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Gallery / Well that was boring...
« Last post by Joules on Today at 08:16:18 AM »
Another deeply roasted job from being on the back burner for over a year.  I made up a tool holder with a Foredom rotary hand piece to drill and light duty grind in the lathe, it can be powered from the Foredom flex drive or a small motor fitted on the back for a more compact unit.  The tool holder has a 1" bore and I have since bought a few more for other tooling. 

Whilst mulling this over I thought, a key slotter/lathe shaper tool would be cool, so I went searching for bearings.  I came up with some 1"x3/4" bronze flanged bearings, ideal thinks me.  Then tried them in the tool holder.....Errr, no go.  On close inspection the tool holder was very roughly bored, as best I could measure the bore also wasn't true to the outer edges, and my bearing slightly oversize !!!  Bummer.  So it got put on the back burner whilst I figured out how to bore the thing.  Holding it in the 4 jaw was a mare, as the thing had runout all over the place. 

Idiot !!! stick it on the tool post and bore between centres, brill, but I don't have a between centres boring bar.  More rummaging found the 20mm silver steel you see in the parts picture below.  More back burner time, and the smell of hot oily metal passed by.  I got round to making the boring bar and then agonised over what size to drill for the cutter.  Looking though the tooling and junk, I didn't have matching drill, reamer and tool bit.  So 5mm it is then as the drilled hole will be undersized.  That worked, the hole was drilled offset on a small machined flat on the bar, a single grub screw inserted from the side.  The tool bit, sometime later I came across some very hard 3/16" HSS, might have got cobalt in it as it was a bit tough cutting it.  Yep 3/16" in an undersize 5mm hole is still a rattle fit.  Answer, have a beer, now cut the tin and use as shim round the 3/16" bit.

Perfect fit, the tool bit has a flat ground length wise for the grub screw, and the cutter edge is ground at roughly 45 degrees to give a tangential cutting action.  The between centres boring bar was now ready for action.  The tool holder internals appears to have work hardened from whatever gnarly tool they used to drill the thing. The bore also drooped towards the tailstock, so the boring bar had quite a bit of work to open out and true the bore.  Still it was nice to be making swarf with a tool I had made.  Plenty of testing the bearing fits as I opened the bore out very carefully.  The bar will have been flexing so the bore won't necessarily be round, I could feel the elliptical shape inserting the bearing and twisting it being very careful not to get it jammed in.  Use plenty of oil, at this point it was so close and stopped using the boring bar.  The bearings left visible material where they contacted, and used this to hand scrap the tool holder for final fit.  Keep a close eye on both ends so one bearing doesn't wander off centre.

Final fit was done with the little machinist hammer I made a while back.  I was able to tap the bearings in and tap them out using a nylon bar so it didn't damage the bearings.  When finally fitted the bearings are tested with a small bar and rocked to make sure no step bearing to bearing that would indicate the pair not inline, check all round and they seem fine.

And on the back burner again...  No 3/4" silver steel to be found....  :(   Had used it to make other stuff a good while back.

This build is very much ad hoc, no plans and just using parts as I find them.
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Composites & Plastics / Re: Glass fibre mould from the slender plug
« Last post by PekkaNF on Today at 06:22:40 AM »
Thank you Steve very much!

That clear my confusion completely. Now I feel pretty stupid....I had read and "knew" all details, but could not connect the dots.

I knew the difference on gelcoat and topcoat, but never knew the fundamental difference on polyester resins. I was baffled, because when I was young I helped one motobike racer to build fairings and cowlings on my summer holiday...I remember him planning everytihing beforehand, and some stuff had to done when "green", some when hardened and some demended peel off ply. Pretty sure he always used tooling resin, because backside was always stricky and had to topcoat it in the end.  I think we were building only molds and remember him showing how different the parts were when laminated from epoxy or polyester.

This was exactly why I had this confusion, because my previous experience did not match my results.

That shop where I bought my resin had only one type of polyester resin. The plan is to use this can of that resin for next mould (will be build on one go then!) and try to find laminating resin for the next week.

Pekka
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Tools / Re: My Cowells ME lathe
« Last post by Joules on Today at 06:16:49 AM »
LOL, a very giddy kipper then....
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Tools / Re: My Cowells ME lathe
« Last post by raynerd on Today at 05:49:51 AM »
Well it took another 4 years but I eventually found the Cowells I've always wanted! 



I'm just making a spindle indexer/divider so I can use the wheel cutter!
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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on June 23, 2018, 08:47:08 PM »
Raining today, and had to prepare for my daughter's birthday, but I managed to make the pulley pattern, which I turned from poplar on the Gingery lathe. Rain predicted for the next few days.

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Composites & Plastics / Re: Glass fibre mould from the slender plug
« Last post by vtsteam on June 23, 2018, 07:58:42 PM »
Pekka, general purpose polyester resin (also sometimes called "finishing resin") generally has wax in it so that it will cure hard on the surface. Wax floats to the surface before cure, insulating it from air. Best for all-at-one-go type work, or as a final coat on a molded part IF you don't plan on attaching anything else to it, since a wax surface isn't good to adhere to. Polyester resin is a poor glue to any hard surface or material. Epoxy resin can be used to glue to polyester, if any surface wax is removed. But polyester itself will not work well with an already cured polyester surface, even after wax removal.

Laminating resin doesn't have wax in it, so that it can be added to by subsequent polyester layers or attachments in a mold. Even cured, it is still tacky on the exposed-to-air-surface, so subsequent layers of polyester WILL stick to and and cure it. Polyester without wax is an air-inhibited cure resin.

Gel coat also is air-inhibited cure, for the same reasons. subsequent layers need to adhere to it. However it does cure (harden) against the mold surface, since that side is not exposed to air.

Because laminating resin stays tacky on the surface, even when cured, you can add subsequent layers without having to rush it or build up too much thickness all at once. If too much thickness is built up all at once, all the resin will cure at the same time and get hot and cause other problems.

Is that any help?
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Project Logs / Re: Building a New Lathe
« Last post by vtsteam on June 23, 2018, 06:39:23 PM »
I'm thinking XL Belt, 18T on the driver and 90T on the driven pulley.  Those are two easy numbers to do on my spin collet, lacking a dividing head, since it does degrees. I should get about 1000 RPM top without a change in the driver pulley.

That pulley would be 5.68" diameter. So I can make a 6" pattern. Aluminum, this time, for easier notching.
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Composites & Plastics / Re: Glass fibre mould from the slender plug
« Last post by PekkaNF on June 23, 2018, 04:50:41 PM »
Started working on another sword mold. Can't get my head around it, but think I'm going to build it in two part and need two moulds: blade/handle and cross piece.

Now the interesting part is that I am not very familiar with polyester resin. Information I read is a little confliking.

One major thing is: Some information emphasis putting a veil over gelcoat, let it dry (to various harness, often completely dry and then continue with structural layer. Some videos people seem to build pretty much (or least seemingly) the whole mould laminate on one go.

Which way it is and why? I never build that thich laminate, taht it will heat up.

I get that adding stiffeners to wet laminate will shine trough, but those I could add day later.

Any advice on mould laminiation sequence?

Pekka
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Gallery / Re: Lidar Build Part II
« Last post by PekkaNF on June 23, 2018, 04:25:22 PM »
Pretty incredible. All that math makes my head spinn.

Pekka
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Gallery / Lidar Build Part II
« Last post by David Cambridge on June 23, 2018, 02:21:19 PM »
Hello again

After getting my home made Lidar up and running, I decided it was time to spend some time at church  :D




David
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