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Member postings for ChrisB

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

Thread: New tool post for my lathe
03/10/2019 15:36:25
Posted by norman valentine on 03/10/2019 15:30:17:

Howard, how can you say that a 4 way toolpost is not slower that a qctp? Farting around with bits of packing, trying to find one the right thickness? A qctp is so much better just as long as you have lots of toolholders. That is the problem, having enough toolholders. I have Dickson but only 4 holders, I would like another 4. I would never go back to a 4 way toolpost. I have to frequently change the tool in one of my holders but it is still much quicker than searching for the right piece of packing!

Edited By norman valentine on 03/10/2019 15:32:09

I suppose if you had 4 tools set in a 4 way tool post, you only need to set them once. Then it's a matter of rotating the post to choose your desired tool, which would be quicker than a qctp. Drawback is being limited to 4 tools. But being cheap, you could easily have more tool posts loaded with tooling....I think.

Thread: Alternative metal sources?
23/09/2019 07:18:10

It's true unknown material is sometimes a gamble, but there's no loss in trying how the material behaves and then either use it or bin it.

For general machining projects requiring mild steel I normally go to the local supplier where I can get off cuts of black mild steel.

I also get quite a bit of scrap metal from worn aircrafts parts, most of the times the materials are of excellent quality but might be a bit hard to turn. I found that cheap second hand CBN inserts from ebay run at high speed will cut through any tough steel I've tried to date and with a mirror fininsh.

Thread: Tool post project
21/09/2019 08:56:41

As I mentioned before I appreciate ALL feedback given and thank you all for that.

The "ploughing" comment is maybe a bit out of place imho, I cannot implement all the suggested ideas into a single design so I might have some preference of one design over an other.

Chris

Thread: Drill running off course
17/09/2019 16:56:41

You can use straight shank stub drills (used mostly for sheet metal) to start the hole. They will not wander off. You cannot drill very deep with them as the flutes are short and they have no side margin, good for about 3x the dia. but that's enough to get you started.

The drill on the right.

20170619_154724.jpg

Thread: Ebay site changes for the worst
17/09/2019 16:23:21

True, cou can see the bids but not the bidder...in my case I often find listings there are no bids on and just put a bid when the auction is almost over. Got a couple of good deals.

Thread: DIY magnetic DRO
14/09/2019 15:10:59

I'm not sure if the photo-etch pcb board have some coating which needs to be removed for solder to adhere.

For mine I applied solder along the traces of the pcb first. The readhead chip has exposed points on it's back side ( like little gold dots) and to prevent shorting them I applied some clear coat on it's back. I then put the RH chip in place on the pcb and applied a minute ammount of superglue to keep it in place for soldering. For soldering I have a Lidl variable temp iron, I replaced the brass tip with a diy pointed copper tip. Applied flux to the contact points and soldered on...pretty straight forward but quite fiddly as every thing is so small. Probably there are better ways how to do it, but this is my way round it.

Thread: Why are insert toolholders so expensive?
11/09/2019 09:54:03
Posted by Hacksaw on 11/09/2019 00:03:43:

Slightly off topic , what are those lathe tools that are bent downwards for ? You see them on secondhand tool stalls , usually the last thing to sell , as they're massive industrial size .. They look like they have huge negative rake and would just scrape metal away

Looks like you're refering to TNMG insert type holder. I use that type of inserts and holder and they work very well for me. They like higher speeds and feeds and the finish I get is mirror like. Not so good on small diameters as the tool tends to push the work a bit. What I specially like about them is the 6 tips in one insert, so one insert will last quite a long time.

Thread: Tool post project
05/09/2019 20:13:46

This the latest amendment to the plans to allow for releasing the tool holder to the side, and without removing the top plate off.

Added three tenons to the tool post block which will engage in slots on the tool holder. This will locate the tool holder for repeatability and prevent the holder moving rearwards.

The top plate wedge and tool holders are slotted with matching grooves. The idea is that to release the tool holder, I release the threaded handle ( half a turn maybe) and slide the top plate rearwards ( the plate centre hole is slotted to accommodate for this). When the top plate slides back the tool holder is disengaged from the "teeth" on the wedge and can slide to the side.

tool post 9.jpg

I guess it's not easy to explain but hopefully the drawings can make better sense...or not!

The below drawing shows the tool post in the closed and tool engaged position (left). Unlocked and tool disengaged position (mid) unlocked and tool exit to the side (right)

tool post 8.jpg

05/09/2019 14:58:10
Posted by JasonB on 05/09/2019 08:59:28:

Chris, I would have thought it quicker and less of a fiddle to just unwind the handle a couple of turns rather than faff about with the "C" washer. You could still retract the holder towards you once the plate is high enough to let the holder move sideways enough to let the lip clear the main block.

One other thing have you checked how much support the holder has for the odd occasion when the toolpost needs to be angled as there will be nothing under the holder ends when at 45deg

Yes Jason, at 45deg, the tool holder will have less support as you pointed out. I calculated the bottom support surface area will decrease by 28%. But, as the top plate applies force to the tool holder at 45 deg (via the wedged top plate ends) , this should result in the tool holder being pushed both down and towards the tool post body. In other words the tool holder is supported both from the bottom and back faces... right? So I suppose the loss of rigidity will not be so much noticeable - I hope!

Regarding tool post entry and exit routes,I could take the top plate off as suggested, or use cam lever (not sure if clamping force of a cam is comparable to that of a fine thread). But I have (yet!) another design in mind - to the drawing board for design no....4, or was it 5..!

05/09/2019 07:53:27

I'm not sure what will qualify a tool post as a QCTP. For me the ability of changing over from one tool to another in a relatively short time without having to adjust the holder is the goal. Shimming the tool in it's holder happens only once during initial setup (talking about insert tooling here) so there's no requirement for adjustment when swapping tool holders.

As to your suggestion Laurent, in theory it is fine, but in practice you would have to take out the whole tool post each time you need to replace a tool, as the retaining screws are at the bottom. Not so convenient.

Ps. Noticed it's your first post, welcome to the forum Laurent!

Edited By ChrisB on 05/09/2019 07:59:09

04/09/2019 21:17:43

Thanks Jason and Michael, thinking about it I'll go for mild steel as suggested, I can use 20mm flat bar for the top plate, as that's readily available at the supplier close by.

Gray, the intention is to take the tool off from the side, rather than undoing the clamping lever several times, all I would need to do is a quarter turn to ease off the tension and slide off the C-washer located under the handle (shown in the drawing a couple of posts above) Then enough space will be available to lift the top plate and slide the tool off. It's a bit fiddly I know, might think of something else.

Chris

04/09/2019 11:15:26

Actually it's 16mm thick at the ends (wedges), and narrows down to 10mm at the centre. So in reality I will need a 16mm thick piece - was thinking...I might try getting away with cutting the 120mm piece on the band saw by turning it? I mean cut a piece up to the saw's limit and then turn the piece a bit more and cut again etc.

Is that material PFC linked above plain mild steel Jason?

04/09/2019 08:08:17

After some online searching regarding what steel to use I think I'm going for EN24T for the top plate. For the tool post block I may go with cast iron - if it does not machine well I'll go with EN24 as well. Tool holders black mild steel. For the solid tool post mount it's cast iron.

Could not find any 80mm square section material locally, so I'm going to have to get round stock and figure out how to cut it. My bandsaw can cut max 105mm round but to fit 80mm square in a round I will need 120mm round bar - not sure if the bandsaw can cut that...

30/08/2019 21:34:03

Did some further modifications and now I think I have the final design for the tool post. Next is materials to make it from - what are the recommendations?

My plan is to use mild steel for all parts apart from the central threaded stud and top plate. The stud I was going to make it from recycled 8.8ht bolt.

My main concern is the tool post top plate as it will carry most of the load, so I'm not sure if mild steel will be up to the job.

29/08/2019 14:53:18

Wow! Where shall I start from!

First of all thanks to all who are giving me input - I take everything in, things that I did not foresee or didn't know about and try to improve on the original design, so don't worry I will not get offended or let down by criticism etc.

I'll try to add most suggestions where practicable but on the other hand as IanT pointed out this will not be a perfect tool post, but it will be good enough for my usage.

For better tool adjustment I may leave some space in the tool holder for shimming. As a side note, it is surprising how close the insert tips (height) of TN** holder and the GTN parting tool, are.

So to Version 3!

I reduced the width of the angles on the top plate and tool holder as suggested by David George. Doing this also freed up space for the tool holder grub screws which now have 14mm thread depth.

I also introduced a 5mm thick C-washer under the retaining nut - the purpose of this washer is to be able to remove the tool holder sideways rather than forwards (as pointed out by DC31k. This is done by releasing the top retaining nut and pulling the C-washer out. The top plate will then have enough upward travel to be able to retrieve the tool holder from the side without moving the crosslide or rotating the tool post

Another remark by Neil was the inability of the tool post to retain it's position when changing tool holders - I have modified the design of the central pillar bolt, and the tool post to achieve this. I have introduced an M16 nut under the top slide face - the centre bolt will be threaded on to this nut. The centre bolt is flanged which will mate to the tool post (which now has a counter bore to accept the flange on the centre bolt). The centre bolt top is finished in a hex shape - when this is tightened the tool post will be clamped to the top slide (but not the top plate) The top plate is tightened in turn by an m16 clamping handle - this will in turn clamp the tool holder down.

It's difficult to explain with words, and my drawings can be misleading - this is how the above mods should look like.

tool post 6.jpg

tool post 7.jpg

28/08/2019 21:21:47

So I took some of the suggestions and replaced the round rods with a sort of a V - groove (a half V to be precise). Added an indexing wing at the forward end of the tool holder such that the tool will always go to the same depth. And increased the tool holder height so now I can use m8 x 10mm grub screws. Are M8 excessive? Would M6 be more suitable? Off hand cannot remember what's installed on the 4 way tool post!

Here's tool post version 2

tool post 4.jpg

Tool holder with beveled edge instead of the round groove. Theory is when tightening the top plate the holder should press down and in against the tool post and top slide. The extended part at the forward of the tool holder is the indexing part which will mate against the tool post. Grub screws should not extend beyond the bevel.

tool post 5.jpg

28/08/2019 20:34:11
Posted by HOWARDT on 28/08/2019 19:57:02:

The four pins won’t all press onto the tool unless the rod deforms substantially. Also I think a key and key way would locate the holder, the key can be a flatted pin.

Rather than use two pins why not make the top with two angled faces one acting on the holder and the other on the main body. This will pull the tool holder into the body.

Hi Howardt, those four pins should be grub screws which in turn clamp the tool to the tool holder. The grub screws will sit lower than the round groove in the holder so the two rods will not be touching the screws.

Making a V-groove may be a good idea, it will introduce some extra setting up to do it but will do away with those rods...food for thought, thanks!

28/08/2019 20:26:44
Posted by bricky on 28/08/2019 19:46:25:

The advantage is that the tool cartridge is tight onto the topslide and gives ridgidity.I made a toolholder which is in my album which is based on the Pratt burnerd holder.Mine, one has to pack the tool in it's holder to centre height but once done your there and unlike this design the holder can be removed and replaced as before and cannot move in the toolpost.I like the toolpost Chris.

Frank

Hi Frank, I've seen your photo album, fine set up! The principle is very similar, how do you like the rigidity of this tool post?

In this design, the tool holder slides forward or backwards when the top nut is loosened, so you can replace with the next tool easily. I thought I'll do away with shimming so I will machine the tool holder to centre height instead.

28/08/2019 20:20:17
Posted by not done it yet on 28/08/2019 20:13:03:

Probably not quite as convenient - I would expect you to need the odd shim for perfect centre height adjustment, but a definite improvement over a non-QCTP.

My plan is to machine the bottom off the holder to the correct centre height and as I'll be using insert tooling no further adjustment should be required - hopefully!

The long-travel on my lathe is far too ‘coarse’ for intricate manual feeding - is yours well geared down?

It is coarse as you say, but still manage manual feeding - very carefully. The top slide is much better for creeping up to the size.

28/08/2019 19:38:42

Posted by ChrisB on 28/08/2019 18:20:51:

The tool holder adjustment is not done like the Aloris, Dickson, Norman with set screws. Actually there's no adjustment as the tool holder will be machined to the correct center height straight away. As the tooling is insert tooling the center should be always the same for that particular tool in it's holder.

Hi Bob, well spotted, the rods can either be spot welded to the top plate or with adhesive. It makes no sense having them running around.

With regards to tool height adjustment, as I mentioned in my original post, I will be using insert tooling. My plan is to make a batch of holders to a standard size, and then machine the bottom surface to obtain the center height for that particular tool. As it's insert tooling once the height is set (by machining the bottom face of the holder) there is no need for further adjustments in the future. This will obviously not work for HSS tooling.

Not sure what the Norton design is, but if you're refering to the Norman tool post, the tool holders are quite large compared to this, less material required, less machining required, and I think this may be more rigid.

Posted by JasonB on 28/08/2019 18:39:59:

Think I would have some way to index the in/out position of the holder so that if you were doing a batch of items that needed a tool change you could swap holders and be able to use the same handwheel settings rather than have to measure each time a tool is holder is changed. Would also stop the holder being pushed back towards you.

Maybe move the half round groove towards the middle so you have more thread depth for the grub screws

Good points Jason, Hadn't thought about indexing the holder, but that's easy fix, can be done. Regarding the round groove, I'm afraid that moving the groove further towards the center of the tool post will make the grip on the holder less effective. I could increase the thickness of the tool holder tho so Icould use longer grub screws. As is the screws are currently M8 x 6mm

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