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Member postings for Pete Rimmer

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

Thread: Metric threading on Imp Lathe
15/06/2019 21:57:56

I always make my first threading pass with a black marker. Just hold it against the tool with the tip touching the work. Check the marks with a thread gauge..

15/06/2019 18:28:19
Posted by JasonB on 15/06/2019 13:19:02:

You won't get an exact 1.5mm pitch using a 63T in the train but the resulting 1.477mm should do for most things.

No you won't but the error is less than the average leadscrew tolerance. Here's a standard metric threading plate from a Colchester with a 6tpi leadscrew. They did metric transposing from the factory without using a 127 tooth gear.

Thread: Dro scale positioning
13/06/2019 18:43:31
Posted by ronan walsh on 13/06/2019 17:22:11:

Just splurged out on a 3 axis dro kit for the Tom Senior. It seems that the way to mount the x-axis scale is to mount it on the rear of the table. This is going to reduce my meagre y-axis travel by an inch or so, which i don't really want to do. I was thinking of mounting it on the front of the table, but this would interfere with the limit switches for the x-axis power feed.

Anyone any novel ideas for mounting this scale without losing y-axis travel ?

I have mine hung on a 2" x 2" aluminium angle off the left end of the table. It took some fiddling with jack screws to get the scale straight and true but it's been performing well enough for the past few years. However, I am considering removing it now that I have heard about the stick-on magnetic scale as used on some ML7 cross-slides. I'm going to investigate if I can adapt this to the 300mm travel of my x-axis.

Thread: Le Blond, 'Regal 10' lathe, circa 1942 and other machines - Help Needed
11/06/2019 19:24:35

Interesting chuck on that LeBlond. Seems to be a 3-jaw with both independent and scroll adjustment.

Thread: Viceroy lathe
08/06/2019 18:35:36

They did make a combination lathe apparently sold to the MOD a lot. There's an example documented here:

Combo machine

 

Edited By Pete Rimmer on 08/06/2019 18:36:05

Thread: Have you ever been here?
06/06/2019 18:08:40
Posted by not done it yet on 06/06/2019 05:23:51:

Fairly obvious? Too tired?

Mill does that as the VFD defaults in direction when the power is cut - simple solution is to set the vertical operation as default setting and the horizontal is easily spotted before trying to cut, if not changed over, as the cutter is running so much more slowly.

An even simpler solution is to swap any two of the three phase wires to the motor. Then the default direction will be the direction you require.

Thread: Motorcycle 'blipping'...
04/06/2019 05:55:10
Posted by not done it yet on 04/06/2019 05:40:28:

Some modern machines have automatic ‘blippers’ when changing gear. Just another bit of expensive electronic wizardry available to the serious bike riders. Matching engine revs to gear ratio can be important at high speed. Little different from ABS, traction control, etc on modern superbikes.

I never heard of this. I don't deny that there might be some kind of aftermarket 'blipper' but I never heard of it and know of no factory bike that has the feature nor would I find it desirable.

For fast up-changes you can get quick-shifters, those are quite common but they simply kill the ignition momentarily - usually around 30ms - and I'm sure you can get some which cause a backfire when the change is done because I've followed bikes that backfired on every change though the one I had on my landspeed bike for a while didn't cause it.

There is unit designed for disabled bikers that power-shifts up and down, I don't know if perhaps that has a blipper function for the down-shifts. It's a large ungainly solenoid that most people would not put on their bike if they didn't have to.

Thread: Nose Radius Question
03/06/2019 17:56:49

The tool in the first post looks like it has been ground on a blunt wheel. If you're not dressing your wheel regularly you're missing out on the best of it's capabilities.

Thread: help with gear calculations
02/06/2019 13:18:11
Posted by Nigel McBurney 1 on 02/06/2019 09:36:25:

After all the theory...

Comes the practice

Hobbing a 14dp pinion

Send me your address Philip and I'll post it on. You'll have to trim the length to suit.

Thread: What are you using for Lathe Way Oil?
02/06/2019 10:40:16

Way oil, if I'm not using coolant oil.

It might not seem cheap but it does go a very long way. I doubt if I get through a litre a year.

Thread: help with gear calculations
02/06/2019 08:57:17

Hobbing is the process of generating a tooth form by rolling a blank in time with a cutter having (normally) straight-sided teeth. The rolling action generates the involute profile, rather than the profile being ground into the cutter. The advantage is that only one cutter is required for a given tooth form. Disadvantage is the machine and hobs are expensive.

Here's a slow-motion video of a small gear hobber working:

Thread: How often do you oil your lathe ways?
02/06/2019 07:50:13
Posted by Neil Wyatt on 01/06/2019 22:54:38:

Do other folks slather on neat oil like I do?

I'm more likely to worry about it pooling up on the ways than them looking dry!

Yes my hobber oil pump leaks from the stuffing gland so I keep a roses tin under the pump. As it fills up I pour it into a jug which I keep on the lathe with a brush in it. The sump was full of dark sulphurised cutting oil when I got it and I marvelled at how good the ways were for a 70 yr old machine, so I figured I would continue the tradition.

Thread: help with gear calculations
01/06/2019 22:37:39

Sadly not. The profile-shifted gear must be hobbed, or else you must make a cutter to suit.

01/06/2019 17:55:26
Posted by Philip Sewell on 01/06/2019 16:44:44:

Peter I am now in Norfolk working for much of this month (I am based in Leicestershire) so haven't got the part with me. I did use a gauge block fitting in the root of a tooth to get a measurement across the gear (ie caliper measurement minus gauge block width) and off the top of my head I think it came to 3.7mm, so the root diameter is (I think) OD minus 7.4mm

Hope that makes some sense to you,

Philip.

It makes perfect sense because I fired up Gearotic and generated a 14DP gear, added in some profile shift to bring the OD up to your 32.64mm which gives us a root diameter of 25.04. Your measurements of 32.64-7.4 = 25.24 is only 8 thou different from that so I guess it's fair to say that your gear is in fact a standard 15 tooth 14DP pinion, generated according to the long-addendum info in Machinery's Handbook.

Edited By Pete Rimmer on 01/06/2019 18:00:37

Edited By Pete Rimmer on 01/06/2019 18:02:21

01/06/2019 09:28:25

Philip can you measure the distance across the bottom of the teeth i.e the root diameter? I realise you can't get the caliper jaws directly opposite with the odd tooth number but get it as close as you can.

31/05/2019 06:40:30
Posted by Andrew Johnston on 30/05/2019 22:31:12:
Posted by Philip Sewell on 30/05/2019 21:19:30:

To cut this gear can you confirm this is the involute cutter I need.

14DP number 7

In a word, yes. But I'm not sure it's that simple? Thanks to Pete for pointing out the need to increase the OD to alleviate the need for undercutting. What I don't understand is how you cut the gear. If one uses a standard involute cutter and cut to the standard tooth depth then the circular pitch will be wrong, and the arc thickness of the tooth and space will be different. Machinery's Handbook is somewhat vague on this matter. Is a special cutter needed or do we just cut deeper with a standard cutter? It would be great if Pete could enlighten us.

Andrew

I'm just an enthusiastic amateur so don't ever take my word as gospel, but I agree with Andrew. The long-addendum profile would be correctly generated if you were hobbing, but not if you are cutting with a single-tooth cutter since the shape is so far departed from the cutter's form. For a small pinion like that I'd grind a form tool from HSS and fly cut them I think, maybe gashing them out with a slitting saw first.

If I weren't so busy I'd have a go at hobbing a new pinion gear for you Philip.

30/05/2019 18:29:07

The numbers don't stack up because of the low tooth count of the pinion. It's normal to increase the diameter of low count gears to prevent undercut and make the tooth stronger. According to Machinery's handbook (30th edition, page 2162, table 8) a 14DP 15 tooth pinion should be increased by 0.07569" (or 76 thou). If you subtract that 76 thou from the measured diameter of the pinion in question the numbers work out very close indeed for 14DP (14.06 actually).

Thread: Hostaform, Nylon or Steel For Mini Mill Gear?
28/05/2019 19:51:35
Posted by Neil Wyatt on 28/05/2019 19:33:25:

Folks who wonder if nylon gears in mini-mill and mini-lathe headstock might be interested to know this is a feature shared with the Denford Synchro.

Neil

The original Denford gears were made form a material called Technyl A90, whatever that is, probably a nylon as the name suggests. I have made quite a few replacements from Delrin.

I found that the original gear was rather mis-shapen on my lathe and it used to bind after it was worked hard and the heat caused it to swell. The delrin replacement never suffered any of this.

28/05/2019 19:47:06
Posted by Neil Wyatt on 28/05/2019 19:33:25:

Folks who wonder if nylon gears in mini-mill and mini-lathe headstock might be interested to know this is a feature shared with the Denford Synchro.

Neil

The original Denford gears were made form a material called Technyl A90, whatever that is, probably a nylon as the name suggests. I have made quite a few replacements from Delrin.

Thread: What are these change gears for?
27/05/2019 23:51:27

I think it is probably Boxford too. Boxford and Denford both used 18DP change gears but the Denford ones were 20pa.

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