Member postings for old mart

If you are cutting a male thread, it helps greatly to have a matching nut to use as a gauge. Start checking after getting to the theoretical size and then creep at 0.001" cut per pass until the nut almost screws on and then take a couple of spring cuts. I always use tapping oil when singlepointing on a lathe for steel and aluminium, but usually cut brass, cast iron and bronze dry. I have just cut a 10tpi ACME leadscrew and nut and had to do a lot of small cuts before they would fit together, fortunately without any noticable loosness. I never use any offset on the compound as the lathe is heavy enough not to need it.

Edited By old mart on 02/08/2023 21:23:10

When you get the lathe repaired, you should research the possibility of a frangigle link that is common tith most lathes. Plastic gears in an accessable part of the drive train or a little drive pin like Smart & brown lathes have. It would lower the likelyhood of a major crash.

You could repair the shaft using a mill if you had a rotary table.

I would buy a metal round offcut and machine one, not having the means to cast metal.

I would find out first just how hard it is and if it is machinable, bore the main shaft and maybe thread it and then fit or screw a new small end into it. Loctite and possibly pin the joint. If your saddle cannot move without the broken part, it is possible to use the tailstock to push it and then back off the tool and pull it back manually. The compound, if aligned dead parallel to the spindle axis can also work for short lengths. The end which goes in the bearing bush should be made a tiny bit big and then rubbed down at low spindle speed with some wet and dry on a file to get a nice finish. Care should be taken not to let the file hit the moving chuck. The pinning can be done using the mill.

I thread internally with a left hand bar with external inserts in it in reverse. This cuts a right hand thread away from the chuck and is much safer. Make sure the chuck is nice and tight if it is a screw on one and use the slowest speed the lathe can do. Locking the chuck on the spindle is good, but Smart & Brown model A lathes are screw thread and their manual allows reverse if slow speeds are used and care is taken not to use big cuts.

Edited By old mart on 01/08/2023 15:13:35

It looks to me that cleaning and painting as a unit would have consumed much less effort than you have wasted on it so far.

The cages usually have the part number on them, try a magnifying glass. Otherwise measure the shaft, the bore and the overall length and get in touch with a firm like The Bearing Boys, they may be able to help.

Can you turn the nut around? Maybe the holes are both offset. If the plate at the front has any sideways adjustment, that might help.

Usually these saws run at much slower rpm than the max allowed for this blade. In the low hundreds and with coolant, plus the work must be really well clamped.

I only bought a small boring head for the mills with an R8 arbor and was not too keen on the brazed toolbits that came with it. Recently, I made some indexable tools for the head out of the supply of 1/2" Densimet that we have at the museum. I have found some pictures og one using DCMT 07 and DCGT 07 inserts. The Densimet is ground 1/2" diameter tungsten alloy with a relative density of around 18, the stiffness of carbide, but nothing like as brittle and machinable and can be tapped. I made several lengths and also used some CCMT 06 inserts for the smaller ones. They are much better than the brazed ones. To mill the various angles, the little vise with the multiple movements was invaluble.

Our tv went wrong after 3 years and I was glad I had bought it from John Lewis. They have given me first class service and will be replacing the tv with a new one as the faulty one cannot be repaired. It's nice to know that there are some firms who go out of their way to give top quality after sales service.

With most drill chucks, you suck it and see, they are not required to be perfect just for drilling. I got lucky when buying a 5-25mm and an R8 arbor to fit it, the runout is better than 0.002" at various diameters, I would have beed satisfied with 0.005". Screwed on chucks are usually meant to be used on portable drills where you would not tend to notice runout so much. Testing a screw threaded chuck clamped onto a true running pin in a lathe would confirm whether the face and counterbore were true and it might be worth a bit of facing and boring if a custom holder were to be made to fit it. My best chuck is a Cutwel brand 1/2" keyless with integral R8 arbor which is 0.001" tir throughout its whole range, bought second hand on ebay.

The spindle will almost certainly come out to the right (chuck end). Look at the left end for threaded rings which control the end float and also hold the spindle in.

Pity the code is Chester's stock code and nothing like an insert code. So if they are discontinued it will not help.

I forgot to add, if two round seats are close together, the counterbores may be better overlapping and the seat inserts with flats where they contact.

Square they are, but very old design, that will be the reason that Chester no longer list them. I agree that the Cutwel insert identification page is well worth using and once a reasonable code is found, then ebay would be the first place I would look. The rads may vary, and a close comparison between the existing inserts and the seats will give a good idea whether slight variations will fit. Sometimes it is easier to give up on the old tooling and get something up to date and easily available.

Another lens fitted on top of the objective would shorten the focussing distance, but what strength would have to be found by trial and error.

I saw that on ebay and was tempted myself just out of curiosity, but overspent on other things and just managed to resist it.

Edited By old mart on 25/07/2023 19:13:58

It might be easier to shrink fit and seal if it were circular, fitting into the bore of the head. Even better sealing if the outer diameter sealed with a head gasket. Normal practice is to make two circular cast iron seats which are shrink/press fitted into counterbored holes in the head and then the seats are finished in line with the valve guides.

Edited By old mart on 25/07/2023 19:20:44

They are triangular type and if you have some worn ones, they could be measured. The size of the triangle, rads clearance angle and thickness are needed. The triangle size is what it would be if the corners were sharp with no rads.

I agree with the cast in place thoughts by Robert. I would see just how similar a replacement switch is to the original and only remove the old mount if there was no other way, and it would get turned off and a new mount made.

There are a number of the plastic gears for about five different makes of these power feeds available on ebay, one might match yours. A replacement for the pot may well be the answer. Shame Maplins no longer exist.

Edited By old mart on 24/07/2023 16:06:13