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Member postings for old mart

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

Thread: TomSeniorMdel E S head
19/01/2021 17:35:30

The spindle bearings in the S head, which is probably the same mechanically are 1" x 2" x 0.591", top and bottom. Code number 07100s/07210x taper roller. The split nut which adjusts the spindle bearings has a left hand thread.The nut is locked by a SHCS reachable through a hole near the top of the quill.

Thread: Fast charging anyone?
19/01/2021 17:16:18

That 500w/ mile could be per mph, then 500 X 60 = 30000w. That would be 30Kw at 60 mph.

pgk pgk's Tesla at 70mph in ideal conditions would require 21000w, about 28hp at the wheels. The car should be pretty aerodynamic and the figures are feasible.

Edited By old mart on 19/01/2021 17:21:07

Edited By old mart on 19/01/2021 17:21:34

Thread: Vertex (V4?) Rotary Table
17/01/2021 15:14:15

Seconds of arc may be beyond the capabilities of your table, my 6" Soba only goes to the nearest minute.

Thread: Boring bar size ?
17/01/2021 15:11:23

Although you will be using a 16mm bar for a depth of 90mm, plus a bit more probably for clearance, the forces on the bar will be minimised with small depth of cuts and the soft material. The inserts for aluminium are very sharp, allowing depths of cut easily down to 0.012mm, 0.0005". Take your time and you may find it safer to do the boring away from the chuck. If you have a stop for the saddle, use it.

Thread: The cheapest way to make a tailstock Dro
17/01/2021 14:53:09

Nice result. There are a couple of things to consider when doing a mod like this. The stainless steel can catch you out when drilling and tapping, it is prone to workhardening. I would recommend sharp drills, slow rpm and good feed rate to minimise the danger. Make any holes to be tapped on the loose side, not tight. With a self extracting quill taper, make sure there is going to be a conflict when clamping on a bracket to the end.

I had trouble drilling one of these hardened stainless readouts and had no option but to resort to a solid carbide drill to finish the hole.

Thread: Chester model b fitting new vise
15/01/2021 16:50:10

A lot of people get by without the tennons and just use a dti to get the jaws parallel each time.

If you bolt down a block or straight piece of material to the bed aligned with the X. axis, you can fit the vise inverted and skim the tennons. After skimming, and removing the vise, it is advisable to recheck the alignment of the block just in case it has moved. I would only skim the rear face of the tennons as it is easier to push the vise away from you when tightening the tee bolts.

_igp2463.jpg

Thread: What nut and bolt material?
15/01/2021 16:29:27

Any stainless steel will rust if the conditions are right, it is the chromium oxide on the surface that helps to reduce corrosion. Look up passivating of stainless steel, its only a google away.

Thread: Coronavirus death stats
15/01/2021 15:56:22

Most countries seem to be giving fairly accurate figures, even Russia recently re evaluated their figures upwards. Only the Chinese figures seem to be politically modified. There was a Chinese comment on the news saying that the Covid 19 did not start in Wuhan.

Thread: Boring bar size ?
15/01/2021 15:48:29

If you can hold a 20mm bar securely, it would be better than a 16mm one. Maybe a special toolpost could be made for large bars. I have made three special toolposts and also a mounting to directly use a larger toolpost on the cross slide expressly for using 25mm boring bars, but which will hold all the standard tooling.

Thread: Machining Brass
15/01/2021 15:39:36

You could check for backlash in the machine leadscrews, not making allowances for it can lead to unexpected errors.

Thread: Manual threading on the lathe - problems
13/01/2021 16:09:11

I only recommend split dies used in at least 2 stages. Having the diestock resting against the front of a drill chuck in the tailstock and advancing the tailstock quill gently helps to keep the die straight. Some steel types do not like being threaded however good the dies are. With a tailstock die holder, you could try not locking the tailstock, just push it gently as you turn the chuck.

Edited By old mart on 13/01/2021 16:12:26

Thread: Schraeder valve threads
13/01/2021 15:54:15

Wikipedia has info on Schrader valves. I have seen them used in compressed air regulators at 3000psi, and the cores look just like the short version and are the same size.

Thread: Boring bar size ?
13/01/2021 15:12:21

A solid carbide boring bar would certainly do the job, but that depth is at the limit of one of my 12mm ones and a 16mm one would probably cost more than a set of larger carburettors. If a 16mm steel bar is used, the compound and cross slide gibs should be tightened up a little and the minimum of tool overhang to reach the required depth is important.

12/01/2021 21:24:58

What carbs are they? Flange or spigot fitting? The old flange type had a habit of being overtightened and the face not being flat, which has to be addressed when mounting them. Keep the speed fairly low and check for any runout before cutting metal. The problem of tiny drillings into the bore getting clogged up and the problem of removing tiny burrs from the holes without changing their fuel or air flow is a worry.

 As already mentioned, the long stickout of a 16mm bar can cause problems, another reason for taking tiny cuts. I, too would prefer 20mm bar size, but it could be difficult to hold in your lathe.

Edited By old mart on 12/01/2021 21:28:51

12/01/2021 16:28:45

Jason B recommends a 16mm boring bar, and I think that is the best size. The actual tip height of boring bars is somewhere near half the nominal tool height, so if the toolpost has enough depth to hold the bar, it can fit a lathe that could not manage a 16mm standard tool.

ARC sell a nice bar 16mm which takes CCMT09 type inserts. 060-325-39516

An insert suitable for zinc or aluminium CCGT09T308. 060-326-01938

The ARC site shows the dimensions of the tool. It will be long enough for your carb bore. I would recommend very small cuts and lubrication such as wd40 or ac90.

Back in the sixties, I had a pair of Amal monoblocks bored out to 1 3/16" for a Royal Enfield Constellation. The centre part of the carbs was in place and bored simultaneously. Some time later, one of the central parts failed, the cause was blowholes in the zinc casting.

Thread: Wooden Gears
12/01/2021 15:55:51

Hardwood lapping sticks are available up to 25 x 6mm section which may not be big enough. They are laminated and very hard and strong.

www.moleroda.com

Thread: microscope graticule cleaning - recommendations required
12/01/2021 15:36:36

Those pesky cosmic rays causing trouble again! laugh

Thread: Collet chuck for workholding on the mill
11/01/2021 16:32:07

It's always interesting to see another way of doing something which adds versatility to existing tooling.

Thread: Chuck backplate error
10/01/2021 21:25:05
Posted by Lathejack on 10/01/2021 01:13:44:
Posted by old mart on 09/01/2021 17:34:47:

Lathejack, you have had good results with close fitting radial registers, but you do not mention any experiance of using loose radial registers. So you are an expert on the subject?

Unfortunately there are times when I feel that you are coming across as rather unpleasant. Surely the rest of us should be able to comment on our experiences and opinions, just as you do, without receiving remarks such as in your last sentence?

Edited By Lathejack on 10/01/2021 01:16:50

Edited By Lathejack on 10/01/2021 01:33:52

Perhaps you could make a comment on the recent post by David Bennet 8.

Thread: Key Cutting
10/01/2021 21:16:21

Why not make the first new key 0.010" longer and hand file it back if it turns out too tight. A thin coat of felt tip on the side would show up any tight parts. There is unlikely to be any specification. Check for wear on the stem of the key and the corresponding hole in the lock

Edited By old mart on 10/01/2021 21:18:22

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