Member postings for old mart

Do you know how far the nylon is in the mast? Could it reach as far as that fitting on the left side of the picture?

Tony Pratt 1 is dead right, I also know someone who worked at Amazon over the Christmas period, the target packing rate was so high that it was easier to chuck things into an oversize box to save time than to pack properly.

Stainless steel requires passivation with acid to dissolve the ferrous particles from the surface. Pickling in citric acid will work well and is more environmentally friendly than some of the other methods. Passivation is particularly important when the SS is in a salt water setting, and the chemicals in an EDM would not be much nicer.

The difference in price between a blank and a 6" Boxford threaded one from Chronos is not much and as long as the boss diameter is big enough on the Boxford one to make it 1.3/4 X 8, it would save a lot of messy machining. I have made a couple of Boxford threaded plates into Smart & Brown ones this way. If your 6" four jaw chuck has front mounting, you can probably use a smaller diameter backplate. It may even be possible to use one backplate for both a three jaw and a four jaw if you are lucky.

I would look at what ARC have going at the moment, they also list the footprint which is good. If you have a choice go for one with an R8 spindle fitting. Your budget is pretty good, add at least 50% onto the machine price for tooling.

I was mistaken about the current price, in the last few months prices have rocketed, maybe due to CO19. This is the cheapest I could find, and the buyer risks paying more if they are unlucky with import duty additions. Of course, you would still have to carry out a lot of modifications to make any of them fit your machine.

**LINK**

Edited By old mart on 21/05/2020 17:04:55

Any time I have to drill a perfect hole, I look for a new quality drill first. I can't sharpen a drill to anything like the precision of the makers, and my efforts are bound to wobble and drill oversize.

Thanks CJ, I was indeed trying to be helpful. I usually use slr's but also have a Samsung without a viewfinder, and it can be almost impossible to see the screen if the sun is shining on it. That's why I prefer my old Nokia phone to my smartphone.

Anything with a viewfinder, then you can see what you are doing in bright sunlight.

Leave the power on when you leave tonight and the moose will finish the job for you.

Whatever you make, be sure it costs less than the purpose made power feeds which go for about £ 130.

The bore of these spindles varies but very probably a length of 10mm studding would go down a tight one as the threads usually measure a little smaller than nominal.

When I modified the Tom Senior from MT2 to R8, I used the top half of the original spindle. The bore was over 10mm, but not quite 7/16" which is 11.1mm. Fortunately, I managed to ream it to 7/16" after silver soldering an extension onto the reamer.

There looks like there is plenty of meat in the smallest diameter of that Centec spindle to make the bore a bit bigger if it is a tight one.

I would give the MT2 taper reamer a miss, if I was you, that taper must be pretty good to have been such a pig to separate. 

Edited By old mart on 20/05/2020 18:33:08

Edited By old mart on 20/05/2020 18:36:16

That SGS link is useful, it is going into my favourites in the browser. The knee of the Tom Senior could do with a bit of assistance, especially when heavy kit is on the bed. I will be checking the dimensions and will have a look to see if they have a suitable strut.

The SGS site rates struts in Newtons, not newton metres.

Edited By old mart on 20/05/2020 18:19:28

Congratulations, it is such a relief to have it dismantled at last. The male taper looks ok, a little rust was expected. The drawbar thread looks a bit odd, I was expecting a 3/8 Whitworth and yours looks finer. You may have to make three drawbars, that mystery thread, a 3/8 W and a 10mm, to suit whatever tooling is fitted.

Start practicing on an external thread. Get a length of 1" bar aluminium and, say, if it is 6" long, then turn down half to 3/4". Turn it round and chuck up the smaller end. You should have a larger diameter outboard with a gap between it and the chuck of an inch. This gives you a runoff area to disengage the leadscrew well before crashing. Run the lathe at its lowest speed. Before engaging the leadscrew, bring the tip of the insert up to the work so it just leaves a witness and zero the cross slide scale. Move the saddle out of the way of the work, and engage the feed nuts when one of the numbers on the threading dial comes round. For a beginner, it is safer to wait for the same number to come round every time you take a cut. Take the first cut at the zero position and the tool should leave a tiny helical groove. Check the pitch of this groove to ensure it is the same as the pitch you have set. The cross slide must be backed off past zero every time you bring the saddle back to the right. Keep the compound parallel to the axis of the bed, any adjustments there are for when you get more practice. The first cut can be up to 1/5 of the thread depth, but as you get deeper, there is progressively more metal cut, so the depth of cut should be less at each pass, ending up at 0.001" and then spring cuts.

No matter how tight that Autolock is, you still need a drawbar to ensure it doesn't fall out when milling.

What is that black painted bar being used for? The collar on these MT2 Autolocks is left hand thread.

I always found that Rawlplug tools ended up making a conical hole as do percussion drills. SDS is a million miles better than either, no effort and a hole that is cylindrical. Where I used to work, a percussion drill would manage the floor as it was standard premix poured concrete, but only an SDS would touch the walls which were precast sections made in a factory.

A professional pipe threading machine has sets of adjustable dies in a die box, they never use split dies. Back in the 70's I used Rigid and Facom machines. Production threading on lathes before cnc's came out was mostly carried out using die boxes rather than single pointing, as it was much quicker.

I expect a damaged tap with a 8 tpi thread would be as rare as hens teeth. I have made a sketch of the thread which shows the main dimensions. The starting bore of the thread is not critical, it could range between 1.59" and 1.614". I have always gone for the smaller size using carbide inserts. The size is right when the first sign of the thread shows in the 1.75" register. It would take multiple passes from just touching the bore to be threaded. The register size needs to be no less than 0.001" greater than the measured spindle size, or it will be very difficult to screw the plate on. 

I would go 12,10,10,8,8,7,6,5,4,3,2, and 1 in thousandths of an inch, keeping an eye out when close to the end for the witness mark on the register.

Edited By old mart on 19/05/2020 21:31:08

Why go to the expense of a 1" Whitworth tap and then destroy it?