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Cutting a keyway without a broach

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Robin Graham09/11/2018 20:39:37
597 forum posts
130 photos

Thanks chaps, as ever. Seems that his is very doable - now I have numbers / pictures for tool geometry I shall grind a tool and proceed with confidence. Well, optimism at least!

Robin.

peak410/11/2018 00:07:35
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870 forum posts
84 photos

Some years ago I had a need to cut some splines on the outside of a gear linkage shaft on the Ducati; I was replacing an old rusty one with a custom stainless shaft.

The method I used was akin to the one shown in Andy Pugh's Historic military Vehicle Forum link earlier.

The machinist there used a home made slotting attachment, but in my case I effectively replicated something similar with the Myford S7 top slide.

I removed the handle, end plate and feed-screw from the top slide, and replaced it with a short section of angle iron; 2 screws fixing it to the top slide casting and with one cross drilled vertical hole in the centre.

That hole then allowed me to use 4 short lengths of flat bar, with a hole in each end and a long length of 1" x !/4" steel as an operating handle, in a similar manner to that shown in the link. ( the operator there used 2 bars and a shackle to link the slotting plunger, handle, and fulcrum point.)

The main pivot point for my handle was a vertical piece of round bar bolted into one of the cross slide T slots. It cut the splines fine, and there was no wear on the saddle rack or handle gear; I locked the saddle for rigidity.

I've since used it to cut slots in pulleys using the same boring bar, still set horizontally in the tool-post but with a square ended HSS insert, rather than a pointed one, as I'd previously used for the splines.
The tool I used was very similar to those shown right at the beginning of this thread by Andrew.

It seemed to me a better way of doing the job than the constant traversing of the saddle with the operating handle.

Also this method allows one to cut slots or splines on a taper, without the need to build a fancy dedicated slotting attachment.

I know a picture tells a thousand words, but the Myford and the slotting handle are about 30 miles away at the moment.

 

Bill

Edited By peak4 on 10/11/2018 00:11:34

peak410/11/2018 00:20:05
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870 forum posts
84 photos

p.s. Just out of curiosity I typed "using top slide as a slotting attachment" into Google and found a post with illustrations on this very forum.

Mine was very similar to that shown in the book, but with the fulcrum on the cross slide.

Finding and linking to that earlier would have saved me a lot of typing. blush

Bill

Les Jones 110/11/2018 11:39:37
2093 forum posts
144 photos

This is a lash up I made to reduce wear on the rack & pinion when cutting keyways.

img_1549 (medium).jpg

A block of wood was cut to fit between the slide ways on the bed and a T bracket made from offcuts of angle and box section. This was bolted through the wooden block to two wooden cross pieces under the bed. I might even get round to making proper pivot points some day rather than just bolts. It is also quicker than using the rack & piniion. One other point. Some times I find it better to mount the tool bit so it cuts when moving towards the tailstock rather than towards the headstock. It hase less temdency to dig in.

Les.

John Baron10/11/2018 16:55:57
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90 forum posts
16 photos
Posted by Michael Cox 1 on 08/11/2018 21:59:27:

Here is an easily made adjustable broach:

http://mikesworkshop.weebly.com/small-hole-slotting-tool.html

I would suggest that you remove most of the material by drilling or milling first and then use the adjustable broach to clean up the slot.

|Mike

That tool is based on the one that I published on another forum some years ago

25.06.2010-003.jpg25.06.2010-004.jpg

One of the things that makes it unique, is the method I used of retaining the cutter.

Michael Cox 110/11/2018 18:43:21
516 forum posts
27 photos
Posted by John Baron on 10/11/2018 16:55:57:
Posted by Michael Cox 1 on 08/11/2018 21:59:27:

Here is an easily made adjustable broach:

http://mikesworkshop.weebly.com/small-hole-slotting-tool.html

I would suggest that you remove most of the material by drilling or milling first and then use the adjustable broach to clean up the slot.

|Mike

That tool is based on the one that I published on another forum some years ago

One of the things that makes it unique, is the method I used of retaining the cutter.

My broach was not based on yours but it does use the same principle. My broach has been on my website for about 10 years and an article on it was published in MEW 184 in December 2011.

Mike

John Baron10/11/2018 19:55:50
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90 forum posts
16 photos

Hello Mike,

Yes I published mine in 2010, so that would have been just before you're article. The similarity prompted my reply to the post. Since I didn't even know that you're web site existed.

I recall that the method of retaining the toolbit caused some interest at the time !

It seems that great minds think alike. I'll have to go and have a wander around and see what else you have done

Regards:

BaronJ.

BW11/11/2018 06:46:59
245 forum posts
40 photos

Does that little bit of wire really hold the toolsteel securely ? Am I missing something here ?

?

 

Edited By BW on 11/11/2018 06:48:45

John Baron11/11/2018 09:50:21
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90 forum posts
16 photos

Hi BW,

Why don't you try it !

I'll guarantee that you can't pull it out by hand !

That retaining method has been around for a great number of years ! One of its uses is to retain two round shafts that are not in perfect alignment and provide drive from one to the other. You can find examples of this in some of the old radios of the 20's and 30's. I do believe that its used in some rotary tools today.

jacques maurel13/11/2018 07:40:38
avatar
67 forum posts
16 photos

This process was also described in "post bag" in the january 2004 issue of ME.

JM

Howard Lewis14/11/2018 23:24:59
2385 forum posts
2 photos

Screwed in keys are known as Dutch keys.

If no hand slotting tool sis available (I use one designed by the late peter "Bushy" Robinson, intended for a Myford 7 Series lathe, using a casting from College engineering Supplies) On a raising block, it still finds use on my larger lathe.

But lacking such a tool, with a toolbit ground to 5mm, in a suitable holder, in either the toolpost , by racking the saddle to and fro and putting on the cut with the Cross Sl;ide, a keyway can be cut. As already said, make life easier by drilling out first of all, so that only the corners need to be cut.

Once needing a central 1/8" square socket, for a speedo drive, I used the tailstock in similar manner.

Howard

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