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Member postings for Howard Lewis

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

Thread: What to do with old reamers
17/04/2021 12:51:45

If the machine reamers are beyond hope, they (or part of them )may still have a use. This assumes that the Taper is in good condition.

If the shank is soft enough to allow the Morse Taper to be sawn, or parted off, the MT could be held in the Mandrel taper, possibly with suitable sleeves, and turned to provide a centre, or or as an arbor onto which other items could be fixed, or tapped and used as an arbor for work holding. if needed.

An extra centre can be useful for centering work in a 4 jaw chuck, using the "Two Centres" method, or on a Mill, or a Rotary table or Dividing Head.

Howard.

Thread: Lathe recommedation
17/04/2021 12:34:21

Thinking in terms of a mini lathe, anyone wanting to make just small parts can cut threads using Taps and Dies, unless they want something that is a "Special".

Taps and Dies for non standard threads can be obtained. Tracy Tools carry a wide range.

If you think that the larger sizes are going to overload the motor, make a Mandrel Handle and use that to rotate the chuck by hand.

Also extremely useful when working up to a shoulder, or in a blind hole, to avoid spoiled work or broken taps..

In which case the changewheels will more likely be used to provide different feed rates.

The finest feed will be ,obtained, using 20: 80/20 :80.

With a 1.5 mm Leadscrew this will give a feed of 0.09375 mm / rev.

With a 16 tpi Leadsrew this will give a feed of 0.00391" per rev.

Howard

Thread: RR Merlin Scale Models
17/04/2021 12:20:48

Try asking the Rolls-Royce Heritage Trust. They may know its whereabouts..

Howard,

Thread: Looking for a block of cast iron please
17/04/2021 12:16:52

Steel would be better than cast iron; cleaner to machine as well.

Look up Dr_ MJN's thread on how he cracked the cast iron rear toolpost. that he made for his lathe.!

It has had to be reinforced with a steel plate.

When you tighten the clamp screws for the tool, the cast iron is subjected to tension. Cast iron is strong in compression, but not in tension, so it cracks.

Howard

Thread: Hello everyone.
17/04/2021 12:01:46

Welcome!

We are pleased to have join the Forum.

Howard

Thread: Two Myfords
16/04/2021 18:14:21

How deep is the rust?

If parts are badly pitted, you are looking at a bed regrind..

If the rust has stopped as surface rust, wire wool and possibly some mild chemical action, such one of the rust products incorporating phosphoric acid might suffice.

You are not looking at a mirror finish. The actual area of the surface left after removing the obvious rust will be far far far greater than that lost to pitting. You could even argue that the pits constitute a reservoir for oil.

It may not look pretty, but will work very much as intended.

What is much more important is wear.

A pitted unworn surface is far better than a shiny worn one.

Howard

Thread: Milling around with bits
16/04/2021 18:03:24

Climb milling will give improved surface finish, ON A MACHINE DESIGNED FOR SUCH WORK, with backlash prevention devices.

Hobby machines are NOT!

You are likely to have the cutter grab and pull the work into it with the risk of damage to both.

The work should travel so that the motion opposes that of the cutter tooth.

Howard.

16/04/2021 17:58:01

What speeds and feed rates are you using?

It is assumed that the work is rigidly clamped, and that your machine has minimal backlash on all axes, with the unused ones being clamped.

Similarly, cutters should be clamped as firmly as possible with minimal overhang.

Feed rates should be based on cutter speed, number of flutes and feed per tooth.

CUTTING SPEEDS

With HSS cutters, taken from my Apprentice Training Notes; think in terms of:

For soft Brass Roughing, 200 - 300 fpm Finishing 600 - 700 fpm

For hard Brass Roughing 150 - 200 fpm Finishing 200 - 300 fpm

Aluminium Roughing 400 -500 fpm Finishing 600 - 700 fpm

FEED per TOOTH Face Mill Slot Drlll End Milll Slitting Saw

Free Cutting Brass 0.022" 0.013" 0.011 0.005"

Hard Brass 0.009" 0.008" 0.005" 0.002"

Aluminium 0.022" 0.013" 0.011" 0.005"

HTH

Howard

Thread: Myford Backplate tapered thread size
16/04/2021 17:28:31

It looks like a ML3 or 4.

A Ml1 or 2 would have a centre height of m3.125" where the 3 and 4 are 3.5"

The ML3 is 15" centre distance, where the 4 is 24" (Confirm with Lathes UK website )

Yours appears to have the optional Tumbler Reverse and the side hinged cover for the Changewheels.

The Leadscrew is 8 tpi, but the Leadscrews for the Cross and Topslide are 12 tpi. The dials for these have 80 divisions, which means that each division is not 0.001" but 0.00104"

Chagewheels are driven by driving collars (secured to the Mandrel and Leadscrew by 1/4 BSF grub or capscrews.

(Virtrually all threads, except possibly the gib adjusters, will be BSW or BSF )

To transfer the drive between the collars and gears, or to compound gears, there is a 3/32" pin in a blind hole in each part.

If you are short of Changewjheels, those from the 7 Series will fit. Dimensionally they are the same, but have a keyway instead of the 3/32 hole.

So you will need to drill through one original gear to use as a template. Fit both gears onto one of the changewheel studs, and drill though into the 7 Series gear, keeping away from the keyway..

With additional gears, you can set up a fine feed, 20:60/20:65/20:60. This will give a fine feed for turning of 0.0000427" / rev. You may need to fettle the inside of the Mandrel end of the Banjo to enable the first stud to move far enough to set the correct mesh for the gears.

My advice is to set the mesh, starting from the Leadscxrew, and working your way to the Mandrel. Just run a piece of paper about 0.003" thick between the gears.

HTH

Howard

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
15/04/2021 16:54:17

If you are using a 48T on the Mandrel, for a 5 tpi, you need a 40T on the Leadscrew, surely?

Unless driving a 30T on the Leadscrew with a 36T on the Mandrel with the 120T as an Idler, in both cases.

For a 8 tpi two start thread, you will need to set up for 4 tpi, and cut a second thread 180 degrees away.

This will mean driving the 6 tpi Leadscrew at 1.5 times the speed of the Mandrel, so a 72T on the mandrel would be needed to drive the 48T on the Leadscrew.

Or a set up giving the same step up ratio. ( 45 : 120: 30 ? 48 : 120 : 32 ? 36 : 120 : 24?  or whatever gears that you have that give the 1.5 :1 step up.

Howard,

Thread: Myford Backplate tapered thread size
15/04/2021 16:21:15

Any chance of pics?

Are you certain that it is a Myford? Is the name cast into the bed anywhere?

If the thread is 1.125 x 12 tpi with a 1.250 register the Mandrel sounds like a Myford 7 Series.

The 7 Series has mounting foot under both Headstock and Tail;stock

The last Myford ML 3 and 4 had a 1.125 thread (See lathes UK ) But they were cantilever beds, with no mounting under the Tailstock.

Howard

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
15/04/2021 15:59:23

Presumably what Old Mart is intending to say is that the important thing is to have the correct ratio between the Leadscrew and the Mandrel.

If the Leadscrew pitch is changed, the ratio must be as well, so that the distance that the Leadscrew moves the tool relative to each revolution of the Mandrel remains the same..

Using the same ratio with a 8 tpi Leadscrew will not produce the same thread pitch with a 1.5 mm pitch one.

Howard

Thread: Advice on Choosing A Mini Lathe
15/04/2021 15:39:58

Above all, do remember that you are buying a hobby machine, built down to a price.

A £600 machine will do the job, but not to the same level of precision, durability, reliability, or "Quality feel" as a Toolroom lathe of the same size, costing 30 or 40 times as much.

Before the flak starts flying; I have one!

Howard

Thread: Drunken pulley
15/04/2021 15:32:18

If there is enough metal outside the present bore, I would make a bush, turning the OD and the bore without disturbing the work inn the chuck. In this way, OD and bore will be concentric.

Choose the OD to keep a sensible wall thickness for both e bush and the boss of the pulley.

Bush length should be same as that of the boss of the pulley.

Measure the OD that you have produced.

Now e get into the Catch 22 land if the pulley is part of the drive to the lathe!

The pulley needs to set in the chuck, or under a milling machine so that the rim of the pulley is square to the required axis. Bore the pulley.

If you are going to Loctite the bush into the pulley, bore it no more than 0.003" (0.075 mm) larger than the OD of the bush.

If the intent is to make the bush an interference fit in the pulley, bore the pulley to 0.0005" SMALLER than the OD of the bush.

If the pulley is alloy, don't overdo the interference, for fear of cracking the pulley!

The bush goes into the freezer overnight. Before taking the bush out of the freezer, put the pulley into a pan of water and boil it for at least 10 minutes.

You may want to make up a simple puller, as a "Just in case". A length of studding (M8? ) and two large washers and nuts.

Then remove the bush from the freezer, and then the pulley from the hot water and press the two together. If you are lucky, the bush will just slide into the pulley. If there is any resistance quickly thread the studding through the bush and pulley, Have spanners to hand. (Fit one washer and nut to studding, in readiness first! ) then fit the second washer and tighten the nuts to pull the bush into the pulley.

If the pulley bis locked to the shaft with a grubscrew, you will need to use the existing tapping as a guide to drill and tap the bush.

Hopefully, by now you will have a pulley that runs true, and is ready to refit.

Howard

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
14/04/2021 14:38:42

Have you got wheels that will allow you to achieve a 1.2:1 ratio simply?

If not you will have look at using a compound gear as an idler, to get the 1.2:1. ratio.

Howard

Thread: Anodising and Passivating
14/04/2021 12:30:15

The danger with any electrolytic treatment of highly stressed steel components is Hydrogen embrittlement.

Thus Galvanising entails dipping the ferrous components into a bath of molten Zinc, (Tapped holes, or studs can be protected by filling/wrapping them with masking tape. To my surprise, this is what Lotus did with their chassis ).

Sherardising entails tumbling the parts with metallic Zinc, whilst in a heated enclosure.

In this way, no electrolysis is involved.

Aluminium can be anodised by electrolysis in a bath of Chromic acid (As the name suggests, the component is the Anode )

I am not advocating this, but Aluminium, or steel, can be passivated by dipping into a bath of concentrated Nitric acid. Nitric acid is such a powerful oxidising agent that it produces a protective oxide film on the surface.

Concentrated Nitric acid is dangerous!

Howard

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
14/04/2021 12:17:07

Unless I have misunderstood, the objective is to cut a 5 tpi thread on a machine with a 6 tpi Leadscrew., and then to cut a second one, 180 degrees out of phase, to produce a double start 10 tip thread..

If so, the ratio between Mandrel and Leadscrew needs to be 1.2 :1 so that the Leadscrew rotates slower than the Mandrel, Suggesting a 50:120:60 set up, or something similar..

If the machine has a Norton box, find the settings that give a 1:1 through the box. (Which would be for 6 tpi ) and use changewheels to give a 1.2:1 reduction..

30:120:36, 40:120:48 or whatever takes your fancy, using the wheels that are available.

Howard

Thread: Parting Tool Holder
14/04/2021 12:00:36

Normally, I advocate absolute rigidity, but in the case of parting tools, a little flexibility could be an advantage, in that it will allow the tool to "give" when the going gets tough, and avoid a dig in.

The holder that I was given, many years ago, is slotted, and when being used in the rear toolpost, it can be seen to yielding slightly. At the risk of asking for problems, dig ins are almost unknown.

Howard

Thread: Bearing tolerances
14/04/2021 11:51:58

Is there enough metal outside the bearing housing to allow it to be bored out and bushed back to correct size?

If so, buy a new bearing, (Carriage will cost more than the bearing! ) and bore the bush to suit, before using Loctite to secure the bush into the housing.

Everything should then be back to standard without fear of wear in either part causing problems.

Howard

Thread: What Did You Do Today 2021
14/04/2021 11:44:09

Making the screw holders for a John Ashton Universal Screw Modification Fixture, all 19 of them!

(To cover from M3 to 5/16" ) So .21 tappings to make and 38 through holes to drill.

Should keep me occupied for a while, before final assembly and finding a box to keep everything in!

Howard

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