem. Also dismantled the barrel reverse switch. The buzzing seems to be down to slop in the forward/stop/reverse lever on the carriage not always returning the barrel switch back to the neutral position. I'll investigate further later and in the mean time will keep checking it.

I finished the thread. Given the mess I made at the start it has come out "usable" but not pretty. It will suffice for what I want it for (it is a stud that will be semi-permanently screwed into a large T nut/plate to secure a new tool post). I'm going to get some EN1A to practice on, the EN16 seems to tear.

11/01/2019 22:54:54

Not a good evening playing with my still new to me Colchester Bantam Mk1, and as I sit down to write this i realise almost all of it was my own fault (long time since I used a lathe).

I set it up to cut my first thread, a 9/16 UNC external thread in a bit of EN16 steel using a cheap Chinese indexable carbide tool from Banggood (which actually seems not too bad).

 

First pass went fine, until i overshot slightly when the inertia kept the chuck turning a bit longer than i anticipated, even at a lowly 35rpm. It didn't occur to me to use the brake!

Reading the instructions, the Bantam should be reversed as it doesn't have a thread dial (and I was cutting imperial on a metric machine anyway). So, i engaged reverse direction and set out to cut on the reverse pass (spot the obvious mistake). To my horror it didn't line up properly with the forward pass, and then to add insult to injury chipped the top off the carbide tip.

Oh well, turn the tip round and use another point. Look at lateral movement in feed screw, of which there seemed to be quite a lot, adjust out end float and have another go, forward. It seemed to line up with the first forward pass OK. I didn't even overrun this time.

Now for cutting on the reverse pass again. It didn't line up, again. Although this time was slightly better than first go. Then i brole the tip off again. Doh! I was now getting frustrated (and had still not realised the obvious mistake).

Lots of looking and measuring the lateral play in the carriage with the feed nut engaged, about 0.1mm. Starting to conclude the feednut must be worn and in need of replacement, which sounded expensive.

At this point things went from bad to worse. Traces of smoke started to emanate from the back of the lathe, the motor to be precise. Ever since I bought it it would occasionally buzz loudly when the forward/reverse lever was in the off position. On this occasion it had been doing that for a minute or so whilst I was distracted looking at the play in the feednut (i'd usually turn it off at the wall when it did it). I suspect something is wrong with the original electrics and it was managing to somehow power one coil and not the other, or one in forward and one in reverse. Anyway, I quickly turned off the power and the faint trace of smoke quickly stopped. Not what you want when you're already frustrated.

Time to give up for the evening and consult the forum as to the state of the feednut. Then, as I started to type it dawns on me. The reason I was breaking the tips and the forward and reverse passes weren't lining up properly was because I'm not meant to be cutting on the reverse pass, only on the forward. Under normal circumstances I'm pretty switched on, but this evening I'd clearly left my common sense in the house. The work was turning backward and the compression force on the underside of the tip was causing to to break. The feednut was loaded against the opposite face of the screw on the return and the backlash mean it was never going to line up. Even it it was a new screw and nut it probably wouldn't have worked.

As usual, the problem was the operator not the machine (except for the now poorly motor).

Hopefully the smoke was just burning oil and not insulation/enamel or the 3 phase and VFD conversion might be upon me earlier than I was planning. I'll have a second attempt tomorrow after checking out th eNVR and reversing electrics. I'll use a HSS tool this time, as carbide at 35 rpm probably wasn't the best choice anyway, even when cutting in the right direction.

 

 

 

Edited By Mark Davison 1 on 11/01/2019 23:07:22

Edited By Mark Davison 1 on 11/01/2019 23:08:05

Thread: Colchester bantam gearbox
01/11/2018 19:56:33
Just got a single speed one myself. Manual is https://wiki.edinburghhacklab.com/_media/colchester_bantam_full_manual.pdf There is a small clutch on the lead screw, is that engaged. Next to gearbox.

Edited By Mark Davison 1 on 01/11/2018 19:58:31

Thread: What Material for a rear tool post
18/10/2018 19:00:21

Newby after material selection advice.

I'd like to make a rear mounted tool post of a (soon to be new to me) MK1 colchester bantam. I've really struggle to find a used one and have decided making one could be a good first project.

My question is, what material for the main body? EN1 or EN3 mild steel seems easy to source, but I can't find a source for anything more exotic, not even EN8 (it all seems to be round bar). Would cast iron be suitable (I can find 60mm x 60mm x 6" on ebay)?

 

Example below from a Bantam 2000 which has incorrect centre height

Edited By Mark Davison 1 on 18/10/2018 19:01:17

Thread: Where to buy imperial taper pins (11/64 x 1.25")
19/05/2018 08:46:14

Problem solved. They actually turned out to be 3/16" and my (almost) local Apex Fasteners in Slough had them over the counter. I was convinced they were a #1 (11/64th) but obviously not.

17/05/2018 23:34:46

Any one any ideas where I can get imperial taper pins from? This appears to be rather an obsure size.

Can I use a longer lenght in next size up (3/16) and cut it short ? Not that I can find any of those either.

Thread: Where to get a running bearing for Ajax AJ8 mill
18/04/2018 08:32:58
I've just polished up the old one and it isn't quite as bad as I first thought but would still replace it if I could find a new one.
18/04/2018 08:31:02
It is a plain steel sleeve, like a spacer but with a ground surface. It runs in a bronze bushing that is pressed into the arbor support arm. Oil is drip fed.
18/04/2018 07:34:43
Having now repaired the casting for my new (old) Ajax horizontal mill I am in need of a new running bearing/sleeve for the arbor. Being a small machine it seems to have an unusual OD (1" I'D x 1.5" OD x 2" long). Any ideas where I could source one? EBay comes up with very little regardless of dimensions.

As the outside surface is ground i assume it will be prohibitively expensive to get one custom made.

The old one is completely shot, as was the bronze Bush. I've managed to source a suitable Bush (1.5" I'D x 1-7/8" OD)

Edited By Mark Davison 1 on 18/04/2018 07:35:44

Edited By Mark Davison 1 on 18/04/2018 07:36:19

Edited By Mark Davison 1 on 18/04/2018 07:36:57

Thread: Ajax AJ8 horizontal Mill - cracked casting
31/03/2018 19:23:33

Spent today shaping a plate, cleaning it all up and bonding and bolting it in place. With a bigger workshop I'm sure it work have been easier to bend the plate, but I got there eventually.

These photos are before I bonded it in but you get the idea.

20180331_151100.jpg

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30/03/2018 07:52:44

20180329_082924.jpg

Edited By Mark Davison 1 on 30/03/2018 07:53:13

30/03/2018 07:47:56

I've now picked up the machine and the crack doesn't go right through to the switch gear aperture. It has however opened up more than it first appeared in the sellers original photos.

Would you try to pull it shut before bonding the plate on? I assume that may result in trouble as a result of putting stress back into It?

The seller had alread stop drilled the closed end. They have also screwed through the crack at the open end from under the foot in an upward/inboard diagonal (effectively pulling the crack closed with the screw in tension). The diameter of the scew/bolt is only about 4mm though, so on its own isn't going to do much.

20180329_082940.jpg20180329_082917.jpg

21/03/2018 18:06:32

This is the end of the arbor on my bench mounted one. As you can see it is quite substantial. I have seen photos of your set up before, but never this one.

 

 

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Edited By Mark Davison 1 on 21/03/2018 18:12:55

21/03/2018 17:38:37

Geoff, I have that model too ! This one is in addition for now, although I will have to sell one as I don't have room for both). Like yours my bench top one had been modified and I've put it back to as near standard as I can (I can't find any photos of one that hasn't been modified). I think they all get modified to reduce the speed to enable use of 6" cutters. This AJ8 appealed partly because the footprint is smaller as the motor is mounted in the pedestal and I'm tight for space, but also because it looks like it has more vertical capacity (although I haven't picked it up yet so can't be sure). This one also has a Morse Taper socket for the arbor so I can add an ER32 Collet chuck and run an end mill. My bench mounted seems to have a proprietry socket.

21/03/2018 16:44:42

i have some 3mm steel plate ear marked or that already as i think the original is missing

21/03/2018 15:15:38

thanks for all the suggestions. i will give the epoxy and plate a go. i may try it without bolting first and see how it fairs. as for power feed, i don't believe it had one, although i do plan to fit a stepper motor to the x axis.

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