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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: Ajax AJ8 horizontal Mill - cracked casting
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.

21/03/2018 08:12:46

aj8 cracked casting.jpgaj8 cracked casting 2.jpg

21/03/2018 08:07:26

Is the wall thickness sufficient? Is that an option if is cracked end to end?

21/03/2018 07:58:08
I've just bought an old Ajax AJ8 mill that has a crack in the main housing (an open bottomed box approx 12" square and 24" tall). The crack runs from a large aperture in the side that accepts the switch gear diagonally out and down to the bottom corner by one of the 4 feet, approx 6" long (a such it has cracked right through from end to end). The wall thickness is unlikely to be much more that 1/8" but I've not measured it (could be 3/16"). I'll try and put a picture up this evening.

Any recommendations on how to fix it? The options as i see it;
Braze - id have to pay someone else to do this.
Weld without preheat - I could try this myself but am reluctant.
Epoxy steel stick.
Patch and bolt across the inside using epoxy to give me a flat surface press the plate against. There is a thick flange at either end of the crack that I could drill and tap to add some thick straps.

Edited By Mark Davison 1 on 21/03/2018 08:00:01

Thread: Correcting drill press runout
31/01/2018 19:27:19
I cleaned out the spindle with fine wet and dry placed against the arbor as suggested.
Turns out it was the arbor/chuck After all, not the spindle. A new arbor and chuck runs as true as the soft ended blank arbor that I tested previously
In hindsight this should have been the most obvious culprit from the start. A previous owner had tack welded the (Jacobs) chuck to the arbor with two small MIG welds. I can old assume one is pulling it off centre slightly. Tried grinding them off but I think the penetration is a fraction too deep so it is junk.

Edited By Mark Davison 1 on 31/01/2018 19:28:50

20/01/2018 08:17:49
Ignore that last bit, they were felt strips not an abrasive stone/diamond strip
20/01/2018 08:07:25
Comparing the reamer with the arbors I have the reamer is best part of 1/2" longer using a fixed diameter (smallest end of the chuck's arbour) as a reference, hence bottoming out.

I bought a soft ended arbor from Warco during the week just to see if the runout was in the spindle or the chuck. It looks as if it could be the chuck as there is very little run out at the end of the arbor (although this could just be related to it only being 1" long of course).

I have previously seen some plastic MT honing things online that looked a lot shorter than the reamer and I wonder if they may be a better solution. Problem is I can no longer find them
17/01/2018 14:03:42
Sobm6 main problem is the reamer appears to be too long and bottoms out of the shoulders of the slot that holds the tang. I'll try grinding it a bit shorter.
17/01/2018 07:09:53
I have recently bought a Medding MF4 drill press that has noticeable run out in the chuck (~0.5mm). I have tried a different chuck/arbor and it is still the same. I'm assuming it is minor damage to the inside of the MT2 taper in the spindle (i can feel some with my finger). How do I correct it without risking making it worse. I don't have a lathe so am anticipating carry out the action in situ.

I bought an MT2 reamer but it appears to bottom out on the tang drive slot before making contact properly with the taper. I could sort this by grinding some material off the end I suppose (of the reamer that is).

My main question is how should I hold the reamer? With a normal tap wrench? Or try to hold it loosely in a drill vise. Do i run a risk of making things worse?

Edited By Mark Davison 1 on 17/01/2018 07:11:09

Edited By Mark Davison 1 on 17/01/2018 07:12:00

Thread: What is preferable, running a motor faster or slower than nominal 50hz rpm?
24/11/2017 21:23:46
Thanks folks. I think i will go 6 pole if i go through with this. I have a spare 4 pole 3 phase motor from a drill, but it is 400 volt and cant be reconfigured for 230v so i will have to buy a new one.

A previous owner had fitted a home made 2 speed gearbox to achieve lower speeds but that required a considerable reconfiguration of the machine, something i'm probably going to reverse to put it back to standard. This will not leave room for the gear box.

Edited By Mark Davison 1 on 24/11/2017 21:24:54

24/11/2017 19:00:50
I'm considering converting a small horizontal mill from single phase to VFD controlled 3 phase in order to provide a broad range of speed control.

It is currently fitted with a 4 pole/1500rpm motor.

I would like to be able to drive it slower that the 1500rpm allows.

Would i be better getting a 6 pole/1000rpm motor and running it above 50hz to achieve the current speed. Or, stick with 4 pole and run it below 50hz when i want to reduce the speed. I am leaning towards 6 pole/1000rpm and running above 50hz when require, but have no idea what the optimal configuration is?


Thread: Medding MF4 drill pulley
13/10/2017 07:40:45

It wasn't a silly question, but no there wasn't. I eventually managed to remove it. I managed to build a revised puller and ended up dragging it half an inch up the shaft before the threads in the cast iron bush failed around the holes i'd drilled and tapped into it for the puller. I re-drilled and tapped them deeper (they were already 3/8" deep) and tried again. I also drilled two large holes down through the bush on the split line, in an attempt to remove some of the stress. This resulted in the bush itself finally giving up and one half coming out. The other remained and had to be separated from the pulley once it was off.. It would appear that it was the bush being stuck to the key amongst other things that was causing the issue. New bush and key ordered for a few pounds, so other the the hassle that bit was cheap to fix.

The expensive bit was discovering that I need to replace one of the two fibre gear wheels in the gear box. It is great that Meddings still sell the parts, but they aren't cheap. My bargin drill had ened up costing more than I budgeted for, but still happy with it.

 

Edited By Mark Davison 1 on 13/10/2017 07:41:59

09/10/2017 23:04:50
Thanks. Problem is the removal hole isnt there in the pulley. The thread in the half hole in the bush doesnt look great either. It also looks like there is a crack in the bush where it is designed to flex at the thin bridge between the two halves. This appears to have allowed one half of the bush to sit fractionally higher than the other causing the threads not to align. That might explain why i cant get a grub screw started in it where i attempted to add the half hole into the pulley.

I now have the exploded diagram from Medding. That would suggest the pulley should just be a push fit onto the parallel shaft secured with a grub screw. I wonder if someone modified the pulley to add the taper bush in place of the grub screw?

Edited By Mark Davison 1 on 09/10/2017 23:06:08

09/10/2017 08:23:04
There is an untapped hole for a grub screw but it is empty and i can see what i think is the shaft. I agree that the shaft is parallel, but i think the centre of the pulley is seperate from the outer alloy part. They fit togther on a taper which causes the bush to clamp the parallel shaft. Will try doubling up the steel bars and use larger diameter bolts for the pushers as they are only M5 and buckling!

Edited By Mark Davison 1 on 09/10/2017 08:24:07

09/10/2017 07:46:39

20171008_194900.jpg

 

I'm trying to remove the pulley from the 2 speed gearbox input shaft, without much success. It looks like it is a taper bush, but the hole on the pulley that would usually be used to remove a taper bush doesn't line up with a hole in the pulley (45 degrees out, which is a bit wierd). I tried to create the half hole in the pulley but then decided to tackle the issue a different way.

I've drilled and threaded a couple of holes into the top of the taper bush (assuming that is what it is) and made up a small puller. It pulley up on the bush and pushes down on the pulley. No joy. All I have done is bent the steel bar that I made the pulley with. I've even tried a very modest amount of heat (hot air gun as opposed to torch).

 

http://www.model-engineer.co.uk/albums/member_photo.asp?a=46419&p=769555

 

Edited By Mark Davison 1 on 09/10/2017 07:47:09

Edited By Mark Davison 1 on 09/10/2017 07:47:44

Edited By Mark Davison 1 on 09/10/2017 07:51:06

Thread: Dismantling a Meddings M4 quill activator gear shaft
08/10/2017 18:42:40

Hi, Can I ask you you removed the input pulley. Is it on a taper bush? Mine looks like it is but I can't for the life of me get the taper bush out of the pulley. The half hole in the pulley doesn't line up with half threaded hole in the pulley, it is approx 45 degrees out. I have drilled and threaded 2 M4 holes into the top face of the bush and made up a little pulley to pull up on the bush and push down on the pulley, but all it has done is bend the mild still bar that I used. Am I doing something very wrong?

Apologies for posting this in multiple Medding drill threads, I'm desperate to get some advice from someone who has removed one of these pulleys.

Thread: Getting into the Meddings MF4 Pillasr Drill gear box
08/10/2017 18:38:25

Hi, Can I ask you you removed the input pulley. Is it on a taper bush? Mine looks like it is but I can't for the life of me get the taper bush out of the pulley. The half hole in the pulley doesn't line up with half threaded hole in the pulley, it is approx 45 degrees out. I have drilled and threaded 2 M4 holes into the top face of the bush and made up a little pulley to pull up on the bush and push down on the pulley, but all it has done is bend the mild still bar that I used. Am I doing something very wrong?

Thread: Meddings Pacera Quill Removal
08/10/2017 10:25:58

I've just bought a 1960 MF4. How do I take the top pulley off the gear box. It looks like it has a taper bush but I can't remove it, it is stuck tight.

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