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Member postings for Chris Trice

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

Thread: Mini-lathe saddle casting error.
01/01/2022 15:19:50

Put a straight edge across the surface and slip a feeler gauge between the part and the straight edge. That should tell the story.

Thread: To harden or not to harden that is the Question
27/12/2021 20:09:04

Female threads are in compression and stronger than their matching male threads which are trying to sheer off the central core of the stud. It's why high tensile bolts can have mild steel nuts.

Thread: 43 TPI
27/12/2021 19:49:07

Yes, it says so in Tubal Cain's excellent book on Drills, Taps and Dies.

26/12/2021 11:56:51

Apparently the smaller Thury threads are BA form anyway. The larger are more akin to metric.

https://www.sizes.com/tools/thread_thury.htm

26/12/2021 11:48:35

That's a thought. The thread is so fine though I'm not sure the actual thread form is going to play a big part. I have to say looking at the thread, it's more akin to a regular 55 or 60 degree thread form than the rather more rounded BA thread.

26/12/2021 03:38:46

devilbiss.jpg

26/12/2021 03:25:15

I know Everything Airbrush as they are the official inheritors of the Devilbiss brand and spares. One of the guys there worked for Devilbiss assembling the airbrushes on the production line. It's not 0.6mm. I took a silicone mould of the internal thread and then compared it to various thread gauges viewed through a jewellers loupe with an engraved scale. As mentioned, 44 gauge is too fine and the 42 gauge is too coarse. Incidentally the originator of the DeVilbiss Aerograph airbrush was American but they have been manufactured exclusively in England for more than a hundred years, essentially unchanged apart from modern materials being introduced. The external air valve thread as mentioned is 3/8 UNEF and the thread in the handle (still available) is 5/16 x 32. The thread I'm chasing (see what I did there?) is the thread in the forward part of the body. All the dimension of the airbrush appear to be imperial (needles are 3/64" diameter rather than the more common 1.2mm. Unless anyone can suggest another thread with a virtually identical pitch, 5BA (43 tpi) is all I've got.

24/12/2021 03:35:58

Thanks everyone for the replies. I managed to get the thread calculator working and managed to get it within 1/10th of a tooth over 1" which is more than enough as I'm only machining about 3/8th" of thread. In answer to the question what's it for, I'm machining the body threads on an old Devilbiss airbrush and although the bore is about 11mm, the thread is the same as a 5BA machine screw. I suspect they may have used 5BA Coventry die head chasers as a cutting tool. It's not 44tpi and it's not 42tpi. The only thread I can find inbetween is 5BA which is 43tpi. I may braze up a tool from a die head as a cutting tool. The important thing is it's close enough to do the job.

23/12/2021 15:39:22

I've got to cut a 5BA thread on something which is a horrendously inconvenient 43 TPI. Can anyone suggest a set of change wheels running off an 8 TPI lead screw (Myford Super 7). A tiny error might not matter but I need to be close. While my maths is good and the principles understood, this is taxing me. Comparing notes will help.

Thread: Wobbly slitting saws
30/06/2019 01:12:13

I'll probably get vilified for sounding like a broken record but I've found the cheap import ones are the worst offenders by far. I usually end up making a wide arbor to grip the cutters nearer to their periphery but of course you lose cutting depth.

Thread: Myford Super 7 Top Slide Base - Alternatives?
30/06/2019 01:08:23

I built the Hemingway kit about ten years ago. It's a nice bit of kit BUT I've never had cause to use it and it's languished in a drawer ever since. I ended up custom making a beefier and larger top slide of my own design that still allows taper turning.

Thread: water supply
17/06/2019 00:53:05

For the record, it's a myth that lemmings fling themselves off cliffs. That misinformation originates with Disney.

Thread: Ebay 'photos'
10/06/2019 20:44:15

The one that gets me is people who sell chuck jaws separately who also have the jawless chuck they obviously came from for sale as well. It's like selling a car without the doors and offering the doors separately. It just comes across as miserly and penny pinching. Just sell the matched set of pieces together.

Thread: Myford boring bar help
01/06/2019 19:27:22

I can't remember if it's Sparey or Mason but the practice employed for setting the Myford Boring bar is to use a micrometer set to measure half the required bore and half the boring bar shaft diameter. I've found it is possible to gently tap the wedge piece to let go of the cutter slightly, then tap the cutter to the right position before re-wedging it tightly. The measurement is taken from the cutting tip of the cutter to opposite side of the bar. Not the most convenient set up but inexpensive.

01/06/2019 11:50:52
Posted by Andrew Tinsley on 31/05/2019 11:34:51:

Hello Mark,

It looks as if your boring bar is faulty, as others have said, do talk to Myford.

Andrew.

No, it is not faulty.

31/05/2019 03:46:25

TB is right. I have one of these and one hole holds the cutter while the other has piece that is flatted on one side in a slight taper. The cutter is wedged in place quite firmly but adjustment is tricky.

Thread: Interesting??
24/05/2019 01:33:44
Posted by Neil Wyatt on 24/05/2019 00:38:16:

Approximately half the population are of below average intelligence.. most people think they are above average...

Neil

By definition, "exactly" half the population are below average intelligence. That's the definition of average.

Thread: HSS or CS taps and dies
21/05/2019 22:30:46

This is Tubal Cain territory (the British one, not the internet pretender) who shows that drilling the tapping hole slightly larger than the Zeus tables (within reason) makes negligible difference to the strength of the resulting thread but vastly reduces the chance of over torquing the tap and breaking it.

Thread: stamford show vandals
21/05/2019 10:10:57

Victim impact statements should definitely form part of the judgement when it comes to sentencing. The psychological impact on these poor guys should not be dismissed as I'm sure many of them are devastated.

Thread: HSS or CS taps and dies
21/05/2019 10:03:46

Almost all mine are HSS as I do find them less prone to breakage. On that point, I think drilling the correct size pilot hole plays a bigger part in tap survival than the material it's made of and assuming of course it's sharp.

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