Myford 7 Capacity Check

[Andy ReynoldsParticipant @andyreynolds]

I have been scratching my head for a while now so I thought I would come and ask the experts…

I am planning on building an engine, the original plans of which can be found here:

https://archive.org/details/motorbicyclebuil00hasliala/page/66

I am concerned that if I purchase a Myford 7 lathe then I will be exceeding the Myford's maximum capacity.

The engine crankcase measures roughly 9" in diameter by 2" in depth.

Does anybody have any practical knowledge as to what I can safely squeeze in without resorting to a homemade spindle raiser?

Cheers,

Andy

[Andy ReynoldsParticipant @andyreynolds]

[JasonBModerator @jasonb]

I'm not really a Myford man but think the part will be too deep for teh gap particularly the half with the timing gear case which will push it away from a faceplate. You may just get away with diameter but would need to work out what the radius is to the corner of teh cylinder flange.

Is it going in a bike? if not you could scale it down to a more manageable size or I have seen similar early bike engine crankcases done as welded fabrications.

[JasonBModerator @jasonb]

Fabricated version of the same engine on Madmodder here plus a bike to put it in.

[Martin of WickParticipant @martinofwick]

7 in. swing over bed 9 in.  in the gap

Barely 1 1/4 in. (31mm) horizontal  in gap between faceplate and bed on a 7

Just over 1 1/2 in. on S7

Edited By Martin of Wick on 02/08/2019 17:04:28

Edited By Martin of Wick on 02/08/2019 17:06:35

[Andy ReynoldsParticipant @andyreynolds]

Thanks to both of you for the quick response.

Well it looks like I have the following options:

(a) change the engine design which is not something I wish to do

(b) look for a larger capacity lathe which is not something I wish to do

(c) go research and then build my own copy of the myford spindle raiser as I am assuming no commercial offerings are available.

I was aware of the madmodder link posted. I found that link a while back and saw that he went away from the original plans that Hasluck gave. My version of the bike is an attempt to be as authentic as possible to see what it would have been like to build and ride back in 1906.

Cheers – Andy

[JasonBModerator @jasonb]

Andy, do you have a milling machine as the crankcase halves could be machined on that as well as cutting the lip and recess around the joint with the aid of a rotary table. A boring head would take care of the bearing holes

Are you proposing to use castings or cut the crankcase halves from solid?

[Andy ReynoldsParticipant @andyreynolds]

I am in the process of sorting out the CAD I have developed to create patterns that will be 3D printed for sand casting. .

I am afraid that I don't have a milling machine hence my attempt at trying to get the parts to fit on a face plate somehow…

[jann westParticipant @jannwest71382]

J A Radford has an elevating head for the Myford in "improvements and accessories for your lathe" TEE Publishing 1998 (from p 57)

It's not a small job, though!

[Andy ReynoldsParticipant @andyreynolds]

Thank you very much Jann that book is now on order. Aside from the additional work in fabricating the spindle raiser I would be worried about the additional load placed on the lathe and the resultant final accuracy one could achieve.

It looks like the sensible option is to cough up for a larger lathe or find a milling machine to complement the myford.

Many thanks – Andy

[DC31kParticipant @dc31k]

Posted by Martin of Wick on 02/08/2019 17:03:45:

7 in. swing over bed 9 in. in the gap

Barely 1 1/4 in. (31mm) horizontal in gap between faceplate and bed on a 7

Just over 1 1/2 in. on S7

Would it be more relevant to measure between spindle nose and bed? Perhaps also between spindle nose and headstock casting.

You could make an offset (towards headstock) faceplate that accommodates the 2" width required.

In a push, buy a bed off one of the spares breakers and cut some off the ways.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by DC31k on 02/08/2019 20:05:45:

.

In a push, buy a bed off one of the spares breakers and cut some off the ways.

.

Good suggestion

A bed that's damaged with hacksaw marks from "parting-off" by some timid former owner should be dirt cheap.

MichaelG.

[Nick Clarke 3Participant @nickclarke3]

If you have the room a larger lathe may quite possibly be no more expensive that an ML7 and probably cheaper than a Super 7 which seem to go for a lot more money.

Unfortunately accessories and tooling follows the original price of an industrial machine, ie can be expensive.

Any used machine is an unknown quantity and need thoroughly checking over I suggest you take (another) knowledgeable person with you – no matter the level of a purchasers experience it is possible to get carried away in front of a machine you want – a calming voice is useful – I know from (bad) experience!!

The sales pages of Lathes.co.uk might be a good place to look for information as well as the lathe itself. **LINK**

[Martin of WickParticipant @martinofwick]

For possible raiser, see **LINK** for myfordboys interpretation. Although his is designed for a ML10, you could try asking if he would be prepared to flog you a casting that you could adapt for a 7.

I would have imagined that T10 timing pulleys and belt would be preferable to gears for a smoother drive – and no need to run in reverse. Just as easy to gear down to suit your intended use.

[JasonBModerator @jasonb]

Posted by DC31k on 02/08/2019 20:05:45:

Would it be more relevant to measure between spindle nose and bed? Perhaps also between spindle nose and headstock casting.

You could make an offset (towards headstock) faceplate that accommodates the 2" width required.

 

Won't help as the bearing housings will touch the end of the spindle so that is the limiting factor in how close to the headstock the parts will go. It would need at least 3" infront of the spindle to be able to swing it in the gap.

Swinging that cylinder casting won't be easy either as it looks like you will need a good 4" between cross slide and lathe axis. With the riser and an extended height tool post you may have a job getting that 6"plus depth of bore parallel. It's also going to be a lot harder to work out how to hold the cylinder than the crannkcase halves which are quite easy to hold without increasing the diameter due to clamps etc.

Edited By JasonB on 02/08/2019 20:46:04

Edited By JasonB on 02/08/2019 20:50:06

[old martParticipant @oldmart]

The biggest faceplate I have seen for a Myford is 9" diameter. A larger faceplate using a backplate with that small 1 1/8" spindle is rather ambitious.

[John OlsenParticipant @johnolsen79199]

Bear in mind that you can't usually get right to the maximum size since you have to be able to hold the job somehow. So it is generally better to have something with a bit to spare.

However…if it is only going to be one or two parts of a job that won't fit the machine, sometimes it is better to just find someone cooperative to help with those bits. Usually best to make a start on the bits you can do, then when people ask how you are going to do the big bits , say you are hoping that something will turn up. People are more likely to offer to help if they can see you are making a good start. This worked for me with my compound launch engine, where some of the bits were too big for my ML7. Speaking of which, by the time you have a face plate on there is not much gap left on the Myford anyway.

John

[JasonBModerator @jasonb]

As I hinted to earlier the crankcase halves are not too difficult to hold and you don't need any large faceplates or chuck to be able to hole them.

The trick is to first tap the bolt holes and then with the use of stand-offs the casting can be screwed to a machining plate or disc that is in turn tapped to suit the spacing of your faceplate slots. Something like this would fit a 7" faceplate and 8"+ part, the central hole in the plate could even be made large enough to accommodate the bearing housing to keep projection as small as possible.

Similar setup on this cylinder head to allow for the rocker arm post

Edited By JasonB on 03/08/2019 07:41:21

[Nigel McBurney 1Participant @nigelmcburney1]

why not go for a 5 inch centre height Boxford ,theres no gap but has the advantage of 5 inch capacity all the way down the bed,takes about the same space as a myford,and has a larger spindle bore.Note ,take care a lot of Boxfords are only 4 1/2 centre height

also consider a Colchester Bantam ,the earlier ones were 5 inch centre height ,later one shave increased centre height,although a bit larger and heavier they are a lot better for engine and motor cycle work as the spindle bore is larger.

[Neil WyattModerator @neilwyatt]

Posted by Andy Reynolds on 02/08/2019 19:39:20:

Thank you very much Jann that book is now on order. Aside from the additional work in fabricating the spindle raiser I would be worried about the additional load placed on the lathe and the resultant final accuracy one could achieve.

It looks like the sensible option is to cough up for a larger lathe or find a milling machine to complement the myford.

Many thanks – Andy

Radford's solution is complex and cumbersome, a bigger project than building that engine.It's pretty much pointless unless you have an overwhelming desire to use the lathe as an underpowered horizontal mill or have some obsessive need to have a variable centre height lathe (to what end?).

Plain riser blocks will do the job just as well.

[Howard LewisParticipant @howardlewis46836]

There are far eastern machines which will swing larger diameters than a Myford 7 series. They may be cheaper than a used British machine. The later ones, less than 20 years old, can have quite a good spec.and be available fairly cheaply, relative to a Myford.

Think Warco BH600, Chester Craftsman, and their successors, as possible contenders. They will swing 12" over the bed, 18" in the gap, and are heavier and more rigid machines, than the 7 Series Myfords.

Obviously, buying any used machine, you need to check for wear and damage.

Machines, ex industry are likely be 3 phase, so the cost of a motor for single phase use, may need to be factored in to the budget. Plus how much space is available for the machine?

HTH

Howard

[Andy ReynoldsParticipant @andyreynolds]

Thanks to everybody who has responded. My apologies for the long gap – it was a result of leaving the office and switching the computer off for a fortnight in order to go away on holiday.

@DC31k @Michael Gilligan

Buying another bed to modify is a good idea. It seems somewhat profligate to chop one up in order to make what I need but I appreciate the lateral thinking.

@Nick Clarke 3 @ Martin of Wick @ JasonB @ old mart @ John Olsen @ Neil Wyatt

A larger lathe does seem to be the answer and I think I was being foolishly naive to think that a Myford could do this job. Whilst on holiday I went back through the original text and started laying out the process steps for each component.

I realised that the cylinder head needs to be mounted to the face plate on an offset in order to bore out the exhaust valve chamber and the flywheel also needs to be mounted on an offset to bore out the taper joints. Both of these jobs need a lot of room…

So that means using a raiser extension or raiser blocks and pushing things right to the very limit with all of the associated problems or simply admitting that I need more capacity…

@ Nigel McBurney 1

Which means that thanks to all of your input on this forum I have arrived at the answer of purchasing a larger capacity Boxford lathe – or similar – as the best answer.

@ JasonB

Thank you very much for taking the time to post the screen grab of the crankcase machining process. The book calls for a 4 jaw chuck but I think I prefer your approach. I also see somebody else has Solidworks

Thanks again to everybody who has taken the time to respond to my initial question. This is the first time I have used this forum and I really appreciate how people are willing to freely offer up their hard won knowledge.

Enjoy your day – Andy

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