Help with dove tailcutter

[Mark WebsterParticipant @markwebster13123]

Can someone please help me out here. I'm making an grinding tool post for the mill sharpener from the book "complete guide to milling" it calls for 30 degree angles made with the dovetail cutter for the sliding bed

Now this may seem like a stupid question but what size cutter do I need. I can't seem to get a 30 deg cutter. It's either 60 or 45 degree that are a available. So I opted to order the 45 degree dovetail cutter Have I done the right thing and will this be ok to use for the sliding beds as long as i make allowances for it. Or should I have gone for the 60 degree one please help as I'm a little confused with how they refer to the angle of the cutter in relation to the plans

[Mark WebsterParticipant @markwebster13123]

What angle degree cutter do I need

[BubbleParticipant @bubble]

Hello Mark

You need a 60 degree cutter to make dovetail slides

its all a matter of where you measure the angle from!

the ones I have are 22 mm and 25 mm

the 25 will do all the dovetails on our sort of projects

regards

Jim

[BubbleParticipant @bubble]

Mark

60 degree 25 mm cutter will do all the dovetail slides in our scale of engineering

regards

Jim

[RobboParticipant @robbo]

Jim is spot on here.

Obviously a square cut is 90 degrees, so 90 – 30 = 60 degrees. The 30 is measured from the horizontal plane, whereas the cutter is working in the vertical plane, so make sure you clamp the job the correct way up.

When you have the pieces in your hands it will become clear.

So send back the 45 and get a 60!

Phil

Edited By Robbo on 18/05/2013 09:41:35

[Mark WebsterParticipant @markwebster13123]

Damn , got home this morning and my 45 deg cutters had arrived already only ordered them yesterday. Looks like I will have to send them back for an exchange. I was thinking about how they were measure hence why I posted this question. I was looking at it from the horizontal only for both but when a looked at a pic of 60 deg it got me confused but now you have explained it I will know in future. I wasn't expecting my order to come next day as I had no dispatch notice. It's too fast this Internet ordering 😀

Thanks for your help I really appreciate it

[Sub MandrelParticipant @submandrel]

Hope you get that sorted OK. Take it gently with the cutters and they will last a long time. If they rub in the corners you can put a TINY amount of extra relief on the corners with a sharpening stone. This only means the inside corner of the dovetail will not bet 100% sharp. It is essential to take the sharp outside corners of dovetails off anyway(as any tiny interference completely spoils the fit) , so this makes no material difference.

Look at the pic below and note how the dovetail only contacts on one of the horizontal surfaces as well.

If you are fitting a gib strip, it should nearly fill the space available for it, and it should not have sharp edges fitting into the corners of the dovetail.

Neil

 

Edited By Stub Mandrel on 18/05/2013 11:11:36

[Mark WebsterParticipant @markwebster13123]

Thanks Neil, I will be using gibb strips. It's the first time of using these cutters so thanks for any advice. I have bought a set so am I better making my way through the range until the desired size is reached I.e. 10 mm then 16 mm then 32 mm or just doing it straight with the 32 mm after millining the centre out. It's obviously mild steel I'm cutting, I've opted for the softer bright mild steel the one with lead added

[Sub MandrelParticipant @submandrel]

Good choice of material, though good cast iron makes it a breeze.

Mill out the centre section square, then take progressive cuts the full depth with the cutter whose depth is the best fit. I normally do about three cuts, then take a final skim that is quite light (say 10 thou), if the starting slot is dead on size, aim to just remove any vertical witness with the final sizing cut.

Cut the dovetail which will be drilled for the gib screws first. The finish on this side is not critical as it doesn't slide on anything, so it makes an excellent opportunity for practice.

Another tip is to mill the dovetails before the outside surfaces are finished. The gib can be both adjusted in size and position to take up small errors, and then the outside surfaces skimmed to give neater joins than you would ever get by trying to get the dovetails exactly positioned.

If your mill is set up so you can take climb-milling cuts (where the mill is effectively pulling the work under the cutter) you may find a final, very light cut this way may give a better finish, but don't use the dovetail cutter to find out if your mill can do this. I suggest having a practice first anyway.

Neil

[Mark WebsterParticipant @markwebster13123]

Thanks Neil for all the help, can't wait to get started my steel will be here on Monday . Think I might just keep these 45 deg ones and order the 60 deg ones, after all you can't have enough tooling

Cheers mate all the best

[John McNamaraParticipant @johnmcnamara74883]

Hi All

Yes The dovetail only contacts on one of the horizontal surfaces, (But the narrower top surface may not be the ideal choice) The much wider surface bearing on the saddle if a lathe, being the better choice for stability. As is was found on my old Colechester and now my a little younger Heidenreich and Harbeck Lathe.

 

The same applies to my milling machines both have their tables bearing on the bottom surface against the main casting.

 

The gib must be fitted to put no pressure on the top and bottom surfaces at all times. otherwise it may lift the slide away from the bearing surfaces.

 

My machines have taper gibs, a bit slow to fit but worth the effort, they stay set for a very long time. The odd non parallel side equalised by the gib is always on the moving part.

 

The screws used to set screw type gibs appear to dig into the gib over time loosening the fit, and they are difficult to adjust so that they bear evenly.

 

To fit a taper gib, I have not done using this method, but I wonder if you machined the gib, then the odd angle side of the slide, and then glued the gib to the odd side. And finally did a light cut on both the glued in gib and the other dovetail side in one setup. Then broke the glue bond with modest heat or by soaking in solvent. What sort of accuracy would you achieve? has anyone used that method?

 

The taper gib should initially be a fair bit longer than needed, this allows you to scrape it in to perfect fit. If needed. You will also need to (fairly deeply) counterbore both ends of the slide for the adjusting screws that bear against each end of the gib holding it in position on my lathe about 20mm of travel. On the small mill about 12mm travel. when new the gib is set to be fully out within the limits of its travel

 

Cheers

John

Edited By John McNamara on 18/05/2013 12:58:58

[Anonymous]

If at all possible rough out as much of the dovetail with a Woodruff or T-slot cutter first. The sharp corners of dovetail cutters are not the most robust edges, and it's better not to wear them out by roughing.

Regards,

Andrew

[Mark WebsterParticipant @markwebster13123]

Hmmm first of all thanks John for your comments now if totally confused. Are you sure you've not gone off the topic as I was talking about making a grinding tool post and mill sharpener fro plans in the book. Are you talking about more heavy duty dovetails as found on lathes and milling machines if not then like I said I'm confused as I thought this would be a simple task oh eck

secondly thanks Andrew , I don't have any of those cutters yet, looks like this is going to be an expensive project after all . I thought the dovetails would be ok seeing as I'm using softer mild steel

[Sub MandrelParticipant @submandrel]

Hi Mark,

If conventional dovetails are specified in the plans for your device, they will be fine.

Taper dovetails are the dog's b**** but much more demanding to get right and not often encountered. I've never made any, neither my lathe nor mill have them, but all my ordinary dovetails work fine.

Neil

[Harold Hall 1Participant @haroldhall1]

Its the nature of forums Mark sometimes to move away from the original posters questions so do not get too confused.

Having made the central recess along the work piece with an end mill, therefore having vertical sides, lower the dovetail cutter into the recess by 4mm and start making the dovetail over part of the depth. Increase the width of the cut until there is just a very small flat left at the top corner.

Lower the cutter a further 4mm, to give the 8mm as per the drawing, and increasing the width of the cut until it just meets the portion already machined. From there, take a fine cut of around ten thou (using Neil's imperial dimension) and carefully machine the full width. Repeat if the result still needs widening to conform to the drawing.

Having gone for leaded steel you should have no problem if you take it steady, though of course we do not know the calibre of the machine you are working with.

Do take note of Neil's comments above re sharp corners, etc.

Harold

[jason udallParticipant @jasonudall57142]

Igus sell “plastic” slide way..travellers and track
Also hepco do dovetail and ball bearing slides
An engineering solution but maybe not what you need

[Mark WebsterParticipant @markwebster13123]

Wow I love this site. I can't believe the amount of help you all have given me. I can't thank you enough. I wish I posted before I placed the order so I got it right in the fist place. I am a beginner to this hobby and I'm loving it. I never expected so much help, you don't know what it means to me I can't thank you all enough. I'm going to order the 60 deg set on Monday and I will keep the 45 deg set as I'm sure they will come in handy

i wish you all the best

kindest regards

mark

[Mark WebsterParticipant @markwebster13123]

Oh I forgot to mention my milling machine is a Chester champion 20vs fitted with dro

regards

mark

[Anonymous]

Posted by Mark Webster on 18/05/2013 17:27:32:

I don't have any of those cutters yet, looks like this is going to be an expensive project after all

Do a search on Ebay for Woodruff cutters; ignore the over-priced buy-it-now ones, and see what is available on auction. That's how I got all my Woodruff cutters, and loads of side and face cutters and slab mills that cost an arm and a leg new. Standard small end mills I just buy new as needed.

Regards,

Andrew

[OuBallieParticipant @ouballie]

Mark,

Welcome to the hobby.

If like myself and no doubt every other member, you will very quickly have a life time's worth of projecta to do, and discounting those on the wish list

If in doubt, ask for advise.

The only advise I can add is, that you take your time, measure 3-5 times then cut, and soon it will be like riding a bike.

After a 30+ year absence, my past experience is gradually coming back, and I am now less frequently shaking my head in dismay at the stupid mistakes I make. So far the biggest of these is me winding the saddle the wrong way and having the tool bit dig into the workpiece. Luckily I have the lathe belts slack, with the Diamont Tool Holder bit being pushed down, otherwise it could very well have been an "Oh bleep, bleep what have I done?" moment, which for a fraction of a second it was.

You will make mistakes, but learn by them, and once again take your time with your first project.

My first few times at the lathe and milling machine where a little nerve wracking, but it soon became much easier, and immensely enjoyable, with hours passing without notice.

I am very much in your shoes, but have past experience to dredge from the depths of the old brain.

You are fortunate in having access to the fount of knowledge on this Forum, so take advantage.

Enough waffle.

Geoff – Ready to put the QC into action!

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