3. The formula below will give you the single depth for undertaking unified threads:

d = P x 0.750

Where d = Single Depth

P = Pitch

n = Number of threads per inch (TPI)

Infeed Depth = .75 / n

THREAD CALCULATIONS

To cut a correct thread on the lathe, it is necessary first to make calculations so that the thread will have proper dimensions. The following diagrams and formulas will be helpful when calculating thread dimensions.

Example: Calculate the pitch, depth, minor diameter, and width of flat for a ¾-10 NC thread.

P = 1 / n = 1 / 10 = 0.100 in.

Depth = .7500 x Pitch = .7500 x .100 = .0750 in.

Minor Diameter = Major Diameter – (D + D) = .750 – (.075 + .075) = 0.600 in.

Width of Flat = P / 8 = (1 / 8) x (1/10) = .0125 in.

Edited By XD 351 on 19/05/2019 14:35:08

Mew #279 - page 55 , photo 119 milling for beginners shows a boring head being used to machine a concave radius in a piece of alloy , you could use the same principle .

A more difficult thing is indexing the now formed radius to the slots and tapped holes then forming the 77mm radius on the outside of the spigot . I’m sure there will be others along soon with a few more suggestions so be patient !.

Ian.

Congratulations Mike !

Hi Ketan,

Yes i know Derek was asking about the collet blocks, i was unaware that the Stevensons blocks were specified as being un matched , i was thinking they would be as per a 123 block set is a matched set.

If Ausee is a seller that sells items from ARC it is only to my advantage ! I am now immensely less irritated now I know they were never meant to be a matched set.

6ian,

Edited By XD 351 on 12/05/2019 12:42:33

You don’t want to know how i sorted a bent rod !

If Ausee has a link to ARC as they say they do then Ketan needs to take a look at some of the stuff they sell ! I got a set of Stevensons blocks from them that were ground with one face at a different height to the other block.,mine are metric and I don’t think the original Stevensons blocks were metric .

Ian.

Also used for threading blind holes like threaded end caps etc .

Do you have a relative who has a credit card ? Maybe get them to buy it and reimburse them for the cost ?

I have a few collet blocks all from China and haven’t had a problem with them , more often than not the collet itself is the problem .

I could be wrong but wouldn’t the Arc units made in China anyway ?

I used to fit and ream the pin bushes on victa engines and used an old piston as a guide for the reamer to help keep it square , i used to have a piece of plate that fitted over the cylinder mounting studs and it had a slot cut for the conrod so i could sit the piston skirt on it and and line the whole lot up and slide the expanding reamer in .

Maybe an open style boat/ launch of some sort ?

I had the same lathe ! I recently sold it to my nephew along with my X2 mill so his young bloke can play on it and over the fifteen years i owned it i replaced the motor caps , half nuts , fitted a nvr switch and maybe two belts - not bad for a little Chinese machine that copped some serious punishment !

wow it probably would have been cheaper for them to just send a new motor to you but to spend another four hours going over your lathe is exceptional service ! I have been buying tools from them for 35 yrs and haven’t had to return anything yet !

Last time i was in Conjola was about two years ago and at Christmas time - it was packed out ! I used to have a van at Ulladulla and dropped in to conjola every so often - usually looking for bait . Fantastic part of the Nsw south coast !

Ian

I can attest that CI dust or chips are abrasive as hell ! I used to work for a company that made industrial roller shutters and inside these are cast iron cores that have to be turned to size and the centre drilled out for the axle , we had an old Cincinnati lathe that was only used for this pretty much every day and for about fifteen years . The ways were so flogged out on the section near the chuck and a section about a 6 inches long back towards the tailstock that if i layed the edge of a 12 inch rule along the way i could slide another rule laying flat in the gap ! This wear area coincided exactly with the carriage movement and on the other end of carriage the ways showed little wear over the same distance of travel . Before that job i used to operate a lathe that was being used as a linishing machine and even though it had been used like this for over twenty years it didn’t have a tenth of the wear of the Cincinnati ! I started using a mask when using the linisher as the dust would really rip into my throat and I carried this over to the next job machining cast iron , we had a guy who spray painted the rollers or drum for the roller shutters - no respirator , no eye protection and the boss was happy with this as long as the overspray didn’t get on his car !

I like to think that Model Engineering is supposed to be enjoyable not life threatening ! PPE is cheap compared to the consequences of not wearing it ! Last night i was watching some YouTube - A channel called two stroke stuffing where the host is modifying two stroke engines and in one video he is explaining how he does some modifications to the cylinder head , His lathe consisted of a power drill clamped in a vise and to mount the head to the drill he simply screwed the spark plug into the head and stuck the ceramic insulator in the drill chuck . I thought this was dangerous enough but when he turned the drill on and started hacking into the combustion chamber with a carbide burr in a die grinder i started to grimace ! Then i noticed he wasn’t wearing any eye protection and you could clearly see the shards of aluminium flying all over the place ! The only thing standing between him and blindness was luck !

Ian.

Hi Jim,

I think a lot of people think that they need this type of lathe or that to fit in or that it will make them a better machinist , unfortunately neither are true ! Sure if someone offers you a boxford or myford etc that you know is in good condition you would be silly to say no wouldn’t you ? I have had three Hare and forbes lathes and two mills - none have given me any real problems and at worst maybe a blown motor capacitor or broken switch .

Added my subs to your channel , looks like some interesting engines on there !

Where in OZ are you ? After seeing the videos on lake conjola i would guess NSW ? Im in Sydney .

Ian

I jam the nozzle of my shop vac up on the cutting tool and it sucks 90% of the cast iron chips and dust away before it can make a mess , i cover the lathe bed with nappa leather held in place with magnets ( i put these in little plastic ziplock bags to make cleaning them easier ) . I also remove any oil off the slide ways so it doesn’t trap any dust and turn it into grinding paste !

I wear a mask , they are cheap insurance against respiratory issues .

Try model engineering supply stores possibly under Model Engineer (M.E) tap set , pretty sure 32 and 40 tpi are M.E pitches or possibly UNEF .

Maybe Stub mandrel will let you post a video on his youtube channel so we can hear what it sounds like 🎶.

And here i was thinking there was something wrong with my keyway broaches 😁

Doesn’t sound like a bearing problem to me because when you change over to a collet chuck the problem goes away , if it were the bearings it would remain the same .

You could have a crook chuck - i would strip it down and have a look at it .

one thing you can check before pulling it apart is the contact pattern of the jaws , take the shank of drill bit (one with no damage on the shank  or a piece of silver steel ( drill rod ) and colour the shank in with a texta or sharpie for a length a little longer than the gripping surface of the chuck jaws then hold this shank very lightly in the chuck so you can grab the shank with pliers and and turn it so it slips in the jaws this will show if the jaw faces are parallel or bell mouthed . If they are you can re grind them but on a cheap chuck it is not worth the hassle .

Other things to check are how well the jaws fit in the chuck body slots - they should be smooth with no play or wobble - if there is some serious play try switching jaws around and see if you can improve it . The scroll should be a nice fit in the body and have no radial play and minimal end float ) if you put the scroll in the body and it floats around all over the place especially on the spigot it rotates on look at getting another chuck .

Check the register surfaces on the spindle and the rear surface of the chuck to ensure there are no burrs or high spots that could be stopping the chuck from seating properly - a very light rub with an oil stone will show up any high spots , don’t go mad with the stone you only want to show up high spots not remove any metal .

I get mine from my local bearing supplier .

Edited By XD 351 on 18/04/2019 09:44:19

I think Keith appleton did a few videos on silver soldering on his youtube channel as did myfordboy - might be worth your while to have a look . I find it easier ( most of the time ) to show how to do something rather than explain it in writing . There tip sheet from Cup alloys somewhere on this forum that i found useful .