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Member postings for Andrew Entwistle

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

Thread: Coventry Quick Change Tool System
17/03/2021 18:24:46

304 coventry er25 chuck.jpg

The balls locate in the groove near the bottom of the taper, as evidenced by the indentations! Surprisingly both flanks seem to be engaged by the balls.

Edited By Andrew Entwistle on 17/03/2021 18:26:24

17/03/2021 16:34:28

The Coventry type system is also available for slightly less from engineeringsupplies.co.uk. I tried making an ER25 holder from 304 stainless, but although it was made accurately, it soon developed runout because of indentations in the taper from the locking balls. It would need to be hardened at least in that region to be successful.

Andrew.

Thread: McMaster-Carr
27/02/2021 21:34:08

Misumi used to be a comparable option, and still are for work, but since January they have slapped a charge of something like £15 on UK orders.

Thread: Advice for surface finishing
19/01/2021 21:52:21

I think Dave is referring to a CCGT type uncoated small radius insert for aluminium and stainless. They work well for lighter cuts in harder materials.

Andrew.

Thread: Removing powder coating finish from metal.
08/01/2021 15:20:37

I have succcessfully used paintstripper to remove powder coating completely, The modern formulation is not as potent as original Nitromors but if covered with clingfilm or foil etc and left for an hour or more still does the job in one or two applications.

Edited By Andrew Entwistle on 08/01/2021 15:21:23

Thread: Collet chuck
13/12/2020 18:00:33

Based on pixel measurements from 100mm OD can't be far off 73mm.

Thread: Jan Ridders coffee cup hot air engine
19/11/2020 19:00:19

Hi Frank,

I got mine to work with a graphite piston in the honed bore of a glass test tube, but I'm sure other pairs will work if clearances are optimised. There needs to be practically no friction for the engine to work as there are only milliwatts of power available. If you look from 1:34 of this video I made about my Jan Ridders engine you can see how free the piston needs to be.

Testing a low temperature difference hot air engine

Andrew.

Thread: Tri-Leva decal artwork?
13/11/2020 11:50:52

Hi Frank,

If you can get a high resolution photo then it can be corrected for lens distortion and perspective in a bitmap manipulation program such as Paintshop Pro:

tri leva.jpg

Andrew.

Edited By Andrew Entwistle on 13/11/2020 11:54:08

Thread: Highlighting Index Lines
18/10/2020 13:00:25

+1 for clockmaker's dial wax. I use a magic sponge (melamine) to remove excess wax without damaging even plastic surfaces.

Thread: Ex-college Warco lathes auction
14/10/2020 15:16:04

They all went for between £2050 and £2350 which is £2830 to £3240 after Buyer's Premium and VAT.

Thread: Soldering stainless steel
16/09/2020 14:22:32

Hi John,

I have had good success soldering approximately 1mm diameter 316 stainless pins into holes in copper using a drop of phosphoric acid as a flux and normal 60/40 tin/lead multicore soft solder. I got the phosphoric acid at the time from a chemical lab at work, but I see it is available on eBay at 85% as a rust remover. I don't know if there is a worry about the toxicity of fumes using phosphoric acid this way.

Andrew.

Edited By Andrew Entwistle on 16/09/2020 14:24:58

Edited By Andrew Entwistle on 16/09/2020 14:26:27

Thread: My Morgan SCARA coming together
18/07/2020 09:13:37

Hi Joe,

I have found little difference between the performance of Cura, Slic3r and Simplify3D slicers, with the exception that Simplify3D supports are easily customisable and they detach cleanly, without the need for tools. If I made my living 3D printing then the time saved in cleaning up prints with supports would easily pay for Simplify3D, but otherwise it is hard to justify the premium.

I have found it useful to be able to raise the bed temperature for the early layers with PLA for adhesion, then drop it later. Also turning the part cooling fan on after a few layers prevents fine parts from melting, but ensures adhesion to the bed. 

Andrew.

Edited By Andrew Entwistle on 18/07/2020 09:33:57

Thread: Britannia Lathe
05/07/2020 19:18:36

James, please do PM me, I can send you a spreadsheet of changewheel configurations I have used, and a program that will calculate the combination for you.

Andrew.

05/07/2020 14:23:14

Hi James, I have the same 1930s 4" Britannia with taper roller bearing headstock. On mine the spindle wall around the MT2 taper is quite thin and I have found that for diameters above about half an inch the spindle is just not rigid enough to get a good finish, unless using razor sharp HSS or xxGT carbide inserts designed for alumumium and stainless. With the right tool, feed and speed it can do anything, in backgear it has happily made its own chuck backplates up to 6" diameter.

Andrew.

Edited By Andrew Entwistle on 05/07/2020 14:24:05

Thread: Starrett type clamps
21/06/2020 16:36:19

Thank you. I used Fairy liquid and hot water, followed by the alkali degreaser that came with the Blackgates Chemical Blacking kit I bought years ago, made up with hot water from the kettle. The kit is way past its expiry date, but still works fine.

Andrew.

21/06/2020 13:43:51

After deburring , thorough degreasing, cold blacking and oiling.After cold blacking and oiling

Thread: Harold Hall - Tool & Cutter Sharpening - How big the base board?
19/06/2020 09:14:39

Hi Peter,

I put mine on a bamboo chopping board with a steel plate at the front for the two magnetic clamps to attach to. I am not at home to measure it, but it is something like 300 x 400 mm. You can see a photo of the assembly in my album, the width is about twice the length of the piece of steel angle the rest mounts on (which is about 150 mm long). I wouldn't want to go any smaller than this for the working space in front of the grinding wheel.

Andrew

Thread: Starrett type clamps
18/06/2020 22:31:28

Got the jaws made this evening, all done apart from softening the edges with wet and dry. Took a bit of trial and error with different spring diameters to get the circlip working reliably. More details in my album.

Andrew.

Long and short jaws retained by internal circlipPair of Starrett type vice clamps on aluminium base

16/06/2020 20:55:11

Will do, when I get the jaws finished - I am determined to implement the ball end leadscrew with circlip attachment.

Edited By Andrew Entwistle on 16/06/2020 20:56:37

16/06/2020 19:05:15

Hi Stew,

Thank you for sharing your design and build log. I found that attaching the two pieces of stock using cyanoacrylate resisted all milling operations and a few minutes in boiling water breaks the bond when required. Instead of welding the knurled knob onto the leadscrew I used Loctite 638 bearing retainer into a slip fit, which has never failed, even on the crankshaft of my power hacksaw.

Andrew.

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