Member postings for JohnF

Hi Chris,

Sorry my error it should have been screwcutting simplified -- look at this link

**LINK**

Your gearbox is the standard Myford Quick Change box or a Norton box in engineering parley

Regards John

Dear Chris,

I have just read your thread on the ML7 and most of what has been said there applies to your S7 however personally I would not bother converting. But if you do I think the DRO is the way to go and there are plenty people who have done this and very successfully.

I've been cutting metal for over 50 years now and everything I own is imperial and the "on board" computer was programmed in imperial, it even has to do a quick computation of anything metric to give a meaningful value. I realise the younger generation will be all metric and wonder what inches are but for me I will stick to that which I understand. If I get a metric drawing a few moments on the calculator and I have all the dimensions in imperial--Oh joy

Regarding screw cutting, I think you said you have a QC gearbox on the S7 ? If so to cut metric you will need to buy the kit from Myford which consists of a new quadrant and some additional change wheels ---will have to look at mine to see which ones. This will allow you to cut a range of metric pitches just by changing the levers on your QC box but you will have to leave the clasp nut engaged for the duration of the operation and reverse the lathe back to the start point after each cut.

There are several cleaver devices that have been designed to overcome this if you want to cut a lot of metric it will be worth considering building one. look at "screw cutting made easy" on this site.

I also have an Emco Maximat and the conversion for metric threads is much easier on this machine so if I REALLY have to cut metric this where I do it now.

Wishing you success in your endeavours whatever you decide to do.

Regards John

PS where are you located? I am in Lancashire

Hi Brett, Have a look at this link to see if it is the type of mount you are thinking of

**LINK**

If it is then the answer is yes! we have both a Brigeport mill and a Smart & Brown 1026 lathe on these without any problem

John

Have a look at this link -- intersting choice of material

**LINK**

Jon, Just to clarify hammer forging of Damascus tubes bears no relationship to todays hammer forging of barrels, the process was devised in Germany after WW1 to get around the surender treaty that prevented Germany from having any rifling machines which was supposed to prevent them manufacturing arms.

Damascus barrel forging is done by winding a flat strip of material around a former and welding it together in a forge to make a rough barrel blank. This would then be spill bored or reamed, chambered, honed and profiled on the outside to make a finished barrel.

Hammer forging today [for say a shotgun tube] starts with a blank which is approximatly 15" long with drilled hole about 3/4" dia, this is then inserted into the hammer forging machine with a male former of exactly the internal barrel and chamber dimensions, the machine has a series of opposing hydraulic hammers and when the finished tube emerge's it is 30" long with a bore of 0.728"//18.5mm for [12g] Process time approx 3/4 mins. The exterior has spiral pattern which is then ground off and polished. Some rifle makers don't remove the spiral pattern and it does look quite decorative.

Many rifle barrels and some shotgun barrels are made today by hammer forging, this is a procees where a male pattern is used and the barrel blank is drilled, the former inserted and then fed into a hammer forging machine thus swaged by the hammers over the former and a finished barrel produced which in the case of a rifle has the rifleing and chamber completed. The machines are of massive proportions and the barrels produced are excellent quality. The process is also quite fast and thus efficient for production.

Not used for naval or artillery barrels or course.

The older methods were and are still used, i.e. deep hole drilling, draw reaming, honeing and either button or cut rifleing.

Nothing beats the human eye for straightening barrels and the method is still used today--no machine has been developed to facilitate the "viewing" of barrels.

Hi in that case I would definatly go for a metric machine with a norton box --quick change screw cutting gearbox.

John

Hi Needleworks, As far as capacity goes I agree with NJH buy the most capacity you think you will need and can afford to buy.

As Wolfie says there are bargains to be had but I would alway go and look at the machine before purchasing--things always look better in the photos than they turn out to be -- buyer beware !!

Screwcutting --- if you are going to predominantly cut metric threads then it may be wise to buy a metric machine. You can cut metric on an imperial machine and vice versa but there are certain difficulties within the process. The main one being that you must [generally] leave the leadscrew engaged for the duration of the machining, [there are of course several devices that will overcome this] Regarding Myford you can purchase a kit to make an imperial M/C cut a selection of metric pitches with the use of change wheels when the machine is fitted with a gearbox or if no gearbox you need a 63 tooth wheel to use with the rest of the change wheels to enable you to cut metric and you have to set up each thread pitch as and when requiered.

hope this helps---John

Hi Clive, Both Clive H and Mike beat me and yes it is comon practice in the UK gun trade to use a smoke lamp for fitting and possibly may be more accurate than engineers blue.

The usual type of lamp uses pariffin oil and I have used a kelly lamp for years for this because it is useful to be able to raise and lower the flame.

Whether its possible to use smoke depends on what you want to fit, e.g. fitting a bearing in say a lathe headstock would be difficult because you need to hold the bearing above the flame to deposit the soot but the method is ideal for smaller work.

As for supplies nearer to "home" try India, I feel sure that it will be used there and remember not everyone uses blue, in continental europe much of the product is orange!

Good luck in your quest. John

Hi Clive, If you need the lap adjustable make a lead lap, I have made many of these to lap barrels. I knurl a BMS rod then drill and taper ream for a taper pin, split this section of the BMS rod and deburr the inside for the taper pin then cast an oversize section of lead over the knurled section. I made a split alluminium mould for this.

lastly turn to the diameter requiered and "load" with lapping paste by rolling the lap on a glass plate. It can of course be expanded by tapping in the taper pin. Oh and don't forget to put some oil in the bore and wash well when fininshed. For an extra fine finish use pumis mixed with oil but I have not used this on bronze.

Good luck John.

Andy I believe Lancaster university has a good reputation for engineering, not too suprising with all the engineering industry in the NW.

Good luck with your studies --- engineers are what we need for the future

Not quite sure what you mean by the edge? do you mean around the outward face of the wheel or on say a 45 deg chamfer on the edge of the wheel.

A sketch might be useful to explain and what diameter, I'm guessing 2 in or so ?

Hi Peter, I don't know what other equipment you have but probably a lathe so why not make a nut from scratch and screw cut it to suit. Check your lead screw for wear first -- not 100% method but is the backlash the same at the two extreem's of travel as it is in the centre? If so then the wear is in the nut, if a little different then the screw is worn as well and it may be best to replace both.

I used to recondition small lathes many years ago and made many of these, it is a little more difficult if it is an acme thread because you need an acurate tool ground to suit but Tracy tools do some acme taps --never used one but its worth a look and if available in your size you could screw cut to near size then finish with the tap.

Best of luck. John

Parallel shank ER holders are available at : -

http://www.glostertooling.co.uk/Download/Engineers%20tool%20catalogue.pdf

Never had this scenario but in general cast iron is easy to file but there is likely to be some crud left in the hole from the casting core so I would start with an old file. Don't assume that there is a skin--might be but there again maybe not.

I agree with Martin diamond files will cut almost anything but they are slow to use, one other type of "file" you may hav seen at the ME exhibitions is the ones with carbide bonded onto a piece of sheet metal and they are considerably courser than diamond files--can't recall the trade name though.

Cheers John

Hi Hansrudolf, I beg to differ regarding it being hard, I have machined this material many times--it is tough not hard, the chrome is there to prevent rusting and is fairly easy to cut through. Even light corrosion would quickly destroy the seals in a hydraulic cylinder. A ram does not need to be hard it needs resistance to bending but most of the stress in service is either is either compression or tensile.

Maybe your bars that you found to be hard were for some other special purpose?

Charlie, try a spark test on your grinder this will give an indication of the type of material--high / low carbon etc.

Regards John

Depends on your budget but I would go for quality every time, Wohlhaupter & Kaiser are I believe two the best you can get and they do turn up on Ebay now and then, you might like to have the UPA1 which is more difficult to find--about 2" O/D the UPA2 is more popular and about 4" O/D

I have no experience eof the other brands mentioned but I do used other Arrand tooling and find it excellent. Only other one I used was an OMT and it was a nightmare -- a real guessing game as to how much cut you had put on !!! That's me 5p anyway.

John

My guess is it is hydraulic ram material which is chrome plated on the outside.

John

Hi Colin, not the easiest thing to do if you are inexpearienced but a few pointers are as follows:-

Brass is fairly easy and if you machine it it will cut with fine swarf that is in small pieces

Gunmetal, look at the bar it usually has a slightly speckled appearance -- not definative only a guide, it is generally softer than brass and adifferent colour

Bronze is a coppery colour but much harder than copper

Ally bronze, almost identical in colour to Admiralty brass -- nice yellow colour but it is much harder to machine and the swarf comse off in spiral or contiuous string [assuming you are not using a chip breaker] The outside of the bar willl probably not show the oxidation associated with brass.

Beware of Aluminium bronze it generally does not make good bearings but it is highly corrosion resistant.

Hope this helps a little

John

Hi Falco, For external threads you should use the nominal diameter i.e. 4; 6; 8 mm etc but I agree starting the die can be a little difficult.

You should always put a chamfer on the end of the bar to the depth of the thread and when starting in the lathe there are several things you can do. I usually start the thread by using the tailstock but lock it on the bed and apply a gentle pressure as you start the thread, you have to make the die "bite" into the work and it will not do this unless you apply some pressure to feed it in. It is a matter of "feel" when doing this.

Another approach is to put a taper on the work or reduce the diameter for a short length [as you have already found out] then remove this when finished.

On large threads it is helpful to truncate the thread diameter by a small ammount, as a guide use 1.5 percent of the diameter per 0.100" e.g. a half inch thread reduce by 0.0075" This is not definative but it works well, to be correct you would need to consult the relevant BS tables but for ME work it is OK. Not necessary when screwcutting them for metric threads but you do need to truncate imperial and unified threads unless you are useing a full form cutter. [sorry digressed a little there]

HSS vs CARBON, generally HSS will be a better quality and the best are ground thread dies & taps but they are considerably more expensive. Carbon will cover most of you needs but I usually byt HSS ground thread to H6 tolerance.

Hope this helps a little.

Regards John