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Member postings for Pete Savage

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

Thread: M8x1 left hand tap.
20/09/2019 14:56:25
 
The nut worked amazingly even without any anti backlash mechanism. The handwheel free spins about 0.01mm worth which isn't too bad.

Edited By Pete Savage on 20/09/2019 14:57:34

20/09/2019 10:27:46

It was branded TWT UK, never heard of them but looked of decent finish etc.

19/09/2019 19:24:10

Yes, they ended up special delivering me one out for 4 quid postage which wasn't bad! Only ordered it yesterday!

19/09/2019 18:22:47

Hopefully Roderick! At least that might actually be useful at some point!

Below is the one I have just received from RotaGrip.

20190919_181259.jpg

And here is the RGD one!

20190919_181141.jpg

19/09/2019 13:22:04

I bought the tap September 2018, I lost interest in sending it back but it was bizarre because all 3 taps in the set were wrong according to my pitch gauge.

I would be interested to look into ball screws, but the unimat is absolutely tiny, I don't think anything more than the m8 leadscrew would fit in the cross slide area

18/09/2019 15:44:50

I just checked back through my emails, and my dodgy tap set did come from rdg tools. They offered me a refund if I sent it back recorded but that would have been half the value of the product.

None of the shops mentioned have one on stock so hopefully ordering they won't just get a bad one from rgd and pass it on!!

18/09/2019 11:18:10

I haven't rung up anyone yet but had a check on the websites, I found an RH m8x1 on tracy tools. 18 quid for the rotagrip HSS looks good as long as it is genuinely a 1mm pitch, 65% discount sounds a bit suspicious.

I must say the only reason I checked the pitch was because it was about a tenner for a set of 3, of a non standard pitch, and if that wasn't uncommon enough it is left hand!

The idea was to make phosphor bronze sacrificial anti backlash nuts to try and get the backlash and friction down to help with the fitting of CNC, so an investment in a tool likely to last a few sets sounds good.

17/09/2019 22:59:50

Hi guys!

I'm making new lead screw nuts for my unimat but I'm having problems. Has anyone ordered an M8x1 left hand tap and received one that was actually correct? The eBay ones seem to all be absolute crap, with the pitch being closer to 1.1mm. I currently don't have access to a lathe with metric screw cutting facility so i can't have a go at making my own. Any trusted sources?

Cheers,

Pete

Thread: Whittle V8 Camshaft and Conrod Collision.
11/10/2018 23:41:47
I have the hemmingway kit, and did wonder whether the springs would be stiff enough, the four stroke RC engines I own have pretty stiff springs.

Maybe it would be possible to make a little valve seat cutting tool that locates into the valve guide to get higher precision.
28/09/2018 15:20:21

I think a chamfer of 1.5-2mm on this edge is enough for clearance.

 

EDIT: It is on the opposite side to in the photo

1538143937266313442542.jpg

Edited By Pete Savage on 28/09/2018 15:31:44

27/09/2018 11:43:00

Emgee, When you were machining your cam shaft, did you assume the radial pin point order was towards the outside of the jig or the inside? As I understand it at the moment, the end of the shaft with the 2 different diameter bits on the end is the rear/cyl 7&8 end, which goes through the clock dial and into the 245 slotted wheel.

I aligned the centre of the lobe to the opposite of this point for the corresponding cam position, assuming the points were on the outside, however the shaft appears to now be a mirror image of what it should be.

On an unrelated note, the purpose of the arbitrary "Index pin hole" seems like an added complexity, those holes could just be numbered with what cam number it was!

27/09/2018 08:40:25
That's the ticket! Didn't notice that, I must have seen it at some point, but I go off and come back to this project quite a lot. Thanks for the help!
26/09/2018 23:30:20
Posted by Emgee on 26/09/2018 20:58:57:

I am in the process of building the same engine, work to date includes all ally bits and the camshaft,

now on the 4th attempt at the crankshaft !!!!

When I get to building, I am going to try doing the crankshaft using a live centre at the right end, but gripping the other side in a 4 jaw chuck using a dial indicator on the tool post to get it parallel.

I hope this will give me a bit extra stiffness at the end, but I have ordered enough bar to make 3 as I have heard other people's problems!

26/09/2018 22:27:46

1.jpg

Here only cylinder 2 is visible but cylinder 1 is at tdc where cams are in overlap area. When rotated around the edge of the conrod touches the cam lobe.

2.jpg

Edited By Pete Savage on 26/09/2018 22:34:28

26/09/2018 22:08:49
I timed it with cylinder 1 at TDC and the cams in the overlap point like the article says.
26/09/2018 20:48:36

Hi Guys,

While sorting out my lathe I decided to draft the engine up in cad. I have assembled everything and turned it over, only to notice the conrod collides with the lobe on the camshaft.

I make the distance between crank and camshaft 0.5625in, which as far as I can tell is correct, so I am calling on anyone else who has made this engine to tell me where I have screwed up?!

Cheers,,

Pete

Thread: Unimat 3 Mill head Modulus
02/01/2018 11:04:04
Posted by Michael Gilligan on 02/01/2018 10:21:40:

Unless you happen to have a decent 'profile projector' to hand, scanning the pinion on a flat-bed scanner, at [say] 600dpi would a useful start.

It's funny you should say that, I work at a testing laboratory which performs metallurgical analysis, and we have an ancient one downstairs! I will have to put a bit of paper behind the teeth for contrast though.

02/01/2018 09:29:02

OD is 12mm yes. I seem to remember something about a pinion cutter and a wheel cutter, presumably the former is for low tooth counts and the latter is for large tooth counts?

The mod 1 cutter has a 6 or a 9 opposite the "M 1.", whether this means a tooth number approximation or not I don't know.

Edited By Pete Savage on 02/01/2018 09:32:30

02/01/2018 02:07:14

20180102_003549.jpg

Here is the bearing carrier with the Mod 1 rack

20180102_003720.jpg

This is the 0.9 cutter, and it may not look too conclusive from the image but the involute curves match pretty closely.

20180102_003812.jpg

None of the involute curves come anywhere close to touching on this gear cutter, yet the gear does not look excessively worn.

02/01/2018 01:44:32
Hi guys, I've just been fiddling with a quite well worn unimat 3 lathe I recently bought, and in trying to sort a few things out, I found something rather interesting/ peculiar about the rack and pinion Z axis.

The rack on the bearing carriage has a pitch of 3.14mm, which is a module of 1 (pi*mod) which I measured over 10 points and divided for better accuracy.

Now when I look at the handle (which I am 99% certain is the original) and offer up gear cutters to it, the closest fit is a 0.9 modulus cutter.

When the pinion is placed in the rack outside of the housing and rolled, it does not seem to move smoothly all the way.

This seems like quite an oversight by emco unless it is for a reason?

The reason I am going through it with a fine toothed comb is that I am looking to make a stepper motor attachment for it and the play that it has at the moment is not good enough.

I will try and add some pictures when I work it out.

I look forward to the discussion!

Pete
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