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Member postings for Ian P

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

Thread: DC Treadmill Motor
18/05/2019 20:26:18

Whilst I was in the 'direct drive will never work' fraternity, I now think (based on what you have said) that your plan will work.

I would be interested to know more about the controller you are going to use, please can you say what make and model is it?

Ian P

Thread: fobco drill
17/05/2019 20:42:28

Nigel, your Fobco speed problem will disappear in a trice if you fit a VFD. It was the best thing I ever did to mine when I swapped the original single phase motor for an elderly 'square' Hoover motors. I mounted a speed pot and three position (Fwd/Off/Rev) on the wiring access panel (the Fobco label plate) which I can reach while operating the quill lever. No belt changing as I use 5 to 150 Hz and its brilliant for tapping, M2 to M10, and countersinking. I have even counterbored a 1" hole to 2" diameter by 1" deep with in aluminium.

For the naysayers who recommend fitting an extra fan for slow motor speed, I have never had any motor heating problems. A fan might be needed if the motor was heavily loaded for long periods but I doubt many drilling operations are done continuously for hour after hour.

Ian P

Thread: Parting off query
17/05/2019 15:21:01

If the parting blade is wedge shaped in section, then its important that its holder clamps it so the side clearance is the same angle each side. Certainly worth checking that there IS clearance on both sides. DAMHIKT.

Another thing I have wondered about with the wedge shaped blade is that the top edge is also at an angle so only go in the holder one way. If the cutting edge is ground dead square then only at one point is the cutting edge at the right height. I assume that causes some differential cutting action across the width of the cut so and therefore some blade deflection?

Ian P

Thread: DC Treadmill Motor
17/05/2019 15:08:46

Dave

Although Mervyn mentioned direct drive, he did also say 4:1 belt drive. so that changes your calculations slightly.

I agree with your remarks about the Cruelty to Motors Society, maybe its a registered charity these daysindecision

Ian P

Thread: Which thread for T nuts
17/05/2019 08:53:18
Posted by Nicholas Farr on 17/05/2019 08:38:54:
Posted by Ian P on 13/05/2019 16:13:25:

If someone tightens a bolt/nut/stud with enough force to break off the slot lugs then I would say they were not using a force commensurate with the job in hand. One has to have some mechanical understanding and sympathy (or use a torque wrench all the time).

Squeezing the slot projections does give by far the strongest fastening but it is not always an option. The machine vice I use has grooves down each side so can only be held down with clamp plates.

Ian P

Hi Ian P, it is the realisation that the bolt/stud is bottoming out that is the important point. You can get a situation where you are tightening the top nut on a stud and the stud turns in the T nut rather than the top nut turning on the stud. You may find that the clamping is still loose, so you give it a bit more and you may not feel the resistance that is capable to break cast iron slots. If this situation where the clamping is not being achieved, the stud will not yet be in tension, but the bottom of the stud will be in compression, which can be greater than you realise.

Caution is better than a blunder.

Regards Nick.

I do follow the logic of preventing anything projecting out of the underside of the T nut. Personally I prefer the nuts fully tapped and rely on myself not damaging the slot.

One reason to fully thread (for me) is that I frequently use T nuts in places other than T slots when I am setting up a job on the mill, typically they are useful as plain nuts when using angle plates as they bridge the (sometimes disproportionally) wide slots that many cast examples seem to have.

Ian P

Thread: fobco drill
16/05/2019 12:25:58
Posted by Clive Brown 1 on 16/05/2019 08:38:43:

My Fobco Star is as others say. The Table is clamped by a through bolt and short ball handle. The slot is closed off at the bottom. I too use a piece of tubing to get more leverage. I put this need down to 50+ years of wear causing a slight increase in clearance on the column. In use I try to minimise the number of times I move the table with an array of wood packing kept by the machine.

The head is clamped by a two-piece clamp, also shown above. It's more effective than the split clamp but there is not enough metal in the table casting to modify it to that type.

Edited By Clive Brown 1 on 16/05/2019 08:39:22

Edited By Clive Brown 1 on 16/05/2019 08:40:31

If one is not bothered about originality then I think there would be enough metal in the table casting to install a split-cotter type clamp (like the one that locks the head from rotating). There would only be enough metal if the centreline of the new hole for the two halves of the clamp was offset so it was nearer to the column. Ideally this would have to be done by boring so you would need access to another machine.

Ian P

14/05/2019 19:55:56
Posted by Philip Burley on 14/05/2019 19:23:12:

Ian points out that there is a loose collar that clamps on the column. There is just a through bolt on mine , not original just a hex head that locates on the one side and a nut on the other . Is there somthing missing ? I have to really tighten the nut hard to get it to hold and a bit frightened of breaking the casting

Phil

I have the same Fobco and although its quite elderly the fit of the column in the table casting is still good enough for the clamp to work. To make operating the clamp handle easier I have a slightly longer (but a bushed plastic) lever about 100mm long and have fitted an M10 bolt. What helps greatly is the fitting of a cheap a ball thrust race which is something I have done to several other machine clamps.

On the Fobco I certainly do not need to apply excessive force for the clamp to grip so suggest that there maybe something preventing the casting closing up on the column. Extending the slit would be a last ditch resort so suggest you investigate further.

Ian P

Thread: NME&MEX Doncaster
14/05/2019 13:10:27
Posted by Phil P on 14/05/2019 13:02:39:

Yes, it is Mike Sayers from the Pickering club.

Phil

I asked because there is an employee of Bentley Motors (who is very much involved with the original of that car) of the same name.

Ian P

14/05/2019 10:25:07
Posted by Phil P on 12/05/2019 18:19:41:

I hobbed the gears for Mike's Bentley blower engine supercharger, it was about eight or nine years ago but the wait has been worth it to see the finished result.

It will either inspire all of us to do better model engineering, or just give up and take up knitting or something. !!

Phil

Is the 1/3 scale Bentley being built by Mike (or is it Malcolm) Sayers?

Ian P

Thread: Which thread for T nuts
13/05/2019 16:13:25
Posted by Neil Wyatt on 13/05/2019 15:54:08:
Posted by Ian P on 13/05/2019 14:58:47:

I have never quite understood the logic of the various methods of preventing a bolt or stud touching the bottom of the slot. Allegedly it to prevent the slot ears being broken off, as I see it the same damage would be the same whether the nut was being pushed from below or pulled upwards from above.

Two reasons:

The main risk if the thread bottoms out without the object clamping and you don't realise you might keep tightening trying to sget some grip and jack the nut up to break the slot.

For heavy clamping ideally the object being clamped pushes down to the t-slot so it is squeezed rather than just pulled up. When applying upwards-only force you need to be careful of over-tightening especially if shock loads can be expected.

If someone tightens a bolt/nut/stud with enough force to break off the slot lugs then I would say they were not using a force commensurate with the job in hand. One has to have some mechanical understanding and sympathy (or use a torque wrench all the time).

Squeezing the slot projections does give by far the strongest fastening but it is not always an option. The machine vice I use has grooves down each side so can only be held down with clamp plates.

Ian P

13/05/2019 15:57:48
Posted by Vic on 13/05/2019 15:31:08:

I agree about the number of different sizes and accepted long ago that it was better to make them myself to fit the machine in question.

How do you “undercut” your T nuts Ian and would you care to share some pictures.

I have used two methods to relieve the top faces of the nuts, One I used on existing nuts was by using an endmill smaller in diameter than the width of the top faces to cut a few thou deep recess either side of the centre leg. I made some nuts from new by tilting the cutter about 1 degree. It means the part of the nut that sits in the slot has tapered rather than parallel sides, not that it matters.

I suppose that it would be easy and quick just to create the relief with a file.

Pictures to follow

Ian P

13/05/2019 14:58:47

I have always found the sizing of Tee nuts and slots rather confusing and can see why the subject in this thread is getting slightly complicated.

Whilst there may be DIN or other standards for slots and nuts, there are a lot of machine manufacturers who seem to make them to whatever dimensions they feel like, that fact in combination with the variety and age range of machines in home workshops means that one can only really be sure of the nut-in-slot fit by trial and error.

I have made an assortment of nuts of different lengths, number of holes and the thread sizes. Mill is smallish with slots 11mm wide so I have metric and imperial ranging from M10 to 1/4" UNF with few M4 and M3. 99% of the time I use M6 as I have lots of different length M6 capheads.

I have never quite understood the logic of the various methods of preventing a bolt or stud touching the bottom of the slot. Allegedly it to prevent the slot ears being broken off, as I see it the same damage would be the same whether the nut was being pushed from below or pulled upwards from above.

As an aside, most of the nuts I make now have the top faces 'undercut' so that the pressure that the nut applies to the slot ears is concentrated at the widest part of the slot. My logic being that the pressure is being applied to the shortest 'lever' possible. The lever in this case being the cantilever that is the ear.

Ian P

Thread: T nut slot channel
08/05/2019 23:04:20

I am imagining a long length of aluminium bar 80mm square but if the T slot is in one face only it must be an unusual product or custom made.

Ian P

Thread: DIY magnetic DRO
07/05/2019 22:51:48

Connecting the screen at both ends introduces the 'possibility' of the screen carrying current. Only connecting one end means that the screen is purely a screen. In sensitive audio or electronic measuring instrumentation it is usually only connected at the amplifier end.

Current flowing through a screen could be induced to the contained (signal) wires by capacitive coupling, in a perfect world no current would flow through a screen connected at both ends because the equipment at both ends should be at the same potential. In practice your lathe motor and lathe metalwork might be plugged into one 13A socket and the PSU for the DRO electronics might be in another socket so there might be a 'loop' of ground/earth wiring that acts as one turn of a transformer that could couple surges and spikes into the signal wires.

To be fair logic level signals in this DRO application are pretty immune to interference and there are a lot of 'could's' and 'possibly's' in my previous paragraphs, in practice grounding the sensor end will be OK. Not sealing everything up yet allows you to test and if necessary make changes.

Ian P

07/05/2019 20:45:02

I would wait before your 'next step' so that you can test everything works before potting.

Are you connecting the cable screen at both ends? There is a case for connecting it only at the 'input' end of the wiring (the TouchDRO PCB connector) but you only seem to have 4 pins.

Ian

Thread: Anglepoise Lamps & CFL/LED lamps
05/05/2019 20:13:20

On some models of the older genuine Anglepoise lamps the springs are adjustable. On the one I have, the springs terminate at one end in a chrome plated machined part that 'screws' into the end of the spring and is tapped through for the cross drilled stud that hooks onto the peg.

Best to check before you start modifying the original springs.

Ian P

PS I have found that some of the latest LED lamps are significantly lighter than the earlier examples

Edited By Ian P on 05/05/2019 20:16:17

Thread: DIY magnetic DRO
03/05/2019 21:40:10

I am not in any rush but I have no doubts that what you are doing is going to work. A few minutes ago I installed the TouchDRO app on my phone just so I could see what it looked like. Obviously not anything I can use yet but can see it will be a big improvement on three separate displays (and on the two axis Sino on my lathe).

The cable you have selected, being polyurethane jacketed is pretty tough stuff and impervious to most things in the workshop.

Ian P

03/05/2019 20:13:32

Impressive progress in a few days Chris. You have got me tempted to go down the same (similar) route. My mill has three separate iGaging type scales and I think I will replace the three displays with TouchDRO running on a tablet. Once that's up and running I can replace the scales later.

How long can the cable be from the encoders? I see the description states 'no line driver' so presumably would not like too much capacitance. What type of cable will you use (and protect and anchor it to the encoder housings)?

Ian P

02/05/2019 14:55:45

Well explained Andrew. having been responsible for getting boards manufactured in a previous existance it is something I should have remembered, although they were mostly flow soldered.

Ian P

02/05/2019 13:00:10

I see there are instructions on the encoder data sheet that refer to soldering it immediately after unpacking it because it is moisture sensitive. I am curious why its not then moisture sensitive after soldering.

What was the actual part number of the RLC2HD encoder you actually ordered and how much do they and the magnetic strip cost?

Ian P

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