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Member postings for William Chitham

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

Thread: Leadscrew suppliers
08/07/2020 09:59:52
Posted by John Haine on 08/07/2020 09:27:50:

Was the original 1/8" pitch? 3 mm is an awkward number for dials. 2.5 mm would surely be better?

For some reason 2.5mm pitch screws are vanishingly rare which is a shame since that is what I need for a Boxford crosslide.

W.

Thread: Mill unexpectedly cutting crooked
01/07/2020 12:06:24

I'm an absolute beginner but it occurs to me that if the cutter isn't perfectly aligned with the spindle it would describe a cone which would create an undercut, for example if the cutter was bent. If it happens with different cutters then maybe there is some crud in the spindle nose that prevents the collet from seating properly or maybe even the spindle is bent?

William.

Thread: Pulley Sizes For An X2 Clone Conversion
25/06/2020 12:19:47

Thanks Neil, is your conversion single speed? Looks like a 4:1 reduction which equates to the low range on the standard machine as far as I can judge.

William.

Edited By William Chitham on 25/06/2020 12:42:56

25/06/2020 12:00:33

Ok, I'm convinced, poly v it is. Some further questions occur to me:

How many ribs? 4 seems common, but I have seen suggestions that 3 or even 2 would be adequate. Less ribs means less "stack" height which might be a good thing but more important seems to be the built in torque limiting safety factor - fewer ribs presumably slip sooner. The weak intermediate gear that we want rid of seems designed as a sacrificial component, primarily protecting the back gears buried behind the spindle which will be redundant anyway but is it realistic to hope that belt slip might reduce damage to cutters or workpiece perhaps in a misread decimal point sort of scenario? It might be interesting to make 4 rib pulleys and try running 4,3 & 2 rib belts to see whether slip could be provoked.

How necessary is the flange? Seems to me that it is only going to make speed change more awkward. If it is keeping the belt on when running then something must be seriously wrong with alignment.

Is there any reason to try to extend the speed range beyond the standard?

William.

24/06/2020 10:02:30
Posted by Clive Foster on 23/06/2020 23:22:18:

The poly vee belt grooves are sufficiently small that you can just go straight in with a tool of the correct shape. Think thread cutting without the traverse along the bed.

Even without a DRO precise spacing is easy with a simple spacer the same thickness as the inter groove spacing and something to clamp on the bed to define the saddle position........

..............If there is no suitable machined surface on the saddle I'd also fit a suitable flat pad to the saddle to give a really good surface to register from. Choose the dimensions so you can add a micrometer later.

Need to generate the shape of single groove pulleys because the Vee is generally too large to be cut in one go with a simple form tool on home shop type machines. Basically you have to cut the two sides separately and maintain the correct spacing. So you are still stuck with getting the spacing right.

Clive

Thanks Clive, that all makes sense to me, I absolutely take the point about the small form tool. I'm actually in the process of making a bed clamp for a dial gauge which would serve the purpose for spacing.

William.

23/06/2020 09:42:05
Posted by oldvelo on 22/06/2020 22:28:05:

Hi

After buying an X2 Mill drill over 10 years ago with 2 speed plastic gears and spring assist on the cutting head. Rebuilt it with Taper roller bearings spindle. Fabricate and fitted Two Speed poly vee belt drive four ribs "J' section. Sold off the motor and controller and replaced with a 1.25 hp DC motor with a AC to DC variable speed Minarik Regenerative Quadrant 4 Drive Controller. Ditched the spring assist for an air spring mounted inside the column with adjustable yoke assembly to get maximum travel of the spindle. Now it is hard to recognise as an X 2 mill both in looks and performance. It is not pretty but is practical.

z-axis 15.jpg

Crikey, there should be a separate thread for most radical X2. Looks as if you've addressed the terrible fine feed as well, does the spur on top of the spindle pulley drive a powered feed?

22/06/2020 15:20:39
Posted by Oldiron on 22/06/2020 12:17:17:

My motor pulley has OD's of 25 & 35mm and the spindle pulley is 60 & 75mm. The V's are 4mm wide x 3.2mm deep

Thanks, is that on a similar machine? Do you use the low speeds much?

Posted by Keith Long on 22/06/2020 12:38:54:

William, look at the page in your link, there are 3 boxes on the right hand side, "Description", "Technical" and "Reviews". Click on the technical box and it tells you the minimum pulley pcd there. Also you can down load the full Optibelt catalogue from www.optibelt.com

Thanks Keith, staring me in the face of course. Spec looks fine, 20mm on the motor and 80 on the spindle gives me the 4:1 and the 2:1 for the high speed should be easy.

I am keen to make this myself because I'd rather invest time than money and I might learn something along the way.

Clive, I can see that a poly belt might be superior but all the conversions I've seen so far use a basic V. Not sure how machining 5 precisely spaced grooves is easier than one big one, could you expand on that?

William.

22/06/2020 11:39:30

Having broken my second intermediate gear I'm contemplating a belt drive conversion for my X2 clone. This looks to be a suitable belt: belt but I can't find any specs for pulleys, specifically I want to know the smallest practical. If I drive the spindle direct I reckon I need a reduction ratio of roughly 4:1 to match the existing low gear setting. The spindle pulley is limited to around 80mm pcd so the motor pulley would need to be 20mm pcd to achieve that - seems a bit tight but it is a small cogged belt. Any thoughts?

William.

Thread: Single point threading
26/05/2020 13:20:39

Three suggestions from a beginner:

Grind an HSS tool with a narrow nose that you can use in with the centre.

Turn the blank long enough to get the centre in to support it then cut to length after threading.

Also maybe skip the gutter or cut it with a radiussed tool to reduce the stress riser.

Thread: Telescopic bore gauges.
30/04/2020 12:55:29

This Old Tony recently posted a video showing how he dismantled and fine tuned bore gauges to make them work smoothly: **LINK** . I suppose he is shortcutting the natural "break in " process that makes old tools feel nicer.

William.

Thread: Boxford change gears for screwcutting.
24/04/2020 15:40:50

Hi Terry, as a fellow metric Boxford user I absolutely agree with you, it is an excellent little program. I do have a copy, I have sent you a message with a link, contact me if it doesn't work

Best, William.

Thread: New DTI "Glass"
11/04/2020 14:57:16

etalon before after.jpgThanks for all the suggestions, looks like I could have bought a watch crystal to fit but I wanted to try making one and it turned out pretty well, an improvement on the original anyway.

If anyone is interested I put some photos of the process in an album. In brief I turned a wooden male form; balanced a 1mm acrylic blank on top; heated with a hot air gun till floppy; pressed down over the form with a plywood "washer"; put the acrylic wrapped form back in the lathe and "parted off". It took a few attempts to learn to read the state of the hot acrylic and it was tricky to cut accurately to a diameter but I managed to get a good snug fit in the bezel eventually and only used one A4 sized piece of material.

30/03/2020 18:13:03

I picked up this DTI at a jumble back in February. It was a bit sticky and the pointers were out of phase so I didn't pay much for it. I dismantled and reassembled it and works fine now but the plastic "glass" is yellowed and loose enough to pop out without much encouragement. Any thoughts about replacing the glass? I'm thinking maybe 1mm acrylic which seems readily available but I don't know if that is oil resistant.dti.jpg

Thread: What is This?
06/02/2020 09:59:50

I think it is for getting Boy Scouts out of horses' hooves.

Thread: Airline Fittings?
02/01/2020 12:42:05

I have split the output from my compressor into clean and oily lines. The clean line has a filter and dryer and everything that plugs into this uses Euro type fittings. The oily line has a filter and lubricator and uses PCL fittings.

Thread: Help with a boxford c
08/10/2019 11:44:59
Posted by Nicholas Farr on 07/10/2019 23:03:31:

there is no tensioning adjustment for this belt on the underdrive models

On my CUD the holes in the brackets for the intermediate shaft are slotted so I was able to adjust the tension somewhat by moving the shaft backwards and forwards.

William.

Thread: Engraving
20/09/2019 15:36:28

I just refurbed a micrometer and used an Edding 950 paintmarker following a You Tube recommendation. I bought it from Zoro, they also do a Markal brand equivalent. They are meant for marking up fabrications, metal stock etc and will supposedly write on dirty rusty oily surfaces and be permanent. Easy enough to apply by the rub on wipe off method, only just done it so can't vouch for permanence.

Thread: Calculating DRO For Mill Z Axis
09/09/2019 17:42:03
Posted by Steve F on 09/09/2019 17:36:46:

I think Machine DRO do a gadget that sums the 2 values together. Yes its here **LINK**

Just the job, I thought it must be possible.

09/09/2019 17:39:36
Posted by HOWARDT on 09/09/2019 17:32:27:

What if you connect the scale to the knee and the reader to the quill. Then you read the distance between the two.

That would work but might require a rather convoluted mechanical connection between the two.

09/09/2019 17:28:47

While my printer toils away I've been pondering the DRO installation on my fantasy mill. Obviously it is a knee mill with a quill and I'm wondering if a 3 axis DRO can be set up so that the Z axis displays the product of two scales, one on the quill and one on the knee? In other words any movement down on the quill would be added to any movement up on the table to show the cumulative result.

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