Here is a list of all the postings ChrisB has made in our forums. Click on a thread name to jump to the thread.
|Thread: Upside down reverse threading|
Regarding holding an endmill in a drill chuck, I think it can be done ( thats what I had to do before I got direct collets) but, it depends on what chuck you use. I was using an old keyed chuck with a threaded arbor. I would be a bit concerned using a keyless chuck with just a jacobs taper to the arbor. Sideloads may knock the chuck off the arbor I think.
|Thread: DIY magnetic DRO|
Not sure if I did this right, I connected the shield to the read head casing, the casing will slide and contact the lathe and mill body (which are grounded) so I'm thinking I should have a ground, did I get it right?
In reality I don't know if cable shielding will be necessary as there will be no other electrical wires routed along the read head cable, so I would think noise should not be an issue - but I might be mistaken.
Good advice re. waiting before sealing everything...hope the touchDro wont take long to arrive!
Some more progress : received the encoders over the weekend, so next step was to solder the encoder to the pcb and then install everything on the readhead casing.
They are indeed small and was a bit concerned I might not be able to solder them as the contact points are really close to eachother, but I managed. I checked continuity and all seem to be fine, the the proof of the pudding will come when I receive the touchDRO, so fingers crossed!
I anodised the aluminium read head casings with chromic acid, the material is 7075 and has a tendency to corrode although it's probably unlikely given it will live in an oily environment.
Next step is to seal the encoder inside the readhead casing, I'm split between resin or sealant, not sure which way to go. I would prefer resin as it will become one piece. On the other hand with resin, once cured there's no way I will open the thing again if I need to.
Hi Ian, you can wait till I get my TouchDRO to make sure it works, I'll be the guinea pig!
I'm using a 5 core felxible shielded cable like this: **LINK**
I the diameter on the housing is a close fit to the cable so that will slide in a tight fit. Then I'm filling the cavity inside the readhead with sealant so that will seal and keep everything together. Cable length is approx 1m, can be much shorter actually as the TouchDRO can be mounted on the saddle (for the lathe) and transmit to the tablet via bluetooth. But I kept the lengths standard so I can move them around and swap if I need to.
I could have used armoured cable but to be honest I think it would be an overkill, I mean I'm not in an industrial environment and with some care and proper routing the cables will be protected - It is chemical resistant so oil and stuff like that should not affect it much.
Next step is mounting the encoder, left Slovenia on Wednesday, so I hope I get them tomorrow, if not it will be next week
Some more progress today. Milled the encoder housings out of aluminium, all ready for mounting the electronics. The encoders should arrive over the weekend, but will have to wait a bit longer to try them out and see if they actually work as the TouchDROs have to come from all the way from the States - might take a while.
First I machined the read heads in to the final outside dimensions and then made a fixture to clamp them.
This is the fixture held in a precision milling vice.
Read head blank clamped on the fixture ready for machining. Clamping action is very simple, I tighten the screw, in turn the countersink pushes a "jaw" away which pushes against the work piece. I could have clamped the piece directly on the milling vice but was afraid the part would distort. Besides that, with this fixture I could get a good degree of repeatability ( had to make 5 pieces)
First read head ready, four to go!
He can spell it right
Edited By ChrisB on 03/05/2019 18:39:32
|Thread: DIY magnetic DRO|
As Andrew well explained, it's for production manufacturing, I'll be hand soldering so I don't think I'll have any major issues there. We'll see when it comes to soldering those miniature joints what difficulties will arise...got low temp lead solder which should help a bit.
The encoders I ordered are all the same and cost €36 and the magnetic tape around €50 per m
Below is the spec I ordered, you can get it with different resolution connectors etc
RLC2HD miniature linear PCB level incremental magnetic encoder
|Thread: Bandsaw speed|
I run a 1/2" 8/12 tpi vari-tooth blade on my Nebes tm101, is variable speed from 30 to 80m/min but most of the time it's set at 80m/min and I have cut both steel and aluminium without any issues. With higher tpi you'll get a better finish but it will take longer and probably load the blade with softer materials, I found the 8/12 vari-tooth works much better to the 14tpi the bandsaw came with.
As for welding a blade, I managed to weld one with a tig welder - acceptable, ie it didn't break again but I needed to grind a bit to remove excess material.
|Thread: DIY magnetic DRO|
Thought so Colin, no problem.
The circuit boards have etched nicely, I will need to trim them to size and drill 1mm holes at the 5 solder points for the wires. Not sure how to cut them to make them identical...might take them on the mill rather than sawing them off.
Works in progress: The PCBs are developed and being etched, so far so good!
If I had to get the read heads only, the cheapest they have is £140 each and those are 6" long I need longer ones. I'm sure the 5 individual read heads will add up close to the £1000 mark.
Hi Les, well noted. The encoder comes with a self adhesive magnetic strip and a protective stainless steel cover strip. It's about 1.6mm thick, the ride height is 0.1 to 0.7mm so there's a bit to play with. I designed the read head to get approx 0.5mm ride height. If you look closely at the first picture, you'll notice the read head sides extend beyond the magnetic tape, that is what will give me the 0.5mm gap.
I ordered the magnetic tape is over sized so I can cut to length as required.
So until I get the encoders which are on order I'll start with the preparation. I need to print/etch a small board to mount the encoder on as I'm never going to be able to solder wires to the encoder chip (the contacts are less than 1mm apart!) Then I'll mill the encoder housing out of aluminium and try to make all fit inside.
Started off with some drawings to get a good I idea of how things will fit in.
Overall read head dimensions will be 25x20x7mm, compact size so it will not get in the way and hopefully makes installation easier.
Internals, encoder inside the read head,
The boards I need to build and the encoders which are on order.
I have a day off today (my birthday!) so I'll get on with these boards this morning - it's an experiment as I never did a board before but youtube and the internet is very helpful!
I'm using a photoresist pcb board, developer and a homebrew ferric chloride etchant... let's see how it goes!
Yes Nick, I saw those, they are even more expensive at £1200 for a 2 and 3 axis sets. I was looking at EMS-i, price wise they are just under £1000.
I have been wanting to buy a couple for my mill and lathe for quite some time now, specially for my mill as it can get quite frustrating and confusing trying to keep in mind backlash, endmill diameter, cutting direction, the small handwheel scales etc.
I got a couple of quotes for a 2 axis and a 3 axis Dro sets with magnetic scales, but these cost roughly £1000 and to be honest I was put off for a while...Lately I have seen quite some posts on DROs, which re-ignited my interest in the subject.
I thought what if I could do something myself, at a fraction of the cost? I want magnetic scales as these are the smallest most compact there is and the least sensitive to dirt and oil, while offering very good levels of precision.
So here is my planned project:
I placed an order for five pcb encoders: **LINK**
and a pair of scales drivers from TouchDRO: **LINK**
I also purchased some miscellaneous items such as blank pcb boards and etching material, pins and sockets and wire, etc. I estimate the total cost to be not more than £400.
Will report on the progress and if it works or no...hope it does!
|Thread: Impressive Workshop in Germany|
Organized shops and going around in socks and sandals must be a German thing!
|Thread: Vickers Bl 8 inch Howitzer cannon of 1917|
Most of the British forts in Malta were built in the Victorian period and were equipped with 12.5in RML 38t guns, might be that's what you saw. Most were scrapped and cut up ages ago and only the ones which were impossible to remove were left such as those at fort Delimara (still there) and a 17.7in RML 100t gun at fort Rinella.
Dont know when the authorities are going to wake up and restore those forts and remaining cannon...such a pity all crumbling and rusting away.
|Thread: MEW 239 Boring Head FreePlan|
Regarding Boring bars, would lathe boring bars work on the boring head? (shortened of course)
|Thread: Notre Dame|
I think you got it wrong Guy, the Notre Dame, is the property of the French State, but taken care of and used by the Church, including it's upkeep. It is also a UNESCO world heritage site, for those who think it's of no practical use.
Regarding donations by the Church to restore the damage, google is your friend...
As far as I can tell from the news the damage, although extensive did not render the cathedral a ruin. So imho it makes sense to repair the damage. I won't get into how it should be done as I'm no restorer nor a history expert.
What amuses me is people suggesting one should not donate to have it fixed. I mean, why should it be a sad thing to donate for such a cause if one had the means? It's a good cause, just as much as donating to the poor...which I believe they all do!
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.