Chester DB10 thread cutting ???

[pa4c pa4cParticipant @pa4cpa4c85075]

Posted by Redsetter on 24/07/2018 20:04:24:

Ian,

I think you are taking an unacceptable risk.

This sort of stuff is just patronising in the extreme. You have absolutely no clue as to how experienced or competent or even incompetent the person is but you have a view.

You don't work for a teaching establishment by any chance?

Crossing the roads around here is unacceptable risk given the number of potholes.

[Ian Skeldon 2Participant @ianskeldon2]

Redsetter with all due respect, I know nothing about you and you know nothing about me or the item being made. The various ones available are all from home workshops. That is to say that they are made by people like me, they come with no test certificate or guarantee, they just work but they are about £100 or over.

I have made them previously (as stated) but with a different entry thread. In this case I want to make something that has already been done many times, the only reason this ones poses a problem is the forming of the correct thread, which is 1/2 bsp (as used on diving bottles).

Now I don't want to alarm you but I have previously worked with lots of different weapons and explosives, my work shop has a few machines in it capable of ripping limbs off should I use them without due caution, my welding equipment might start a workshop fire, some of my tools are sharp and pointy, so although I agree with your sentiment that care should always be exercised, maybe you should get to know what your talking about, before talking about it?

[Anonymous]

Posted by Ian Skeldon 2 on 24/07/2018 19:25:29:

…………….. it is confirmed as 1/2" bsp as already mentioned.

I'm confused, in t'other thread on this subject the thread was identified as 5/8" BSP. The numbers discussed for ODs and IDs certainly related to a 5/8" BSP thread. At least a female 1/2" BSP thread on a male 5/8" BSP thread will be one hell of a tight fit, and should be gas tight!

Andrew

[Ian Skeldon 2Participant @ianskeldon2]

Posted by JasonB on 24/07/2018 20:24:46:

Posted by Ian Skeldon 2 on 24/07/2018 19:25:29:

and many thanks to you all for the advice offered, thanks again to Andrew for a very kind offer and confirming that the Harrison 300 will cut both (true imperial) and very close metric threads.

If you do go shopping for an M300 just be aware that Andrew has one with an imperial lead screw and that is why he can cut true imperial threads. If you buy one with a metric lead screw it will cut true metric threads and close imperial much the same as your DB10.

Also make sure whatever you buy that the correct change wheels are included otherwise you won't be cutting many threads. They do have a habit of getting lost when machines change hands.

Thanks Jason, duely noted. To be honest I could do with a more capable lathe and a M300 seems to be a good compromise between cost, size and ability. Spindle bore is also a consideration as this has stopped a few projects in it's tracks.

[Ian Skeldon 2Participant @ianskeldon2]

Posted by Andrew Johnston on 24/07/2018 20:36:12:

Posted by Ian Skeldon 2 on 24/07/2018 19:25:29:

…………….. it is confirmed as 1/2" bsp as already mentioned.

I'm confused, in t'other thread on this subject the thread was identified as 5/8" BSP. The numbers discussed for ODs and IDs certainly related to a 5/8" BSP thread. At least a female 1/2" BSP thread on a male 5/8" BSP thread will be one hell of a tight fit, and should be gas tight!

Andrew

haha what a cock up, your right it is 5/8"bsp, I just copied 1/2 bsp through in replying to redsetter, love the humour Andrew.

[Ian Skeldon 2Participant @ianskeldon2]

Posted by Martin Connelly on 24/07/2018 14:57:38:

Ian the change gears you have do not have any odd values that could get a closer approximation than the 14.1TPI already suggested. The question already posted is can you fit a 127 tooth gear in position a. If so this would give accurate TPI values for future use and would be an option worth considering.

Martin C

Hi Martin,

It might fit, if it were available but it would be very tight. In fact just checked and my 120 tooth gear looks like it could be a 126 tooth gear with poor stamping of the numbers !

[JasonBModerator @jasonb]

When shopping around you may find a similar size industrial machine that came with a 127T gear which would give a true conversion. Possible a Colchester Bantum or Student.

[Ian Skeldon 2Participant @ianskeldon2]

Thanks Jason,

Must admit I have been busy measuring diameters (ID and OD) just to see if there is a wheel from something else that would fit on my lathe.

For some reason my lathe didn't come with a 127 tooth wheel, although it's a cracking lathe and cuts very true I think it's days in my workshop are now numbered.

[JasonBModerator @jasonb]

As I said earlier the change wheels don't take a lot of load so a 3D printed gear would work on your machine and would be cheaper than a metal one. If you got a 127T printed and used the second 70T gear from your supplied set and used position 1 on the gearbox you would be spot on 14tpi as 127/70 = 1.8142857.

May well be cheaper than a new lathe.

The only thing to watch is as pointed out above by Martin is whether the 127/70 combination would fit but that is easily enough tested with a paper disc to represent the 127T gear. If they don't fit all is not lost as the 127 does not mesh with the gear sabove you could print both the 127 and 70 in a smaller MOD size to bring the PCD down

Edited By JasonB on 25/07/2018 19:14:00

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 25/07/2018 19:10:23:

[ … ] If they don't fit all is not lost as the 127 does not mesh with the gear sabove you could print both the 127 and 70 in a smaller MOD size to bring the PCD down

.

Ian,

I'm not sure if you saw the 'Martin Cleeve' photo that I posted on page_2

… As Jason has explained, the principle is good.

MichaelG.

[Ian Skeldon 2Participant @ianskeldon2]

Hi Jason, Hi Michael,

Yes I have downloaded the chart for gear ratios and that will be very useful ( Thank you Martin ). Well for now I have decided that the lathe stays as it is good in all other respects.

I do have a 3d printer and could give printing a gear a good go, as mentioned by Jason I could possibly reduce the od slightly and still acheive good meshing.

I have also decided to buy a set of 5/8 bsp taps from tracy tools to do the immediate job in hand.

Finally I have to say that I am extremely impressed at the fantastic help offered from forum members and hope that I will be in a position to help others out at some point.

[Ian Skeldon 2Participant @ianskeldon2]

This is the back end of my DB10,

[Ian Skeldon 2Participant @ianskeldon2]

Am I right in thinking that if I put the 126 tooth wheel on 'A' and the 70 tooth wheel on 'B' I can cut a thread with 1.8 pitch, which is very close to the 1.82 required?

If not, I have got something wrong in my understanding of the ratios and this is also quite likely !

[Les Jones 1Participant @lesjones1]

Hi Ian,
You are correct with what you say but the gerbox must also be in position 1. The 1.8mm pitch will give a TPI value of 25.4/1.8 = 14.11 TPI A 127 tooth gear in place of the 126 tooth gear will give a pitch of 127/70 = 1.814285714285714. This converts to 25.4/1.814285714285714 = 14 TPI. The 126 tooth gear will only give the same result as as the method I suggested in my post at 08:52 on 23/7/18 (gearbox set to 9 ans a 120 tooth in position A driving a 40 tooth in position B.) Just out of interest I worked out all the gearbox ratios

1 1 : 1
2 1 : 0.924
3 1 : 0.858
4 1 : 0.80
5 1 : 0.75
6 1 : 0.706
7 1 : 0.667
8 1 : 0.632
9 1 : 0.60

These values were calculated using the table from Martin's post at 17:00 on 23/7/18.

I could not work out anything closer using any of these ratios.

Les.

Edited By Les Jones 1 on 25/07/2018 22:51:47

[Martin ConnellyParticipant @martinconnelly55370]

I can't imagine the lathe would be supplied with a 126 tooth gear but not a 127 tooth gear and since the tables mounted on the lathe refer to a 120 tooth gear I think that must be what you have. Count the teeth on your largest gear and make sure it is clearly marked with the correct count.

Martin C

[Ian Skeldon 2Participant @ianskeldon2]

Les and Martin thank you, I will count the teeth on that gear and let you know the outcome but now cleaned up, it is definitely stamped 126, strange I agree, but with chinese machinery, who knows ?

[Ian Skeldon 2Participant @ianskeldon2]

Well teeth counted, 120 as first thought, I have ground the six down and I think it has been stamped twice, once with a 6 and then again with a 0 ?

I will try the 120 to 40 gearing a go. Thanks again.

Ian

[Howard LewisParticipant @howardlewis46836]

Is it possible to buy (probably secondhand) a 127T gear for another machine (Myford or a Boxford will be DP, more recent Far eastern Machines will be metric Module gears) and modify to fit into your machine?

It may need boring out, or bushing, to fit the spindles on your machine.

As a last resort, could someone make one for you? Assumes that there is room to fit it in. Possibly the exact position may not matter, unless used as an idler.

You would then be able to cut a variety of Imperial thread pitches, with greater precision, should you wish so to do, in the future. (Probably with some head scratching and trial and error before cutting the final thread)

Howard

[Ian Skeldon 2Participant @ianskeldon2]

Hi Howard,

your point is very valid, I could buy a metal 127 tooth wheel of ebay (is it ok to mention it by name?), if the exact spindle bore size is not available I would prefer one that is smaller and then bore it out and add a key way, I don't fancy making a bush of maybe 1/32" or whatever but could do so if really needed.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian Skeldon 2 on 28/07/2018 17:44:15:

… I could buy a metal 127 tooth wheel of ebay …

.

Ian,

With apologies if I have missed it … Have you checked what diameter [and width] of '127' would fit in the space available?

I have a large steel '127' which I was keeping for one of those infamous future projects … but if it's a suitable size, perhaps we could agree a price.

MichaelG.

[Les Jones 1Participant @lesjones1]

The Chester DB-10G lathe I have uses modulus 1.0 gears with a 5/8" bore (Correction the bore is not 5/8" it is 16mm.) I think it is likely that the DB10 uses the same gears. If this is the case then the outside diameter of the gears = (number of teeth + 2) * 1mm. This would mean thet a 127 toothe gear had an outside diameter of 129mm. Arceurotrade sell a 63 tooth gear for the mini-lathe which is modulus 1.0 and has a 12mm bore. Ibougt one of these and bored it out to 5/8" and this give me some more screwcutting options. Chester normally have a box of assorded gears for sale at the shows. I have bought a number of different gears to give even more options. They all neaded boring out or bushing but it was worth the effort. Using the 63 tooth gear and a 25 tooth gear bought from the assorted gear box I can cut a near perfect 14 TPI thread which is actually 13.999 TPI.

Les.

Edited By JasonB on 03/08/2018 13:21:53

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Les Jones 1 on 28/07/2018 20:05:33:

The Chester DB-10G lathe I have uses modulus 1.0 gears with a 5/8" bore. I think it is likely that the DB10 uses the same gears. If this is the case then the outside diameter of the gears = (number of teeth + 2) * 1mm. This would mean thet a 127 toothe gear had an outside diameter of 129mm.

.

Thanks, Les … If that's the case, my steel 127 is much too big for Ian's DB10

MichaelG.

[not done it yetParticipant @notdoneityet]

Posted by Les Jones 1 on 28/07/2018 20:05:33:

The Chester DB-10G lathe I have uses modulus 1.0 gears with a 5/8" bore…

That is a right mixture. Metric gears with an imperial bore?

[Ian Skeldon 2Participant @ianskeldon2]

Posted by Michael Gilligan on 28/07/2018 18:50:59:

Posted by Ian Skeldon 2 on 28/07/2018 17:44:15:

… I could buy a metal 127 tooth wheel of ebay …

.

Ian,

With apologies if I have missed it … Have you checked what diameter [and width] of '127' would fit in the space available?

I have a large steel '127' which I was keeping for one of those infamous future projects … but if it's a suitable size, perhaps we could agree a price.

MichaelG.

Hi Michael,

The 120 tooth gear that came supplied does fit, but only just, it's a fiddle to get it on. Having said that, I think I have got it wrong. I have cut a test thread (external) and am getting about 22 tpi. I have uploaded a photo showing the new gearing. Red gears unchanged, other gears shown and numbered, any ideas what have I got wrong?

Thanks,

Ian

[Ian Skeldon 2Participant @ianskeldon2]

Managed to spot the mistake, I need the gearbox selector in position 9, not 1, doh…..

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